Heat Exchanger with Improved Performance

Abstract

A heat exchanger for use in a heating, ventilation, and air-conditioning (“HVAC”) system. The heat exchanger includes at least two sections with each section having a set of heat transfer tubes. A first section of the heat exchanger may include an inlet header, a first intermediate header, and a first set of heat transfer tubes fluidly coupling the inlet header to the first intermediate header. A second section of the heat exchanger may include an outlet header, a second intermediate header, and a second set of heat transfer tubes fluidly coupling the second intermediate header to outlet header. At least one fluid line fluidly couples the first section to the second section. As a fluid (e.g., refrigerant) flows through the heat exchanger, the heat exchanger provides multiple passes for the fluid to undergo phase changes before the fluid exits the heat exchanger as a single-phase refrigerant.

Description

BACKGROUND

This section is intended to introduce the reader to various aspects of the art that may be related to various aspects of the presently described embodiments—to help facilitate a better understanding of various aspects of the present embodiments. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.

Heat exchangers are used to transfer heat or exchange thermal energy between fluids (i.e., refrigerant and air), for industries such as residential, light commercial, and commercial applied HVAC systems. For example, the fluid will pass through heat transfer tubes, such as tubes or coils, of the heat exchangers and the temperature of the fluid may change before exiting the heat exchanger. Additionally, the heat exchanger may change a phase state of the fluid such that the fluid may change from a gas phase state (i.e., vapor) to a liquid phase state, or vice versa, before exiting the heat exchanger. A conventional single row, two-pass heat exchanger 10 is illustrated in FIG. 1. The heat exchanger 10 includes a single row of heat transfer tubes 11 extending between an inlet/outlet header 12 and an intermediate header 13. The single row of heat transfer tubes 11 have one end fluidly coupled to the inlet/outlet header 12 and a second end fluidly coupled to the intermediate header 13. The inlet/outlet header 12 may include a baffle 14 to split the inlet/outlet header 12 into an inlet header portion 12a and an outlet header portion 12b. Additionally, as illustrated by a dash-dot line P, the baffle 14 position in the inlet/outlet header 12 may also sperate the single row of heat transfer tubes 11 into a first pass (see block arrow P1) and a second pass (see block arrow P2) flow of the fluid undergoing a heat transfer. The heat transfer tubes of the single row of heat transfer tubes 11 are typically microchannel multiport flat tubes. However, other tube configurations such as round or oval tubes may be used.

In operation as condenser, a fluid, such as a high temperature and pressure refrigerant vapor discharged by a compressor, enters (see arrow E1) the heat exchanger 10 via an inlet 15 attached to the inlet header portion 12a. From the inlet header portion 12a, the fluid is distributed through a certain number of heat transfer tubes 11 in in the first pass (see block arrow P1). An external crossflow air stream flowing across the heat transfer tubes 11 cools the fluids which then gradually condenses portion of vapor into liquid on the way to the intermediate header 13. In the intermediate header 13, the vapor and liquid mixture gets redistributed and makes a turn (see block arrow T) in a flow direction. The vapor may get completely condensed into a liquid when it enters in the heat transfer tubes 11 in the second pass (see block arrow P2). From the second pass (see block arrow P2), the condensed and subcooled liquid is collected in the outlet header portion 12b and exits (see arrow E2) the heat exchanger 10 via an outlet 16 attached the outlet header portion 12b as a subcooled liquid.

Conventional heat exchangers, such as the heat exchanger 10 described in FIG. 1, may develop fluid distribution issues in the intermediate header that affect the heat exchanger performance and intended utilization. As the fluid arrives in the intermediate header in a two-phase state, liquid and vapor, the vapor of the fluid stays at a top of the intermediate header and the liquid of the fluid is forced down (i.e., gravity) to a bottom of the intermediate header. However, this may result in an inefficient or incomplete phase change as both phases enter the heat transfer tubes. Additionally, maldistribution may develop when the vapor of the fluid also enters the heat transfer tubes in the second pass. This maldistribution significantly reduces the subcooling, jeopardizes inlet conditions to a thermal expansion valve (TXV) connected to the outlet, and affects the overall heat transfer performance of the heat exchanger. In addition, heat transfer loss may also occur when two steams of liquid with different temperatures mix at the outlet header. Furthermore, the condensed refrigerant creates a heat transfer barrier for the remaining vapor leading to a reduced ability for this refrigerant vapor to condense. In conventional methods, to compensate for such deficiencies, the number of heat transfer tubes is increased, the size of the heat transfer tubes is increased to accommodate more ports, or the number of passes is increased. These solutions result in a size growth of conventional heat exchangers leading to additional cost, weight, labor, time, capital investment, refrigerant charge, corrosion, and leak opportunities. In addition, the crossflow configuration becomes more inefficient, from the thermal performance standpoint, with the increase in size of the heat transfer tubes or increase in size for the heat exchanger itself.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects, and advantages of certain embodiments will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings.

FIG. 1 is a schematic view of a heat exchanger in accordance with the prior art.

FIG. 2 is a perspective view of a heat exchanger operating as a condenser in accordance with one or more embodiments of the present disclosure.

FIG. 3 is a side view of the heat exchanger of FIG. 2 in accordance with one or more embodiments of the present disclosure.

FIGS. 4A and 4B are perspective views of a heat exchanger operating as a condenser in accordance with one or more embodiments of the present disclosure.

FIGS. 4C and 4D are perspective views of a heat exchanger operating as a evaporator in accordance with one or more embodiments of the present disclosure.

FIGS. 5A and 5B are perspective views of a heat exchanger operating as an evaporator in accordance with one or more embodiments of the present disclosure.

FIG. 6 is a block diagram of an HVAC system in accordance with one or more embodiments of the present disclosure.

FIG. 7 is a block diagram of an HVAC system in accordance with one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation may be described. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

The present disclosure relates to a heat exchanger to transfer heat of a fluid (i.e., refrigerant) flowing therein. In one or more embodiments, the heat exchanger disclosed herein may be used in an HVAC system for residential, light commercial, and commercial applied systems. The heat exchanger may be used as a condenser or evaporator. The heat exchangers may be microchannel heat exchangers that include a plurality of tubes that each include microchannels for flowing refrigerant from one side of the heat exchanger to the other, or one “pass” across the heat exchanger. The heat exchangers may also be round tube and plate fin (“RTPF”) heat exchangers that include a plurality of tubes that pass from one side of the head exchanger to the other through a slab made of fins. Other tube shapes such as oval tubes are also within the scope of this invention. The fluid may make two or more passes across the heat exchanger, with each successive pass being a different pass, or stage. One or more tubes that flow fluid in a given direction across the heat exchanger at the same stage in the flow circuit are grouped together into a section and multiple sections are fluidly connected via the headers or manifolds. The tubes may also be bonded to the fins therebetween by brazing, welding, press fit, chemical bonding or other means. Furthermore, the fins can be continuous spanning multiple rows of heat transfer tubes, or each row of heat transfer tubes may each have their own fin. It is further envisioned that various parameters for each row may be also varied such as, fin density, fin configuration, tube geometry, and other parameters.

Further, in the microchannel heat exchanger, the adjacent sections of tubes are separated, as discussed in more detail below. The separation between the adjacent sections of tubes is sufficient enough to reduce the cross-transfer of heat between the sections, improving the performance of the microchannel heat exchanger and reducing the size of the microchannel heat exchanger when compared to a heat exchanger without a separation. The separation also reduces the thermal stress on the joints between the tubes and the header since there is a smaller temperature differential between the tube and the header.

In the heat exchanger, a pass or fluid pass refers to one passage of fluid from one header at one end of the heat exchanger to the opposing header at the opposing end of the heat exchanger. For each pass, the fluid flows through a row of heat transfer tubes that carry the fluid from one end of the heat exchanger to an opposing end of the heat exchanger for a given stage of the flow through the heat exchanger.

In one or more embodiments, the heat exchanger of present disclosure includes at least two sections, each having a set of heat transfer tubes. For example, a first section of the heat exchanger may include an inlet header, a first intermediate header, and a first set of heat transfer tubes fluidly coupling the inlet header to the first intermediate header. A second section of the heat exchanger may include an outlet header, a second intermediate header, and a second set of heat transfer tubes fluidly coupling the second intermediate header to outlet header. Additionally, at least one fluid line fluidly couples the first section to the second section. In this arrangement, a fluid (e.g., refrigerant) flows into the inlet header and through the first set of heat transfer tubes. As the fluid flows through the first set of heat transfer tubes, an air stream flows across the first set of heat transfer tubes to either cool or warm the fluid. Once the fluid enters the first intermediate header from the first set of heat transfer tubes, at least some of the fluid has undergone a phase change due to exchanging heat or thermal energy from flowing through the first set of heat transfer tubes. The two phases of the fluid are allowed to separate into two separate phases (e.g., gas and liquid). At least one of the phases is then transported through the at least one fluid line to travel into the second section. In the second section, the at least one of the two phases undergoes phase change by flowing through the second set of heat transfer tubes as the air stream flows across the second set of heat transfer tubes. Overall, the fluid enters the first section of the heat exchanger in one phase and exits the second section of the heat exchange as another phase due to the phase changes in the first and second sets of the heat transfer tubes. By transporting the fluid in such a manner through the first section and the second section, the heat exchanger is to be able to more efficiently produce a complete phase change of the fluid (e.g., liquid to vapor or vapor to liquid). For example, one of the intermediate headers separates a flow of the fluid in two separate phases to allow a complete phase change of all of the fluid more effectively. As described above, the fluid undergoes a partial phase change in the first section to produce a two-phase fluid (e.g., a second fluid and a third fluid). Further, at least one of the phases of the two-phase fluid undergoes a phase change in the second section to provide a more efficient phase change in the second section than if the two-phase fluid was not separated. Advantageously, the two intermediate headers improve a phase change and distribution of the fluid into two phases through the heat exchanger to avoid incomplete phase change and maldistribution.

As described above, conventional methods merely increase a number of heat transfer tubes per pass, use wider heat transfer tubes with more ports, and/or increase the number of passes to address an inefficient or incomplete phase change of the fluid, as well as a maldistribution of the fluid. Additionally, conventional methods keep the multiple phases of the fluid together when undergoing a phase change through a heat exchanger, and this makes the phase change process is less efficient. These conventional solutions merely focus on the heat exchanger size growth and do not focus on separating a flow of the fluid after a phase change. However, the heat exchanger of the present disclosure is to be able to more efficiently produce a complete phase change of a fluid, such as liquid to vapor or vapor to liquid. For example, the heat exchanger of the present disclosure may sperate the fluid once a phase change has occurred such that the separated fluids may undergo further phase change to complete the phase change of all of the fluid flowing therein. As will be explained in further detail below, by arranging the heat exchanger of the present disclosure to have at least two sets of heat transfer tubes and two intermediate headers, the overall system has improved fluid phase change efficiency and distribution, and improved performance, lowers cost, reduces weight, improved compactness, and reduced refrigerant charge.

Turning now to the figures, FIG. 2 is a block diagram of a perspective view of a heat exchanger 100 used in an HVAC system in accordance with one or more embodiments in the present disclosure. The heat exchanger 100 may be used as a condenser to condense a fluid (e.g., refrigerant) for the HVAC system. The heat exchanger 100 includes a first section 101 fluidly coupled to a second section 102 to phase change the fluid (e.g., refrigerant) flowing therein. For example, the fluid flows through the heat exchanger 100 in a first phase (e.g., vapor) such that the first section 101 and the second section 102 condense the fluid into a second phase (e.g., liquid) by the time the fluid flows out of the heat exchanger 100. It is noted that while only two sections are illustrated, this is merely for example purposes only, and any number of sections more than two sections may be used without departing from the scope of the present disclosure.

In one or more embodiments, the first section 101 includes an inlet header 103 with an inlet pipe 104 to receive a fluid (see block arrow F), a first set of heat transfer tubes 105, and a first intermediate header 106. The first set of heat transfer tubes 105 fluidly couple the inlet header 103 at a right-hand side (RHS) of the first section 101 to the first intermediate header 106 at a left-hand side (LHS) of the first section 101. For example, a first end of the first set of heat transfer tubes 105 is in fluid communication with the inlet header 103 such that an opening at the first end receives the fluid from the inlet header 103. The first set of heat transfer tubes 105 axially extends from the inlet header 103 such that a second end of the first set of heat transfer tubes 105 is positioned in fluid communication with the first intermediate header 106 to flow the fluid out an opening at the second end into the first intermediate header 106. Additionally, the inlet header 103 and the first intermediate header 106 are both orientated in a vertical direction.

The first set of heat transfer tubes 105 may be tubes known as flat tubes that are wider than high. Each heat transfer tube may include a plurality of microchannels for carrying the fluid. The first set of heat transfer tubes 105 are stacked in row, thus defining a size or volume of the first section 101 along the fluid flow direction F1. It will be understood that while the first set of heat transfer tubes 105 are shown “horizontally” stacked in FIG. 2, a heat exchanger may include tubes that are “vertically” stacked. A plurality of fins (not shown) may be arranged between each tube to aid in heat transfer from the plurality of microchannels. The first section 101 in operation receives an air flow (see block arrow AF) across the first set of heat transfer tubes 105 and exchanges heat between the air flow (see block arrow AF) and the fluid flow (see block arrow F1). It is noted that while the air flow (see block arrow AF) is shown going into the first section 101, this is merely for example purposes only, and the air flow may flow in an opposite direction such that the air flow goes into the second section 102 first.

In one or more embodiments, the second section 102 may have a similar arrangement to the first section 101 to have a fluid flow through heat transfer tubes from one header to an opposing header. Additionally, the first section 101 and the second section 102 are spaced a distance D apart from each other to have the second section 102 adjacent to the first section 101 in a side-by-side arrangement. The distance D is a small enough distance that the headers 103, 106, 107, 109 of the respective sections 101, 102 do not typically touch each other. Additionally, the distance D is also a small enough distance that the air flow (see block arrow AF) can travel through the first section 101 across the first set of heat transfer tubes 105 and then reach the second section 102 without a significant drop in temperature and flow rate. However, the distance D is also a large enough distance to reduce a cross-heat transfer from a temperature differential the first section 101 than the second section 102. The gap may be large enough to reduce, or even minimize, this cross-heat transfer. In some embodiments, the distance D is may be determined by an outer diameter of the headers 103, 106, 107, 109 since the outer diameter of the headers 103, 106, 107, 109 is larger than a width of the heat transfer tubes 105, 108.

As illustrated in FIG. 2, the second section 102 includes a second intermediate header 107 to receive the fluid from the first section 101, a second set of heat transfer tubes 108, and an outlet header 109 to exit the fluid out of the heat exchanger 100. The second set of heat transfer tubes 108 fluidly couple the second intermediate header 107 at a LHS of the second section 102 to the outlet header 109 at a RHS of the second section 102. For example, a first end of the second set of heat transfer tubes 108 is positioned in fluid communication with the second intermediate header 107 such that an opening at the first end receives the fluid from the second intermediate header 107. The second set of heat transfer tubes 108 axially extend from the second intermediate header 107 such a second end of the second set of heat transfer tubes 108 is positioned in fluid communication with the outlet header 109 to flow the fluid out an opening at the second end into the outlet header 109. Additionally, the second intermediate header 107 and the outlet header 109 are both orientated in a vertical direction.

The second set of heat transfer tubes 108 may be tubes known as flat tubes that are wider than high. Each heat transfer tube may include a plurality of microchannels for carrying the fluid. The second set of heat transfer tubes 108 are stacked in row, thus defining a size or volume of the second section 102 along the fluid flow direction (F4 or F5 shown in FIG. 3). It will be understood that while the second set of heat transfer tubes 108 are shown “horizontally” stacked in FIG. 2, a heat exchanger may include tubes that are “vertically” stacked. Additionally, the first set of heat transfer tubes 105 and the second set of heat transfer tubes 108 may be sized the same or have volumetric flow rate. For example, a diameter of the heat transfer tubes of the first set of heat transfer tubes 105 may be larger than a diameter of the heat transfer tubes of the second set of heat transfer tubes 108. A plurality of fins (not shown) may be arranged between each tube to aid in heat transfer from the plurality of microchannels. The second section 102 in operation receives an air flow (see block arrow AF) traveling through the first section 101 to then flow across the second set of heat transfer tubes 108 and exchanges heat between the air flow and the fluid flow. Alternatively, the air flow may be flowing in an opposite direction such that the air flow travels through the second section 102 first and then the first section 101. It is further envisioned that the second set of heat transfer tubes 108 may have the same or a different number of heat transfer tubes than the first set of heat transfer tubes 105. For example, the second set of heat transfer tubes 108 may have more heat transfer tubes than the first set of heat transfer tubes 105. Furthermore, the second set of heat transfer tubes 108 may be of a different form, size and/or shape than the first set of heat transfer tubes 105. For example, the first set of heat transfer tubes 105 may be larger than the second set of heat transfer tubes 108.

Still referring to FIG. 2, the second intermediate header 107 includes a baffle 110 disposed therein. For example, the baffle 110 is coupled or fixed to an inner wall of the second intermediate header 107 via mechanical fasteners, welding, brazing, soldering, or other means. By having the baffle 110, the second intermediate header 107 is separated into a top tank 111 and a bottom tank 112. The baffle 110 prevents any cross flow between the top tank 111 and the bottom tank 112. The baffle 110 may be any type of plate or vane to obstruct flow. In some embodiments, the baffle 110 is positioned at a predetermined height within the second intermediate header 107 such that the top tank 111 accounts for one-third to two-thirds or around 30 to 60 percent of an internal volume of the second intermediate header 107 and the bottom tank 112 accounts respectively for the remaining two-third to one-third of the internal volume of the second intermediate header 107. The baffle 110 position may be generally determined by a void fraction of the refrigerant vapor as compared to the liquid refrigerant. Additionally, a respective pressure drop in the second section 102 for the vapor flow from the top tank 111 and the liquid flow from the bottom tank 112 may also be used to determine the position of the baffle 110. Furthermore, the baffle 110 position may be optimized to cover a range of indoor and outdoor operating conditions for the heat exchanger 100 or an overall HVAC system.

To facilitate fluid communication between the first section 101 and the second section 102, fluid communication lines 113, 114, such as headers, jumpers, or header connections, fluidly couple the first intermediate header 106 to the second intermediate header 107. For example, a first fluid communication line 113 has a first end in fluid communication with a top portion of the first intermediate header 106 and a second end in fluid communication with the top tank 111. The first fluid communication line 113 establishes a flow path from the first intermediate header 106 to the top tank 111. Additionally, the first fluid communication line 113 may be positioned in an upper half portion of the top tank 111 to assure vapor flow. A second fluid communication line 114 has a first end in fluid communication with a bottom portion of the first intermediate header 106 and a second end in fluid communication with the bottom tank 112. The second fluid communication line 114 establishes a flow path from the first intermediate header 106 to the bottom tank 112. Further, the second fluid communication line 114 may be positioned in a bottom half portion of the bottom tank 112 to assure no additional obstruction to the liquid flow. Both fluid communication lines 113 and 114 may be a rigid pipe, jumper flow line, or umbilical conduit. It is noted that while the two fluid communication lines 113, 114 are shown matching, this is for example purpose only, and the two fluid communication lines 113, 114 may have different diameters, length and layout, and may include multiple tubes respectively. Additionally, the first intermediate header 106 may include one or more bypass fluid communication lines to promote at least some of the fluid flow bypass the second section 102 and flow straight to the outlet pipe 115.

As described above, the heat exchanger 100 acts as a condenser to condense the refrigerant vapor. For example, a compressor may discharge a high temperature and pressure refrigerant vapor (e.g., in a gaseous state) as a fluid into the heat exchanger 100, when the heat exchanger 100 is a condenser. The fluid enters the heat exchanger 100 as a first fluid (see block arrow F) in a single phase as a refrigerant vapor via the inlet pipe 104 to enter the inlet header 103. From the inlet header 103, the first fluid flows into the first set of heat transfer tubes 105. As the first fluid flows through (see block arrow F1) the first set of heat transfer tubes 105 for a first pass, the air flow (see block arrow AF) flows across a surface of the first set of heat transfer tubes 105 to provide heat transfer (i.e., temperature and phase change) of the first fluid. In the first pass, a portion of the first fluid condenses such the first fluid separates into a second fluid and a third fluid that are different phases (e.g., refrigerant liquid and refrigerant vapor). The second fluid is predominantly a liquid refrigerant, and the third fluid is predominantly a vapor refrigerant. Gravity separation and/or a pressure differential in the first intermediate header 106 forces the liquid refrigerant (i.e., the second fluid) to flow into the bottom portion of the first intermediate header 106 and the vapor refrigerant (i.e., the third fluid) into the top portion of the first intermediate header 106.

From the first intermediate header 106, the liquid refrigerant (i.e., the second fluid) and the vapor refrigerant (i.e., the third fluid) flow into the second intermediate header 107. For example, the liquid refrigerant (i.e., the second fluid) flows through (see block arrow F2) the second fluid communication line 114 and into the bottom tank 112 from the bottom portion of the first intermediate header 106. The vapor refrigerant (i.e., the third fluid) flows through (see block arrow F3) the first fluid communication line 113 and into the top tank 111 from the top portion of the first intermediate header 106. The flow of the liquid refrigerant (i.e., the second fluid) and the vapor refrigerant (i.e., the third fluid) in the second section 102 is illustrated in FIG. 3 as discussed below. It is further envisioned that fluid communication lines 113, 114 may have different diameters, lengths, layouts, and include multiple tubes without departing from the scope of the present disclosure.

Now referring to FIG. 3, FIG. 3 shows a block diagram of a side view of the second section 102 of the heat exchanger 100. The first section 101 of the heat exchanger 100 is not illustrated in FIG. 3 for example purposes only to provide better clarity of the fluid flow in the second section 102. As the liquid (i.e., the second fluid) and the vapor (i.e., the third fluid) flow (see block arrows F2 and F3, respectively) into the second intermediate header 107 from the fluid communication lines 113, 114, the baffle 110 aids in keeping the liquid (i.e., the second fluid) and the vapor (i.e., the third fluid) separated in the second intermediate header 107.

As described above, the baffle 110 in the second intermediate header 107 prevents cross flow between the top tank 111 and the bottom tank 112. This allows a first plurality of heat transfer tubes in an upper section 108A of the second set of heat transfer tubes 108 to be in fluid communication with only the top tank 111 and a second plurality of heat transfer tubes in a lower section 108B of the second set of heat transfer tubes 108 to be in fluid communication with only the bottom tank 112. With this arrangement, the liquid (i.e., the second fluid) and the vapor (i.e., the third fluid) flow into the second set of heat transfer tubes 108 via different passes. For example, the vapor (i.e., the third fluid) flows through (see block arrow F4) the upper section 108A of the second set of heat transfer tubes 108 and the liquid (i.e., the second fluid) flows through (see block arrow F5) the lower section 108B of the second set of heat transfer tubes 108. As the vapor (i.e., the third fluid) flows for a second pass through (see block arrow F4) the upper section 108A, the same air flow that passes through the first section (see 102 in FIG. 2) also flows (see block arrow AF′) across the second set of heat transfer tubes 108. In the second pass with the air flow (see block arrow AF′), the vapor (i.e., the third fluid) in the upper section 108A may get completely condensed and subcooled into a liquid before arriving at the outlet header 109. Concurrently to the second pass of the vapor refrigerant (i.e., the third fluid), the liquid (i.e., the second fluid) undergoes a second pass through the lower section 108B. The air flow (see block arrow AF′) also flows across the lower section 108B to further cool and lower a temperature in the lower section 108B such that the liquid refrigerant (i.e., the second fluid) stays in a liquid state and gets further subcooled before entering the outlet header 109.

The upper section 108A and the lower section 108B may have a different number of heat transfer tubes. For example, the upper section 108A may have more heat transfer tubes than the lower section 108B to account for a higher flow volume of the vapor (i.e., the third fluid) than the liquid (i.e., the second fluid). The second plurality of heat transfer tubes in the lower section 108B may have one-third to two-thirds of the total number of heat transfer tubes in the second set of heat transfer tubes.

Still referring to FIG. 3, in the outlet header 109, the refrigerant vapor which is condensed into a subcooled liquid from the second pass merges with the further subcooled liquid from the third pass to form a single-phase fluid (i.e., a fourth fluid). From the outlet header 109, the fourth fluid exits (see block arrow F6) the heat exchanger 100 via an outlet pipe 115 attached to the outlet header 109 as a subcooled liquid refrigerant. It is noted that while the outlet pipe 115 is shown at a bottom portion of the outlet header 109, this is merely for example purposes only, and the outlet pipe 115 may be positioned at any height along the outlet header 109 without departing from the scope of the present disclosure. The subcooled liquid refrigerant is now optimized before entering an expansion device, such as a thermal expansion valve (e.g. TXV), in fluid communication with the heat exchanger 100 via the outlet pipe 115. The optimally subcooled liquid refrigerant from the heat exchanger 100 improves a refrigerant side capacity, functionality of the expansion device and refrigerant system reliability. By separating the liquid and the vapor in the intermediate headers (106, 107) and allowing their respective flows through the different passes in the second section 102, heat transfer and pressure drop characteristics of the heat exchanger 100 are improved. Overall, the heat exchanger 100 of FIGS. 2 and 3 has optimized thermal performance, extended system operational envelope and improved reliability, and enhanced expansion device functionality. It is further envisioned that the heat exchanger 100 may include more than two sections and multiple intermediate headers where vapor and liquid separation means may be integrated into the header design for the heat exchanger 100. Furthermore, an over-under single-row configurations, instead of the side-by-side configuration show, may be used without departing from the scope of the present disclosure. For example, the second section 102 may be positioned below the first section 101. In some embodiments, hybrid configurations (e.g., a side-by-side and over-under configurations) may be used for a heat exchanger with three or more sections without departing from the scope of the present disclosure.

As described above, the heat exchanger 100 may be used as a condenser to condense a fluid (e.g., refrigerant) for the HVAC system. However, the heat exchanger 100 may also be used as an evaporator to evaporate a fluid (e.g., refrigerant) for the HVAC system. For example, an expansion device may discharge a low temperature and pressure refrigerant liquid (e.g., in a predominantly liquid state) as a fluid into the heat exchanger 100, when the heat exchanger 100 is an evaporator. The refrigerant liquid enters the heat exchanger 100 as the first fluid in a single phase as a refrigerant liquid via the inlet pipe 104 to enter the inlet header 103 and through the first set of heat transfer tubes 105. As the first fluid flows through the first set of heat transfer tubes 105 for a first pass, the air flow flows across a surface of the first set of heat transfer tubes 105 to provide heat transfer (i.e., phase change) of the first fluid. In the first pass, a portion of the first fluid evaporates such the first fluid separates into a second fluid and a third fluid that are different phases (e.g., refrigerant liquid and refrigerant vapor). The second fluid is predominantly a liquid refrigerant, and the third fluid is predominantly a vapor refrigerant. Gravity separation and/or a pressure differential in the first intermediate header 106 forces the liquid refrigerant (i.e., the second fluid) to flow into the bottom portion of the first intermediate header 106 and the vapor refrigerant (i.e., the third fluid) into the top portion of the first intermediate header 106. From the first intermediate header 106, the liquid refrigerant (i.e., the second fluid) and the vapor refrigerant (i.e., the third fluid) flow into the second intermediate header 107. For example, the liquid refrigerant (i.e., the second fluid) flows through the second fluid communication line 114 and into the bottom tank 112 from the bottom portion of the first intermediate header 106. The vapor refrigerant (i.e., the third fluid) flows through (see block arrow F3) the first fluid communication line 113 and into the top tank 111 from the top portion of the first intermediate header 106. From the second intermediate header 107, the vapor (i.e., the third fluid) flows through (see block arrow F4) the upper section 108A of the second set of heat transfer tubes 108 and the liquid (i.e., the second fluid) flows through (see block arrow F5) the lower section 108B of the second set of heat transfer tubes 108. In the second pass with the air flow, the liquid (i.e., the second fluid) in the lower section 108B may get completely evaporated and superheated into a vapor before arriving at the outlet header 109. Concurrently to the second pass of the liquid (i.e., the second fluid), the vapor refrigerant (i.e., the third fluid) also undergoes a third pass in the upper row 109A such that the vapor refrigerant (i.e., the third fluid) stays in a gaseous state and gets further superheated before entering the outlet header 109. In the outlet header 109, the refrigerant liquid, which is evaporated into vapor, that may or may not be superheated, from the second pass merges with the further superheated gas from the third pass to form a fourth fluid (i.e., a superheated vapor refrigerant). The superheated vapor refrigerant is now optimized before entering a compressor in fluid communication with the heat exchanger 100 via the outlet pipe 115.

Turning to FIG. 4A, another embodiment of a heat exchanger 400 according to embodiments herein is illustrated, where like numerals represent like parts. The embodiment of FIG. 4A is similar to that of the embodiment of FIGS. 2 and 3. For clarity purposes only, a second section 402 of the heat exchanger 400 is shown above the first section 401 of the heat exchanger 400 instead of being behind and side-by-side to better illustrate the fluid communication between the sections 401, 402. This is merely done for example purposes only to avoid causing confusions in the visualization of the fluid flow paths. However, FIG. 4B is provided to illustrate the heat exchanger 400 of FIG. 4A in a side-by-side configuration as would be used in operation. It is further envisioned an over-under configuration where the second section 402 is positioned below the first section 401 may be used for the heat exchanger 400 without departing from the scope of the present disclosure without departing from the scope of the present disclosure.

As shown in FIG. 4A, the first section 401 of the heat exchanger 400 is arranged similar to the first section 101 of the heat exchanger 100 of FIG. 2. However, instead the second section 102 of the heat exchanger 100 being arranged to have the second intermediate header 107 at the LHS and the outlet header 109 at the RHS (see FIGS. 2 and 3), the second section 402 of the heat exchanger 400 is arranged to have a second intermediate header 407 at the RHS and a third intermediate header 409 at the LHS. Additionally, instead of the baffle 110 being disposed in the second intermediate header 407, a baffle 410 is disposed in the third intermediate header 409. The baffle 410 separates the third intermediate header 409 to have a top tank 411 and a bottom tank 412 with an outlet pipe 415. The bottom tank 412 acts as an outlet header.

In one or more embodiments, the fluid flow in the first section 401 of FIG. 4A is similar to the fluid flow in the first section 101 shown in FIG. 2 as described above. However, instead of the first intermediate header 407 redistributing the liquid (i.e., the second fluid) and the vapor (i.e., the third fluid), both into in the second intermediate header (see 107 in FIGS. 2 and 3), the liquid (i.e., the second fluid) and the vapor (i.e., the third fluid) from the first section 401 are redistributed into different headers 407, 409. For example, the liquid (i.e., the second fluid) flows from the bottom portion of the first intermediate header 406 through (see block arrow F2′) a second fluid communication line 414 and into a bottom portion of the second intermediate header 407. Concurrently, the vapor (i.e., the third fluid) flows from the top portion of the first intermediate header 406 through (see block arrow F3′) a first fluid communication line 413 and into the top tank 411.

As shown in FIG. 4A, from the top tank 411, the vapor (i.e., the third fluid) flows through (see block arrow F4′) an upper section 408A of the second set of heat transfer tubes 408. As the vapor (i.e., the third fluid) flows for the second pass through (see block arrow F4′) the upper section 408A, the same air flow that passes through the first section 401 (see block arrow AF) also flows (see block arrow AF′) across the upper section 408A. In the second pass with the air flow (see block arrow AF′), the vapor (i.e., the third fluid) in the upper section 408A may get completely condensed and even subcooled before arriving at second intermediate header 407 as a liquid.

In the second intermediate header 407, the liquid (i.e., the second fluid) merges with the now completely condensed and potentially subcooled liquid (i.e., the third fluid) from the upper section 408A to form a single-phase liquid (i.e., the fourth fluid). Additionally, a gravity force may help the fluids merge in the second intermediate header 407. It is further envisioned that the gravity force and proper sizing of the fluid communication lines 413 and 414 help balance the pressure drop and refrigerant flow between the vapor (i.e., the third fluid) in the second pass and the liquid (i.e., the second fluid) from the second fluid communication line 414 to achieve a smooth transition and mixing in the second intermediate header 407.

From the second intermediate header 407, the subcooled liquid (i.e., the fourth fluid) flows through (see block arrow F5′) a lower section 408B of the second set of heat transfer tubes 408 for a third pass. During the third pass, the air flow flows (see block arrow AF′) across the lower section 408B such that the subcooled liquid (i.e., the fourth fluid) gets further subcooled and enters the bottom tank 412. The fourth fluid now exits (see block arrow F6′) the heat exchanger 400 via the outlet pipe 415 attached to the bottom tank 412 as a subcooled liquid refrigerant. By separating the condensed liquid in the heat exchanger intermediate header(s) 406, 407, 409 and allowing the condensed liquid to bypass one or more subsequent heat exchanger tube sections (i.e., the upper section 408A of the second set of heat transfer tubes 408), the heat exchanger 400 has enhanced heat transfer characteristics for the remaining vapor portion to be condensed (i.e., the vapor portion flowing through the upper section 408A of the second set of heat transfer tubes 408). For example, the condensed liquid does not create a heat transfer barrier or additional thermal resistance for the remaining vapor portion to be condensed that would have typically prevented the remaining vapor portion to be condensed from make direct contact with the heat exchanger tube inner wall. Additionally, a power consumption for the compressor in fluid communication with the heat exchanger 400 is reduced by not having to pump the liquid through the respective heat exchanger tubes 405, 408. Furthermore, due to interfacial shear forces between a liquid and vapor, a pressure drop for the two-phase flow is higher than a single-phase flow, which requires even higher power consumption by the compressor. However, the heat exchanger 400 eliminates this higher power consumption by the compressor by separating the liquid and vapor. Overall, the improved heat transfer and pressure drop characteristics in the heat exchanger 400 lead to better system performance, extended operational envelope and enhanced reliability. It is further envisioned that the heat exchanger 400 may even be downsized, while still maintaining equivalent performance characteristics.

As described above, the heat exchanger 400 may be used as a condenser to condense a fluid (e.g., refrigerant) for the HVAC system. However, the heat exchanger 400 may also be used as an evaporator to evaporate a fluid (e.g., refrigerant) for the HVAC system, as illustrated in FIGS. 4C and 4D. For clarity purposes only, the second section 402 of the heat exchanger 400 is shown above the first section 401 of the heat exchanger 400 instead of being behind and side-by-side to better illustrate the fluid communication between the sections 401, 402. This is merely done for example purposes only to avoid causing confusions in the visualization of the fluid flow paths. However, FIG. 4D is provided to illustrate the heat exchanger 400 of FIG. 4C in a side-by-side configuration as would be used in operation. It is further envisioned an over-under configuration where the second section 402 is positioned below the first section 401 may be used for the heat exchanger 400 without departing from the scope of the present disclosure.

As shown in FIG. 4C, the first section 401 of the heat exchanger 400 is the same as described above in FIG. 4A. For example, an expansion device may discharge a low temperature and pressure refrigerant liquid (e.g., in a predominantly liquid state) as a fluid into the heat exchanger 400, when the heat exchanger 400 is an evaporator. The refrigerant liquid enters the heat exchanger 400 as the first fluid in a single phase as a refrigerant liquid via the inlet pipe 404 to enter the inlet header 403 and through the first set of heat transfer tubes 405. As the first fluid flows through the first set of heat transfer tubes 405 for a first pass, the air flow flows across a surface of the first set of heat transfer tubes 405 to provide heat transfer (i.e., phase change) of the first fluid. In the first pass, a portion of the first fluid evaporates such the first fluid separates into a second fluid and a third fluid that are different phases (e.g., refrigerant liquid and refrigerant vapor). The second fluid is predominantly a liquid refrigerant, and the third fluid is predominantly a vapor refrigerant. Gravity separation and/or a pressure differential in the first intermediate header 406 forces the liquid refrigerant (i.e., the second fluid) to flow into the bottom portion of the first intermediate header 406 and the vapor refrigerant (i.e., the third fluid) into the top portion of the first intermediate header 406. However, the flow from the first section 401 to the second section 402 is directed to different headers, as explained below.

In one or more embodiments, the liquid (i.e., the second fluid) flows from the bottom portion of the first intermediate header 406 through (see block arrow F2′) the second fluid communication line 414 and into the bottom tank 412 of the third intermediate header 409. From the bottom tank 412, the liquid (i.e., the second fluid) through (see block arrow F4′) the lower section 408B of the second set of heat transfer tubes 408. As the liquid (i.e., the second fluid) flows for the second pass, the liquid (i.e., the second fluid) may or may not get completely evaporated and even superheated before arriving at the second intermediate header 407 as a gas. Concurrently to the second pass, the vapor refrigerant (i.e., the third fluid) is transported to the second intermediate header 407 via the first communication line 413. In the second intermediate header 407, the vapor refrigerant (i.e., the third fluid) merges with the now evaporated and potentially superheated vapor (i.e., the third fluid) from the lower section 408B to form a predominantly single-phase vapor (i.e., the fourth fluid). Additionally, a gravity force may help the fluids merge in the second intermediate header 407. It is further envisioned that the gravity force and proper sizing of the fluid communication lines 413 and 414 help balance the pressure drop and refrigerant flow between the liquid (i.e., the second fluid) in the second pass and the vapor (i.e., the third fluid) from the first fluid communication line 413 to achieve a smooth transition and mixing in the second intermediate header 407.

Still referring to FIG. 4C, from the second intermediate header 407, the refrigerant vapor (i.e., the fourth fluid) flows through (see block arrow F5′) the upper section 408A of the second set of heat transfer tubes 408 for a third pass. During the third pass, the air flow flows (see block arrow AF′) across the upper section 408A such that the refrigerant vapor (i.e., the fourth fluid) is maintained and may get further superheated and then enters the top tank 411 of the third intermediate header 409. The top tank 411 acts as an outlet header in this arrangement. The fourth fluid now exits (see block arrow F6′) the heat exchanger 400 via the outlet pipe 415 attached to the bottom tank 412 as a superheated vapor refrigerant. The superheated vapor refrigerant is now optimized before entering a compressor in fluid communication with the heat exchanger 400 via the outlet pipe 415.

Now referring to FIG. 5A, another embodiment of a heat exchanger 500 according to one or more embodiments herein is illustrated similar to that of the embodiment of FIGS. 2-4B. However, the heat exchanger 500 is related to evaporator applications. For clarity purposes only, a second section 502 of the heat exchanger 500 is shown offset to a first section 501 of the heat exchanger 500 instead of being behind and side-by-side to better illustrate the fluid communication between the sections 101, 102. This is merely done for example purposes only to avoid causing confusion in the visualization of the fluid flow paths. However, FIG. 5B is provided to illustrate the heat exchanger 500 of FIG. 5A in a side-by-side configuration as would be used in operation. It is further envisioned that the heat exchanger sections 501, 502 may also be positioned in the single-row arrangement such that the one sections is arranged below the other section.

As shown in FIG. 5A, the first section 501 and the second section 502 of the heat exchanger 500 are arranged similar to the heat exchanger of FIG. 2. However, instead of having two fluid communication lines 113, 114 between the first intermediate header 506 and the second intermediate header 507 (see FIG. 2), the heat exchanger 500 has only a first fluid communication line 513 fluidly coupling the first intermediate header 506 to the second intermediate header 507. Additionally, a second fluid communication line 514 fluidly couples the first intermediate header 506 directly to an outlet pipe 515 of the outlet header 509. Furthermore, instead of having the headers in a vertical orientation (see FIGS. 2 and 3), all the headers 503, 506, 507, 509 of the heat exchanger 500 are arranged to in a horizontal orientation (which is typical for the evaporator applications) to have the first set of heat transfer tubes 505 and the second set of heat transfer tubes 508 extending axially in a vertical direction between the headers 503, 506, 507, 509. The vertical orientation of the first set of heat transfer tubes 505 and the second set of heat transfer tubes 508 help facilitate condensate drainage on the external surfaces of the heat transfer tubes 505 and 508, which happens when the air temperature is reduced and reaches a dew point of the air. With the horizontal orientation, one or more nozzles 516 may be provided in the inlet header 503 to mix and distribute the two-phase fluid up the vertically oriented first set of heat transfer tubes 505. It is further envisioned that no baffle is included in the headers 503, 506, 507, 509 of the heat exchanger 500. It is further envisioned that the that each section 501 and 502 may be oriented to allow the refrigerant to flow upward or downward (i.e., flipping the heat exchanger sections). The configuration depicted in FIG. 5A is exemplary, and it may be beneficial to reverse the refrigerant flow direction for one or both sections 501 and 502.

In one or more embodiments, the heat exchanger 500 may be an evaporator vaporize a fluid flowing therein. For example, a first fluid (e.g., predominantly liquid) enters (see block arrow F51) the inlet header 503 via the inlet 504 after leaving a thermal expansion device 517. Alternatively, the heat exchanger 500 may be a condenser condensing a fluid flowing therein. For example, the first fluid may be predominantly liquid that enters (see block arrow F51) the inlet header 503 via the inlet 504 after leaving the expansion device 517. In the inlet header 503, the one or more nozzles 516 spray the first fluid up (see block arrow F52) the first set of heat transfer tubes 505. Additionally, an air flow (see block arrow AF5) flows over the first set of heat transfer tubes 505 to provide a heat transfer to the first fluid in a first pass, causing at least some of the first fluid to undergo a phase change and producing a two-phase fluid.

Still referring to FIG. 5A, once the two-phase fluid arrives in the first intermediate header 506, the two-phase fluid is separated to have the vapor (i.e., a second fluid) and the liquid (i.e., a third fluid) flow in different fluid communication lines 513, 514. For example, a pressure differential between the vapor (i.e., a second fluid) and the liquid (i.e., a third fluid) forces the vapor (i.e., a second fluid) to flow to one end of the first intermediate header 506 and the liquid (i.e., a third fluid) to an opposite end of the first intermediate header 506. Additionally, a gravity separation process may also be used to move the vapor (i.e., a second fluid) to the top of the first intermediate header 506 and the liquid (i.e., a third fluid) to the bottom of the first intermediate header 506. Further, the first fluid communication line 513 and the second fluid communication line 514 may be positioned at different heights on the first intermediate header 506 based on the separation of the two-phase fluid. For example, the second fluid communication line 514 may be at a higher position than the first fluid communication line 513 to aid the flow of the vapor (i.e., a second fluid) and the liquid (i.e., a third fluid) out of the first intermediate header 506. This positioning, and gravity forces, may allow for the liquid (i.e., a third fluid) to flow out of the lower flow line (e.g., the first fluid communication line 513) and the vapor (i.e., a second fluid) to flow out of the upper flow line (e.g., the second fluid communication line 514).

The first fluid communication line 513 transports (see block arrow F53) the liquid (i.e., the third fluid) from the first intermediate header 506 to the second intermediate header 507. The liquid (i.e., the third fluid) then flows up (see block arrow F54) the second set of heat transfer tubes 508 to be evaporated in a second pass. In the second pass, the same air flow that passes over the first intermediate header 506 also flows (see block arrow AF5′) across second set of heat transfer tubes 508 to provide a heat transfer (e.g., the phase change and potentially increase a temperature) to the liquid (i.e., the third fluid). The evaporated liquid (i.e., the third fluid) then enters the outlet header 509. Alternatively, when the heat exchanger 500 is a condenser, the first fluid communication line 513 transports the vapor as the third fluid to the second intermediate header 507. From the second intermediate header 507, the vapor flows through (see block arrow F54) the second set of heat transfer tubes 508 to be condensed in the second pass. In the second pass, the air flow (see block arrow AF5′) provides a heat transfer (e.g., the phase change and potentially decrease a temperature) to the gas such that the vapor condenses into a liquid, potentially subcooled, and then enters the outlet header 509.

The vapor (i.e., a second fluid) in the first intermediate header 506 is transported (see block arrow F55) from the first intermediate header 506 to the outlet pipe 515 extending out of the outlet header 509 via the second fluid communication line 514. The second fluid communication line 514 acts as a bypass line for the vapor (i.e., a second fluid) to bypass the second section 502. In some embodiments, the bypass line may be used to transport a vapor refrigerant to bypass the section 502. In the outlet pipe 515, the vapor (i.e., a second fluid) merges with evaporated liquid (i.e., the third fluid) to form a superheated vapor (i.e., a fourth fluid). Additionally, to balance a flow contact between the vapor (i.e., the second fluid) and the evaporated liquid (i.e., the third fluid), a diameter of the second fluid communication line 514 and the outlet pipe 515 may be optimized to ensure a formation of the superheated vapor (i.e., a fourth fluid). Alternatively, when the heat exchanger 500 is a condenser, the second fluid communication line 514 transports the liquid as the second fluid to the outlet pipe 515. In the outlet pipe 515, the liquid merges with the condensed vapor to form a subcooled liquid as the fourth fluid. The superheated vapor or the subcooled liquid (i.e., the fourth fluid) is now optimized before entering (see block arrow F56) another device, such as a compressor or a thermal expansion valve, in fluid communication with the heat exchanger 500 via the outlet pipe 515. Forming the superheated vapor or the subcooled liquid (i.e., the fourth fluid) in the outlet pipe 515 minimizes or eliminates any fluid (e.g., liquid or vapor) impeding heat transfer in the second section 502 of the heat exchanger 500 and additional compressor power consumption required by the extra pressure drop requirements of the two-phase flow (as described above). Overall, in addition to the benefits cited above, the heat exchanger 500 improves a fluid (e.g., refrigerant) phase change and distribution in and out of the heat exchanger 500 for enhanced performance and improved system operation.

Turning to FIG. 6, an HVAC system 600 in accordance with one or more embodiments is illustrated. As depicted, the HVAC system 600 provides heating and cooling for a residential structure 602. However, the concepts disclosed herein are applicable to numerous of heating and cooling situations, which include residential, industrial, and commercial settings.

The described HVAC system 600 is divided into two primary portions: (1) the outdoor unit 604, which mainly comprises components for transferring heat with the environment outside the structure 602; and (2) the indoor unit 606, which mainly comprises components for transferring heat with the air inside the structure 602. To heat or cool the illustrated structure 602, the indoor unit 606 draws ambient indoor air via return ducts 610, passes that air over one or more heating/cooling elements (i.e., sources of heating or cooling), and then routes that conditioned air, whether heated or cooled, back to the various climate-controlled spaces 612 through the supply ducts or ductworks 614—which are relatively large conduits that may be rigid or flexible. A blower 616 provides the motivational force to circulate the ambient air through the return ducts 610 and the supply ducts 614. Additionally, although a split system is shown in FIG. 6, the disclosed embodiments can be equally applied to the packaged or other types of the HVAC system configurations.

As shown, the HVAC system 600 is a “dual-fuel” system that has multiple heating elements, such as an electric heating element or a gas furnace 618. The gas furnace 618 located downstream (in relation to airflow) of the blower 616 combusts natural gas to produce heat in furnace tubes (not shown) that coil through the gas furnace 618. These furnace tubes act as a heating element for the ambient indoor air being pushed out of the blower 616, over the furnace tubes, and into the supply ducts 614. However, the gas furnace 618 is generally operated when robust heating is desired. During conventional heating and cooling operations, air from the blower 616 is routed over an indoor heat exchanger 620 and into the supply ducts 614. The indoor heat exchanger 620 has an arrangement according to the one or more heat exchangers described in FIGS. 2-5B. The blower 616, the gas furnace 618, and the indoor heat exchanger 620 may be packaged as an integrated air handler unit, or those components may be modular. In other embodiments, the positions of the gas furnace 618, the indoor heat exchanger 620, and the blower 616 can be reversed or rearranged.

The indoor heat exchanger 620 acts as a heating or cooling means that adds or removes heat from the structure, respectively, by manipulating the pressure and flow of refrigerant circulating within and between the indoor and outdoor units via refrigerant lines 622. Alternatively, the refrigerant could be circulated to only cool (i.e., extract heat from) the structure, with heating provided independently by another source, such as, but not limited to, the gas furnace 618. There may also be no heating of any kind. HVAC systems 600 that use refrigerant to both heat and cool the structure 602 are often described as heat pumps, while HVAC systems 600 that use refrigerant only for cooling are commonly described as air conditioners.

Whatever the state of the indoor heat exchanger 620 (i.e., absorbing or releasing heat), the outdoor heat exchanger 624 is in the opposite state. More specifically, if heating is desired, the illustrated indoor heat exchanger 620 acts as a condenser, aiding transition of the refrigerant from a high-pressure gas to a high-pressure liquid and releasing heat in the process. The outdoor heat exchanger 624 acts as an evaporator, aiding transition of the refrigerant from a low-pressure liquid to a low-pressure gas, thereby absorbing heat from the outdoor environment. Additionally, the outdoor heat exchanger 624 has an arrangement according to the one or more heat exchangers described in FIGS. 2-5B. If cooling is desired, the outdoor unit 604 has flow control devices 626 that reverse the flow of the refrigerant, allowing the outdoor heat exchanger 624 to act as a condenser and allowing the indoor heat exchanger 620 to act as an evaporator. The flow control devices 626 may also act as an expander to reduce the pressure of the refrigerant flowing therethrough. In other embodiments, the expander may be a separate device located in either the outdoor unit 604 or the indoor unit 606. To facilitate the exchange of heat between the ambient indoor air and the outdoor environment in the described HVAC system 600, the respective heat exchangers 620, 624 have tubing that winds or coils through heat-exchange surfaces, to increase the surface area of contact between the tubing and the surrounding air or environment.

The illustrated outdoor unit 604 may also include an accumulator 628 that helps prevent liquid refrigerant from reaching the inlet of a compressor 630. The outdoor unit 604 may include a receiver 632 that helps to maintain sufficient refrigerant charge distribution in the HVAC system 600. The size of these components is often defined by the amount of refrigerant employed by the HVAC system 600.

The compressor 630 receives low-pressure gas refrigerant from either the indoor heat exchanger 620 if cooling is desired or from the outdoor heat exchanger 624 if heating is desired. The compressor 630 then compresses the gas refrigerant to a higher pressure based on a compressor volume ratio, namely the ratio of a discharge volume, the volume of gas outputted from the compressor 630 once compressed, to a suction volume, the volume of gas inputted into the compressor 630 before compression. In the illustrated embodiment, the compressor is a multi-stage compressor 630 that can transition between at least two volume ratios depending on whether heating or cooling is desired. In other embodiments, the HVAC system 600 may be configured to only cool or only heat, and the compressor 630 may be a single-stage compressor having only a single volume ratio.

The compressor 630 receives electrical power from a control system 634 that may include an inverter system, which converts the AC power received by the HVAC system 600 to DC power for use by the compressor 630. The control system 634 controls the speed of the compressor 630, as well as the switching between compressor stages for multi-stage compressors, based on the required heating or cooling that must be provided by the HVAC system, i.e., the load on the HVAC system 600. In some embodiments, the control system may also control the speed of a fan 636 that blows air across the heat exchanger 624.

Referring now to FIG. 7, FIG. 7 shows a block diagram of an HVAC system 700. The HVAC system 700 includes a first heat exchanger 702, an expansion device 704, a second heat exchanger 706, and a compressor 708. Additionally, the heat exchangers 702, 706 may be either indoor or outdoor heat exchangers, depending on the configuration of the HVAC system 700. Additionally, the heat exchangers 702, 706 have an arrangement according to the one or more heat exchangers described in FIGS. 2-5B. The HVAC system 700 may also include the equipment shown in FIG. 6 and function as discussed above with reference to FIG. 6. Additionally, the expansion device 704 may be a thermal expansion valve or thermostatic expansion valve. Accordingly, the function of the expansion device 704 and the compressor 708 will not be discussed in detail except as necessary for the understanding of the HVAC system 700 shown in FIG. 7.

As shown in FIG. 7, high-pressure refrigerant flows from the compressor 708 to the first heat exchanger 702, where it is condensed. The high-pressure liquid refrigerant then flows to the expansion device 704, where it is expanded to low-pressure refrigerant. The low-pressure refrigerant is then evaporated in the second heat exchanger 706 and the low-pressure vapor flows into the compressor 708 as a vapor, to begin the cycle again.

While the aspects of the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. But it should be understood that the invention is not intended to be limited to the particular forms disclosed. Rather, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the following appended claims. For example, certain embodiments disclosed here envisage usage with a powered fan rather than an inducer fan, or no fan at all. Moreover, the rotating equipment (e.g., motors) and valves disclosed herein are envisaged as being operable at specified speeds or variable speeds through inverter circuitry, for example. Moreover, the internal and external communication of the furnace may be accomplished through wired and or wireless communications, including known communication protocols, Wi-Fi, 802.11(x), Bluetooth, to name just a few.

Claims

1. A heat exchanger comprising:

an inlet header, wherein the inlet header is configured to receive a first fluid;

a first set of heat transfer tubes fluidly coupling the inlet header to a first intermediate header, wherein the first intermediate header is configured to receive the first fluid from the first set of heat transfer tubes and to allow the first fluid to separate into a second fluid and a third fluid;

a second intermediate header in fluid communication with the first intermediate header and configured to receive at least one of the second fluid or the third fluid from the first intermediate header; and

a second set of heat transfer tubes fluidly coupling the second intermediate header to an outlet header, wherein the outlet header is configured to receive the at least one of the second fluid or the third fluid through the second set of heat transfer tubes,

wherein the second fluid and the third fluid exit the heat exchanger via an outlet pipe as a single-phase fluid.

2. The heat exchanger of claim 1, wherein the first fluid is a vapor, the second fluid is predominantly a liquid, the third fluid is predominantly a vapor, and the single-phase fluid is a liquid,

wherein the first fluid is flowable through the first set of heat transfer tubes for a first pass and the first set of heat transfer tubes is configured to apply a heat transfer to the first fluid such that at least a portion of the first fluid undergoes a first phase change to produce the second fluid and third fluid,

wherein the third fluid is flowable through the second set of heat transfer tubes for a second pass and the second set of heat transfer tubes is configured to apply a heat transfer to the third fluid such that third undergoes a second phase change to exit the heat exchanger with the second fluid as the single-phase fluid.

3. The heat exchanger of claim 1, wherein the first fluid is a liquid, the second fluid is predominantly a vapor, the third fluid is predominantly a liquid, and the single-phase fluid is a vapor,

wherein the first fluid is flowable through the first set of heat transfer tubes for a first pass and the first set of heat transfer tubes is configured to apply a heat transfer to the first fluid such that at least a portion of the first fluid undergoes a first phase change to produce the second fluid and third fluid,

wherein the third fluid is flowable through the second set of heat transfer tubes for a second pass and the second set of heat transfer tubes is configured to apply a heat transfer to the third fluid such that third undergoes a second phase change to exit the heat exchanger with the second fluid as the single-phase fluid.

4. The heat exchanger of claim 1, further comprising:

a baffle disposed in the second intermediate header, wherein the baffle separates the second intermediate header into a top tank and a bottom tank;

a first fluid line fluidly coupling a top portion of the first intermediate header and the top tank such that the second fluid is flowable through the first fluid line into the top tank; and

a second fluid line fluidly coupling a bottom portion of the first intermediate header and the bottom tank such that the third fluid is flowable through the second fluid line into the bottom tank.

5. The heat exchanger of claim 4, further comprising:

a first plurality of heat transfer tubes of the second set of heat transfer tubes fluidly coupling the top tank and the outlet header such that the second fluid is flowable through the first plurality of heat transfer tubes into the outlet header; and

a second plurality of heat transfer tubes of the second set of heat transfer tubes fluidly coupling the bottom tank and the outlet header such that the third fluid is flowable through the second plurality of heat transfer tubes into the outlet header.

6. The heat exchanger of claim 5, wherein a total number of the second plurality of heat transfer tubes comprises one third to two-thirds of a total number of the second set of heat transfer tubes.

7. The heat exchanger of claim 1, wherein the outlet header is a bottom tank of a third intermediate header, and further comprising:

a baffle disposed in the third intermediate header, wherein the baffle separates the third intermediate header into a top tank and the bottom tank;

a first fluid line fluidly coupling a top portion of the first intermediate header and the top tank such that the second fluid is flowable through the first fluid line into the top tank; and

a second fluid line fluidly coupling a bottom portion of the first intermediate header and the second intermediate header such that the third fluid is flowable through the second fluid line into the second intermediate header.

8. The heat exchanger of claim 7, further comprising:

a first plurality of heat transfer tubes of the second set of heat transfer tubes fluidly coupling the top tank and the second intermediate header such that the second fluid is flowable through the first plurality of heat transfer tubes into the second intermediate header,

wherein the second intermediate header is configured to allow the second fluid and the third fluid to flow together into the single-phase fluid; and

a second plurality of heat transfer tubes of the second set of heat transfer tubes fluidly coupling the second intermediate header and the bottom tank such that the single-phase fluid flows through the second plurality of heat transfer tubes into the bottom tank.

9. The heat exchanger of claim 1, further comprising:

a first fluid line fluidly coupling a bottom portion of the first intermediate header and a bottom portion of the second intermediate header; and

a second fluid line fluidly coupling a top portion of the first intermediate header and the outlet pipe to bypass the second set of heat transfer tubes.

10. The heat exchanger of claim 9, wherein the first intermediate header is configured to allow the separation of the second fluid and the third fluid via a gravity separation and/or pressure differential such that the second intermediate header is configured to receive the second fluid from the first intermediate header and allow the second fluid to flow through the second set of heat transfer tubes to an outlet header and the second fluid line is configured to flow the third fluid to the outlet pipe, wherein the second fluid and the third fluid flow together as the single-phase fluid in the outlet pipe.

11. The heat exchanger of claim 1, wherein the first set of heat transfer tubes and the second set of heat transfer tubes are positioned adjacent to each other to allow an air flow across both the first set of heat transfer tubes and the second set of heat transfer tubes.

12. The heat exchanger of claim 1, wherein a diameter of each heat transfer tube of the first set of heat transfer tubes is larger than a diameter of each heat transfer tube of the second set of heat transfer tubes.

13. The heat exchanger of claim 1, further comprising one or more bypass fluid communication lines fluidly coupling the first intermediate header and the outlet pipe and configured to allow at least one of the second fluid or the third fluid to bypass the second set of heat transfer tubes.

14. A heating, ventilation, and air-conditioning (“HVAC”) system, the HVAC system comprising:

a refrigerant circuit for use with a first refrigerant and comprising a compressor, at least one heat exchanger, and an expansion device, wherein the at least one heat exchanger is operable as at least one of a condenser or an evaporator; and

wherein the at least one heat exchanger has at least two sections and comprises: a first section of the at least two sections comprising an inlet header configured to receive the first refrigerant from the refrigerant circuit, a first set of heat transfer tubes fluidly coupling the inlet header to a first intermediate header, wherein the first intermediate header is configured to receive the first refrigerant from the first set of heat transfer tubes and to allow the first refrigerant to separate into a second refrigerant and a third refrigerant; a second section of the at least two sections comprising a second intermediate header configured to receive at least one of the second refrigerant or the third refrigerant from the first intermediate header, a second set of heat transfer tubes fluidly coupling the second intermediate header to an outlet header, wherein the outlet header is configured to receive the at least one of the second refrigerant or the third refrigerant from the second set of heat transfer tubes, wherein the second refrigerant and the third refrigerant flow together to form a single-phase refrigerant; and an outlet pipe attached to the outlet header and the outlet pipe is configured to circulate the single-phase refrigerant back into the refrigerant circuit.

15. The heat exchanger of claim 14, wherein the second section is positioned behind or above the first section.

16. The heat exchanger of claim 14, wherein the heat exchanger is configured to operably allow at least three or more fluid passes of the first refrigerant.

17. The HVAC system of claim 14, wherein the at least one heat exchanger further comprises:

a baffle disposed in the second intermediate header, wherein the baffle separates the second intermediate header into a top tank and a bottom tank such that the second refrigerant is flowable from the first intermediate header through a first fluid line into the top tank and the third refrigerant is flowable from the first intermediate header through a second fluid line into the bottom tank;

a first plurality of heat transfer tubes of the second set of heat transfer tubes configured to flow the second refrigerant from the top tank to the outlet header; and

a second plurality of heat transfer tubes of the second set of heat transfer tubes configured to flow the third refrigerant from the bottom tank to the outlet header,

wherein the outlet header is configured to allow the second refrigerant and the third refrigerant to flow together to form the single-phase refrigerant.

18. The HVAC system of claim 14, wherein the outlet header is a bottom tank of a third intermediate header, and the at least one heat exchanger further comprising:

a baffle disposed in the third intermediate header to separate the third intermediate header into a top tank and a bottom tank;

a first plurality of heat transfer tubes of the second set of heat transfer tubes configured to flow the second refrigerant from the top tank to the second intermediate header,

wherein the second intermediate header is configured to allow the second refrigerant and the third refrigerant to merge into the single-phase refrigerant; and

a second plurality of heat transfer tubes of the second set of heat transfer tubes configured to flow the single-phase refrigerant from the second intermediate header to the bottom tank,

wherein the outlet pipe is fluidly coupled to the bottom tank.

19. The HVAC system of claim 18, wherein the at least one heat exchanger is configured to receive the first refrigerant from the compressor or the expansion device, and the expansion device or the compressor is configured to receive the single-phase refrigerant from the at least one heat exchanger.

20. The HVAC system of claim 14, wherein the first intermediate header is configured to allow separation of the second refrigerant and the third refrigerant via a gravity separation and/or pressure differential, and the at least one heat exchanger further comprising:

a first fluid line fluidly coupling a bottom portion of the first intermediate header to the second intermediate header such that the second refrigerant is flowable through the first fluid line into the second intermediate header, and the second intermediate header is configured to flow the second refrigerant through the second set of heat transfer tubes and into the outlet header; and

a second fluid line fluidly coupling a top portion of the first intermediate header and the outlet pipe such that the third refrigerant is flowable through the second fluid line into the outlet pipe, wherein the outlet pipe is configured to allow the second refrigerant and the third refrigerant to merge into the single-phase refrigerant.