Heat exchanger

Abstract

A short, compact heat exchanger is disclosed to include an inner tube, an intermediate tube and an outer tube concentrically arranged together to form a triple-tube structure, a thermal fluid flowing through the intermediate tube, a heat-transfer medium flowing through the outer tube and the inner tube to make heat exchange with the thermal fluid. If the thermal fluid can be a refrigerant and the heat-transfer medium can be room temperature water so that the heat exchanger can be used in an air-conditioning refrigerating system to substitute for a condenser or evaporator.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to heat exchangers and more particularly, to a triple-tube structure type heat exchanger.

2. Description of the Related Art

A heat exchanger is a device built for efficient heat transfer from one medium to another. Within the equipment, at least two media are separated by a solid wall for heat transfer, i.e., high temperature medium discharges heat energy, and low temperature medium absorbs heat energy. Heat exchangers are widely used in our daily life, for example, for cold making application or hot application.

Heat exchangers are classified into double-pipe heat exchangers, shell and tube heat exchangers, plate type heat exchangers, . . . and etc., wherein:

(1) In double-pipe heat exchangers, two tubes are concentrically arranged together so that two fluids respectively flow through the inner path surrounded by the inner tube and the outer path surrounded by the outer tube outside the inner tube, and the wall of the inner tube transfers heat from one fluid to the other. The outer tube is usually covered with a layer of heat insulation material to reduce heat loss. A double-pipe heat exchanger has the advantages of simple structure, low cost and ease of maintenance. The significant drawback of a double-pipe heat exchanger is its limited heat transfer surface area.

(2) In shell and tube heat exchangers, a bundle of tubes is set inside a shell (a large pressure vessel). One fluid runs through the tubes, and another fluid flows over the tubes (through the shell) to transfer heat between the two fluids. Shell and tube heat exchangers can be classified into fixed head exchangers, floating head exchangers, and U-tube exchangers. In a fixed head exchanger, the bundle of tubes has the both ends affixed to flanges of the shell by screw bolts. A fixed head exchanger has the advantages of simple structure and low cost, however the connectors of the tubes of a fixed head exchanger may break to cause leakage when the tubes expand due to heat. In a floating head exchanger, the bundle of tubes has one end affixed to a flange of the shell and the other end fastened to a float floatable relative to the shell. A floating head exchanger eliminates tube connector leakage; however it has a complicated structure and high manufacturing cost. In a U-tube exchanger, the tubes are bent in the shape of a U, and the ends of each tube are connected to plenums through holes in tubesheets. A U-tube exchanger has the advantages of simple structure and low manufacturing cost and allows the bundle of tubes to curve when expands due to heat, however, due to the drawback of cleaning difficulty, a U-tube exchanger is not suitable for fluids that are easy to scale the tubes.

(3) In plate type heat exchangers, multiple, thin, slightly-separated plates that have very large surface areas and fluid flow passages for heat transfer are fastened together in a stacked-plate arrangement. Stainless steel plates are commonly used in plate type heat exchangers. Some plates may be stamped with “chevron” or other patterns, where others may have machined fins and/or grooves to enhance heat transfer effect. Plate type heat exchangers have the advantages of small dimension, light weight, ease of maintenance and plate number adjustability, and high fluid disturbance in heat exchanger. However, due to a great sealing peripheral area, a plate type heat exchanger tends to cause leakage. Further, a plate type heat exchanger has low processing capacity and low heat and pressure resisting power. The working temperature of a plate type heat exchanger must be controlled below 150° C. When the plates are covered with a coat of hard substance, the plate type heat exchanger must be dismounted for cleaning.

Accordingly, it has been determined that there is a continuous need for heat exchangers that overcome, alleviate, and/or mitigate one or more of the aforementioned and other deleterious effects of the prior art heat exchangers.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is one object of the present invention to provide a heat exchanger, which utilizes a triple-tube structure type and effectively transfers the surface and core energy of a hot or cold thermal fluid, for example, refrigerant with oil through a heat-transfer medium, for example, water, achieving an excellent heat exchange effect. It is another object of the present invention to provide a heat exchanger, which not only effectively increases the conducting heat area to correspond with the speed and capacity of the flow and increases the efficiency of heat exchanging and has simple structure and low cost characteristics.

To achieve these and other objects of the present invention, a heat exchanger comprises an inner tube, an intermediate tube and an outer tube concentrically arranged together to form a triple-tube structure, a thermal fluid flowing through the intermediate tube, and a heat-transfer medium flowing through the outer tube and the inner tube, enabling the surface energy and core energy of the thermal fluid to be transferred through the peripheral wall of the intermediate tube and the peripheral wall of the inner tube to make heat exchange with the heat-transfer medium that travels

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational view of a heat exchanger in accordance with the present invention.

FIG. 2 is sectional view of the heat exchanger in accordance with the present invention.

FIG. 3 is a schematic drawing showing an application example of the present invention in an air-conditioning refrigerating system

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIGS. 1 and 2, a heat exchanger in accordance with the present invention comprises an inner tube 11, an intermediate tube 12, and an outer tube 13. The inner tube 11, the intermediate tube 12 and the outer tube 13 are metal tubular members made from a metal material having a high coefficient of thermal conductivity, preferably, copper. The outer tube 13 surrounds the intermediate tube 12, which surrounds the inner tube 11, i.e., the inner tube 11, the intermediate tube 12 and the outer tube 13 are concentrically mounted together to form a triple tube structure. For heat exchange, a thermal fluid 2, for example, refrigerant with lubricating oil is filled to travel through the intermediate tube 12 in one direction, and a heat-transfer medium 3, for example, room temperature water is filled to travel through the outer tube 13 and the inner tube 11 in a direction reversed to the flowing direction of the thermal fluid 2.

Referring to FIG. 2 again, the surface energy and core energy of the thermal fluid 2 are transferred through the peripheral wall of the intermediate tube 12 and the peripheral wall of the inner tube 11 to make heat exchange with the heat-transfer medium 3 that travels through the outer tube 13 and the inner tube 11 in a direction reversed to the flowing direction of the thermal fluid 2. Therefore, the length and dimension of the heat exchanger can be greatly reduced while achieving the expected heat exchange performance. As stated above, the thermal fluid 2 can be a refrigerant, such as high-temperature gaseous refrigerant or low-temperature fluid refrigerant, and the heat-transfer medium 3 can be room temperature water. By means of heat transfer functioning of the triple tube structure of the heat exchanger, the heat exchanger has the functions of a condenser and an evaporator. However, it is to be understood that the thermal fluid 2 and the heat-transfer medium 3 are not limited to the aforesaid refrigerant and water. Alternatively, the thermal fluid 2 can be any of a variety of other cold or hot fluids or gasses, and the heat-transfer medium 3 can be any of a variety of other hot or cold fluids or gasses. Therefore, the heat exchanger of the present invention can be used in an air-conditioning refrigerating system as well as any other industry, such as chemical industry, petroleum industry, dynamic industry or nuclear energy industry.

FIG. 3 illustrates an application example of the present invention in an air-conditioning refrigerating system. As illustrated, the air-conditioning refrigerating system comprises a compressor 4, a delivery line 5, a first heat exchanger 6, a reinforcing condensation device 7, an expansion device 8, and a second heat exchanger 9.

The compressor 4 uses a motor to suck in (recycle) a thermal fluid 2 from the delivery line 5, such as, low-pressure low-temperature gaseous refrigerant, for example, RS-22 with lubricating oil (hereinafter called as oil) and to compress it into a high-pressure high-temperature, for example, 500 psi, 168.6° C. gaseous refrigerant with oil, enabling the high-pressure high-temperature gaseous refrigerant with oil to be discharged out of the compressor 4 into the delivery line 5 in direction “a”.

The delivery line 5 has one end connected to the discharge end of the compressor 4, and the other end connected to a first intermediate tube 62 of the first heat exchanger 6.

The first heat exchanger 6 converts the high-pressure high-temperature gaseous refrigerant into a fluid refrigerant by means of a heat exchange action with a heat-transfer medium 3, for example, water. The first heat exchanger 6 further comprises a first inner tube 61 concentrically inserted through the first intermediate tube 62, and a first outer tube 63 concentrically surrounds the first intermediate tube 62. For enabling the first heat exchanger 6 to work as a condenser, a linking manifold is respectively connected to the upstream and downstream ends of the first intermediated tube 62 to deliver the refrigerant, a three-way shunt tube 64 is connected to the downstream ends of the first inner tube 61 and the first outer tube 63 to guide the heat-transfer medium 3, for example, 28.4° C. room temperature water into the first inner tube 61 and the first outer tube 63 in direction “b1”, enabling the heat-transfer medium 3 to flow through the first inner tube 61 and first outer tube 63 toward the upstream end of the first heat exchanger 6 and to perform a heat exchange process with a high-temperature, for example, 140.5° C. refrigerant with oil that flows through the first intermediate tube 62 from the downstream toward the upstream, so that the three-way gather tube 65 that is connected to the upstream ends of the first inner tube 61 and the first outer tube 63 discharges the gathered two flows of hot water in direction “b2”. According to test, the temperature of the discharged hot water is as high as 75.3° C. After condensed through the first heat exchanger 6, the liquid refrigerant with oil flows through the downstream end of the first intermediate tube 62 into the delivery line 5.

Therefore, by means of the heat exchange process between the thermal fluid 2 and the heat-transfer medium 3 through the first heat exchanger 6, the temperature of the refrigerant with oil is effectively lowered and then delivered by the delivery line 5 to the reinforcing condensation device 7.

The reinforcing condensation device 7 is formed of a plurality of capillary tubes 71. These capillary tubes 71 guide in the liquid refrigerant with oil and bubbles from the first heat exchanger 6 and function as a condensing efficiency enhancement device like Taiwan Patent Publication Number 494222 that is issued to the present inventor, thereby regulating flowing of liquid, air and oil. Therefore, when the liquid refrigerant with oil flows through the capillary tubes 71 of the reinforcing condensation device 7, bubbles are stopped outside the capillary tubes 71, enhancing the condensing efficiency. After passed through the capillary tubes 71, the liquid refrigerant with oil is gathered together again and guided into the delivery line 5 at the downstream so that the temperature of the liquid refrigerant with oil is lowered to 33° C. after a secondary condensing process.

The expansion device 8 can be, for example, an expansion valve or a single capillary tube, adapted to force the liquid refrigerant passing therethrough into a mist, lowering the pressure of the liquid refrigerant to, for example, about 50 psi for evaporation by the posterior second heat exchanger 9, enabling the mist of refrigerant to be evaporated under a low pressure and low temperature status.

The second heat exchanger 9 guides the aforesaid mist of refrigerant discharged by the expansion device 8 into the second intermediate tube 92 and toward the maniford of the downstream. Similar to the aforesaid first heat exchanger 6, the second heat exchanger 9 comprises a second inner tube 91, a second intermediate tube 92 surrounds the second inner tube 91 concentrically, and a second outer tube 93 surrounds the second intermediate tube 92 concentrically. For enabling the second exchanger 9 to work as an evaporator, a three-way shunt tube 94 is connected to the downstream ends of the second inner tube 91 and the second outer tube 93 to guide the heat-transfer medium 3, for example, 28.4° C. room temperature water into the second inner tube 91 and the second outer tube 93 in direction “c1”, enabling the 28.4° C. room temperature water to perform a heat exchange process with the high-temperature refrigerant with oil that flows through the second intermediate tube 92 from the upstream toward the downstream, so that the mist of refrigerant is evaporated into a gaseous refrigerant. At this time, the three-way gather tube 95 that is connected to the downstream ends of the second inner tube 91 and the second outer tube 93 discharges the gathered two flows of icy water in direction “c2”. According to test, the temperature of the discharged icy water is as low as 17.4° C. After evaporation through the second heat exchanger 9, the gaseous refrigerant with oil flows through the downstream end of the second intermediate tube 92 into the delivery line 5, which has its other end connected to the intake end of the compressor 4 for enabling the gaseous refrigerant to be further compressed and discharged by the compressor 4. The icy water is delivered to the cooling coil at each air outlet so that the cooling coil at each air outlet absorbs heat energy from surrounding air, enabling low temperature air to flow out of each air outlet into the inside of the house to lower the temperature in the house. Thus, an air conditioning circulation system is established.

The aforesaid second heat exchanger 9 converts the refrigerant from a mist (liquid state) into a gaseous state, enabling the refrigerant with oil to absorb heat and to have its temperature be raised to 11.1° C. Further, as shown in FIG. 3, the refrigerant with oil and the water flow through the first heat exchanger 6 and the second heat exchanger 9 in the reversed directions. Further, to avoid loss of heat energy, the first heat exchanger 6 and the second heat exchanger 9 are respectively wrapped with an insulation material, for example, insulation polymer compound.

Further, to make sure that the temperature of the gaseous refrigerant reaches 168.6° C. at the time when it is discharged, the two segments of the delivery line 5 that are respectively connected to the intake end and discharge end of the compressor 4 are attached together and wrapped with an insulation material for making a heat exchange process so that the temperature of the gaseous refrigerant with oil can be raised to about 30.9° C. before returning to the compressor 4. By means of raising the temperature of the gaseous refrigerant with oil before returning to the compressor 4, the oil is softened, facilitating smooth running of the compressor 4. Because the discharge capacity is enhanced, heat is effectively released from the coil of the compressor 4 to increase the temperature of the discharged gaseous refrigerant, thereby raising the compression ratio and lowering the ampere level.

Therefore, the application of the invention has the advantage of utilizing triple-tube structure type heat exchangers to effectively transfer the surface and core energy of a hot or cold thermal fluid through a heat-transfer medium. A heat exchanger in accordance with the present invention effectively increases heat transfer surface area to enhance heat exchange performance and has simple structure and low cost characteristics. Further, a triple-tube structure type heat exchanger constructed in accordance with the present invention can be used as a condenser or evaporator in a heat-exchange circulation system, enabling the heat-exchange circulation system to provide hot/icy water, avoiding waste of heat energy and reducing discharge of waste heat.

Although a particular embodiment of the invention has been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.

Claims

1. A heat exchanger, comprising:

a triple-tube structure, said triple-tube structure comprising an inner tube, an intermediate tube concentrically surrounding said inner tube, and an outer tube concentrically surrounding said intermediate tube, said inner tube and said intermediate tube and said outer tube having different diameters;

a thermal fluid flowing through said intermediate tube; and

a heat-transfer medium flowing through said outer tube and said inner tube; and

wherein the surface energy and core energy of said thermal fluid are respectively transferred to said heat-transfer medium through said intermediate tube and said outer tube.

2. The heat exchanger as claimed in claim 1, wherein the flowing direction of said thermal fluid in said intermediate tube is reversed to the flowing direction of said heat-transfer medium in said outer tube and said inner tube.

3. The heat exchanger as claimed in claim 1, wherein said inner tube and said outer tube have a three-way pipe respectively connected to the upstream and downstream ends thereof to delivery the heat-transfer medium; said intermediate tube has a linking manifold respectively connected to upstream and downstream ends thereof to delivery said heat-transfer medium.

4. The heat exchanger as claimed in claim 1, wherein said thermal fluid is a cold or hot liquid or gas; said heat-transfer medium is a hot or cold liquid or gas.

5. The heat exchanger as claimed in claim 4, wherein said thermal fluid is a refrigerant and lubrication oil; said heat-transfer medium is room temperature water.

6. The heat exchanger as claimed in claim 1, further comprising an insulation material wrapped about said triple-tube structure.

7. The heat exchanger as claimed in claim 1, wherein said inner tube, said intermediate tube and said outer tube are made of a metal material.

8. The heat exchanger as claimed in claim 1, wherein said metal material is copper.