COMPACT HIGH PERFORMANCE CONDENSER
A thermal management system includes an evaporator and a fluid circuit that directs a cooling medium through a condenser. The example condenser provides improved heat transfer coefficients and stable operation by reducing condensate thickness and films that build up within fluid passages of the condenser to provide improved thermal communication between the cooling medium and a cold plate. Each of the fluid passages defined by the condenser is tapered such that an ever-decreasing flow area in a direction of flow from the inlet toward the outlet is provided. The ever-decreasing area maintains a high shear velocity of the vapor such that the liquid film formed on the walls of the passages remains thin.
This disclosure generally relates to heat exchangers and particularly to condensers for maintaining high heat transfer during a phase change of a fluid under adverse inertial loading. A two phase system is often used to transfer heat from a heat source to a remotely located heat sink. If a compressor and expansion device is used in the loop, the heat sink can be at a higher temperature than the heat source, as with a vapor cycle system. The heat is dissipated to a heat sink in a condensing heat exchange assembly called a condenser. The heat sink may be in an environment of another flow loop. In the condenser, the coolant transitions between vapor and liquid phases. As an example, the heat from an electronics assembly may be removed by evaporative cold plates and dissipated by condensation to a heat sink. The heat exchange assembly therefore includes a condenser for removing heat from the cooling medium. The liquid/vapor cooling medium is routed through the condenser for transforming the vapor phase of the cooling medium back to mostly a liquid phase. Using the latent heat property of the coolant, heat is rejected from the condenser as heat is transferred from coolant through walls of the condenser to transform vapor into liquid. A primary resistance to heat transfer is the ever increasing thickness of liquid that accumulates on walls of fluid channels.
SUMMARYA disclosed example thermal management system includes an evaporator and a fluid circuit that directs a cooling medium through a condenser. The example thermal management system utilizes a two-phase cooling medium that shifts between liquid and vapor phases as it rejects and accepts thermal energy. The example condenser has a shear driven flow and provides higher heat transfer coefficients by reducing condensate thickness and films that build up within fluid passages of the condenser to provide improved thermal communication between the cooling medium and a cold plate. Each of the fluid passages defined by the condenser is tapered such that an ever-decreasing flow area in a direction of flow from the inlet toward the outlet is provided. The ever-decreasing area maintains a high shear velocity of the vapor such that the liquid film formed on the walls of the passages remains thin. Additional benefits with the shear flow arrangement are that the liquid inventory in the condenser is minimized and stable. This is important for a vapor cycle system for stable operation and reduces the amount of refrigerant required. Tapered passages in the direction of flow thin the condensed liquid film, improve heat transfer.
These and other features disclosed herein can be best understood from the following specification and drawings, the following of which is a brief description.
Referring to
The example condenser 16 is a shear driven condenser 16 that provides higher heat transfer coefficients by reducing condensate thickness and films that build up within fluid passages of the condenser 16 to provide improved thermal communication between the cooling medium and the cold plate 20.
Referring to
The inlets 26 in turn communicate the vapor 15 to a plurality of flow passages 36 (
Referring to
The overall heat transfer performance of a heat exchanger is (ηHA), the product of the fin efficiency (η), heat transfer coefficient (H) and the wetted area (A) for a cooler. This condenser 16 provides high values of all three factors. Excellent performance is achieved because the multi-layer construction of bonded interconnecting channels provides over ten times more wetted surface area than the heat flux footprint. Furthermore, the heat transfer coefficients are high because shear flow and disrupted flows create thin liquid film that in turn provide high convective condensation coefficients. Additionally, the fin efficiencies are high because the example condenser 16 provides nearly a 50% conduction area between the passages and the fin lengths relatively short.
The disclosed example heat exchanger 16 is constructed using a plurality of smaller passages rather than a few larger ones to provide a much higher wetted surface per footprint area. The higher surface area density minimizes conduction resistance because the conduction paths to the heat sink are short. With a high condensing heat transfer coefficient, the overall resistance to heat transfer is small because the conductive paths are generally very thermally efficient.
The fluid flow passages 36 are defined between the plurality of plates 32 that are stacked one on top the other. The fluid flow passages 36 originate from the inlets 26 that are disposed about the outer periphery 30, and extend generally radially inward and terminate at the central core than connects to the radially central outlet 22. The flow is generally radially inward, but must move periodically slightly laterally between layers within the lamination stack. The radial direction of fluid flow within the tapered passages 36 provides the desired shear driven or high velocity flow through the condenser 26.
Referring to
In this example, the decreasing area is provided by a reduction in the width of each slot in a direction toward the outlet opening 48. A first width 37 (
The shape each of the flow passages 36 is not required to be rectangular or trapezoidal, but may also include oblong shaped or any shape that provides a desired reduction in flow area in a direction toward the outlet opening 48.
Referring to
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The example condenser 16 is constructed of a bonded stack of alternating first and second plates 40, 44. Each of the plates can be referred to as a lamination and is stacked upon each other to provide the desired flow passage configuration. In one example embodiment, each of the plates 40, 44 is formed as chemically photo etched copper laminations that are diffusion bonded to each other. Alternatively, each of the plates can be brazed or bonded stacks of aluminum or other types of material as is suitable for a specific application. As appreciated, the specific type of material and bonding process that is utilized to attach and provide the sealed flow passages are dependent on the application. As appreciated, certain materials are capable of withstanding temperatures of specific applications. The environmental conditions in which the condenser will need to operate are considered into developing and manufacturing and assembling each of the example condensers.
The previous example discloses a symmetrical condenser with radially outermost inlet such that flow was directed symmetrically and radially inward towards the central outlet 22. However, in some applications it is desired to have a more rectangular or non-symmetrical configuration where an inlet and outlet are disposed in a different orientation as may be desired for application specific parameters.
Referring to
The fluid passages 58 are defined to include an ever-decreasing flow area in a direction toward the outlet 62 and away from the inlet 60. In other words, the flow passages 58 comprise a tapered or decreasing flow area in the direction of flow.
Referring to
The even layer 54 includes a first slot configuration 70 and the odd layer includes a second slot configuration 72. The first and second slot configurations 70, 72 correspond with one another to provide a flow path between the inlet 60 and the outlet 62. Neither of the plates 54, 56 alone defines the entire flow path. Because the plates 54,56 are stacked one on top of each other, the flow passages 58 include significant of disruptions and discontinuities such that flow is alternately directed upward or downward between adjacent plates 54,56 to prevent the build of condensation or liquid films on each of the passages. Each of the slots in each of the first and second slot patterns 70, 72 includes a decreasing area in a direction of flow from the inlet 60 toward the outlet 62. The ever decreasing or tapered flow pattern provides the desired shear driven condenser that increases the velocity of the cooling medium as it is condensed to prevent the buildup of liquid film on the walls.
The flow passage configuration of the disclosed condensers provides high heat transfer in a compact and lightweight package. The stacked plates and radial flow path configuration provides short thermal conduction paths to improve heat transfer capability. The short conduction paths and the increased performance are provided because each of the condensers provides thin condensate layers that thin out any liquid buildup along the surfaces of the flow passages. Shear driven and tapered flow passages also provide a high degree of insensitivity to orientation and external inertial forces. Moreover, the fabrication of the example condenser is provided by alternately stacking different plates to define the desired flow passage patterns. The stacked plates are also designed to include and utilize common configurations of plates to reduce manufacturing cost.
Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this disclosure. For that reason, the following claims should be studied to determine the scope and content of this invention.
Claims
1. A condenser assembly comprising:
- a stacked plurality of plates that define a plurality of flow passages; and
- an inlet and outlet in fluid communication with the flow passages, wherein the plurality of flow passages defined by the stacked plurality of plates includes a decreasing flow area in a direction of flow.
2. The assembly as recited in claim 1, wherein each of the plurality of flow passages includes a width that decreases in a direction away from the inlet and toward the outlet.
3. The assembly as recited in claim 1, wherein each of the stacked plurality of plates include open slots in fluid communication with open slots within another of the stacked plurality of plates such that each of the plurality of flow passages is defined by open slots within at least two of the stacked plurality of plates.
4. The assembly as recited in claim 3, wherein each of the stacked plurality of plates include a first plate with a first pattern of open slots and a second plate with a second pattern of open slots that are in fluid communication with the first pattern of open slots.
5. The assembly as recited in claim 3, wherein each of the slots include a decreasing area in a direction toward the outlet and away from the inlet.
6. The assembly as recited in claim 1, wherein the plurality of flow passages extend radially inward from an outer periphery of the stacked plurality of plates and the inlet is in fluid communication with the outer periphery of the stacked plurality of plates and the outlet is disposed radially inward of the inlet.
7. The assembly as recited in claim 1, wherein the stacked plurality of plates are mounted to a cold plate.
8. A thermal management system comprising:
- a flow path for a cooling medium;
- an evaporator for transferring heat into the cooling medium; and
- a condenser for transferring heat from the cooling medium, the condenser comprising a stacked plurality of plates that define a plurality of flow passages, an inlet and outlet in fluid communication with the flow passages, wherein the plurality of flow passages defined by the stacked plurality of plates includes an ever decreasing flow area in a direction from the inlet toward the outlet.
9. The thermal management system as recited in claim 8, wherein each of the plurality of flow passages includes a width that decreases radially in a direction away from the inlet and toward the outlet.
10. The thermal management system as recited in claim 8, wherein each of the stacked plurality of plates include open slots in fluid communication with open slots within another of the stacked plurality of plates such that each of the plurality of flow passages is defined by open slots within at least two of the stacked plurality of plates.
11. The thermal management system as recited in claim 10, wherein each of the slots include a decreasing area in a direction toward the outlet and away from the inlet.
12. The thermal management system as recited in claim 8, wherein the plurality of flow passages extend radially inward from an outer periphery of the stacked plurality of plates and the inlet is in fluid communication with the outer periphery of the stacked plurality of plates and the outlet is disposed radially inward of the inlet.
13. The thermal management system as recited in claim 8, wherein the stacked plurality of plates are mounted to a cold plate.
14. A method of assembling a condenser comprising:
- providing at least one first plate having a first slot structure;
- providing at least one second plate having a second slot structure that corresponds with the first slot structure; and
- alternating stacking of the first plate onto the second plate to define a flow passage from an inlet toward an outlet, wherein the first slot structure and the second slot structure define flow areas that decrease in the direction of flow, such that the defined flow passage includes a decreasing flow area in the direction of flow.
15. The method of assembling a condenser as recited in claim 14, including bonding the first plate to the second plate.
16. The method of assembling a condenser as recited in claim 14, including a bottom plate on which the stacked first and second plates are mounted and a top plate that is disposed on the stacked first and second plates.
17. The method of assembling a condenser as recited in claim 14, including forming the first slot structure and the second slot structure to define flow passages that decrease in a direction radially inward of an outer periphery.
Type: Application
Filed: Jan 14, 2011
Publication Date: Jul 19, 2012
Inventor: Robert Scott Downing (Rockford, IL)
Application Number: 13/006,671
International Classification: F28F 3/08 (20060101); B21D 53/02 (20060101); F28F 3/14 (20060101);