US20110024083A1

US20110024083A1 - Heat exchanger

Info

Publication number: US20110024083A1
Application number: US12/533,285
Authority: US
Inventors: John C. Steimel
Original assignee: Individual
Current assignee: Haier US Appliance Solutions Inc
Priority date: 2009-07-31
Filing date: 2009-07-31
Publication date: 2011-02-03
Also published as: CA2708802A1

Abstract

A heat exchanger including a heat exchange fluid inlet, tubing coupled to the heat exchange fluid inlet, the tubing being configured to direct a flow of heat exchange fluid through the heat exchanger, the flow of fluid having a main fluid flow direction, and an air inlet configured to direct a flow of air in a generally collinear relationship with the main fluid flow direction.

Description

BACKGROUND OF THE INVENTION

The present disclosure relates generally to heat exchangers. More specifically, the present disclosure relates to heat exchangers having a relatively low refrigerant charge.
In a refrigerant-based heat exchange system, there are numerous reasons why the amount of refrigerant may need to be limited. These can include, for example, cost considerations, regulatory/environmental requirements and safety requirements. This presents a challenge to refrigerant system designers because to maintain satisfactory performance of the system, the system needs to be designed to flood the heat exchanger as much as possible with the restricted refrigerant charge level.
In a typical refrigerant-based heat exchange system, the general refrigerant flow and air flow through the heat-exchanger (for example, an evaporator) are not collinear or in the same direction. For example, referring to FIG. 1, the refrigerant-based heat exchanger for, as an example, a refrigerator/freezer generally comprises one or more fluid passages or tubes 105 running through a plurality of fins 110. The direction of the airflow 120 through the heat exchanger is generally from front to back while the general or main direction of refrigerant flow through the heat exchanger is generally from bottom to top. More specifically, as indicated in FIG. 1, the direction of the refrigerant flow alternates between front to back and back to front from row to row. For example, in the lower most row, the refrigerant flows from front to back. However, in the row immediately above the lower most row, the refrigerant flows from back to front. However, the general or main direction of the refrigerant flow in the heat exchanger is from bottom to top because the refrigerant flows from a lower row to a higher row. Alternatively, the main direction of the refrigerant flow can be from top to bottom when the refrigerant flows from a higher row to a lower row. However, in both situations, the main direction of the refrigerant flow is substantially transverse to the direction of the airflow 120. This non-collinear or transverse flow relationship can result in stagnation of the refrigerant within the tubing 105 of the heat exchanger. Stagnation of the refrigerant generally decreases the performance of the heat exchanger. This decrease in performance may be compounded by a limited amount of refrigerant flowing through the heat exchange system.
The size (e.g. internal volume) of the heat exchanger can be reduced to maintain satisfactory performance in a system that needs to use a limited amount of refrigerant. However, decreasing the size of the heat exchanger also decreases the heat exchange ability of the system as the surface area available to heat or cool the refrigerant within the heat exchanger is reduced.
It would be advantageous to have a refrigerant-based heat exchange system that is capable of satisfactorily exchanging heat with a limited amount of refrigerant running through the heat exchange system.

BRIEF DESCRIPTION OF THE INVENTION

As described herein, the exemplary embodiments overcome one or more of the above, or other disadvantages known in the art.
One aspect of the exemplary embodiments relates to a heat exchanger. The heat exchanger includes a heat exchange fluid inlet, tubing coupled to the heat exchange fluid inlet, the tubing being configured to direct a flow of heat exchange fluid through the heat exchanger, the flow of fluid having a main fluid flow direction, and an air inlet configured to direct a flow of air in a generally collinear relationship with the main fluid flow direction.
Another aspect of the disclosed embodiments relates to a heat exchange system for a refrigerator/freezer. The heat exchange system includes a heat exchanger comprising tubing having a serpentine configuration, the tubing being configured to direct a flow of heat exchange fluid in a main fluid flow direction; and a fan configured to effect an airflow through the heat exchanger in a substantially collinear relationship with the main fluid flow direction. A substantially even distribution of liquid heat exchange fluid flows throughout the heat exchanger.
A further aspect of the disclosed embodiments relates to an appliance. The appliance includes a housing, a heat exchanger having heat exchange fluid flowing within the heat exchanger, and an airflow duct configured to allow an airflow to circulate within the housing and through the heat exchanger. The heat exchanger is configured to direct a flow of the heat exchange fluid in a main fluid flow direction, the airflow through the heat exchanger moving in a substantially co-directional relationship with the main fluid flow direction, effecting a substantially even distribution of liquid heat exchange fluid throughout the heat exchanger.
These as other aspects and advantages of the exemplary embodiments will become more apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims. Moreover, the drawings are not necessarily to scale and that, unless otherwise indicated, they are merely intended to conceptually illustrate the structures and procedures described herein. In addition, any suitable size, shape or type of elements or materials could be used.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a schematic illustration of prior art heat exchanger;

FIG. 2 is a schematic sectional view of a refrigerator including an exemplary heat exchanger system of the invention;

FIG. 3 is a schematic illustration of an exemplary heat system of the invention; and

FIG. 4 is a schematic illustration of a portion of the refrigerant flow through the heat exchanger system of FIG. 3.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS OF THE INVENTION

Referring to FIG. 2, one embodiment of a heat exchange system 210 is shown installed within a side by side style refrigerator/freezer 200 (referred to herein as a “refrigerator” for exemplary purposes). It should be understood that while the aspects of the invention are described herein with respect to refrigerator 200, the aspects of the invention can be equally applied to any suitable refrigeration appliance.
The aspects of the disclosed embodiments provide a heat exchange system 210 capable of providing sufficient cooling for the refrigerator 200 where the amount of heat exchange fluid such as, for example, refrigerant, that can be used in the heat exchange system 210 is limited. In one embodiment, the heat exchange system 210 is configured so that the heat exchanger 220 is flooded with as much of the limited amount of heat exchange fluid, in liquid form, as possible. The heat exchanger 220 is configured such that the air flow over and/or through the heat exchanger 220 is substantially co-directional, that is, generally in the same direction as the main flow of heat exchange fluid through the heat exchanger 220 so that the amount of stagnant heat exchange fluid within the heat exchanger 220 is minimized. The main flow refers to the direction in which the refrigerant flows from one row or column of tube to the next row of column of tube. To promote a heat exchange fluid flow with minimized stagnation, the relationship of vapor pockets 410 (FIG. 4) and liquid slugs 400S (FIG. 4) within the fluid flow is such that the vapor pockets 410 push the liquid slugs 400S through the tubes or interior conduits of the heat exchanger 220 rather than flow over the top of (or otherwise around) the liquid slugs so that the liquid slugs 400S are substantially evenly distributed throughout the heat exchanger 220. The co-directional relationship between the airflow and the main flow of the heat exchange fluid in the heat exchanger of the invention promotes the liquid slug type of heat exchange fluid flow.
The aspects of the disclosed embodiments will generally be described herein with respect to the freezer side of the refrigerator 200. However, the aspects of the disclosed embodiments may also apply to any suitable portion or portions of the refrigerator, a standalone refrigerator or freezer, an air conditioning unit or any other suitable appliance with a heat exchanger. In this example, the refrigerator 200 includes a housing 200H, the heat exchanger 220, a fan 230, an icemaker 240, an ice bucket 245, freezer shelves 250 and freezer baskets 260. In other examples the refrigerator 200 may include any suitable components arranged in any suitable configuration. The heat exchanger 220 and the fan 230 are connected to the housing 200H and form part of the heat exchange system 210 (other components of the heat exchange system are not shown for clarity purposes). In this example, the heat exchanger 220 and the fan 230 are located towards the top 200T of the refrigerator 200, but in other examples the heat exchanger 220 and the fan 230 may be positioned in any suitable location of the refrigerator 200. The fan 230 may be any suitable fan configured to circulate a flow of air (e.g. airflow 280 indicated by the arrows in FIG. 2) throughout the interior of the refrigerator 200. The refrigerator 200 may include any suitable baffles or ductwork 270 to guide the airflow 280 in a circulatory manner throughout the various portions of the refrigerator 200. In one example, the ductwork 270 may be integral to or mounted within the housing 200H. For exemplary purposes only, the airflow 280 is guided through the interior of the refrigerator housing 200H so that the airflow 280 generally flows towards the bottom 200B of refrigerator 200 along the back side 200R of the refrigerator 200 and towards the top 200T of the refrigerator 200 along the front side 200F of the refrigerator 200. The airflow 280 transitions from the back side 200R to the front side 200T of the refrigerator 200 as directed by the ductwork 270 so that the air passes over and/or through the icemaker 240, ice bucket 245, freezer shelves 250 and freezer baskets 260 to draw heat from, for example, items stored in or on a respective one of the icemaker 240, ice bucket 245, freezer shelves 250 and freezer baskets 260. The airflow travelling up the front side 200F of the refrigerator 200 is directed by, for example, ductwork 270 or pulled/pushed by, for example, the fan 230 so that the airflow travels over or through the heat exchanger 220. In the example of FIG. 2, the ductwork forms an air inlet to the heat exchanger while in other examples the inlet may be integral to the heat exchanger 220. In other examples, the airflow 280 may flow along any suitable path suitable for cooling the contents of the refrigerator 200.
Referring to FIGS. 3 and 4, the heat exchanger 220 of the invention will be described in greater detail. The heat exchanger 220 may be any suitable type of heat exchanger such as, for example, a natural convection or forced air heat exchanger. In this example, the heat exchanger 220 includes tubing 350 and a plurality of fins 360 connected to the tubing. The tubing 350 forms a passage through which the heat exchange fluid 400 flows through the heat exchanger 220. In this example, the plurality of fins 360 are arranged parallel to the direction of the airflow 280 so that the airflow 280 passes through channels created by adjacent fins 360 and over the tubing 350 connected to the fins 360. The fins 360 are configured to draw heat from the airflow 280 so that heat is transferred between the airflow 280, the tubing 350 and the heat exchange fluid 400 within the tubing 350. It is noted that while in the exemplary embodiments heat is described as being drawn from the airflow so that the airflow is cooled, in other examples heat may be drawn from the heat exchange fluid for warming the airflow.
In this example the heat exchange fluid 400 may be any suitable refrigerant such as, for exemplary purposes, R-600a refrigerant, and compared to other systems using other refrigerants, the amount of the heat exchange fluid 400 can be limited. For example, the amount of heat exchange fluid 400 used in the heat exchange system 210 may be limited to approximately 50 grams of heat exchange fluid. In alternate embodiments, the amount of heat exchange fluid 400 used can be greater or less than approximately 50 grams.
As shown in FIG. 3, the flow 300 of heat exchange fluid 400 enters the tubing 350 through a fluid inlet 310 located on a first lateral side 220S1 of the heat exchanger 220 at, for example, the bottom front corner of the heat exchanger 220. In other examples, the fluid inlet 310 may be positioned in any suitable location of the heat exchanger 220 in order to provide a co-directional flow of the heat exchange fluid 400 and air through the heat exchange 220. The tubing 350 may have a serpentine configuration that passes through the fins 360 of the heat exchanger 220 to form any suitable number n of columns 330A-330 n of tubing. For example, the heat exchanger 220 may include n number of columns 330A-330 n, where n is an integer having a value of one or greater. Each column n bends in a serpentine manner (e.g. back and forth along a height H of the column) to form x number of rows 335A-335 x in the respective columns n where x is an integer having a value of one or greater. In one embodiment, the number n of columns 330A-330 n may be 8 and the number x of rows 335A-335 x in each respective column may be 8. In alternate embodiments, any suitable number of columns and rows, or combination thereof, can be used.
The heat exchange fluid 400 travels through the tubing 350 in the directions indicated by the arrows shown in FIG. 3. As shown in FIG. 3, the heat exchange fluid 400 generally travels in a main fluid flow direction 390 from the first side or front 220F of the heat exchanger 220 to the second side or back 220R of the heat exchanger 220. The main fluid flow direction 390 is substantially in the same direction or co-directional with the airflow 280 passing through/over the heat exchanger 220. In this example, the heat exchange fluid 400 travels from the inlet 310 back and forth between the first lateral side 220S1 and the second lateral side 220S2 of the heat exchanger 220 through rows 335A-335 x of a first column 330A of tubing. Thus, the heat exchange fluid generally travels from the bottom 220B towards the top 220T of the heat exchanger 220. When the heat exchange fluid 400 reaches the top of the first column 330A it travels through a substantially 180° bend in the tubing that directs the heat exchange fluid 400 into a second column 330B of tubing. In a like fashion, the heat exchange fluid 400 travels back and forth between the first lateral side 220S1 and the second lateral side 220S2 of the heat exchanger 400 from the top 220T towards the bottom 220B of the heat exchanger as the fluid travels through rows 335A-335 x of the second column 330B of tubing. The heat exchange fluid 400 continues to travel through the remaining columns of tubing in this manner generally in a direction from the front 220F of the heat exchanger 220 to a back 220B of the heat exchanger 220 until the heat exchange fluid 400 reaches the n^thcolumn 330 n and respective x^throw 335 x. The heat exchange fluid 400 can then exit the heat exchanger 220 through the fluid outlet 320.
In one embodiment, the fan 230 shown in FIG. 2 is configured to force the airflow 280 through the heat exchanger 220 to effect a flow of air through/over the heat exchanger 220 in a direction that is generally from the front 220F of the heat exchanger 220 to the back 220R of the heat exchanger 220 so that the direction of airflow 280 is substantially co-directional as the main fluid flow direction 390. It is noted that while the exemplary embodiments describe the main fluid flow direction 390 and the direction of the airflow 280 as being in a direction flowing from the front 220F to the back 220R of the heat exchanger 220, in other examples, the main fluid flow direction 390 and the direction of the airflow 280 may be any suitable direction relative to the front, back, top or bottom of the heat exchanger as long as the main fluid flow direction 390 and the direction of the airflow 280 are generally in substantially the same direction. As described above, the co-directional flow relationship between the main fluid flow through the heat exchanger and the direction of the airflow 280 minimizes the stagnation of the liquid heat exchange fluid 400 within the tubing 350 of the heat exchanger 220.
In operation of the heat exchanger 220, the heat exchange fluid 400 is primarily liquid as it enters the inlet 310 of the heat exchanger 220. As the airflow 280 passes over/through the heat exchanger 220, the heat transfer from the air to the fluid 400 promotes boiling of the heat exchange fluid 400 inside the tubing 350. The boiling of the heat exchange fluid 400 causes vapor pockets 410 to form within the tubing 350 with liquid slugs 400S formed between the vapor pockets 410. As shown in FIG. 4, the size of each vapor pocket 410 generally fills the diameter D of the tubing 350. These vapor pockets 410 act to push the liquid slugs 400S through the heat exchanger 220. To optimize the formation of the vapor pockets 410, which in turn will push the heat exchange fluid 400 through the remainder of the heat exchanger 220, the flow of heat exchange fluid 400 and the airflow 280 are configured with the co-directional flow relationship described above. Since the air entering the front 220F of the heat exchanger 220 is warmer than the air exiting the back 220R of the heat exchanger 220 because the heat exchange fluid 400 draws heat from the airflow 280 thus allowing the formation of the vapor pockets 410 within the tubing 350, the co-directional flow relationship causes a greater amount of vapor pockets 410 to form at the front of the heat exchanger 220 where the heat exchange fluid is primarily in a liquid form (e.g. a point in the heat exchanger where there is a maximum amount liquid heat exchange fluid) and the air is the warmest. Formation of the vapor pockets 410 in an area where the heat exchange fluid is primarily in liquid form promotes the formation of vapor pockets 410 suitably sized to bridge an internal diameter D of the tubing 350. The vapor pockets 410 push the liquid slugs 400S through the tubing 350 such that a greater amount of heat exchange fluid 400 is provided towards the back 220R of the heat exchanger 220 than in the prior art configuration due to the alternating front to back flow in such configurations. The increased amount or presence of the heat exchange fluid 400 (in the form of liquid slugs 400S) in the tubing towards the back 220R of the heat exchanger 220 provides more fluid for drawing heat from the air through the conversion of the liquid slugs 410 into vapor. Accordingly, the flow of the liquid slugs 400S through the tubing 350 allows for a substantially even distribution of heat exchange fluid 400 throughout the heat exchanger 220 thereby maximizing the effectiveness of the heat exchanger 220 in transferring heat with the air flow by providing liquid for the airflow to boil towards the back 220R of the heat exchanger 220.
For testing purposes only, a comparison was made between the conventional heat exchanger as in FIG. 1 and a heat exchanger 220 of the invention when installed in a General Electric Monogram 42 inch side by side refrigerator. Each was tested with 55 grams of R-600a refrigerant. The conventional heat exchanger 100 was installed in the refrigerator such that the flow of the refrigerant through the heat exchanger 100 and the flow of air over the heat exchanger were as described with reference to FIG. 1. Test data on this heat exchanger arrangement indicated that only half of the conventional heat exchanger 100 was being filled with liquid refrigerant. In this test, the heat exchanger temperatures were saturated up to about a mid point of fluid travel through the conventional heat exchanger 100, and refrigerant temperatures beyond about the mid-point of fluid travel through the heat exchanger 100 were superheated by, for example, 11-13° F.
The same General Electric Monogram 42 inch side by side refrigerator was modified with a heat exchanger 220 of the invention so that the flow of refrigerant within the heat exchanger 220 and the airflow over the heat exchanger 220 were substantially collinear or co-directional. The refrigerant charge in this example was maintained at 55 grams of R600a refrigerant. Tests on the modified refrigerator with the heat exchanger 220 indicated that optimum heat exchanger flooding occurred and that heat exchanger temperatures were saturated up to a point about seven-eighths of the way through the heat exchanger. Refrigerant temperatures at the exit of the heat exchanger 220 exhibited only 1° F. of superheat.
Thus, while there have been shown and described and pointed out fundamental novel features of the invention as applied to the exemplary embodiments thereof, it will be understood that various omission and substitutions and changes, in the form and details of devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same way to achieve the same results are with the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

Claims

1. A heat exchanger comprising:

a heat exchange fluid inlet;

tubing coupled to the heat exchange fluid inlet, the tubing being configured to direct a flow of heat exchange fluid through the heat exchanger, the flow of fluid having a main fluid flow direction; and

an air inlet configured to direct a flow of air in a generally collinear relationship with the main fluid flow direction.

2. The heat exchanger of claim 1, wherein the tubing has an internal diameter and the airflow promotes boiling of the heat exchange fluid inside the tubing such that vapor pockets form within the tubing, the vapor pockets being configured to bridge the internal diameter so that liquid slugs are formed between the vapor pockets.

3. The heat exchanger of claim 2, further comprising a first side and a second side, the heat exchange fluid inlet being disposed proximate the first side, and the main fluid flow direction is in a direction moving from the first side to the second side to cause a greater amount of vapor pockets to form at the first side where the heat exchange fluid is primarily in a liquid form.

4. The heat exchanger of claim 2, further comprising a heat exchange fluid outlet, the substantially collinear relationship between the direction of air flow and the main fluid flow direction causing the vapor pockets to push the liquid slugs through the tubing so as to increase the amount of liquid heat exchange fluid that is provided towards the heat exchange fluid outlet.

5. The heat exchanger of claim 1, wherein an amount of the heat exchange fluid comprises approximately 50 to approximately 55 grams of refrigerant.

6. The heat exchanger of claim 5, wherein the heat exchange fluid comprises R-600a refrigerant.

7. A heat exchange system for a refrigerator/freezer, the heat exchange system comprising:

a heat exchanger comprising tubing having a serpentine configuration, the tubing being configured to direct a flow of heat exchange fluid in a main fluid flow direction; and

a fan configured to effect an airflow through the heat exchanger in a substantially collinear relationship with the main fluid flow direction,

wherein a substantially even distribution of liquid heat exchange fluid flows throughout the heat exchanger.

8. The heat exchange system of claim 7, wherein the tubing has an internal diameter, vapor pockets forming within the tubing from the boiling of the heat exchange fluid inside the tubing, the vapor pockets being configured to bridge the internal diameter of the tubing so that liquid slugs are formed between the vapor pockets.

9. The heat exchange system of claim 8, wherein the vapor pockets are configured to push the liquid slugs through the heat exchanger.

10. The heat exchange system of claim 8, wherein the heat exchanger further comprises a first side and a second side, the heat exchange fluid being primarily in a liquid form at the first side of the heat exchanger, the main fluid flow direction being in a direction moving from the first side to the second side to cause a greater amount of vapor pockets to form at the first side where the heat exchange fluid is primarily in a liquid form.

11. The heat exchange system of claim 8, wherein the heat exchanger further comprises a heat exchange fluid outlet, wherein the substantially collinear relationship between the airflow direction and the main fluid flow direction causes the vapor pockets to push the liquid slugs through the tubing such that a greater amount of liquid heat exchange fluid is provided towards the heat exchange fluid outlet.

12. The heat exchange system of claim 7, wherein an amount of the heat exchange fluid is in the range of 50 to 55 grams of refrigerant.

13. The heat exchange system of claim 12, wherein the heat exchange fluid comprises R-600a refrigerant.

14. An appliance comprising:

a housing;

a heat exchanger having heat exchange fluid flowing within the heat exchanger; and

an airflow duct configured to allow an airflow to circulate within the housing and through the heat exchanger,

wherein the heat exchanger is configured to direct a flow of the heat exchange fluid in a main fluid flow direction, the airflow through the heat exchanger moving in a substantially co-directional relationship with the main fluid flow direction, effecting a substantially even distribution of liquid heat exchange fluid throughout the heat exchanger.

15. The appliance of claim 14, wherein the heat exchanger comprises tubing having an internal diameter where the airflow through the heat exchanger promotes boiling of the heat exchange fluid inside the tubing such that vapor pockets form within the tubing, the vapor pockets being configured to bridge the internal diameter so that liquid slugs are formed between the vapor pockets.

16. The appliance of claim 15, wherein the vapor pockets are configured to push the liquid slugs through the heat exchanger.

17. The appliance of claim 15, wherein the heat exchanger comprises a first side and a second side such that the main fluid flow direction is in a direction moving from the first side to the second side to cause a greater amount of vapor pockets to form towards the first side where the heat exchange fluid is primarily in a liquid form.

18. The appliance of claim 15, wherein the heat exchanger further comprises a heat exchange fluid outlet, the substantially co-directional relationship of the airflow direction to the main fluid flow direction causing the vapor pockets to push the liquid slugs through the tubing such that a greater amount of liquid heat exchange fluid is provided towards the heat exchange fluid outlet.

19. The appliance of claim 14, wherein an amount of the heat exchange fluid is in the range of 50 to 55 grams of refrigerant.

20. The appliance of claim 19, wherein the heat exchange fluid comprises R-600a refrigerant.