US20200196776A1

US20200196776A1 - Refrigerated display case having a central return air duct

Info

Publication number: US20200196776A1
Application number: US16/229,844
Authority: US
Inventors: Pavan Kumar PUTTALINGARAJU; Ajay Chidambaram Pillai SWORNALATHA; Jon Douglas
Original assignee: Heatcraft Refrigeration Products LLC
Current assignee: Kysor Warren EPTA US Corp
Priority date: 2018-12-21
Filing date: 2018-12-21
Publication date: 2020-06-25

Abstract

A refrigerated display case includes a base. A first wall extends from the base and has a first supply air duct defined therein. A second wall extends from the base and has a second supply air duct defined therein. The first wall and the second wall define a product area therebetween. A return air duct is disposed in the product area between the first supply air duct and the second supply air duct. An evaporator coil is disposed in an equipment space defined between the product area and the base. The equipment space is fluidly coupled to the first supply air duct, the second supply air duct, and the return air duct. A first circulation fan is disposed in the equipment space proximate the first supply air duct. A second circulation fan disposed in the equipment space proximate the second supply air duct.

Description

TECHNICAL FIELD

The present disclosure relates generally to refrigerated display cases and more particularly, but not by way of limitation to refrigerated display cases having a centrally-located return air duct and dual supply ducts.

BACKGROUND

This section provides background information to facilitate a better understanding of the various aspects of the disclosure. It should be understood that the statements in this section of this document are to be read in this light, and not as admissions of prior art.
Display cases that are capable of refrigerating contents are common features in many retail outlets. Refrigerated display cases often include a fan that circulates refrigerated air over the contents of the refrigerated display case. Often times, such refrigerated display cases experience significant product temperature variation depending to the positioning of the product within the refrigerated display case. Such a scenario can cause products to fail to meet product safety standards. One approach to ensuring compliance with safety standards is to lower a temperature of an evaporator coil; however, this approach can cause localized product freezing.

SUMMARY

Various aspects of the disclosure relate to a refrigerated display case. The refrigerated display case includes a base. A first wall extends from the base and has a first supply air duct defined therein. A second wall extends from the base and has a second supply air duct defined therein. The first wall and the second wall define a product area therebetween. A return air duct is disposed in the product area between the first supply air duct and the second supply air duct. An evaporator coil is disposed in an equipment space defined between the product area and the base. The equipment space is fluidly coupled to the first supply air duct, the second supply air duct, and the return air duct. A first circulation fan is disposed in the equipment space proximate the first supply air duct. A second circulation fan disposed in the equipment space proximate the second supply air duct.
Various aspects of the disclosure relate to a cooling system. The cooling system includes a first supply air duct and a second supply air duct. A first circulation fan is disposed in the first supply air duct. A second circulation fan is disposed in the second supply air duct. A return air duct is positioned between the first supply air duct and the second supply air duct. An evaporator coil is thermally exposed to the first supply air duct, the second supply air duct, and the return air duct.
Various aspects of the disclosure relate to a method of constructing a refrigerated display case. The method includes forming a first supply air duct in a first wall of the refrigerated display case and forming a second supply air duct in a second wall of the refrigerated display case. A product area is defined between the first wall and the second wall. A return air duct is formed between the first supply air duct and the second supply air duct. A first circulation fan is positioned proximate the first supply air duct. A second circulation fan is positioned proximate the second supply air duct. An evaporator coil is positioned to be thermally exposed to the first supply air duct, the second supply air duct, and the return air duct.
This summary is provided to introduce a selection of concepts that are further described below in the detailed description. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used as an aid in limiting the scope of claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic diagram of a cooling cycle;

FIG. 2 is a cross-sectional view of an existing refrigerated display case;

FIG. 3 is a schematic view of the existing refrigerated display case of FIG. 2 illustrating air flow therethrough;

FIG. 4 is a cross-sectional view of a refrigerated display case according to aspects of the disclosure;

FIG. 5 is a schematic view of the refrigerated display case of FIG. 4 illustrating air flow therethrough according to aspects of the disclosure; and

FIG. 6 is a diagram illustrating a side-by-side comparison of air velocity in the refrigerated display case of FIG. 4 compared to the refrigerated display case of FIG. 2 according to aspects of the disclosure:

FIG. 7 is a diagram illustrating a side-by-side comparison of air temperature in the refrigerated display case of FIG. 4 compared to the refrigerated display case of FIG. 2 according to aspects of the disclosure;

FIG. 8 is a graph illustrating a relationship between air flow rate, sensible cooling load, and product temperature standard deviation of the refrigerated display case of FIG. 2 compared to the refrigerated display case of FIG. 4 according to aspects of the disclosure:

FIG. 9 is a graph illustrating a relationship between air flow rate and average product temperature of the refrigerated display case of FIG. 4 compared to the refrigerated display case of FIG. 2; and

FIG. 10 is a flow diagram illustrating a method of constructing a refrigerated display case.

DETAILED DESCRIPTION

Various embodiments will now be described more fully with reference to the accompanying drawings. The disclosure may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.
FIG. 1 is a schematic diagram of a cooling system 100. The cooling system 100 includes an evaporator coil 102, a condenser coil 104, a compressor 106, and a metering device 108. During operation, a circulation fan 110 circulates air around the evaporator coil 102. In various embodiments, the compressor 106 is, for example, a single-stage compressor, a multi-stage compressor, a single-speed compressor, or a multi-speed compressor. The circulation fan 110, sometimes referred to as a blower, may, in various embodiments, be configured to operate at different capacities (i.e., variable motor speeds) to circulate air through the cooling system 100, whereby the circulated air is conditioned and supplied to a conditioned space 112. In a typical embodiment, the metering device 108 is, for example, a thermostatic expansion valve or a throttling valve. The evaporator coil 102 is fluidly coupled to the compressor 106 via a suction line 114. The compressor 106 is fluidly coupled to the condenser coil 104 via a discharge line 116. The condenser coil 104 is fluidly coupled to the metering device 108 via a liquid line 118.
Still referring to FIG. 1, during operation, low-pressure, low-temperature refrigerant is circulated through the evaporator coil 102. The refrigerant is initially in a liquid/vapor state. In a typical embodiment, the refrigerant is, for example, R-22, R-134a, R-410A, R-744, or any other suitable type of refrigerant as dictated by design requirements. Air from within the conditioned space 112, which is typically warmer than the refrigerant, is circulated around the evaporator coil 102 by the circulation fan 110. In a typical embodiment, the refrigerant begins to boil after absorbing heat from the air and changes state to a low-pressure, low-temperature, super-heated vapor refrigerant. Saturated vapor, saturated liquid, and saturated fluid refer to a thermodynamic state where a liquid and its vapor exist in approximate equilibrium with each other. Super-heated fluid and super-heated vapor refer to a thermodynamic state where a vapor is heated above a saturation temperature of the vapor. Sub-cooled fluid and sub-cooled liquid refers to a thermodynamic state where a liquid is cooled below the saturation temperature of the liquid.
The low-pressure, low-temperature, super-heated vapor refrigerant is introduced into the compressor 106 via the suction line 114. In a typical embodiment, the compressor 106 increases the pressure of the low-pressure, low-temperature, super-heated vapor refrigerant and, by operation of the ideal gas law, also increases the temperature of the low-pressure, low-temperature, super-heated vapor refrigerant to form a high-pressure, high-temperature, superheated vapor refrigerant. The high-pressure, high-temperature, superheated vapor refrigerant leaves the compressor 106 via the discharge line 116 and enters the condenser coil 104.
Still referring to FIG. 1, outside air is circulated around the condenser coil 104 by a condenser fan 120. The outside air is typically cooler than the high-pressure, high-temperature, superheated vapor refrigerant present in the condenser coil 104. Thus, heat is transferred from the high-pressure, high-temperature, superheated vapor refrigerant to the outside air. Removal of heat from the high-pressure, high-temperature, superheated vapor refrigerant causes the high-pressure, high-temperature, superheated vapor refrigerant to condense and change from a vapor state to a high-pressure, high-temperature, sub-cooled liquid state. The high-pressure, high-temperature, sub-cooled liquid refrigerant leaves the condenser coil 104 via the liquid line 118 and enters the metering device 108.
In the metering device 108, the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant is abruptly reduced. In various embodiments where the metering device 108 is, for example, a thermostatic expansion valve, the metering device 108 reduces the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant by regulating an amount of refrigerant that travels to the evaporator coil 102. Abrupt reduction of the pressure of the high-pressure, high-temperature, sub-cooled liquid refrigerant causes sudden, rapid, evaporation of a portion of the high-pressure, high-temperature, sub-cooled liquid refrigerant, commonly known as “flash evaporation.” The flash evaporation lowers the temperature of the resulting liquid/vapor refrigerant mixture to a temperature lower than a temperature of the air in the conditioned space 112. The liquid/vapor refrigerant mixture leaves the metering device 108 and returns to the evaporator coil 102.
FIG. 2 is a cross-sectional view of an existing refrigerated display case 200. For purposes of illustration. FIG. 2 is described herein relative to FIG. 1. The refrigerated display case 200 includes a shell 202 having a supply air duct 204 and a return air duct 206 defined therein. Often, the supply air duct 204 is vertically arranged in an upstanding rear wall 208 of the refrigerated display case 200 and the return air duct 206 is vertically arranged in an upstanding front wall 210 of the refrigerated display case 200. A product area 212 is defined between the supply air duct 204 and the return air duct 206. Conditioned air exits the supply air duct 204 through a honeycomb diffuser 214. The conditioned air passes over the product area 212 forming an air curtain after exiting the supply air duct 204 and enters the return air duct 206 through a return grill 216. A floor 218 is positioned in the product area 212. An equipment space 220 is defined between the floor 218 and the shell 202 and is fluidly coupled to the supply air duct 204 and the return air duct 206. The circulation fan 110 and the evaporator coil 102 are positioned in the equipment space 220. The circulation fan 110 circulates air from the return air duct 206, through the evaporator coil 102, and into the supply air duct 204.
FIG. 3 is a schematic view of the refrigerated display case 200 illustrating air flow there through. For purposes of illustration, FIG. 3 is described herein relative to FIGS. 1-2. Air flows through the refrigerated display case 200 in the direction indicated by the arrows 302. Thus, the circulation fan 110 pushes air through the evaporator coil 102 and into the supply air duct 204 disposed in the upstanding rear wall 208. The air exits the supply air duct 204 and travels over the product area 212 to the return air duct 206 disposed in the upstanding front wall 210. The air enters the return air duct 206 disposed in the upstanding front wall 210 and returns to the circulation fan 110. As illustrated in FIG. 3, ambient air is entrained into the air curtain and is then spilled over the upstanding front wall 210 and does not enter the return air duct 206. Such a phenomenon results in reduced efficiency of the refrigerated display case 200.
FIG. 4 is a cross-sectional view of a refrigerated display case 400. For purposes of illustration, FIG. 4 is described herein relative to FIG. 1. The refrigerated display case 400 includes a base 402, a first wall 404 that is arranged substantially vertical relative to the base 402, and a second wall 406 that is arranged substantially vertical relative to the base 402. A first supply air duct 408 is vertically arranged in the first wall 404 and a second supply air duct 410 is arranged in the second wall 406 of the refrigerated display case 400. A product area 412 is defined between the second wall 406 and the first wall 404. In various embodiments, one or more product racks 414 may be positioned in the product area 412 to facilitate display of product 416 to customers. In various embodiments, a solid plate may be positioned below the product rack in an effort to restrict the flow of air towards the return air duct 422. A floor 418 is positioned at a bottom of the product area 412. An equipment space 420 is defined between the floor 418 and the base 402. The equipment space 420 is fluidly coupled to the first supply air duct 408 and the second supply air duct 410. A return air duct 422 is arranged in an approximate center of the product area 412 and is fluidly coupled to the equipment space 420. The evaporator coil 102 is arranged in the equipment space 420 below the return air duct 422. A first circulation fan 424 is positioned in the equipment space 420 near the first supply air duct 408 and a second circulation fan 426 is positioned in the equipment space 420 near the second supply air duct 410. In various embodiments, for example, the first circulation fan 424 and the second circulation fan 426 are positioned on opposite sides of the evaporator coil 102.
Still referring to FIG. 4, during operation, the first circulation fan 424 pushes air exiting the evaporator coil 102 into the first supply air duct 408. At the same time, the second circulation fan 426 pushes air exiting the evaporator coil 102 into the second supply air duct 410. Air exits the first supply air duct 408 via a first diffuser 428 and air exits the second supply air duct 410 via a second diffuser 430. In various embodiments, the first diffuser 428 and the second diffuser 430 are, for example, honeycomb structures positioned near an outlet of the first supply air duct 408 and an outlet of the second supply air duct 410, respectively. Upon exiting the first supply air duct 408 and the second supply air duct 410, air is drawn inwardly towards a center of the product area 412 and downwardly towards the return air duct 422. Upon entering the return air duct 422, the air is circulated through the evaporator coil 102. In various embodiments, a substantially transparent glass pane 432 is inserted into at least one of the first wall 404 and the second wall 406 to facilitate visualization of the products 416 by the customer.
FIG. 5 is a schematic view of the refrigerated display case 400 illustrating air flow there through. For purposes of illustration. FIG. 5 is described herein relative to FIGS. 1 and 4. Air flows through the refrigerated display case 400 in the direction indicated by the arrows 502. During operation, the first circulation fan 424 pushes air from the evaporator coil 102 into the first supply air duct 408. At the same time, the second circulation fan 426 pushes air from the evaporator coil 102 into the second supply air duct 410. The air exits the first supply air duct 408 and the second supply air duct 410 through the first diffuser 428 and the second diffuser 430, respectively, and passes over the product area 412. Upon leaving the first diffuser 428 and the second diffuser 430, the air is drawn downwardly and towards a center of the product area 412 in a direction of the return air duct 422. The air enters the return air duct 422 and is returned to the evaporator coil 102.
Still referring to FIG. 5, the arrangement of the first supply air duct 408, the second supply air duct 410, and the return air duct eliminate spillage of air over at least one of the first wall 404 and the second wall 406. Additionally, the arrangement of the first supply air duct 408 and the second supply air duct 410 induce formation of eddy currents 504 in the air as the air is drawn towards the return air duct 422. The eddy currents 504 facilitate formation of a thermal barrier 506 that reduces a volume of ambient air that is in contact with the products 416.
FIG. 6 is a diagram illustrating a side-by-side comparison of air velocity in the refrigerated display case 400 compared to the refrigerated display case 200. The arrangement of the first supply air duct 408, the second supply air duct 410, and the return air duct 422 result in a shorter air curtain being formed when compared to the refrigerated display case 200. The shorter air curtain, coupled with the air being directed towards a center of the product area 412 reduces spillage of air over at least one of the first wall 404 and the second wall 406 when compared to the refrigerated display case 200.
FIG. 7 is a diagram illustrating a side-by-side comparison of air temperature in the refrigerated display case 400 compared to the refrigerated display case 200. As noted above, discharge of air from the first supply air duct 408 and the second supply air duct 410 in the direction of the return air duct 422 induces the formation of eddy currents 504. The eddy currents 504 facilitate the creation of a thermal barrier 506 that reduces the infiltration of ambient air into the product area when compared to the refrigerated display case 200.
FIG. 8 is a graph illustrating a relationship between air flow rate, sensible cooling load, and product temperature standard deviation of the refrigerated display case 400 compared to the refrigerated display case 200. Line 802 illustrates the variance of sensible cooling load with air flow rate of the refrigerated display case 200. Line 804 illustrates the variance of sensible cooling load with air flow rate of the refrigerated display case 400. Line 802 and line 804 illustrate that the refrigerated display case 400 demonstrates a lower sensible cooling load than the refrigerated display case 200. Line 806 illustrates the variance of product temperature standard deviation with air flow rate of the refrigerated display case 200. Line 806 illustrates that the standard deviation of product temperature falls as the air flow rate through the refrigerated display case 200 increases. Line 808 illustrates the variance of product temperature standard deviation with air flow rate of the refrigerated display case 400. Line 808 illustrates that the standard deviation of product temperature in the refrigerated display case 400 is unaffected by air flow rate. Thus, in the refrigerated display case 400, uniformity of product temperature is improved at lower air flow rates when compared to the refrigerated display case 200.
FIG. 9 is a graph illustrating a relationship between air flow rate and average product temperature of the refrigerated display case 400 compared to the refrigerated display case 200. Line 902 illustrates the variance of average product temperature with air flow rate of the refrigerated display case 200 and line 904 illustrates the variance of average product temperature with air flow rate of the refrigerated display case 400. Line 902 and line 904 demonstrate that, at a certain air flow rate, such as, for example 40 ft³/min, the refrigerated display case 400 demonstrates a lower average product temperature than the refrigerated display case 200.
FIG. 10 is a flow diagram illustrating a process 1000 of constructing the refrigerated display case 400. For purposes of illustration, FIG. 10 is described herein relative to FIGS. 1 and 4. The process starts at step 1002. At step 1004, the first supply air duct 408 is formed in the first wall 404 and the second supply air duct 410 is formed in the second wall 406. The product area 412 is defined between the first wall 404 and the second wall 406. At step 1006, the return air duct 422 is formed between the first supply air duct 408 and the second supply air duct 410. At step 1008, the first circulation fan 424 is positioned proximate the first supply air duct 408 and the second circulation fan 426 is positioned proximate the second supply air duct 410. At step 1010, the evaporator coil 102 is positioned to be thermally exposed to the first supply air duct 408, the second supply air duct 410, and the return air duct 422. The process 1000 ends at step 1012. The arrangement of the first supply air duct 408, the second supply air duct 410, and the return air duct 422 results in a shorter air curtain being formed when compared to the refrigerated display case 200. The shorter air curtain, coupled with the air being directed towards a center of the product area 412 reduces spillage of air over at least one of the first wall 404 and the second wall 406 when compared to the refrigerated display case 200. Discharge of air from the first supply air duct 408 and the second supply air duct 410 in the direction of the return air duct 422 induces the formation of eddy currents 504. The eddy currents 504 facilitate the creation of a thermal barrier 506 that reduces the infiltration of ambient air into the product area when compared to the refrigerated display case 200.
The term “substantially” is defined as largely but not necessarily wholly what is specified (and includes what is specified; e.g., substantially 90 degrees includes 90 degrees and substantially parallel includes parallel), as understood by a person of ordinary skill in the art. In any disclosed embodiment, the terms “substantially,” “approximately.” “generally,” and “about” may be substituted with “within 10% of” what is specified.
Conditional language used herein, such as, among others. “can.” “might,” “may,” “e.g.,” and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.
While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the devices or algorithms illustrated can be made without departing from the spirit of the disclosure. As will be recognized, the processes described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others. The scope of protection is defined by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.

Claims

What is claimed is:

1. A refrigerated display case, comprising:

a base;

a first wall extending from the base and having a first supply air duct defined therein;

a second wall extending from the base and having a second supply air duct defined therein, the first wall and the second wall defining a product area therebetween;

a return air duct disposed in the product area between the first supply air duct and the second supply air duct;

an evaporator coil disposed in an equipment space defined between the product area and the base, the equipment space being fluidly coupled to the first supply air duct, the second supply air duct, and the return air duct;

a first circulation fan disposed in the equipment space proximate the first supply air duct; and

a second circulation fan disposed in the equipment space proximate the second supply air duct.

2. The refrigerated display case of claim 1, wherein:

the first wall is a front wall of the refrigerated display case; and

the second wall is a rear wall of the refrigerated display case.

3. The refrigerated display case of claim 2, comprising a glass pane disposed in the front wall.

4. The refrigerated display case of claim 3, wherein the glass pane is substantially transparent.

5. The refrigerated display case of claim 1, wherein the product area comprises a floor.

6. The refrigerated display case of claim 5, wherein the equipment space is defined between the base and the floor.

7. The refrigerated display case of claim 1, comprising:

a first diffuser disposed at an exit of the first supply air duct; and

a second diffuser disposed at an exit of the second supply air duct.

8. The refrigerated display case of claim 7, wherein:

the first diffuser comprises a honeycomb structure; and

the second diffuser comprises a honeycomb structure.

9. A cooling system, comprising:

a first supply air duct;

a second supply air duct;

a first circulation fan disposed in the first supply air duct;

a second circulation fan disposed in the second supply air duct;

a return air duct positioned between the first supply air duct and the second supply air duct; and

an evaporator coil thermally exposed to the first supply air duct, the second supply air duct, and the return air duct.

10. The cooling system of claim 9, wherein the cooling system is incorporated in a refrigerated display case.

11. The cooling system of claim 10, wherein discharge of air from the first supply air duct and the second supply air duct creates a thermal barrier to ambient air infiltrating the refrigerated display case.

12. The cooling system of claim 10, wherein positioning of the return air duct between the first supply air duct and the second supply air duct prevents spillage of air over a wall of the refrigerated display case.

13. The cooling system of claim 9, wherein the first circulation fan and the second circulation fan are positioned on opposite sides of the evaporator coil.

14. The cooling system of claim 9, comprising:

a first diffuser disposed at an exit of the first supply air duct; and

a second diffuser disposed at an exit of the second supply air duct.

15. The cooling system of claim 14, wherein:

the first diffuser comprises a honeycomb structure; and

the second diffuser comprises a honeycomb structure.

16. A method of constructing a refrigerated display case, the method comprising:

forming a first supply air duct in a first wall of the refrigerated display case;

forming a second supply air duct in a second wall of the refrigerated display case, a product area being defined between the first wall and the second wall;

forming a return air duct between the first supply air duct and the second supply air duct;

positioning a first circulation fan proximate the first supply air duct;

positioning a second circulation fan proximate the second supply air duct; and

positioning an evaporator coil to be thermally exposed to the first supply air duct, the second supply air duct, and the return air duct.

17. The method of claim 16, comprising positioning the evaporator coil between the first circulation fan and the second circulation fan.

18. The method of claim 16, comprising disposing the first circulation fan, the second circulation fan, and the evaporator coil in an equipment space.

19. The method of claim 18, wherein the equipment space is fluidly coupled to the first supply air duct, the second supply air duct, and the return air duct.

20. The method of claim 16 comprising:

positioning a first diffuser in an exit of the first supply air duct; and

positioning a second diffuser in an exit of the second supply air duct.