METHOD AND SYSTEM TO VARY SUCTION TEMPERATURE TO POSTPONE FROST FORMATION
A cooling system includes an evaporator coil and a compressor fluidly coupled to the evaporator coil. A circulation fan is arranged to direct air through the evaporator coil and through a discharge air duct into a conditioned space. At least one sensor is disposed in at least one of the discharge air duct, the conditioned space, and the evaporator coil. An HVAC controller is electrically coupled to the at least one sensor and electrically coupled to the compressor. The HVAC controller is configured to receive a measurement of an HVAC parameter from the at least one sensor, determine if the HVAC parameter indicates frost formation on the evaporator coil, and, responsive to a determination that the HV AC parameter indicates frost formation on the evaporator coil, raise a saturated suction temperature of the evaporator coil.
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The present disclosure relates generally to refrigerated display cases and more particularly, but not by way of limitation to refrigerated display cases that vary saturated suction temperature in order to delay frost formation.
BACKGROUNDThis 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 contents of the refrigerated display case. Such display cases require periodic defrosting. Frost formation will often occur quickly after completion of a defrost cycle. Frost formation leads to diminished efficiency of an evaporator coil. Additionally, frost formation interferes with an air curtain on the display cases allowing increased infiltration of warmer ambient air and leading to elevated product temperatures.
SUMMARYVarious aspects of the disclosure relate to a cooling system. The cooling system includes an evaporator coil and a compressor fluidly coupled to the evaporator coil. A circulation fan is arranged to direct air through the evaporator coil and through a discharge air duct into a conditioned space. At least one sensor is disposed in at least one of the discharge air duct, the conditioned space, and the evaporator coil. An HVAC controller is electrically coupled to the at least one sensor and electrically coupled to the compressor. The HVAC controller is configured to receive a measurement of an HVAC parameter from the at least one sensor, determine if the HVAC parameter indicates frost formation on the evaporator coil, and, responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, raise a saturated suction temperature of the evaporator coil.
Various aspects of the disclosure relate to a method for operating a refrigerated display case. The method includes measuring, by at least one sensor, an HVAC parameter. An HVAC controller, electrically coupled to the at least one sensor, determines if the HVAC parameter indicates frost formation on an evaporator coil. Responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, by the HVAC controller signals an evaporator pressure regulator (“EPR”) to reduce a flow of refrigerant from an evaporator coil to a compressor thereby raising a saturated suction temperature of the evaporator coil.
Various aspects of the disclosure relate to a method for operating a refrigerated display case. The method includes measuring, by at least one sensor, an HVAC parameter. An HVAC controller, electrically coupled to the at least one sensor, determines if the HVAC parameter indicates frost formation on an evaporator coil. Responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, signaling, by the HVAC controller, a compressor to modulate a speed of the compressor thereby raising a saturated suction temperature of the evaporator coil.
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.
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.
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.
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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.
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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.
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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 a percentage 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
1. A cooling system, comprising:
- an evaporator coil;
- a compressor fluidly coupled to the evaporator coil;
- a circulation fan arranged to direct air through the evaporator coil and through a discharge air duct into a conditioned space;
- at least one sensor, the at least one sensor being disposed in at least one of the discharge air duct, the conditioned space, and the evaporator coil;
- an HVAC controller electrically coupled to the at least one sensor and electrically coupled to the compressor;
- wherein the HVAC controller is configured to: receive a measurement of an HVAC parameter from the at least one sensor; determine if the HVAC parameter indicates frost formation on the evaporator coil; and responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, raise a saturated suction temperature of the evaporator coil.
2. The cooling system of claim 1, wherein the at east one sensor is a first temperature sensor.
3. The cooling system of claim 2, wherein the first temperature sensor is disposed at a location that is selected from a group consisting of:
- in the evaporator coil; and
- on an exterior surface of the evaporator coil.
4. The cooling system of claim 3, wherein the HVAC parameter is at least one of:
- the saturated suction temperature of the evaporator coil; and
- a surface temperature of the evaporator coil.
5. The cooling system of claim 1, wherein the at least one sensor is at east one of:
- a second temperature sensor disposed in the conditioned space; and
- a flow meter disposed in the discharge air duct.
6. The cooling system of claim 5, wherein the HVAC parameter is at least one of:
- a discharge air temperature measured by the second temperature sensor; and
- a discharge air velocity measured by the flow meter.
7. The cooling system of claim 1, comprising an evaporator pressure regulator (“EPR”) fluidly coupled between the evaporator coil and the compressor, the EPR being electrically coupled to the HVAC controller.
8. The cooling system of claim 7, wherein, responsive to the determination that the HVAC parameter indicates frost formation on the evaporator coil, the HVAC controller is configured to signal the EPR to reduce flow of a refrigerant from the evaporator coil to the compressor thereby raising the saturated suction temperature of the evaporator coil.
9. The cooling system of claim 1, wherein, responsive to the determination that the HVAC parameter indicates frost formation on the evaporator coil, the HVAC controller is configured to signal the compressor to modulate a speed of the compressor thereby raising the saturated suction temperature of the evaporator coil.
10. The cooling system of claim 9, wherein the HVAC controller is configured to at least one of:
- reduce the speed of the compressor; and
- cycle the compressor between an activated state and a deactivated state.
11. A method for operating a refrigerated display case, the method comprising:
- measuring, by at least one sensor, an HVAC parameter;
- determining, by an HVAC controller electrically coupled to the at least one sensor, if the HVAC parameter indicates frost formation on an evaporator coil; and
- responsive to a determination that the 1-IVAC parameter indicates frost formation on the evaporator coil, signaling, by the HVAC controller, an evaporator pressure regulator (“EPR”) to reduce a flow of refrigerant from an evaporator coil to a compressor thereby raising a saturated suction temperature of the evaporator coil.
12. The method of claim 11, wherein:
- the at least one sensor is a first temperature sensor disposed proximate the evaporator coil; and
- the HVAC parameter is at least one of the saturated suction temperature of the evaporator coil and a surface temperature of the evaporator coil.
13. The method of claim 11, wherein:
- the at least one sensor is a second temperature sensor disposed in a conditioned space; and
- the HVAC parameter is a discharge air temperature.
14. The method of claim 11, wherein:
- the at least one sensor is a flow meter; and
- the HVAC parameter is a discharge air velocity.
15. A method for operating a refrigerated display case, the method comprising:
- measuring, by at least one sensor, an HVAC parameter;
- determining, by an HV AC controller electrically coupled to the at least one sensor, if the HVAC parameter indicates frost formation on an evaporator coil; and
- responsive to a determination that the HVAC parameter indicates frost formation on the evaporator coil, signaling, by the HVAC controller, a compressor to modulate a speed of the compressor thereby raising a saturated suction temperature of the evaporator coil.
16. The method of claim 15, wherein:
- the at least one sensor is a first temperature sensor disposed proximate the evaporator coil; and
- the HVAC parameter is at least one of the saturated suction temperature of the evaporator coil and a surface temperature of the evaporator coil.
17. The method of claim 15, wherein:
- the at least one sensor is a second temperature sensor disposed in a conditioned space; and
- the HVAC parameter is a discharge air temperature.
18. The method of claim 15, wherein:
- the at least one sensor is a flow meter; and
- the HVAC parameter is a discharge air velocity.
19. The method of claim 15, wherein responsive to the signaling the speed of the HVAC controller is reduced.
70. The method of claim 15, wherein, responsive to the signaling, the compressor is cycled between an activated state and a deactivated state.
Type: Application
Filed: May 8, 2019
Publication Date: Nov 12, 2020
Applicant: Heatcraft Refrigeration Products LLC (Richardson, TX)
Inventor: Fardis NAJAFIFARD (Decatur, GA)
Application Number: 16/406,431