EP4137755A1

EP4137755A1 - Enhanced economizer operation in a chiller

Info

Publication number: EP4137755A1
Application number: EP22190720.7A
Authority: EP
Inventors: Biswajit Mitra; Hsihua Li
Original assignee: Carrier Corp
Current assignee: Carrier Corp
Priority date: 2021-08-21
Filing date: 2022-08-17
Publication date: 2023-02-22
Also published as: US20230053834A1; CN115711497A

Abstract

A refrigeration system 20 includes a compressor 22, a heat rejecting heat exchanger 24, an expansion device 28, and a heat absorbing heat exchanger 30 fluidly connected to form a closed loop through which a refrigerant is configured to circulate. An economizer heat exchanger 30 is located downstream from an outlet of the heat rejecting heat exchanger 24 and upstream from the expansion device 28 relative to a flow of the refrigerant. The economizer heat exchanger 30 has a main flow path 36 and an economizer flow path 38 formed therein. All liquid refrigerant provided at an outlet of the heat rejecting heat exchanger 24 is provided to the main flow path 36.

Description

BACKGROUND

Exemplary embodiments of the present disclosure relate to refrigeration systems, and more particularly, to an economizer heat exchanger for use in a chilled refrigeration system.
One of the most common technologies in use for residential and commercial refrigeration and air conditioning is the vapor compression refrigerant heat transfer loop. These loops typically circulate a refrigerant having appropriate thermodynamic properties through a loop that comprises a compressor, a heat rejection heat exchanger (i.e., heat exchanger condenser), an expansion device and a heat absorption heat exchanger (i.e., heat exchanger evaporator). Vapor compression refrigerant loops effectively provide cooling and refrigeration in a variety of settings, and in some situations can be run in reverse as a heat pump.
Existing refrigeration systems sometimes include an economizer. An economizer is a refrigerant-refrigerant heat exchanger having a main pass and an economizer pass. At a location upstream from the economizer, the refrigerant is separated and provided to the main pass and the economizer pass in parallel. However, in applications where the refrigeration system additionally includes a subcooler, there is a possibility that the refrigerant provided to the economizer may include refrigerant vapor bypass from the condenser, which would negatively impact the operation of the expansion device, and therefore the efficiency of the refrigeration system.

BRIEF DESCRIPTION

According to an aspect, a refrigeration system includes a compressor, a heat rejecting heat exchanger, an expansion device, and a heat absorbing heat exchanger fluidly connected to form a closed loop through which a refrigerant is configured to circulate. An economizer heat exchanger is located downstream from an outlet of the heat rejecting heat exchanger and upstream from the expansion device relative to a flow of the refrigerant. The economizer heat exchanger has a main flow path and an economizer flow path formed therein. All liquid refrigerant provided at an outlet of the heat rejecting heat exchanger is provided to the main flow path.
A portion of the refrigerant may be provided to the main flow path and the economizer flow path in series.
The refrigeration system may further comprise a subcooler arranged directly downstream from and in fluid communication with the heat rejecting heat exchanger, wherein an outlet of the subcooler may be fluidly connected to an inlet of the main flow path.
All the liquid refrigerant provided at the outlet of the subcooler may be provided to the main flow path.
The expansion device and the economizer flow path may be arranged in parallel relative to an outlet of the main flow path.
The compressor may include a primary suction inlet and an economizer suction inlet, the heat absorbing heat exchanger being fluidly connected to the primary suction inlet, and the economizer flow path being fluidly connected to the economizer suction inlet.
The refrigeration system may further comprise an economizer expansion device arranged downstream from the outlet of the main flow path and directly upstream from the economizer flow path.
An inlet of the main flow path may be arranged at a first side of the economizer heat exchanger and an inlet of the economizer flow path may be arranged at a second, opposite side of the economizer heat exchanger.
According to an aspect, a refrigeration system includes a compressor, a heat rejecting heat exchanger, an expansion device, and a heat absorbing heat exchanger fluidly connected to form a closed loop through which a refrigerant is configured to circulate. An economizer heat exchanger is located downstream from an outlet of the heat rejecting heat exchanger and upstream from the expansion device relative to a flow of the refrigerant. The economizer heat exchanger has a main flow path and an economizer flow path formed therein. An inlet of the economizer flow path is fluidly coupled to an outlet of the main flow path such that a portion of the refrigerant is provided to the main flow path and the economizer flow path in series.
All liquid refrigerant output from the heat rejecting heat exchanger may be provided to the main flow path.
The expansion device and the economizer flow path may be arranged in parallel relative to the outlet of the main flow path.
The compressor may include a primary suction inlet and an economizer suction inlet, the heat absorbing heat exchanger being fluidly connected to the primary suction inlet, and the economizer flow path being fluidly connected to the economizer suction inlet.
The refrigeration system may comprise an economizer expansion device arranged downstream from the outlet of the main flow path and directly upstream from the economizer flow path.
The refrigeration system may comprise a subcooler arranged directly downstream from and in fluid communication with the heat rejecting heat exchanger, wherein an outlet of the subcooler may be fluidly connected to an inlet of the main flow path.
All of the liquid refrigerant provided at the outlet of the subcooler may be provided to the main flow path.
An inlet of the main flow path may be arranged at a first side of the economizer heat exchanger and the inlet of the economizer flow path may be arranged at a second, opposite side of the economizer heat exchanger.
According to an aspect, a method of operating a refrigeration system includes condensing and cooling a refrigerant, further cooling the refrigerant within a main flow path of an economizer heat exchanger, separating the refrigerant at an outlet of the main flow path into a first portion and a second portion, and heating the second portion of the refrigerant provided within an economizer flow path of the economizer heat exchanger.
The condensing and cooling may occur within a subcooler and all liquid refrigerant at the outlet of the subcooler may be provided to the main flow path.
The method may further comprise lowering an enthalpy of the second portion of the refrigerant, wherein lowering the enthalpy may occur prior to heating the second portion of the refrigerant within the economizer flow path.
The method may further comprise providing the first portion of the refrigerant at the outlet of the main flow path to an expansion device and a heat absorbing heat exchanger in series.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way. With reference to the accompanying drawing, like elements are numbered alike.
Certain exemplary embodiments will now be described in greater detail by way of example only and with reference to the accompanying drawing in which:
Fig. 1 (the Figure) is a schematic diagram of an exemplary refrigeration system.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosed apparatus and method are presented herein by way of exemplification and not limitation with reference to the Figure.
With reference now to the Figure, a schematic diagram representing a refrigeration circuit of a refrigeration system 20 is illustrated. As shown, the refrigeration system 20 includes a compressor 22, a heat rejecting heat exchanger 24, an economizer heat exchanger 26, an expansion device 28, and a heat absorbing heat exchanger 30 arranged in fluid communication to form a closed loop circuit. Those of skill in the art will appreciate that the schematics and configuration shown are merely an example of a refrigeration system and are not intended to be limiting. For example, other components or configurations are possible with departing from the scope of the present disclosure. For example, refrigeration systems may include controllers, receivers, filters, dryers, additional valves, heat exchangers, sensors, indicators, etc. without departing from the scope of the present disclosure.
In operation, high temperature, high pressure refrigerant vapor R is configured to exit from a discharge port 32 of the compressor 22 and is provided to the heat rejecting heat exchanger (i.e., a condenser or a gas cooler). In an embodiment, the heat rejecting heat exchanger 24 is a shell and tube heat exchanger. In such embodiments, a secondary fluid, such as water for example, is configured to flow through the interior of the tubes and the refrigerant may be configured to flow over the outside of the tubes, through the shell. By removing latent heat from the refrigerant within the heat rejecting heat exchanger 24, the refrigerant condenses to a high pressure, high temperature liquid.
In the illustrated, non-limiting embodiment, all of the refrigerant output from the heat rejecting heat exchanger 24 is configured to flow to a subcooler 34, which increases the refrigerant subcooling. The subcooler 34 may be positioned adjacent to or integrally formed with the heat rejection heat exchanger such that within the subcooler 34, the water flowing through the tubes therein is configured to further cool the refrigerant flowing around the tubes. However, embodiments where the fluid used to cool the refrigerant within the subcooler 34 is distinct from the fluid used to cool the refrigerant within the heat rejecting heat exchanger 24 are also contemplated herein. Further, embodiments where the subcooler 34 is a separate from the heat rejection heat exchanger 24 are also within the scope of the disclosure. In such embodiments, the configuration of the subcooler 34 may be different than the configuration of the heat rejection heat exchanger 24. For example, other suitable types of configurations of the subcooler include a refrigerant to air heat exchanger.
Located downstream from the subcooler 34 is the economizer heat exchanger 26. Although the economizer heat exchanger is illustrated as being located directly downstream from the outlet of the subcooler 34, it should be understood that embodiments where one or more other components of the refrigeration system are located between the subcooler 34 and the economizer heat exchanger 26 are also contemplated herein. In an embodiment, the economizer heat exchanger 26 is a brazed plated fin heat exchanger. However, other suitable types of heat exchangers are also within the scope of the disclosure. Further, the economizer heat exchanger 26 is a refrigerant-refrigerant heat exchanger and therefore has a plurality of distinct fluid flow paths formed therein. In the illustrated, non-limiting embodiment, the economizer heat exchanger 26 has a first flow path and a second flow path, represented at 36 and 38, respectively.
In an embodiment, the outlet of the subcooler 34 is fluidly coupled to an inlet of the first flow path 36, also referred to herein as the "main flow path", of the economizer heat exchanger 26. Although any remaining refrigerant vapor within the subcooler 34 may be returned to the compressor 22, the substantially entire flow of liquid refrigerant provided at the outlet of the subcooler 34 is delivered to the main flow path 36 of the economizer heat exchanger 26. Although the main flow path 36 is illustrated as a single pass through the economizer heat exchanger 26, it should be understood that in other embodiment the main flow path 36 may include a plurality of passes through the economizer heat exchanger 26.
At the outlet of the main flow path 36 of the economizer heat exchanger 26, the flow of refrigerant is divided into a first portion R1 and a second portion R2 configured to flow in parallel to separate components of the refrigeration system. The first portion R1 of the refrigerant provided at the outlet of the main flow path 36 of the economizer heat exchanger 26 is configured to flow to the expansion device 28. Located downstream from the expansion device 28 is the heat absorption heat exchanger (i.e., an evaporator) 30. In the illustrated, non-limiting embodiment, the heat absorption heat exchanger is a shell and tube heat exchanger. In such embodiments, a secondary fluid, such as water for example, is configured to flow through the interior of the tubes and the refrigerant may be configured to flow over the outside of the tubes, through the shell. The resulting cooled water may then be used to condition an air flow to be delivered to an area of a building or another location to be conditioned by the refrigeration system. However, embodiments where the heat absorbing heat exchanger 30 is a refrigerant to air heat exchanger such that the heat absorbing heat exchanger 30 directly conditions the air flow to be provided to an area to be conditioned are also within the scope of the disclosure.
The first portion R1 of refrigerant output from the heat absorbing heat exchanger 30 is provided via a first compressor inlet path to a primary suction inlet 40 of the compressor 22. Accordingly, the fluid loop of the first portion R1 of the refrigerant includes the compressor 22, heat rejecting heat exchanger 24, subcooler 34, main flow path 36 of the economizer heat exchanger 26, expansion device 28, and heat absorbing heat exchanger 30.
An economizer expansion device 42 is arranged downstream from the outlet of the main flow path 36 of the economizer heat exchanger 26, and upstream from the second flow path 38, also referred to herein as the "economizer flow path" of the economizer heat exchanger 26. Accordingly, the second portion R2 of the refrigerant is provided to the economizer expansion device 42 which serves to expand and cool the second portion R2 of refrigerant. From the economizer expansion device 42, the second portion of the refrigerant is provided to an inlet of the economizer flow path 38 of the economizer heat exchanger 26. Accordingly, the second portion R2 of the refrigerant is configured to flow through the main flow path 36 and the economizer flow path 38 of the economizer heat exchanger 26 in series.
In the illustrated, non-limiting embodiment, the inlet of the main flow path 36 and the inlet of the economizer flow path 38 are arranged at opposite sides or ends of the economizer heat exchanger 26. However, in other embodiments, it should be understood that the inlets of both flow paths could be arranged at the same side of the economizer heat exchanger 26 or at adjacent sides of the economizer heat exchanger 26. Similarly, the outlets of both the main flow path 36 and the inlet of the economizer flow path 38 may be arranged at opposite sides, the same side, or adjacent sides depending on the desired flow configuration of the economizer heat exchanger 26. Although the economizer flow path 38 is illustrated as a single pass, it should be understood that in some embodiments, the economizer flow path 38 may include a plurality of passes through the economizer heat exchanger 26.
Within the economizer flow path 38, the second portion R2 of the refrigerant is configured to absorb heat from the refrigerant R within the main flow path 36, thereby cooling the refrigerant R within the main flow path 36. As a result of this heat transfer, the second portion R2 of the refrigerant within the economizer flow path 38 may become a vapor. From the outlet of the economizer flow path 38, the second portion of the refrigerant is provided to an economizer suction inlet 44 located at an in intermediate portion of the compressor 22. Accordingly, the second portion R2 of the refrigerant bypasses the expansion device 28 and the heat absorbing heat exchanger 30 of the refrigeration system 20. Within the compressor 22 the first portion R1 and the second portion R2 of refrigerant are mixed before being provided to the discharge port 32 to repeat the cycle. Accordingly, the fluid loop of the second portion R2 of the refrigerant includes the compressor 22, heat rejecting heat exchanger 24, subcooler 34, main flow path 36 of the economizer heat exchanger 26, economizer expansion device 42, and economizer flow path 3 8 of the economizer heat exchanger 26.
By arranging the economizer flow path 38 in series with and downstream from the main flow path 36 of the economizer heat exchanger 26, the piping configuration of the refrigeration system 20 is simplified. Further, such a configuration ensures that the second portion R2 of the refrigerant provided to the economizer flow path 38 has a lower enthalpy and amount of vapor therein, thereby enhancing operation of the economizer heat exchanger 26 and the refrigeration system 20.
The term "about" is intended to include the degree of error associated with measurement of the particular quantity based upon the equipment available at the time of filing the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present disclosure. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and/or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, element components, and/or groups thereof.
While the present disclosure has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the present disclosure without departing from the essential scope thereof. Therefore, it is intended that the present disclosure not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this present disclosure, but that the present disclosure will include all embodiments falling within the scope of the claims.

Claims

A refrigeration system (20) comprising:
a compressor (22), a heat rejecting heat exchanger (24), an expansion device (28), and a heat absorbing heat exchanger (30) fluidly connected to form a closed loop through which a refrigerant is configured to circulate;

an economizer heat exchanger (30) located downstream from an outlet of the heat rejecting heat exchanger and upstream from the expansion device (28) relative to a flow of the refrigerant, the economizer heat exchanger (30) having a main flow path (36) and an economizer flow path (38) formed therein, wherein:
all liquid refrigerant provided at an outlet of the heat rejecting heat exchanger (24) is provided to the main flow path (36); or

an inlet of the economizer flow path (38) is fluidly coupled to an outlet of the main flow path (36) such that a portion of the refrigerant is provided to the main flow path (36) and the economizer flow path (38) in series.
The refrigeration system (20) of claim 1, wherein a portion of the refrigerant is provided to the main flow path (36) and the economizer flow path (38) in series.
The refrigeration system (20) of claim 1 or 2, further comprising a subcooler (34) arranged directly downstream from and in fluid communication with the heat rejecting heat exchanger (24), wherein an outlet of the subcooler (34) is fluidly connected to an inlet of the main flow path (36).
The refrigeration system (20) of claim 3, wherein all the liquid refrigerant provided at the outlet of the subcooler (34) is provided to the main flow path (36).
The refrigeration system (20) of any preceding claim, wherein the expansion device (28) and the economizer flow path (38) are arranged in parallel relative to an outlet of the main flow path (36).
The refrigeration system (20) of claim 5, wherein the compressor (22) includes a primary suction inlet (40) and an economizer suction inlet, the heat absorbing heat exchanger (30) being fluidly connected to the primary suction inlet (40) and the economizer flow path (38) being fluidly connected to the economizer suction inlet.
The refrigeration system (20) of claim 5 or 6, further comprising an economizer expansion device (42) arranged downstream from the outlet of the main flow path (36) and directly upstream from the economizer flow path (38).
The refrigeration system (20) of any preceding claim, wherein an inlet of the main flow path (36) is arranged at a first side of the economizer heat exchanger (30) and an inlet of the economizer flow path (38) is arranged at a second, opposite side of the economizer heat exchanger (30).
The refrigeration system (20) of any preceding claim, wherein all liquid refrigerant output from the heat rejecting heat exchanger (24) is provided to the main flow path (36).
A method of operating a refrigeration system (20), the method comprising:
condensing and cooling a refrigerant;

further cooling the refrigerant within a main flow path (36) of an economizer heat exchanger (30);

separating the refrigerant at an outlet of the main flow path (36) into a first portion and a second portion; and

heating the second portion of the refrigerant provided within an economizer flow path (38) of the economizer heat exchanger (30).
The method of claim 10, wherein the condensing and cooling occurs within a subcooler (34) and all liquid refrigerant at the outlet of the subcooler (34) is provided to the main flow path (36).
The method of claim 10 or 11, further comprising lowering an enthalpy of the second portion of the refrigerant, wherein lowering the enthalpy occurs prior to heating the second portion of the refrigerant within the economizer flow path (38).
The method of claim 10, 11 or 12, further comprising providing the first portion of the refrigerant at the outlet of the main flow path (36) to an expansion device (28) and a heat absorbing heat exchanger (30) in series.