GB2562495A

GB2562495A - Refrigeration system

Info

Publication number: GB2562495A
Application number: GB1707835.3A
Authority: GB
Inventors: Scott Franzen Nicholas; John Green Christopher; Knight Patrick
Original assignee: Arctic Circle Ltd
Current assignee: Arctic Circle Ltd
Priority date: 2017-05-16
Filing date: 2017-05-16
Publication date: 2018-11-21
Also published as: GB201707835D0

Abstract

A refrigeration system 10 comprising a refrigeration circuit 20 for receiving thermal energy from a thermal load and a ground source heat pump circuit 40 having at least one mode of operation to absorb thermal energy from the refrigeration circuit. The ground source heat pump circuit may comprise a ground loop circuit 60 installed beneath a car park. The system may allow the degree of absorption of thermal energy by the ground source heat pump circuit to be varied by altering operation of one or more of the refrigeration circuit and the ground source heat pump circuit. The heat pump circuit may transfer thermal energy to a heating system and/or from a cooling system. The refrigeration circuit and ground source heat pump circuit may be separate circuits where the system further comprises a refrigeration heat exchanger 30 for transferring thermal energy between the refrigeration circuit and the ground source heat pump circuit. The ground source heat pump circuit may comprise a heat pump circuit 50 and a separate ground loop circuit, the refrigeration heat exchanger transferring thermal energy between the refrigeration circuit and the ground loop circuit.

Description

(54) Title of the Invention: Refrigeration system

Abstract Title: Refrigeration system having a ground source heat pump circuit (57) A refrigeration system 10 comprising a refrigeration circuit 20 for receiving thermal energy from a thermal load and a ground source heat pump circuit 40 having at least one mode of operation to absorb thermal energy from the refrigeration circuit. The ground source heat pump circuit may comprise a ground loop circuit 60 installed beneath a car park. The system may allow the degree of absorption of thermal energy by the ground source heat pump circuit to be varied by altering operation of one or more of the refrigeration circuit and the ground source heat pump circuit. The heat pump circuit may transfer thermal energy to a heating system and/or from a cooling system. The refrigeration circuit and ground source heat pump circuit may be separate circuits where the system further comprises a refrigeration heat exchanger 30 for transferring thermal energy between the refrigeration circuit and the ground source heat pump circuit. The ground source heat pump circuit may comprise a heat pump circuit 50 and a separate ground loop circuit, the refrigeration heat exchanger transferring thermal energy between the refrigeration circuit and the ground loop circuit.

21A

1/3

ΙΑ

2/3

3/3

TITLE: REFRIGERATION SYSTEM

DESCRIPTION

The present invention relates to a refrigeration system, and particularly but not exclusively to a refrigeration system configured for use in a supermarket site.

Refrigeration devices such as refrigerated chillers and freezers are commonly used in supermarkets to store refrigerated and frozen produce.

Refrigeration devices typically achieve cooling of a thermal load by means of a vapour compression refrigeration cycle in which a refrigerant is first compressed in gaseous form, then condensed by an air-cooled condenser to release heat to ambient, and the resulting liquid refrigerant is then cooled by expansion and subsequently evaporated to absorb heat from the thermal load.

The present applicant has identified the need for an improved refrigeration system capable of providing additional gains in efficiency compared with refrigeration systems of the prior art.

In accordance with the present invention there is provided a refrigeration system comprising: a refrigeration circuit operative to receive thermal energy from a thermal load; and a ground source heat pump circuit operative in at least one mode of operation to absorb thermal energy from the refrigeration circuit.

In this way, a refrigeration system is provided in which heat extracted from a thermal load can either be rejected to ambient, used to replenish the heat extracted from the ground, or stored in the ground for use at a later time. Advantageously, the ability of the refrigeration system to reject heat at a temperature lower than ambient allows the refrigeration circuit to operate at an improved efficiency.

In one embodiment, the ground source heat pump circuit comprises a ground loop installed beneath an external hard surface (e.g. a road surface or paved area). In one particularly embodiment, the ground loop is installed beneath a car park (e.g. outside car park). Advantageously a car park may provide a significant area for a ground source loop and may be readily installed during construction of a site (e.g. construction of a supermarket or industrial site).

In one embodiment, the refrigeration circuit is one of a plurality of refrigeration circuits thermally coupled to the ground source heat pump circuit.

In one embodiment, the system is configured to allow the degree of absorption of thermal energy by the ground source heat pump circuit to be varied by altering operation of one or more of the refrigeration circuit and the ground source heat pump circuit. In one embodiment, the system is configured to vary the degree of absorption between maximum and minimum absorption levels (e.g. including levels therebetween).

In one embodiment, the heat pump circuit is operative to transfer thermal energy to a heating system and/or from a cooling system. In one embodiment, the heating system comprises an air handling unit operative to blow heated air. In one embodiment, the cooling system comprises an air handling unit operative to blow cooled air. In the case of a combined heating/cooling system a common air handling unit may be used for heating and cooling.

In one embodiment, the heating system and/or cooling system comprises a separate circuit to the ground source heat pump circuit.

In one embodiment, the refrigeration circuit and ground source heat pump circuit are separate circuits (e.g. refrigeration circuit comprising a first working fluid and a heat pump circuit comprising a second working fluid) and the system further comprises a refrigeration heat exchanger for transferring thermal energy' between the refrigeration circuit and the ground source heat pump circuit.

In one embodiment, the ground source heat pump circuit comprises a heat pump circuit and a separate ground loop circuit.

In one embodiment, the refrigeration heat exchanger is operative to transfer thermal energy between the refrigeration circuit and the ground loop circuit.

In one embodiment the ground loop circuit comprises a pump for circulating a fluid (e.g. liquid such as water or glycol).

In one embodiment, the refrigeration system comprises: a circuit for circulating a first working fluid; a compressor operative to compress and heat the first working fluid in a gaseous state; a condenser for condensing the heated first working fluid from a gaseous state to a liquid state; an expander operative to expand the first working fluid after exposure to the condenser; and an evaporator for receiving the first working fluid in a liquid state from the expander, the evaporator being operative to receive thermal energy from a thermal load and cause the first working fluid to evaporate to a gaseous state before the first working fluid is returned to the compressor.

In one embodiment, the refrigeration heat exchanger is configured to transfer thermal energy to the ground source heat pump circuit (e.g. ground loop circuit) at a point between the compressor and expander (e.g. between the condenser and the expander).

In one embodiment, the system is configured to vary flow of the first working fluid through the condenser relative to flow of the first working fluid through the refrigeration heat exchanger.

In one embodiment, the system comprises a flow splitter (e.g. condenser bypass) operative to allow at least a portion of the flow of the first working fluid bound for the refrigeration heat exchanger to bypass the condenser.

In one embodiment, the condenser and refrigeration heat exchanger are connected in series.

In one embodiment, the system is configurable to allow the proportion of flow through the condenser bypass to be varied relative to the flow through the condenser.

In one embodiment, the system is configured to allow the flow through the ground loop circuit to be varied (e.g. by varying pump speed or switching off the pump). In this way, the transfer of heat via the refrigeration heat exchanger may be varied regardless of the operation of the refrigeration circuit.

In one embodiment, the heat pump circuit comprises: a circuit for circulating a second working fluid; a first heat pump heat exchanger operative to transfer thermal energy between the ground (e.g. ground loop circuit) and the second working fluid; a compressor operative to compress and heat the second working fluid; a second heat pump heat exchanger operative to transfer thermal energy between the heat pump circuit and the heating system and/or cooling system; and an expander operative to expand the second working fluid after exposure to the second heat pump heat exchanger.

In one embodiment, the heat pump circuit is configured to operate a cycle in which the second working fluid is evaporated in the first heat exchanger and condenses in the second heat pump heat exchanger.

In one embodiment, the heat pump circuit is reversible.

In a heating mode the heat pump circuit is operative to: compress the working fluid after receiving thermal energy from the ground loop circuit via the first heat pump heat exchanger; transfer thermal energy to the heating system via the second heat pump heat exchanger; and expand the working fluid after exposure to the second heat pump heat exchanger. In the ground loop circuit the flow is initially cooled by exposure to the first heat pump and then receives thermal energy from the refrigeration circuit as it flows through the refrigeration heat exchanger.

In a cooling mode the heat pump circuit is operative to: compress the working fluid after exposure to the second heat pump heat exchanger; transfer thermal energy to the ground (e.g. ground loop circuit) via the first heat pump heat exchanger; expand the working fluid after exposure to the first heat pump heat exchanger; and receive thermal energy from the cooling system via the second heat pump heat exchanger. In the ground loop circuit the flow is warmed by exposure to the first heat pump heat exchanger and then transfers thermal energy to ground before receiving thermal energy from the refrigeration circuit via the refrigeration heat exchanger.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 is a schematic view of a refrigeration system with integrated ground source heat pump in accordance with a first embodiment of the present invention;

Figure 2 is a schematic view of a refrigeration system with a reversible integrated ground source heat pump in accordance with a second embodiment of the present invention in a heating mode of operation; and

Figure 3 is a schematic view of the refrigeration system of Figure 2 in a cooling mode of operation.

Figure 1 shows a refrigeration system 10 comprising a refrigeration circuit 20 defining a first circuit 21 (with a solenoid control valve 21 A) for recirculating a first working fluid and a ground source heat pump (GSHP) circuit 40 thermally coupled to a combined heating/cooling system 80.

As illustrated, refrigeration circuit 20 comprises: a compressor 22 operative to compress and heat a first working fluid in a gaseous state; a condenser 24 for condensing the heated first working fluid from a gaseous state to a liquid state; an expander 26 operative to expand the first working fluid after exposure to condenser 24; and an evaporator 28 for receiving the first working fluid in a liquid state from expander 26, evaporator 28 being operative to receive thermal energy from a thermal load (e.g. refrigerator or freezer load) and cause the first working fluid to evaporate to a gaseous state before the first working fluid is returned to compressor 22. In addition, refrigeration circuit 20 includes a refrigeration heat exchanger (e.g. plate heat exchanger) 30 positioned between condenser 24 and expander 26 and in series with condenser 24, and a cooling control stage 32 comprising condenser bypass 34 operative to allow at least a portion of flow of the first working fluid to bypass condenser 24 before reaching refrigeration heat exchanger 30, a three-way valve 36 and a non-retum valve 38.

Ground source heat pump circuit 40 comprises: a heat pump circuit 50 defining a second circuit 51 (with a solenoid control valve 51 A) for recirculating a second working fluid flow; and a separate ground loop circuit 60 defining a third circuit 61 with a pump 62 for recirculating a water/glycol flow through a series of ground loops 64.

Heat pump circuit 50 comprises: a first heat pump heat exchanger (e.g. plate heat exchanger) 52 operative to transfer thermal energy between ground loop circuit 60 and the second working fluid; a compressor 54 operative to compress and heat the second working fluid; a second heat pump heat exchanger (e.g. plate heat exchanger) 56 operative to transfer thermal energy between the heat pump circuit 50 and the heating/cooling system 80; and an expander 58 operative to expand the second working fluid after exposure to the second heat pump heat exchanger 56.

Combined heating/cooling system 80 defines a fourth circuit 81 with a pump 82 for recirculating a fluid flow between second heat pump heat exchanger 56 and air handling unit 84.

In use refrigeration circuit 20 operates in a conventional manner to cool the thermal load. However, rather than rejecting heat solely by exposure of the first working fluid to condenser 24, the first working fluid additionally passes through refrigeration heat exchanger 30 in order to transfer heat to the (typically much cooler) flow in ground loop circuit 60 which is chilled via second heat pump heat exchanger 56.

First heat pump heat exchanger 52 operates as an evaporator heat exchanger with heat from ground loop circuit 60 causing evaporation of the second working fluid. Second heat pump heat exchanger 56 operates as a condenser heat exchanger with heat from the second working fluid being transferred to heating/cooling system 80.

A controller (not shown) is used change operation of refrigeration system 10 between different modes.

In a first mode of operation three-way valve 36 is set to fully bypass condenser 24 whereby the full flow of the first working fluid is cooled and condensed by exposure to refrigeration heat exchanger 30. In this way, all of the rejected heat from the refrigeration circuit is rejected to ground (e.g. for heat storage for later use, to replenish heat already taken from ground, and/or to increase efficiency of the refrigeration system in high ambient conditions).

In a second mode of operation three-way valve 36 is set to partially bypass condenser 24, whereby: a first portion of the flow of the first working fluid is cooled by condenser 24 and then further cooled by exposure to refrigeration heat exchanger 30; and a second portion of the flow of the first working fluid is cooled solely by exposure to refrigeration heat exchanger 30.

In a third mode of operation three-way valve 36 is set to allow the full flow of the first working fluid to pass through condenser 24 prior to being further cooled by exposure to refrigeration heat exchanger 30.

In the second and third modes some of the rejected heat from the refrigeration circuit is rejected at condenser 24 and some is rejected to ground. Depending upon how the system is configured, operation in the second and third modes may involve: a) the first working fluid condensing to ambient in condenser 24 and then subcooling in refrigeration heat exchanger 30; or b) de-superheating of the first working fluid to ambient in condenser 24 and then condensing in refrigeration heat exchanger 30. The latter may be useful for keeping C0₂ (R744) refrigeration systems permanently subcritical in high ambient conditions.

In this way, three-way valve 36 and condenser bypass 34 allow refrigeration heat exchanger 30 to act as either a condenser or as a heat exchanger for subcooling of the first working fluid. Advantageously subcooling and/or lowering the condensing temperature of the refrigeration circuit 20 provides a significant energy benefit by enhancing the efficiency of the refrigeration circuit.

In a fourth mode of operation the ground source heat pump circuit 40 is configured so that none of the heat from refrigeration circuit 20 is rejected to ground (eg. by switching off ground loop circuit pump 62 or altering the flow through ground loop circuit 60 to bypass refrigeration heat exchanger 30 altogether). This mode may be useful where the ground temperature has reached a maximum permissible temperature or in low ambient conditions when it is more efficient to reject heat to ambient.

Figures 2 and 3 show a refrigeration system 10’ based on refrigeration system 10 (with features in common are labelled accordingly) in which ground source heat pump circuit 40’ is reversible by virtue of a heat pump reversing valve 90 and replacement of the single expander 58 of heat pump circuit 50 by a pair of expanders 58A, 58B each associated with directional expander bypass lines 92A, 92B.

Figure 2 shows refrigeration system 10’ in a heating mode of operation (with heating/cooling system 80’ operating to heat the building in which refrigeration system 10’ is installed) in which heat pump circuit 50’ is operative to: compress the second working fluid after receiving thermal energy from ground loop circuit 60’ via first heat pump heat exchanger 52’; transfer thermal energy to heating/cooling system 80’ via second heat pump heat exchanger 56’; and expand the second working fluid after exposure to second heat pump heat exchanger 56’. At the same time, ground loop circuit 60’ is cooled by exposure to first heat pump heat exchanger 52’ and then receives thermal energy from the refrigeration circuit 20’ via refrigeration heat exchanger 30’.

Figure 3 shows refrigeration system 10’ in a cooling mode of operation (with heating/cooling system 80’ operating to cool the building in which refrigeration system 10’ is installed) in which heat pump reversing valve 90 is set to reverse flow from compressor 54’. In this mode, heat pump circuit 80’ is operative to: compress the second working fluid after exposure to second heat pump heat exchanger 56’; transfer thermal energy to ground loop circuit 60’ via first heat pump heat exchanger 52’; expand the second working fluid after exposure to first heat pump heat exchanger 52’; and receive thermal energy from heating/cooling system 80’ via second heat pump heat exchanger 56’. At the same time, ground loop circuit pump 62’ is set in reverse so that the flow of water/glycol in ground loop circuit 60’ is warmed by exposure to first heat pump heat exchanger 52’ and transfers the absorbed thermal energy to ground before receiving thermal energy from refrigeration circuit 20’ via refrigeration heat exchanger 30’.

Claims

1. A refrigeration system comprising:

a refrigeration circuit operative to receive thermal energy from a thermal load; and a ground source heat pump circuit operative in at least one mode of operation to absorb thermal energy from the refrigeration circuit.

2. A refrigeration system according to claim 1, wherein the ground source heat pump circuit comprises a ground loop installed beneath a car park.

3. A refrigeration system according to claim 1 or claim 2, wherein the refrigeration circuit is one of a plurality of refrigeration circuits thermally coupled to the ground source heat pump circuit.

4. A refrigeration system according to any of the preceding claims, wherein the system is configured to allow the degree of absorption of thermal energy by the ground source heat pump circuit to be varied by altering operation of one or more of the refrigeration circuit and the ground source heat pump circuit.

5. A refrigeration system according to any of the preceding claims, wherein the heat pump circuit is operative to transfer thermal energy to a heating system and/or from a cooling system.

6. A refrigeration system according to claim 5, wherein the refrigeration circuit and ground source heat pump circuit are separate circuits and the system further comprises a refrigeration heat exchanger for transferring thermal energy between the refrigeration circuit and the ground source heat pump circuit.

7. A refrigeration system according to claim 6, wherein:

the ground source heat pump circuit comprises a heat pump circuit and a separate ground loop circuit; and the refrigeration heat exchanger is operative to transfer thermal energy between the refrigeration circuit and the ground loop circuit.

8. A refrigeration system according to claim 7, wherein the ground loop circuit comprises a pump for circulating a fluid.

9. A refrigeration system according to claim 7 or claim 8, wherein the refrigeration system comprises:

a circuit for circulating a first working fluid;

a compressor operative to compress and heat the first working fluid in a gaseous state;

a condenser for condensing the heated first working fluid from a gaseous state to a liquid state;

an expander operative to expand the first working fluid after exposure to the condenser; and an evaporator for receiving the first working fluid in a liquid state from the expander, the evaporator being operative to receive thermal energy from a thermal load and cause the first working fluid to evaporate to a gaseous state before the first working fluid is returned to the compressor;

wherein the refrigeration heat exchanger is configured to transfer thermal energy to the ground source heat pump circuit at a point between the compressor and expander.

10. A refrigeration system according to claim 9, wherein the system is configured to vary flow of the first working fluid through the condenser relative to flow of the first working fluid through the refrigeration heat exchanger.

11. A refrigeration system according to claim 10, wherein the system comprises a flow splitter operative to allow at least a portion of the flow of the first working fluid bound for the refrigeration heat exchanger to bypass the condenser.

12. A refrigeration system according to claim 11, wherein the condenser and refrigeration heat exchanger are connected in series.

13. A refrigeration system according to any of claims 9-12, wherein the heat pump circuit comprises:

a circuit for circulating a second working fluid;

a first heat pump heat exchanger operative to transfer thermal energy between the ground and the second working fluid;

a compressor operative to compress and heat the second working fluid;

a second heat pump heat exchanger operative to transfer thermal energy between the heat pump circuit and the heating system and/or cooling system; and an expander operative to expand the second working fluid after exposure to the second heat pump heat exchanger.

14. A refrigeration system according to claim 13, wherein the heat pump circuit is reversible.

15. A refrigeration system according to claim 14, wherein in a heating mode the heat pump circuit is operative to:

compress the working fluid after receiving thermal energy from the ground loop circuit via the first heat pump heat exchanger;

transfer thermal energy to the heating system via the second heat pump heat exchanger; and expand the working fluid after exposure to the second heat pump heat exchanger.

16. A refrigeration system according to claim 14, wherein in a cooling mode the heat pump circuit is operative to:

compress the working fluid after exposure to the second heat pump heat exchanger; transfer thermal energy to the ground via the first heat pump heat exchanger;

expand the working fluid after exposure to the first heat pump heat exchanger; and receive thermal energy from the cooling system via the second heat pump heat exchanger.

Intellectual

Property Office

Application No: GB1707835.3 Examiner: Ms Janet Kohler