GB2491582A

GB2491582A - Energy Recovery System

Info

Publication number: GB2491582A
Application number: GB1109397.8A
Authority: GB
Inventors: Gareth Neil Holden
Original assignee: EXCALIBUR Ltd LPA
Current assignee: EXCALIBUR Ltd LPA
Priority date: 2011-06-06
Filing date: 2011-06-06
Publication date: 2012-12-12
Anticipated expiration: 2031-06-06
Also published as: GB201109397D0; GB2491582B

Abstract

An energy recovery system 13 for a refrigeration system 1 has a heat exchanger array comprising at least a first heat exchanger 15, a second heat exchanger 17, and a heater 19 for heating a heat transfer fluid. The heater is fluidly coupled between the first heat exchanger and the second heat exchanger, and the first heat exchanger draws heat from the refrigerant and outputs heated heat transfer fluid via the heater to the second heat exchanger for further heating. The heater further heats the heated heat transfer fluid output from the first heat exchanger en-route to the second heat exchanger. The heater may be a solar heater, a boiler, or the hot side of a heat pump.

Description

ENERGY RECOVERY SYSTEM

Field

This invention relates to energy recovery systems.

In one illustrative implementation the teachings of the invention are embodied in a system for recovering energy from a thermodynamic heat transfer system, such as a refrigeration system. lt will be appreciated, however, that this implementation is merely illustrative of the teachings of the present invention, and hence that the following description should not be read as being a limitation of the scope of the present invention.

Background

In certain commercial enterprises, such as the meat processing industry for example, it is commonplace for an enterprise to have a need for a refrigeration system (for example for storing meat products) as well as a system for providing hot water that can be used for tasks such as washing down surfaces on which meat products have been prepared.

In such circumstances it is usual for the enterprise concerned to install and operate a dedicated refrigeration system and a separate dedicated heating system, often in the form of one or more boilers that are configured to heat mains water to temperatures of 50 degrees or more, typically around 65 degrees centigrade.

Whilst modern boilers are comparatively efficient devices, fuel for those boilers remains expensive and it appears that it will continue to became yet mare expensive as time goes by. As a consequence, the operating costs of such boilers tend to constitute a significant proportion of the operating costs of the enterprise as a whole -to say nothing of the environmental consequences of using relatively large amounts of fossil fuels, both in terms of the finite nature of such fuels and the C02 generated when they are burnt.

In a similar fashion, a typical commercial refrigeration system will require significant amounts of energy to operate. Furthermore, a typical refrigeration system on a commercial scale will employ relatively large condensers that function to remove heat from the refrigerant circulating through the refrigeration system. Such condensers typicafly comprise a heat exchanger (such as a vaned radiator) and a means, such as a bank of fans, for blowing or drawing air (at ambient temperature) over the heat exchanger. Heat from the refrigerant circulating through the refrigeration system is drawn from the vaned radiator and warms the air as it is blown or drawn over the radiator. Once warmed, the air (which is now significantly warmer than the ambient air) is vented to atmosphere.

As will be appreciated, in a typical commercial refrigeration system a significant amount of heat is drawn from the refrigerant in the condenser, and clearly it would be advantageous if the amount of heat energy that is typically lost to atmosphere could be reduced without impairing the proper operation of the refrigeration system. lt would also be advantageous if an enterprise's reliance on boilers could be reduced, and it would be particularly advantageous if each of these goals could be simultaneously achieved.

The present invention has been formulated with the foregoing in mind.

Summary

In one presently preferred embodiment of the present invention there is provided an energy recovery system for a refrigeration system, the energy recovery system comprising: a heat exchanger array comprising at least a first and a second heat exchanger, and a heater for heating a heat transfer fluid, said heater being fluidly coupled to said first heat exchanger for the receipt of heat transfer fluid therefrom, and to said second heat exchanger for the supply of heat transfer fluid thereto; said energy recovery system being configured so that, when installed in a said refrigeration system: (i) said first heat exchanger draws heat from said refrigerant and outputs heated heat transfer fluid; (ii) said heater further heats the heated heat transfer fluid output from said first heat exchanger, and (iii) said second heat exchanger further heats the heat transfer fluid output from said heater An advantage of this arrangement is that energy (typically heat) that would otherwise be lost to atmosphere through the condenser of the refrigeration system can be captured and used to heat a heat transfer fluid. Where the heat transfer fluid is water, one consequence of this is that an organisation who has installed such a system can reduce the extent to which they need to run boilers to provide a supply of hot water.

Other features, aspects, advantages and aims of arrangements embodying the teachings of the invention will be apparent from the detailed description provided below.

Brief Description of the Drawin_gs

Various aspects of the teachings of the present invention, and arrangements embodying those teachings, will hereafter be described by way of illustrative example with reference to the accompanying drawings, in which: Fig. I is a schematic representation of an illustrative energy recovery system that embodies the teachings of the invention; and Fig. 2 is a schematic representation of another energy recovery system that also embodies the teachings of the invention.

pçg_Deçripqq In the following detailed description the teachings of the present invention will be described with particular reference to an illustrative refrigeration system, but it should be noted -unless otherwise specifically indicated -that the refrigeration system described does not form part of the teachings of the present invention, and further that the teachings of the present invention may be employed with other thermodynamic or heat transfer systems than the ones hereafter described.

Referring now to Fig. 1, there is depicted a schematic representation of an illustrative energy recovery system that functions in conjunction with a traditional refrigeration system 1.

The refrigeration system 1 comprises a receiver 3 that is fluidly coupled, via an expansion valve 5, to an evaporator 7. The evaporator 7 is fluidly coupled to a compressor 9, and the compressor is fluidly coupled to a condenser 11 that is in turn fluidly coupled to the aforementioned receiver 3.

As will be appreciated by persons skilled in the art, the aforementioned refrigeration system operates as follows: low temperature, low pressure gaseous refrigerant is compressed by the compressor 9 to form a hot, high pressure gaseous refrigerant that condenses in the condenser 11 to form a lower temperature, high pressure liquid refrigerant that flows to the receiver 3. The high pressure liquid refrigerant then flows from the receiver 3 to the expansion valve 5, whereupon the high pressure liquid refrigerant boils to form a low temperature, low pressure gaseous refrigerant that flows through the evaporator 7 and cools the surrounding atmosphere before being drawn into the compressor 9.

As mentioned above, in a traditional system, a significant amount of energy -in the form of heat -is extracted by the condenser 11 and lost to atmosphere. ln accordance with the teachings of the present invention, an energy recovery system 13 is employed to recover at least a proportion of this heat that would -in the absence of the recovery system -otherwise be lost.

In this embodiment of the present invention, the energy recovery system 13 comprises an array of heat exchangers and a heater 19. In this particular example, the array consists of a first 15 and a second 17 heat exchanger, with the heater 19 fluidly coupled between them, but it will be appreciated by persons skilled in the art that a different number of heat exchangers may instead be provided. For example, in one contemplated arrangement the array may comprise three heat exchangers with the heater coupled between the first and second, or the second and third heat exchangers.

In the example illustrated, the first heat exchanger 15 receives a heat transfer fluid (typically, but not necessarily, water) through inlet "a", and outputs that heat transfer fluid via outlet "b" to the heater 19. The heat transfer fluid flows in the opposite direction (i.e. in contra-flow) to the flow of refrigerant in the refrigeration system. So long as: (i) the heat transfer fluid flowing into inlet "a" is at a lower temperature than the refrigerant in the refrigeration system I that exits the heat exchanger 15 at outlet "c", and (ii) the temperature of refrigerant that enters the heat exchanger 15 at inlet "d" is greater than the temperature of the refrigerant exiting the heat exchanger at outlet "c' ,then a transfer of heat will take place from the refrigerant to the heat transfer fluid flowing from "a" to "b".

As will be appreciated, the extent of heat transfer that takes place will depend on the relative temperatures at inlet d" and inlet a" and the amount of time that the heat transfer fluid is in heat exchange with the refrigerant (typically governed by the length of the heat exchanger 15).

Heat transfer fluid exits from outlet "b" and flows to the heater 19 where it is heated before flowing to inlet e" of heat exchanger 17, and onwards out of outlet f". So long as: (i) the heat transfer fluid flowing into inlet "e" is at a lower temperature than the refrigerant in the refrigeration system I that exits the heat exchanger 17 at outlet "g", and (ii) the temperature of refrigerant that enters the heat exchanger 15 at inlet "h" is greater than the temperature of the refrigerant exiting the heat exchanger at outlet "g" , then a transfer of heat will take place from the refrigerant to the heat transfer fluid flowing from "e" to f". The extent of heat transfer that takes place will depend on the relative temperatures at inlet "h" and inlet "e" and the amount of time that the heat transfer fluid is in heat exchange with the refrigerant (typically governed by the length of the heat exchanger 17).

As will be appreciated, as the heater 19 is heating fluid from outlet "V that has already been heated, the amount of heat that the heater needs to input to the heat transfer fluid (and hence the energy consumption of the heater) to provide fluid at an acceptable temperature at outlet 1 is reduced as compared with a heater (such as a boiler) that operates to raise the temperature of a heat transfer fluid from the temperature of the fluid input at "a" directly to the temperature of fluid at outlet "f". For example, if fluid is supplied at 10 degrees centigrade to inlet "a", the refrigerant at inlet "d" is at 40 degrees centigrade and the refrigerant at outlet c" is at 15 degrees centigrade, then the fluid output at outlet "b" will be at about 35 degrees centigrade. If refrigerant at inlet "h" is at 60 degrees centigrade, the refrigerant at outlet "g" is at 50 degrees centigrade, and the desired fluid temperature at outlet "f" is 55 degrees centigrade, then the heater 19 need only heat the fluid output at outlet "b" at about 35 degrees to about 45 degrees centigrade, and the energy required to provide this heating will be reduced as compared with a heater that had to raise the temperature of the fluid from 10 degrees to 55 degrees.

In a particularly preferred arrangement, the heat transfer fluid is water, and the hot water output at "f" can be used directly, or stored (for example in an appropriately lagged hot water tank) for later use. In one envisaged implementation a pump (not shown) may be provided to move fluid from inlet "a" to outlet f". In another envisaged arrangement inlet "a" is coupled to a pressurised supply (such as to a mains water supply), and a pump may not necessarily be required.

The heater 19 may comprise one of a plurality of different types of heater. For example, the heater may comprise a traditional oil-or gas-fired boiler. Alternatively, an environmentally friendlier heater may be utilised. For example, a wood chip boiler burning wood from a sustainable source, or (depending on the temperatures involved) a solar powered heater.

As will be appreciated by persons skilled in the art, the length and/or number of heat exchangers, the achievable temperature of fluid output at 1, and the energy cost of the boiler (or indeed the number of boilers) will depend on the power of the refrigeration system as a whole and other factors such as the ambient temperature, choice of refrigerant and the temperature at which heat transfer fluid is supplied to the system.

This notwithstanding, it will be apparent to persons skilled in the art that the system proposed provides a useful means for extracting energy that would otherwise be lost to air drawn through the condenser 11.

It is also anticipated that with such a system, the condenser 11 may be smaller than would otherwise be required were the system 13 not installed, or may be operated at a lower heat transfer capacity (for example by running the fans intermittently or at a lower RPM) thereby providing further energy savings. It is even conceivable that the system 13 could be designed so that liquid refrigerant exits from outlet "c', and in such an arrangement the condenser 11 could be omitted entirely.

However, whilst it might theoretically be possible to omit the condenser 11, it is likely that a condenser 11 would still be provided to guard against the possibility of other factors, such as ambient temperature fluctuations, combining to cause a gas/liquid mixture to be output at outlet "c". With this in mind, it may also be beneficial to provide a gas/liquid separator between outlet "c' and the condenser 11 (if provided). Many gas/liquid separators are known in the art, and in principle any of these devices could be employed. In a particularly preferred arrangement, the separator may be coupled to an appropriately valved bypass line so that liquid refrigerant collected by the separator can bypass the condenser 11 and feed into the receiver 3.

Fig. 2 is a schematic representation of another energy recovery system that also embodies the teachings of the invention.

In this arrangement7 a heat pump 21 has been substituted for the heater 19, and a further heat exchanger 23 has been introduced into the refrigeration system between the first heat exchanger 15 and the condenser 11.

The heat pump 21 comprises a compressor 25 that compresses low temperature, low pressure gaseous refrigerant to form a high temperature, high pressure gas that flows to a condenser that comprises, in this arrangement, a heat exchanger 27.

In the heat exchanger 27, the high pressure high temperature gaseous refrigerant condenses to form a high pressure, low temperature iquid refrigerant that passes to an expansion valve 29 where the high pressure, ow temperature liquid refrigerant boils to form a low temperature, low pressure gaseous refrigerant that flows through an evaporator 31 (in this instance, another heat exchanger) before being drawn into the compressor 25.

As will be appreciated by persons skiHed in the art, heat exchanger 27 forms the so-called "hot side" of the heat pump, and heat exchanger 31 forms the so-called "cold side" of the heat pump 21. As shown in Fig. 2, the hot side of the heat pump 21 is configured to heat the heat transfer fluid flowing from outlet "b" to inlet "e". The cold side of the heat pump 21 cools a heat transfer fluid that flows in a circuit 31 from the heat exchanger 31 to an inlet i" of the heat exchanger 23 (between the first heat exchanger and the condenser 11) before returning from outlet "k' to heat exchanger 31. If the temperature of the heat transfer fluid at inlet i' is less than the temperature of the refrigerant at inlet "j" of the heat exchanger 23, then heat will flow from the refrigerant to the heat transfer fluid. The heated transfer fluid then flows back to the heat exchanger 31 and heats the refrigerant circulating through the heat pump 21.

An advantage of this arrangement is that the heat pump 21 simultaneously heats the heat transfer fluid flowing between outlet "b' and inlet "e", and cools (via heat exchanger 23) the refrigerant flowing through the refrigeration system 1 -thereby reducing the energy consumed by the condenser 11.

As with the embodiment depicted in Fig. 1, it is anticipated that a liquid/gas separator (for example of the type previously described) may be provided between heat exchanger 23 and condenser 11, and optionafly this separator may be coupled to a vSved bypass line that enables liquid refrigerant to bypass the condenser 11.

It will be appreciated that whilst various aspects and embodiments of the present invention have heretofore been described, the scope of the present invention is not limited to the particular arrangements set out herein and instead extends to encompass all arrangements, and modifications and alterations thereto, which fall within the scope of the appended claims.

It should also be noted that whilst the accompanying claims set out particular combinations of features described herein, the scope of the present invention is not limited to the particular combinations hereafter claimed, but instead extends to encompass any combination of features herein disclosed.

Claims

CLAIMS1. An energy recovery system for a refrigeration system, the energy recovery system comprising: a heat exchanger array comprising at least a first and a second heat exchanger, and a heater for heating a heat transfer fluid, said heater being fluidly coupled to said first heat exchanger for the receipt of heat transfer fluid therefrom, and to said second heat exchanger for the supply of heat transfer fluid thereto; said energy recovery system being configured, when installed in a said refrigeration system, so that: (i) said first heat exchanger draws heat from a refrigerant circulating through said refrigeration system and outputs heated heat transfer fluid; (ii) said heater further heats the heated heat transfer fJuki output from said first heat exchanger, and (iii) said second heat exchanger further heats the heat transfer fluid output from said heater.
2. An energy recovery system according to Claim 1, wherein the energy recovery system is configured, when installed in a said refrigeration system, so that heat transfer fluid flows through said array in an opposite direction to a direction in which the refrigerant flows through said refrigeration system.
3. An energy recovery system according to Claim I or 2, wherein said heater comprises a boiler.
4. An energy recovery system according to Claim I or 2, wherein said heater comprises a solar heater.
5, An energy recovery system according to Claim 1 or 2, further comprising a heat pump having a hot side and a cold side, said heater comprising the hot side of said heat pump.
6. An energy recovery system according to Claim 5, further comprising a secondary circuit through which heat transfer fluid circulates, said secondary circuit being fluidly coupled to the cold side of said heat pump.
7. An energy recovery system according to Claim 6, wherein said secondary circuit comprises a heat exchanger installable in said refrigeration system to extract heat from the refrigerant circulating through saki refrigeration system.
8. An energy recovery system according to Claim 7, wherein heat transfer fluid flows through said secondary circuit in the same direction as that in which refrigerant flows through said refrigeration system.
9. An energy recovery system according to Claim 8, wherein said secondary circuit heat exchanger is located after said heat exchanger array in the direction of refrigerant flow through said refrigeration system.
10. An energy recovery system according to any preceding claim, further comprising a fluid/gas bypass valve for location in front, in a direction in which the refrigerant flows through said refrigeration system, of a condenser of said refrigeration system.
11. An energy recovery system substantially as hereinbefore described with reference to the accompanying drawings.
12. An energy recovery system according to any preceding claim in combination with a refrigeration system.