GB2451091A

GB2451091A - Waste Heat Recovery from a Refrigeration Circuit

Info

Publication number: GB2451091A
Application number: GB0713855A
Authority: GB
Inventors: Jack Culley
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-07-16
Filing date: 2007-07-16
Publication date: 2009-01-21
Also published as: GB0713855D0

Abstract

A refrigeration system has a circuit that includes heat recovery apparatus 31 as a means to increase system efficiency. The heat recovery apparatus is a heat exchanger having inlet and outlet headers and at least one pipe or tube or coil or plate. The refrigeration system includes a compressor (9 fig 2), a condenser 11, an expansion device (13 fig 2) and an evaporator (14 fig 2), and the heat exchanger may recover heat directly as part of the refrigeration circuit, or indirectly by an intermediate fluid. The refrigeration system may be a heat pump system 25, and the heat recovery apparatus can be applied to both new and retrofit applications. The invention finds application in supermarket refrigeration and building services heat pump circuits.

Description

BOILER FREE ALL YEAR ROUND HEAT PUMP APPARATUS

The present invention relates to a new way of stabilising heat pump mechanical refrigeration operation during winter periods without the use of an external heating energy input system such as boilers and it can be applied for both new and existing heat pump circuits.

The present invention can be either applied for externally or alternatively internally for conventional air conditioning and refrigeration condensing units either as a factory fitted option or alternatively on site as a retrofit applications.

Conventional heat rejection systems such as air-cooled condensers, dry coolers, evaporative coolers and cooling towers generally rely on ambient air temperature to reject the heat from the refrigeration circuit. Traditionally, large heat rejection systems use cooling towers or evaporative coolers in order to reduce the heat rejection equipment size as well as the overall energy consumption due to lower condensing temperatures.

It will readily be apparent to those skilled in the art that any additional boiler usage to heat up cooling side of the heap pump circuit during winter periods adds not only extra installation, maintenance costs but most importantly results in significant energy penalty for the overall efficiency of the heap pump operation. If one can introduce additional heating source without using any energy input i.e. heat rejection from another system such as refrigeration condensers, cooling towers otherwise normally rejected to air, the heat pump system overall system efficiency can be improved dramatically.

The present invention utilise this waste heat from the external refrigeration machinery to improve the overall efficiency of a heat pump circuit as well as reducing initial investment cost and life-time maintenance costs.

Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings, in which: Figure 1 illustrates Pressure-Enthalpy chart of a conventional refrigeration cycle.

Figure 2 illustrates the conventional refrigeration cycle.

Figure 3 illustrates typical heat pump circuit.

Figure 4 illustrates the conventional heat pump wet system circuit winter operation.

Figure 5 illustrates the conventional heat pump wet system circuit summer operation.

Figure 6 illustrates the proposed heat pump heat addition concept via refrigeration condenser circuit.

Figure 7 illustrates the proposed heat rejection concept for water chiller circuits.

Figure 8 illustrates proposed heat rejection concept for the direct expansion refrigeration circuits.

Figure 9 illustrates the internal set up for an air cooled refrigeration machinery circuit.

Figure 10 illustrates the internal set up for a water cooled refrigeration machinery circuit.

A typical refrigeration cycle is illustrated in Figure 1. Low pressure super-heated gas 15 is compressed by the compressor 9 to high pressure high temperature gas 10 which is condensed by a heat rejection equipment 11 to a high pressure liquid form 12. Later this sub-cooled high-pressure liquid refrigerant 12 is expanded via an expansion device 13 to provide a low pressure but cold liquid and gas mixture 14 as part of the evaporator operation.

Typical refrigerant cycle is restricted between the gas line 3, critical point 4 and liquid line 5 with the super-heated region 7 and sub-cooled liquid region 8 as well as the mixture of liquid-gas state 6 regions and any refrigeration cycle operates with these phase change envelops.

The evaporation of the refrigerant 14 within the cooler circuit generally called evaporator provides the cooling effect for the process I fluid. The pressure I and enthalpy 2 lines indicate a conventional envelop of a refrigeration cycle and the refrigeration cycle is subjected to additional sub-cooling the solid line envelop illustrated in Figure 1 between lines 12-1 3-14-1 5.

A typical HFCF-22 refrigeration cycle based on the operation conditions of 35°C (95 °F) refrigerant liquid 12 requires approximately 0.022 kg/s (2.96 Lb/mm) per Ton of Refrigeration (TR). Ignoring pipe friction, an open drive compressor operating at those conditions would have a specific power requirement of between 1.4 and 1.5 hp per Ton of Refrigeration, depending on whether it were a reciprocating or screw compressor and depending on its size.

There is an apparent benefit to utilise the waste heat rejection line 10-11-12 from a refrigeration cycle for any external use such as heat pump stabilising circuits during winter periods. In particular, application such as supermarket refrigeration and associated heat pump circuits lend them to this present invention as the refrigeration units operate 24 hours on a continuous basis and therefore this waste heat rejection is available through out the day and night for the heat pump circuit.

Figure 3 illustrates a typical heat pump circuit whereby the evaporator 14 and condenser 11 are reversed via diverting valves 16 and the hot circuit 17 goes into the original evaporator 14 in stead of the original cooling circuit condenser 11 and the role of the original condenser 11 is equally reversed as evaporator 14 for the heating circuits via diverting valve 16.

A heat pump system by reversing the refrigerant flow, it enables the machine in stead of cooling the system circuit as in the case of summer operation, it heats the system circuit during winter operations as illustrated in Figure 3.

In most applications 18,19 the heat pump 25 winter operation requires an additional heat source 21 to cool the cold side 24, 29 of the heat pump whereby the other side of the heat pump heat up the system 23, 26, 28 kept operational by simple using an additional boiler 21 as illustrated in Figure 4.

On the other hand during summer operation as illustrated in Figure 5 a heat pump 25 by reversing the refrigerant flow it can cool a system 18 by using the cooling circuit 20, 27, 28 but this time as the other side of the heat pump 25 rejects heat from the system 18, 20, 27 and 28 via the heat rejection circuit 22, 24 and 30.

The present invention is illustrated in Figure 6 is based on simply adding an internal or external heat rejection recovery unit 31 as part of the external refrigeration heat rejection unit 11 which otherwise wasted energy. This additional heat recovery unit 31 acts as a heat source like the boiler 21 in a conventional heat pump circuit and it will readily be apparent to those skilled in the art that any additional boiler usage to heat up cooling side of the heap pump circuit during winter periods adds not only extra installation, maintenance costs most importantly results in significant energy penalty for the overall efficiency of the heap pump operation.

The present invention can be applied for both new and retrofit applications.

Although the ideal application is the refrigeration condensers as illustrated in Figure 6 but if a process or water chillers are available as part of the overall installation the same heat recovery unit 31 can be incorporated for both new and retrofit chillers as illustrated in Figure 7. If the water circuit 32, 33 is reversed as water heat pump the heat recovery unit 31 can also be incorporated as part of the reversed condenser 14.

The present invention suits ideally for the supermarket refrigeration and integrated building services heat pump circuits as the refrigeration runs continuously and therefore this waste heat available through out the years on a 24 hourly basis as illustrated in Figure 8. As a supermarket refrigeration is designed to run all year round to remove heat from the cabinets and cold store coolers 14 even in winter the proposed heat recover unit 31 additions either as part of the new or retrofit installation can easily run the heat pump circuit and eliminates the use of a boiler.

The present invention is further illustrated in Figure 9 for the most commonly used heat rejection equipments. They could be either wet systems 37 like cooling towers or evaporative condensers or any dry systems such an flat bed 36, boxed 38, "V" shape 39 and Vertical 40 condenser layouts by simple adding the heat recovery unit 31 either based on direct refrigeration or secondary fluid principal after the heat rejection coil.

As the heat recovery unit 31 is positioned after the condenser coil 11 circuit the present invention heat recovery unit 31 would have no detrimental impact for the operation of the original heat rejection machinery.

The same air rejection concept covered above can be simple applied for the wet system heat rejection condensers 41 either as part of an internally or externally as illustrated in Figure 10. The proposed heat recovery unit 31 either based on direct refrigeration or secondary fluid principal can be applied for both new and retrofit applications.

Conventional rooftop / wall mounted condensing units, air I water cooled condenser and chillers can be fitted either in the factory as part of the manufacturing process or alternatively on site as a retrofit application to accommodate the present invention.

Alternatively, the present invention can be applied as an external unit either on a one-to-one basis or alternatively multiple formats on common condensing unit applications.

Claims

CLAIMS; 1) A heat recovery unit module or apparatus consists of a pipe, tube, coil, plate or the combination of these as part of the refrigerant heat rejection circuit with or without any extended surface complete with inlet and exit headers for the purpose of recovering waste heat from the refrigeration circuit based on direct refrigeration or secondary fluid principal for any supermarket, commercial, domestic, process or industrial applications.
2) A heat recovery module or apparatus according to claim 1 wherein the heat exchanger surface is coil, circular, oval, square, rectangular or any other geometry in any aspect ratios to form a heat transfer surface which is placed within or external part of the heat rejection circuit in order to provide heat recovery.
3) A heat recovery module or apparatus unit according to claims I to 2 either directly applied as part of the heat rejection equipment or apparatus internally as part of the machine or alternatively applied externally in order to provide heat rejection system equipment or apparatus.
4) A heat recovery module or apparatus according to claims 1 to 3 wherein the heat recovery is provided from the refrigeration circuit.
5) A heat recovery cooling module or apparatus according to claims I to 4 wherein the heat recovery unit applied for either as direct cooling or reversible heat pump equipment or apparatus.
6) A heat recovery unit module or apparatus according to claims I to 5 wherein the heat recovery is achieved by the heat rejection side of a conventional refrigeration circuit for the purpose of utilising as heat source for the external heat pump circuits.
7) A heat recovery module or apparatus according to claims I to 6 wherein the heat recovery concept is applied either in the form of single or multiple combinations of all the options.
8) A heat recovery module or apparatus comprising a plurality of the heat recovery modules or apparatus applied into a single or common heat rejection circuit(s) according to any one of claims I to 7.
9) A heat recovery module or apparatus in accordance with claims I to 8 wherein the units are connected in series and/or parallel.
10) An air conditioning, refrigeration, process, food preparation, industrial process, supermarket refrigeration heat recovery system incorporation a heat recovery unit module or apparatus according to any one of the claims I to 9.
11) A heat recovery module or apparatus substantially as hereinbefore described with reference to Figure 6, 7, 8, 9 and 10.