GB2488827A

GB2488827A - Refrigeration System with Liquid Cooled Condenser

Info

Publication number: GB2488827A
Application number: GB201104085A
Authority: GB
Inventors: Michael John Filmer
Original assignee: MF REFRIGERATION Ltd
Current assignee: MF REFRIGERATION Ltd
Priority date: 2011-03-10
Filing date: 2011-03-10
Publication date: 2012-09-12
Anticipated expiration: 2031-03-10
Also published as: GB201104085D0; GB2488827B

Abstract

A refrigeration system has a compressor 32, a condenser 36, an expansion device 44, and an evaporator coil 20, all arranged within a closed refrigerant fluid circuit. The condenser is liquid cooled, and arranged in a circuit which may include a thermostatically controlled pump 46, which is controlled according to the temperature of refrigerant leaving the condenser. The liquid coolant is passed to a remote heat dispersal unit, and the unit may include a heat exchange coil in association with a cooling air fan 49 which blows ambient air onto the coil to cool the liquid coolant. The liquid refrigerant may be a water/ethylene glycol mixture.

Description

I

REFRIGERATION SYSTEM

This invention relates to a refrigeration system, and in particular to a system having a circuit for the simple and safe discharge of heat to a remote location.

In a refrigeration system, such as may be used for cooling ambient air, for example in a cellar, or for chilling beverages, a fluid refrigerant flows around a circuit in a cycle that involves successive stages of compression, condensation, expansion and evaporation, the latter step greatly reducing the temperature of the refrigerant and its surroundings by the absorption of latent heat and, the refrigerant then being used for cooling purposes.

The condensation step on the other hand causes the liberation of latent heat, raising the temperature of the fluid. Heat exchange is therefore needed to remove heat liberated by the refrigerant. In the case of for example a domestic refrigerator or freezer, where the cooling required takes place in a closed and thermally insulated cabinet, the heat generated by the system can simply be released to the atmosphere and may indeed contribute to warming a room in which the refrigerator stands.

There are however other applications in which the heat generated by the system must be removed to a remote location for cooling to be effective. One such application is where the system is used for cooling ambient air, for example in an air conditioning system or a cellar-cooling system.

In a typical air conditioning system, the liquid refrigerant circuit may have to be quite long and may even have to pass from the inside to the outside of a building in order to remove the heat so that it does not interfere with the circulation of cooled air. Fluid refrigerants are expensive and likely to be toxic, and breakdowns can be difficult to handle where a liquid refrigerant circuit extends over substantial distances within a building.

The present invention provides a refrigeration system wherein a fluid refrigerant circulates within a closed circuit while undergoing successive cycles of condensation with the liberation of latent heat, followed by expansion and evaporation to absorb latent heat and cause cooling, wherein heated fluid refrigerant from the condensation step passes through a heat exchanger wherein it gives up heat to a circulating liquid coolant, said coolant circulating in a circuit which includes a cooling unit remote from the refrigeration system.

The fluid refrigerant circuit may be of the compression type wherein refrigerant in the vapour phase passes through a compressor, for example a scroll compressor and thence through a condenser at which heat is liberated.

According to the invention, at least a pad of the condenser comprises a heat exchanger in which the refrigerant gives up heat to the circulating liquid coolant, which may suitably be water or a water/ethylene glycol mixture. Refrigerant from the condenser then passes to an expansion valve at which it evaporates and then passes through a cooling device as required for refrigeration before returning to the compressor.

Alternatively, the refrigeration system of the invention could be of the absorption type, wherein the circulating refrigerant is an aqueous ammonia solution, since in this case also the refrigerant is condensed and passed through a heat exchanger.

One advantage of the present invention is that all the components through which the fluid refrigerant circulate can be at a single location. This can reduce the amount of expensive fluid refrigerant needed as well as improving safety since a safe and non volatile coolant such as a water/ethylene glycol mixture can be used to travel the significant distances needed to convey heat to a remote location.

In a preferred embodiment of the invention, a refrigeration evaporator coil is provided in a first unit for cooling, the compressor, expansion valve and heat exchanger being in a second unit, connectable to but separable from the first, for easy replacement in the event of breakdown.

A preferred embodiment on the invention will now be described with reference to the accompanying drawings, wherein: Figure 1 is a rear elevation of an air conditioning unit embodying the present invention; Figure 2 is a front elevation of the unit of Figure 1 with a front grille removed; Figure 3 is a cross sectional view on the line Ill to Ill of Figure 1; and Figure 4 is a schematic circuit diagram of a refrigeration system embodying the invention.

Referring first to Figures 1 to 3, an air cooling unit 10 comprises a housing 11 containing a cooling coil 20 for fluid refrigerant circulating through the coil from a refrigeration unit 12. The coil 20 forms pad of the evaporation of a fluid refrigerant circuit and comprises five successive banks of serpentine tubing of which a first can be seen in Figure 2. The successive banks can be seen in cross section in Figure 3, which also shows one of the two air fans 14 at the back of the unit and a front grille 30. Although the drawings show a continuous length of tubing, this could be replaced by one or more manifolds with loops extending from them.

The cooling coil 20 is fed by a feed line 13 from unit 12, and has a return line 15 to unit 12. These lines are tightly sealed but detachable for replacement of the refrigeration unit 12 when needed.

Refrigeration unit 12 houses a scroll compressor 32, an accumulator 34 and a heat exchanger 36, these being connected into the refrigeration circuit as will be described in more detail with reference to Figure 4.

In the schematic diagram of Figure 4, the housing of unit 12 is indicated by a dotted line surrounding those components of the system located within unit 12.

Within unit 12, a refrigerant, preferably a hydrofluorocarbon such as HFC-41 OA, flows in gaseous form from an accumulator 34 through a pipe 56 to a scroll compressor 32 where it is compressed to a liquid state. The liquid refrigerant flows through pipe 50 to heat exchanger 36, its temperature rising rapidly owing to the evolution of latent heat on condensation. The liquid refrigerant flows through a heat exchange coil 45 to an outlet pipe 52 from the heat exchanger, and while in the heat exchanger it undergoes heat exchange with a coolant liquid flowing around the heat exchange coil 45 from an inlet 60 to an outlet 65. The residence time in the heat exchanger of the liquid coolant, for example a water-ethylene glycol mixture, is increased by baffles 47 between turns of the coil 45, causing the liquid to flow in a tortuous path.

From the outlet 52 from the heat exchanger, liquid refrigerant flows to an expansion valve 44 where it is caused to evaporate by sudden expansion through a nozzle into an expansion chamber. Passing from the expansion valve to the inlet pipe 13 to the evaporator coil 20, its temperature rapidly drops and latent heat of evaporation is rapidly absorbed. The cooled refrigerant flows through the evaporator coils 20, as ambient air is blown through the coils by fan 14 and out through grille 30 to cool the ambient atmosphere.

From the evaporator coil 20, the gaseous refrigerant flows through outlet pipe 15 back to the unit 12 where it returns to an accumulator 34, which retains excess fluid and in particular collects any remaining liquid refrigerant, preventing such liquid from entering the compressor.

The coolant circuit through heat exchange 36 will now be described.

A reserve of liquid coolant such as a water/glycol mixture is retained in a header tank 42, which feeds coolant as required into the circuit in which it passes through a line 64, via a pump 46, to the inlet 60 to heat exchanger 36. As already described, the coolant flows around baffles 47 and around the coils 45 through which the hot condensed refrigerant flows.

Having absorbed heat from the refrigerant, the liquid coolant flows through outlet 65 and thence through a line 62 to a remote unit 40 which may be outside or in another part of the building that does not require cooling. In the remote unit 40 coolant flows through a coil 48 while a fan 49 blows ambient air through the unit and out through a grille 49 in a way analogous to the air conditioning unit 10 except that the unit is releasing heat to the ambient air rather than cooling it. The coolant then returns through a line 64 to the heat exchanger 36, passing header tank 42, which may conveniently be incorporated in remote cooler unit 40.

Since the unit 40 is at a remote location, it may be preferable for fan 49 to be driven not at mains voltage but at a reduced voltage, for example 24v from a transformer located within the building. Depending on the ambient temperature around unit 40, the fan 49 may only need to be driven intermittently, or indeed not at all if the outside temperature is sufficiently low to cool the liquid coolant as required. The motor of fan 49 is therefore preferably controlled thermostatically.

While water could be used as the coolant in the circuit running to cooler unit 40, it is preferable to use a liquid of lower freezing point, such as a water/glycol mixture so as to avoid the possibility of freezing in cold weather, particularly if the cooler unit is located outside.

Operation of the refrigeration unit 12 will also be thermostatically controlled, the motor driving scroll compressor 32 operating intermittently as required to maintain the ambient temperature at a predetermined level.

Because the entire refrigeration circuit is confined to the two housings 11 and 12, any problems arising with the circuit such as refrigerant leakage can be dealt with much more easily and safely. In the event of a breakdown in unit 12, the entire unit can be detached simply by disconnecting the refrigerant inlet and outlet pipes 13, 15 and the liquid coolant pipes 16, 18, and substituting a spare unit to which the pipes can easily be reconnected. The damaged or faulty unit 12 can then be sent for repair without any significant interruption of operation.

Claims

CLAIMS: 1. A refrigeration system wherein a fluid refrigerant circulates within a closed circuit while undergoing successive cycles of condensation with the liberation of latent heat, followed by expansion and evaporation to absorb latent heat and cause cooling, said closed circuit comprising, a condenser and heat exchanger, an expansion valve and an evaporator, the system further comprising a coolant circuit wherein a liquid coolant is arranged to pass through said heat exchanger to absorb heat from said fluid refrigerant whose temperature is raised in the condensation phase and thereafter to flow to a remote location at which heat is liberated.
2. A system according to claim I wherein the liquid refrigerant is a water/ethylene glycol mixture.
3. A system according to claim I or claim 2 further comprising, at said remote location, a heat dispersal unit comprising a coil through which said liquid coolant passes and a fan to blow ambient air onto said coil.
4. A system according to any preceding claim wherein said liquid coolant circuit includes a pump the operation of which is thermostatically controlled according to the temperature of refrigerant leaving said heat exchanger.
5. A refrigeration system substantially as herein described with reference to and as illustrated in the accompanying drawings.