In order to effectively store fresh food stuffs a combination of temperature and humidity particular to a particular type of food stuff is the optimum, although very often for short term storage, such as in a normal domestic residence, conventional refrigerators are used which whilst not optimum for many products provides a reasonable compromise for many foodstuffs.

However, for longer term storage, such as a fruit or vegetable producer's store or storage in a camp in extreme temperatures where re-supply is irregular, specific stores can be established for particular products.

For example, pears are best stored at-1°C at 85% to 90% relative humidity while pumpkins are best stored at +13°C at 75% relative humidity.

It is the principal object of the present invention to provide a refrigeration method and apparatus whereby articles can be stored at a place with a low ambient external temperature with the energy needed to effect the storage being reduced over conventional refrigerator coolers.

The invention includes a refrigeration apparatus including an arrangement whereby fluid radiators are located both in the area to be maintained at a particular temperature and in ambient temperature external to this, the radiators being interconnected so that fluid can pass between the two radiators to thereby permit cooling of the storage area.

Thus, there is no necessity of mechanical cooling arrangements as long as the ambient temperature remains below the required temperature of the cooling area.

It is preferred that at least one pump be provided to circulate the fluid. Means can be provided to maintain a required temperature which means can control the operation and the speed of operation of the pump (s).

It is also preferred that at least one buffer tank be provided in the system which can prevent rapid variations of temperature and which can also permit connection to a standard refrigeration system if this be required.

The invention also includes a method of maintaining areas at a required temperature by the use of an apparatus similar to that described herein.

In order that the invention may be more readily understood we shall describe a particular embodiment of the invention in relation to the accompanying drawing.

The illustrated embodiment will be notionally considered to be in an Antarctic environment (although it can also be used in any other area where the ambient temperature is normally below the required temperature in the storage area). This can be, for example, 1° C.

The storage area may either be free standing, as by a separate building or it could be built into another building and can have the general properties of a cool store, that is the floor, walls and ceiling are insulated and the entry door is normally sealed so that the air inside the area tends to be held without great movement and heat loss from the area is minimised. As illustrated, we show two storage areas, a first coldstore, which, for exemplification can be held at 1.87° C and a humidity of 71.3% and a second coldstore 11, which is to be held at 6.51° C and a humidity of 63.4%.

Within the each coldstore this is at least one radiator 12,13, which in each case is shown as being a fan coil radiator. The fans permit variations in heat transfer therefrom into the area and, at the same time ensure that the area within the coldstores is of uniform temperature. Alternatively, the radiator could be plate radiators located to enable movement of air by convection.

Also, there may be more than one radiator in any particular area and these radiators are preferably connected in parallel exterior of the area so that they maintain approximately the same working temperature.

The radiator (s) in the area is/are in connection with at least one further radiator 20 exterior of the volume to be maintained, and generally exterior to the building 55 in which this is located and preferably in a position whereby it is isolated from direct heat sources, such as the sun or other heat sources. That is, this external radiator or radiators will tend to approach the ambient temperature. In areas where there is normally substantial wind, this or these radiators can be plate radiators, as illustrated. However, if required, the radiator (s) could have associated fans.

As illustrated, there are six (6) radiators, 20a, 20b, 20c, 20d, 20e, 20f in a parallel arrangement.

In the simplest form of the invention, not illustrated, a cooling fluid is provided in the pipework between the two radiators and this may be a water/glycol (anti-freeze) fluid and there is provided at least one pump which can cause the fluid to circulate around the system which could be an open or a closed system.

It will be appreciated that the radiator the storage area, which will be cold when circulation is being effected will absorb heat from the area concerned thus causing the temperature in this to drop, and the radiator external of the area will receive this heat

which will be dissipated to the atmosphere as the ambient temperature is colder than the radiator, which is warm.

We can provide thermostatic arrangements so that once the temperature within the area reaches a required value, circulation of the cooling fluid ceases. The speed of the pump can also be varied to maintain a required temperature. The number of fans operating and the speed of operation can also be varied to maintain the temperature on the area.

As illustrated, we provide two buffer tanks 21,22 between the two radiators, the tank 22 being in connection by pipe works 23 with the ambient radiators 20 and being adapted to be maintained at-2.7° C. The output from this tank passes by pipe 24 to recirculating pump 25, through pipe 26, which can be split to pipes 27,28 to the radiators 13,12 respectively.

From the outputs of the radiators 13,12, pipes 31,32 are joined to pipe 33 and pass to cold tank 21. As heat has been removed from the cool rooms, the temperature in this tank can be of the order of-1.0° C. The outlet from this tank is connected to pump 34, and by way of pipe 35 to the radiator 20.

These tanks 10,11 enable compensation for short term changes in ambient or storage area temperature so that the overall fluctuations in the temperature of the storage area are damped.

Also, it will be appreciated that the two cold stores are at different operating temperatures and their operating parameters can be individually maintained by individual thermostated controls 51,52 in each area which can simply control the fan operation or the fan and fluid flow by the pump 25 can be automatically controlled.

When the ambient temperature is very low, say colder than-15°C, we control the speed of the external pump to maintain fluid flow through the radiator 20 rather than having it

stop and start, and this in association with the cold tanks to provide required operating conditions.

Pump 25 then effects the circulation through the cold stores as described above.

Also, the cold tank 22 is provided with refrigeration units 40,41 associated therewith which has its evaporator or a heat exchanger associated with these 41 in the cold tank so that if the ambient temperature comes to a level close to or higher than the required temperature inside the storage area then the buffer tanks are interconnected by pipe 36 so the fluid does not pass through the external radiator, the auxiliary refrigeration unit 40 commences operation so that cool fluid passes through the inlet buffer tank and this can be maintained at a temperature sufficient to maintain the storage area at its required level.

Thermostat 53 can control the operation of the refrigeration unit 40.

Thus, if the temperature in the cold tank 22 is too high to maintain the correct temperature in the storage area, operation of the refrigeration unit is initiated and when the ambient temperature again reaches a predetermined level then the refrigeration system is shut down and circulation of the fluid is once again between the radiators.

In one form of the invention, instead of there being two buffer tanks, there may be a single buffer tank and the fluid to pass to the area has its input and output near the bottom of the tank and that from the area to the external radiator (s) at the top. The difference in the temperatures of the two parts of the coolant will cause this to stratify so there will be minimal mixing of the two parts of the fluid. In this embodiment, the refrigerator coil can be adjacent the bottom of the tank so that, when this is operating, it cools the fluid to pass to the radiator (s) in the area.

Referring now more specifically to aspects of the illustrated cold store:

A calculated number of standard wall panel radiators 20a, 20b, 20c, 20d. 20e. 20f (or any efficient heat rejecting medium) are mounted outside in free air away from direct sunlight or other heat sources. Pipe connections are made in a parallel configuration for maximum efficiency.

Two insulated buffer tanks 21,22 with a balancing pipe 36 between, are fitted into the system between the panel radiators and the cold stores 10,11. The tanks provide more precise control and allows the standby refrigeration plant to take over the cooling role when ambient temperatures are too high.

A standard water circulating'fan-coil unit'12,13 is mounted inside each cold store 10,11 to absorb heat from the cold store.

Two circulating pumps 25,34 transfer the anti-freeze fluid from the cold store, through the buffer tank to the external panel radiators. One pump 25 transfers anti-freeze to and from the fan-coil unit to the buffer tanks, the second pump 34 transfers anti-freeze to and from the buffer tanks to the panel radiators 20.

There is a temperature difference between the two tanks. One tank 22 stores the coldest liquid from the panel radiators 20 and the second tank 21 stores the warmest liquid from the fan coil units 12,13. Liquid is pumped from the warmer tank 21 to the panel radiators 20 and returns to the colder tank 22. Conversely, liquid is pumped from the colder tank 22 to the fan-coil units 12,13 in the cold stores and returns warmed liquid to the warmer tank 21. A balance pipe 36 connected between the two tanks allows the liquid to find it's own level when one or the other pump is not called upon to operate.

The refrigeration plant 40,41, when operating, directly chills the colder tank.

The system works most efficiently when there is a temperature difference of more than 5°C between the set-point of the cold store and the local ambient air. Delicate control of excessive pump on/off operation is obtained by controlling the speed of the pumps.

It is possible by the use of the method to cool a number of areas at different temperatures to provide optimum storage conditions for different articles using only one coolant and pump system.

As illustrated, the fluid from the colder tank is split and passed to two different cold rooms. By controlling the operation of the fan coil units 12,11 so the different operating parameters in the two areas can be maintained.

Alternatively, if a number of different areas are to be maintained at different temperatures, the coolant passes from area to area, preferably from the area to be maintained coolest to those which are to be maintained at different temperatures. and by control of the fans in the areas so the temperatures in each area can be maintained at the required conditions.

In some applications it is possible to use a system of the invention without the use of auxiliary refrigeration even where the ambient temperature rises to an unacceptable level but where there is still, say, lying snow.

In such circumstances a heat exchanger can be located within the snow and the fluid can be diverted from the external radiator through to this heat exchanger which rejects heat to the snow. Conditions satisfactory for this to operate could occur during the Antarctic summer where, whilst the ambient temperature rises somewhat, there is still a snow coverage available.

It will be seen from the foregoing that the current invention can provide a substantial part of the heat load to maintain storage areas at a required temperature in areas of cold ambient temperature with minimum use of mechanical refrigeration which, although efficient, can still be expensive to operate where large volumes are being maintained. We have described certain embodiments of the invention and it is to be understood that variations can be made in the various apparatus to provide effectively the same result.

All such variations and modifications are to be deemed to be within the scope of the invention.