GB2213920A - Cooling system - Google Patents

Abstract

An enclosure (1), such as a housing for a digital telephone sub-station (2), is cooled by apparatus comprising a first bank (5) of finned tubes within the enclosure (1) and a second bank (12) of finned tubes outside the enclosure (1), at a height above the first bank (5) and connected to the first bank (5) by pipes (18, 19). Refrigerant within the banks (5, 12) and the pipes (18, 19) will be caused, by the effects of air currents passing over the banks (5, 12) of tubes, to move in a circuit formed by the pipes and tubes and to change state to extract heat from the enclosure. A completely passive system can therefore by obtained. <IMAGE>

Description

COOLING SYSTEM The invention relates to a cooling system.

Powered cooling systems are well known and frequently use the latent heat of change of state between solid, liquid and gaseous phases to extract heat from a space. Such systems rely on an external power source to drive a compressor or pump.

Many electronic control systems are temperature sensitive and may not only cease to function correctly but may be permanently damaged if the temperature thereof is permitted to rise above a determined level, whereby cooling systems are required to maintain operation of and prevent damage to electronic installations.

If these installations are in unvented or uncooled enclosures the temperature within the enclosures can rise to unacceptable levels even in temperate climates and are even more likely to in hot climates.

Digital telephone sub-stations in remote areas may operate on low voltage direct current supplied from a mains supply through a rectifier, the rectifier also charging a battery system which, in the event of a mains electricity supply power failure, will maintain operation of the sub-station. A battery system to power a cooling system to maintain the space enclosing the electronic apparatus of the telephone sub-station below a temperature at which damage could occur to the electronic apparatus would however be prohibitively expensive and unwieldly, particularly in countries which experience very high ambient day-time temperatures.

Standby generators can be provided but this is costly, requires frequent maintenance for assured start-up and can cause problems of undue noise.

According to the invention there is provided apparatus for cooling an enclosure comprising first and second banks of finned tubes Joined by connection pipes and so provided that the first bank is within the enclosure and the second bank is outside the enclosure and at a height above the first bank and a refrigerant within the tubes and pipes, the arrangement being such that the heating and cooling effects of air currents passing over the f;rst and second banks will cause the refrigerant to move in a circuit including the first and second banks and the connection pipes and to change state to extract heats from the enclosure.

The air currents may flow due to convection and/or as a result of a fan. By 'banks' is meant any convolution of tubes. Thus the first and second banks of finned tubes may be provided with baffles and be zig-zagged or coiled to create a stack or chimney effect to create an enhanced airflow thereover due to natural convection currents.

Warm air in the enclosure passing over the first bank of tubes will cause the refrigerant in the first bank of tubes to vapourize and rise to the top of the first bank and since the second bank of tubes is at a height above the first bank, to pass through one of the connecting pipes to the second bank. Cooler air passing over the second bank will cause the refrigerant therein to condense and to fall to the bottom of the second bank and to return via another of the connection pipes to the bottom of the first bank.

The banks of tubes may be provided in a twin arrangement to promote even cooling.

The apparatus can be completely passive that is to say without any external power input or may be assisted by fans to create airflow and by valves, for example, thermostatically controlled solenoid valves to control refrigerant flow.

The phase change may be between liquid and vapour or may be between solid and liquid.

The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which: Figure 1 is a side view of one embodiment of cooling apparatus according to the invention including part of an enclosure cooled by the cooling apparatus; Figure 2 is a view to a smaller scale showing the entire enclosure cooled by cooling apparatus according to the invention; and Figure 3 is a diagram showing refrigerant flow in cooling apparatus according to the invention.

Referring to the drawings, an enclosure 1 contains equipment 2 which is to be protected against undue temperature rise. The equipment 2 may, for example, comprise digital telephone switching gear free-standing in the enclosure t and spac=-4. from 313a walls thereof 3, 4. At the upper eni of tne equipment 2 first banks 5 of finned tubes are mounted on support brackets. Baffles 6, 7 are preferably provided at the lower and upper edges. A deflecting baffle 8 is provided on the underside of the roof 9 of the enclosure 1.Heat produced by the equipment 2 will cause convection air currents as indicated by arrows 10, that is to say rising through the equipment 2, being deflected sidewardly beneath the roof 9 of the enclosure 1 by the deflecting baffle 8 to pass through the finned banks 5 of tubes, passing downwardly between the equipment 2 and the sidewalls 3, 4 of the enclosure 1 and re-entering the equipment 2 at the lower end thereof.

Above the enclosure 1 in a housing 11 second banks 12 of finned tubes are mounted on support brackets. The banks 12 are preferably provided in a V formation, the sidewalls 13, 14 of the housing 11 have louvres 15 therein and a deflecting baffle 16 is preferably provided between the two banks 12 of finned tubes thereby to create convection currents as indicated by arrows 17 that is to say entering througn the louvres 15 at lower parts of the sidewalls of the housing 11, passing through the banks 12 of finned tubes, passing upwardly and being deflected outwardly by the deflecting baffles 16 to leave the housing 11 through the louvres 15 in the upper parts of the sidewalls 13, 14.

As shown in Figures 2 and 3 the banks 5, 12 of finned tubes are connected by connection pipes comprising connection pipes 18 which join the upper end of the banks 5 to the upper ends of the banks 12 and connection pipes 19 which join the lower ends of the banks 12 to the lower ends of the banks 5. As shown in Figure 3 a valve 20, for example a thermostatically controlled solenoid valve, may be provided in one of the connection pipes, as shown in the connection pipe 19.

The support brackets for the banks 5, 12 are preferably provided by frames 21 above the banks 5 and secured to the underside of the roof 9 of the enclosure 1 and frames 22 below the banks 12 and secured to the upper side of the roof 9. The banks 5, 12, pipes 18, 19 and frames 21, 22 may be a sub-assembly preformed before mounting in the enclosure 1 and the housing 11.

With the equipment 2 producing heat, the convection currents 10 will transfer such heat to the banks 5 of finned tubes and the refrigerant in the tubes will be heated causing the refrigerant to vapourize and rise to the top of the banks 5 of tubes and to pass through the connection pipes 18 to the top of the banks 12 of tubes.

The air currents 17 passing over the banks of tube 12 will cool the refrigerant causing it to condense and fall to the bottoms of the banks 12 thence to return, through the open valve 20, through the connection pipes 19 to the bottom of the banks 5 of tubes so that the cycle can be repeated. The banks 5, 12 of tubes may be in coil form, preferably in double coil form, to intensify cooling.

If desired additional banks of tubes producing a cooling effect may be provided on or adjacent the banks 12 of finned tubes and may contain a substance which will solidify when cooled and become liquid upon being heated, the change of state causing a high degree of heat absorption. Thus the substance in the additional tubes may, for example, phase change at 310C. In desert countries the day-time temperature may be 1450C to 500C but the night-time temperature only 280C or lower. Thus the substance in the additional tubes will solidify at night and extract large quantities of heat from the banks 5, 12 of tubes upon changing to the liquid phase in the day-time.

Claims (6)

1. Apparatus for cooling an enclosure comprising first and second banks of finned tubes joined by connection pipes and so provided that the first bank is within the enclosure and the second bank is outside the enclosure and at a height above the first bank and a refrigerant within the tubes and pipes, the arrangement being such that the heating and cooling effects of air currents passing over the first and second banks will cause the refrigerant to move in a circuit including the first and second banks and the connection pipes and to change state to extract heat from the enclosure.

2. Apparatus according to claim 1, including a fan to assist or cause the air currents.

3. Apparatus according to claim 1 or claim 2, in which the first and second banks of finned tubes are provided with baffles and are zigzagged or coiled to create a stack or chimney effect to create an enhanced airflow thereover due to natural convection currents.

14. Apparatus according to any one of claims 1 to 3, in which in operation warm air in the enclosure passing over the first bank of tubes will cause the refrigerant in the first bank of tubes to vapourize and rise to the top of the first bank and, since the second bank of tubes is at a height above the first bank, to pass through one of the connecting pipes to the second bank, and cooler air passing over the second bank will cause the refrigerant therein to condense and to fall to the bottom of the second bank and to return via another of the connection pipes to the bottom of the first bank.

5. Apparatus according to any one of claims 1 to 14, in which the banks of tubes are provided in a twin arrangement to promote even cooling.

6. Apparatus according to claim 1, which is completely passive that is to say without any external power input.