EP0304189A1

EP0304189A1 - Cooling equipment

Info

Publication number: EP0304189A1
Application number: EP88307143A
Authority: EP
Inventors: John Parsons
Original assignee: British Telecommunications PLC
Current assignee: British Telecommunications PLC
Priority date: 1987-08-14
Filing date: 1988-08-02
Publication date: 1989-02-22
Also published as: GB8719345D0

Abstract

Cooling equipment within housing 11 includes coils 30 and 31 for cooling the room air which then passes back into the room. Outside air is available for cooling purposes - but does not pass into the room itself beyond the housing 11. Heat exchanger coil 34 receives this outside air and under valve control can pass to condenser coil 33 or coil 30. A compressor 40 is associated with coil 32 and the direct expansion evaporator coil 31. Whenever the outside air temperature is low, the refrigerator system is not employed, to allow more economical cooling of room air to be achieved.

Description

The invention relates to cooling equipment.
Standard cooling equipment installed in buildings is typically configured as an integrated system to provide the required cooling. Installation costs of such systems are very high. There have however been moves to modular construction since integral unit failure can lead to serious problems in locations such as computer rooms or electronic telephone exchanges. Several stand alone, self-contained, self-controlled units in an area provide a safeguard should one go into a failure mode. Such modular units are connected to the outside via a wall louvre to exhaust room air and to take in fresh air which is used to cool the room. If the external air temperature is insufficiently cool relative to the room temperature then the room air is cooled by the refrigeration unit within the equipment.
Sometimes however although the temperature differential is sufficient for external air cooling, its relative humidity is too high to be employed (greater than 70% RH) so that mechanical refrigeration has again to be employed.
In the UK this humidity aspect can reduce the potential for external 'free' air cooling from the region of 70% to 50% of the year so increasing running costs.
The present invention is concerned with providing a system which seeks to overcome the above problems.
According to the invention there is provided a cooling system for use inside a building said system including:-
a housing;
means within said housing for receiving air from outside the building;
means within said housing for receiving air from inside the building;
means within said housing for restricting the passage of outside air into the building;
cooling means within said housing for providing cooling of the inside air by use of the separated outside air, said cooling means including first and second heat exchangers interconnected by conduit means for carrying coolant therebetween, said first heat exchanger being configured to receive warm room air and transfer heat therefrom to said coolant and said second heat exchanger being configured to receive said warmed coolant and to transfer heat therefrom to the incoming outside air; and
refrigeration means within said housing for providing an alternative cooling source when required, and a third heat exchanger associated with the cooling means for transferring heat from the refrigeration means to the coolant of said cooling means.
The invention will now be described by way of example with reference to the accompanying drawings in which:-

Figure 1 shows a side view of an embodiment of the invention to illustrate the internal components;
Figure 2 shows a front view with the access doors open;
Figure 3 shows a schematic diagram of the system within the housing including operational paths and data associated with economy (winter) operation; and
Figure 4 shows a schematic diagram including operational paths and data associated with summer operational mode.

An embodiment of the system is shown in Figure 1. The cooler unit 10 is a single modular unit within a generally rectangular steel housing 11. The housing 11 includes a pair of access doors 12 with an air grille 13 which receives returning room air. Air from the unit is available to the room via aperture 15. Outside air to the unit is available through aperture 16 which also allows for the passage of air from the Unit to the outside. Such air would pass via an outside wall louvre (not shown) adjacent the unit.
The warm room air to be cooled passes through grille 13 past filters 29 over cooling coils 30 and 31 and out through aparture 15 under fan assistance from fan 36 via non-return dampers 17.
Unlike the prior art systems, the outside air is not allowed to pass into the room itself beyond the housing 11 so that its humidity cannot present problems in operation. (To meet statutory requirements a small aperature 14 allows a few percent of fresh air into the room circulation system as represented by the broken line). The cool incoming outside air passes over a secondary heat exchanger coil 34 and the warmed air returns to the outside under the assistance of one or more fans 42 (e.g. a high speed and a low speed fan). A pump 35 and a first coil 33 of a coaxial condenser are associated with the secondary heat exchanger 34 and the glycol second coil 30. A compressor 40 is associated with the direct expansion (DX) evaporator coil 31 and a second coil 32 of the coaxial condenser. As seen from Figure 3 a number of control valves 37-39 are operable to select the system paths under the control of box 48. These paths are formed by means of piping 41.
The refrigeration part of the system including the evaporator coil 31, compressor 40, condenser coil 32, liquid receiver 44, drier 45, sight glass 46 and valve 37 form a closed fluid path for the refrigerant.
The dry cooling part of the system can be considered as having two paths. The first path includes coil 30, pump 35, heat exchanger 34 and valve 39. The second path includes coil 33, pump 35, heat exchanger 34, valve 39 and valve 38. The fluid in the dry cooler is a water/glycol mixture. The first and/or second path is chosen dependent on temperature conditions.
The location of the coils 30 and 31 allow both to receive the warm room air for cooling, the coil 30 being in circuit during the economy winter (or night time) mode when outside temperature is low, and coil 31 being operable when the refrigeration portion is in operation during hot weather.
The second heat exchanger path (see Figure 4) will be operable during hot weather whilst the refrigeration system is operating. On initial operation of the refrigeration system, the compressor 40 draws liquid refrigerant through the evaporator coil 31 where it absorbs heat from the warm room air passing over it so changing its state into vapour and this enters the compressor and the hot gas is then pushed into the condenser coil 32 for cooling. The liquid leaving the condenser then passes through the liquid receiver 44 to drier 45 which removes any moisture from the system and thence via the sight glass 46 (which allows for visual checks) through the thermostatic expansion valve 37 to the evaporater coil 31 once again.
The valve 37 allows sensed temperature indicative of excess pressure to be relieved via the equalising line. The intimately located dual coils of the coax condenser allow heat exchange therebetween so that heat from coil 32 is absorbed by the liquid in coil 33 and this is pumped to the secondary heat exchanger 34 which hot liquid is cooled by the flow of incoming outside air.
Valve 38 is provided with a sensor in the liquid receiver 44 to allow actuation to divert the path of the glycol mixture away from the coax condenser.
In winter or at cool times of the day, the refrigeration system is not employed (see Figure 3) and the cooler fluid takes the first path so that coil 30 is used to cool the room air and the warm liquid is pumped to heat exchanger 34 for cooling with the incoming outside air. Because of the indirect cooling employed by the incoming outside air, the relative humidity of this air is not a critical operating factor so the air is available for use in this 'economy' mode of operation for longer portions of the day/year. This gives significant operational savings. Such a saving can be as high as 20% and the only additional cost of operation is the small pump 35.
The incorporation of both modes in a single unit gives greater flexibility without increased installation costs as a single wall aperture is all that is required. Silencers within the wall cavity may be provided as required.
The control box 48 will have access to the output of standard temperature sensors (e.g. nickel sensors with a resistance of 1 K at 0 c). These can be used to indicate air and glycol temperatures. Humidity of return air can be sensed by a condenser device (e.g. a gold foil sensor generating a voltage proportioned to the range 20 - 90% R.H.). Standard electronics components (e.g. chips or a microprocessor) can be employed to actuate the valves dependant on the sensors and the system setpoint which can be preset.
Thus the control loops operate as follows:

1. Dry cooling with glycol valve

When return air temperature exceeds the appropriate set point by a preset amount (e.g. 1° K) the glycol pump 35 and the condensor fan 41 will be switched on and the return air temperature will be controlled by the continuous adjustment of the glycol valve 39. When the glycol temperature exceeds room temperature minus 2°K the glycol valve 39 will close and the pump and condenser fan will switch off. The pump and condenser fan thereafter is switched on every 30 minutes to sample the glycol temperature.

2. DX cooling

When the return air temperature exceeds the set point the DX cooling mode becomes active. The controller 48 switches the compressor 40 on or off depending on the return air temperature.

(a) DX and dry cooling - when in DX cooling mode, if the glycol temperature falls to 14K below the system setpoint the dry cooling mode will be maintained in parallel with the DX cooling mode.
(b) DX without dry cooling - when in DX cooling mode, if the glycol temperature exceeds the system setpoint minus 12 K the dry cooling mode remains switched off or will be switched off when this point is reached.
(c) High speed condenser fan - when the glycol temperature exceeds the glycol setpoint the condenser fan 42 high speed will be switched on.

Typical operating parameters for the system in economy or summer mode are shown on Figures 3 and 4 respectively.
Although the Figure 1 unit is shown as returning the air to the room through an upward facing aperture, a header box could be provided for placing on the unit to divert the returning air frontwards into the room.
The system described is self contained, requires no external pipework so keeping installation costs down. The system is configured to require only a single wall opening to allow outside air to be received and exhausted for cooling purposes.
By incorporating a heater 50 as illustrated in Figure 1 (e.g. a multistage switchable heater) it is possible to heat the room air in winter so that returning air is kept at an approximately constant temperature, switching in dependent on the system set-point.
By incorporating a humidity sensor, a remote humdifier placed somewhere else in the room but controlled by the system allows the option that the relative humidity of the room air can be raised should this fall below its set-point. The controller 48 can control this function also.
With suitable interfacing (e.g. RS232C) a remote station (e.g. a personal computer) can be provided for exchange of information from one or more such systems, such as setpoint allocation for example.

Claims

1. A cooling system for use inside a building said system including:
a housing;
means within said housing for receiving air from outside the building;
means within said housing for receiving air from inside the building;
means within said housing for restricting the passage of outside air into the building;
cooling means within said housing for providing cooling of the inside air by use of the separated outside air, said cooling means including first and second heat exchangers interconnected by conduit means for carrying coolant therebetween, said first heat exchanger being configured to receive warm room air and transfer heat therefrom to said coolant and said second heat exchanger being configured to receive said warmed coolant and to transfer heat therefrom to the incoming outside air; and
refrigeration means within said housing for providing an alternative cooling source when required, and a third heat exchanger associated with the cooling means for transferring heat from the refrigeration means to the coolant of said cooling means.

2. A system as claimed in Claim 1 wherein the third heat exchanger comprises a dual coiled condenser, one of said coils being associated with the refrigeration means and the other of said coils being associated with the cooling means, said coils being located adjacent each other to allow heat transfer therebetween.

3. A system as claimed in Claim 2 wherein the dual coils are coaxial.

4. A system as claimed in Claim 1, 2 or 3 wherein control means are provided to divert the coolant to said first or second heat exchanger and said third heat exchanger dependent on the temperature of the received outside air relative to the warm air within the building.

5. A system as claimed in Claim 4 where the control means are configured to automatically operate the refrigeration means when the temperature differential between the air in the building and the outside air is too small to provide effective cooling.

6. A system as claimed in any preceeding claim; wherein the coolant for the cooling means is water based.

7. A system as claimed in any preceding claim including air assistance means for assisting the flow of room air circulating from the building into the housing and/or the outside air circulating in the housing.

8. A system as claimed in claim 7 wherein the assistance means includes at least one electrically operable fan.

9. A system as claimed in any preceeding claim wherein the incoming and returned outside air is provided through a common aperture.

10. A system as claimed in any preceeding claim including interfacing means for allowing remote information access.

11. A system as claimed in any preceeding claim, wherein humidity sensor means within the housing are provided to allow a remote humidifier to add moisture to the air if the humidity in the building falls below a predetermined value.

12. A system as claimed in any preceeding claim, wherein heater means are provided to heat room air if below predetermined temperature.

13. A system as claimed in any preceding claim, wherein electronic interfacing means are provided to allow remote access to be provided.