GB2251064A

GB2251064A - Air conditioning unit

Info

Publication number: GB2251064A
Application number: GB9027644A
Authority: GB
Inventors: Manmohan Singh Dhanjal
Original assignee: Creda Ltd
Current assignee: Creda Ltd
Priority date: 1990-12-20
Filing date: 1990-12-20
Publication date: 1992-06-24
Anticipated expiration: 2010-12-20
Also published as: ES2051185R; GB2251064B; ES2051185A2; GB9027644D0; ES2051185B1

Abstract

An air conditioning unit for a room comprises a refrigeration system including an evaporator 14 and a condenser 13 over which air is drawn by fans 5, 6, and means for varying the air flow through the unit such that, in use, air passing to the room either flows over evaporator 14 to cool the room or over condenser 13 to heat the room. In the illustrated construction the air flow is changed by a valve 17. For cooling. the valve is set to the position shown so that air sucked from the room by the fan 6 passes to the outside atmosphere via apertures 21, 24 (arrows B), and air drawn from the atmosphere by the fan 5 passes over the evaporator 14 to be cooled, and then into the room via aperture 18 and outlet 9 (arrows A). In the heating mode, the air valve is pivoted clockwise through 90 DEG so that air withdrawn from the room via inlet 10 is heated by the condenser 13 and is returned to the room via the outlet 9, and outside air is drawn over the evaporator 14 and exhausted via aperture 24. Air passing to the room may be further heated by an electric element 16, and a part 15 of the evaporator may be positioned as shown to dehumidify room air recirculated from inlet 10 to outlet 9 in the heating mode of the unit. Alternatively, valve 17 could be replaced by a fixed member in the position shown, air flow variation then being achieved by reversing the direction of the fans 5, 6. <IMAGE>

Description

Air ConditioninQ Unit This invention relates to an air conditioning unit for a room, and especially to a unit for space heating or cooling a room.

It is known to employ for this purpose a refrigeration system including an evaporator and a condenser together with respective fans for assisting the flow of air through the evaporator and condenser.

Referring to Figure 1, in one known system, a compressor 1 draws refrigerant vapour from an evaporator 2, in which evaporator refrigerant was vaporised by heat extracted from the air flowing past the evaporator. The compressor 1 compresses and, in so doing heats, the refrigerant vapour, which condenses in condenser 3, thereby heating the air flowing past the condenser. The liquid refrigerant then returns to the evaporator through an expansion valve 4, which maintains the vapour pressure in the condenser high and that in the evaporator low. Fans (not shown) are provided to assist air flow through the condenser and the evaporator.

Such an air conditioning unit allows a room to be heated by the flow of fan-assisted air via the condenser (air also flowing through the evaporator and being cooled by it before being vented to a region outside the room). To enable the room to be cooled, the compressor is connected to the pipes communicating with the condenser and evaporator by means of a reversing valve (not shown), so that the output of the compressor can be alternatively connected to the evaporator 2 and the input to the condenser 3. When the valve is reversed in this way, the evaporator 2 now acts as a condenser and the condenser 3 now acts as an evaporator, so that the air flow into the room past the latter now cools the room.Reversing valves are however unreliable and expensive, and the system performance is penalised due to heat transfer between the hot and cold refrigeration streams in the vicinity of the reversing valve.

The units were positioned in the room and communicated with the atmosphere by a section cut out of the wall, or either the condenser or the evaporator was positioned in the room and the other was positioned outside the room.

The invention provides an air-conditioning unit for a room, comprising a refrigeration system including an evaporator and a condenser and a valve arranged to permit expansion of vapour through the valve, and respective fans for assisting the flow of air past the evaporator and the condenser, and means for varying the ducting of the air flow through the evaporator and the condenser, so that in use, the room is cooled by fan-assisted air flow via the evaporator or heated by fan-assisted air flow via the condenser.

By varying the ducting of the airflow through the condenser and the evaporator into the room, rather than by maintaining a fixed air flow pattern through the condenser and evaporator as hitherto, it is possible to omit the reversible valve.

The ducting may be varied by channelling air withdrawn from the room via the condenser before returning it to the room in the heating mode and by channelling air from outside the room through the evaporator before impelling it into the room in the cooling mode.

The evaporator may be positioned in two parts, with one section of its coil (preferably, the superheating section) being located in the path of the air drawn from the room before it reaches the condenser, so that moist air will be partly condensed on this section of the evaporator before passing the condenser and being returned to the room, thereby providing a dehumidifying function.

By arranging a slight overall suction from the room, the air conditioning unit may perform a ventilation function as well.

An air conditioning unit for a room constructed in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 2 is a schematic plan view of the unit with an air valve in the cooling mode; and Figure 3 is a schematic plan view of the unit with the air valve in the heating mode.

Referring to Figure 2, the unit is housed in a weatherproof enclosure 7 which projects from the outside of an external wall 8 of a room and communicates with the interior of the room by means of two apertures 9, 10 in the wall, which are covered, in the interior of the room by a panel 11 containing a grille (not shown) and the controls for the unit (not shown).

The unit comprises the vapour compression circuit as shown in Figure 1, except that no reversing valve is provided. The compressor 1 is located in region 12, the condenser 3 is located in region 13 and the evaporator 2 is in two separate sections, an upstream main section of finned tubes in the region 14 connected to a downstream superheating coil 15. Two centrifugal fans 5, 6 are provided, each drawing in air axially and expelling it radially, and an electric heating element 16 is also provided.

In operation in the cooling mode, an air valve 17 uncovers an aperture 18 to allow communication between a duct 19 containing the main section of the evaporator 2 and a passageway 20 which leads via the fan 5 to the outlet duct 9 leading into the room. The air valve equally allows communication via an aperture 21 between a duct 22 containing the condenser and leading from the room via aperture 10 to a passageway 23 containing air extraction fan 6. In this mode, the extraction fan 6 sucks air from the room, past the superheating coil 15, where it is cooled, and past condenser 3, where it is heated, before expelling it into the atmosphere via an outlet grille 24 - see arrows B.

Cooled air is impelled into the room by fan 5 from the atmosphere via grille 25. The air is cooled by passage over the main section of the evaporator in the region 14 - see arrows A In the heating mode, the controls on the unit are altered to pivot the air valve to the position shown in Figure 3. In this position, the apertures 18 and 21 are closed, and apertures 26, 27 are uncovered. These apertures were of course covered in the mode operation shown in Figure 2.

Air sucked into the air conditioning unit in the heating mode is returned to the room. Thus, air is sucked in by impeller 5 via the aperture 10 into the duct 22, and passes over superheating coil 15 and past condenser in the region 13 passing via the aperture 26 to the passageway 20 to aperture 9 - arrows C. There will be some cooling of the air at the superheating coil 15, and some moisture in the air will condense on the coil, but there will be a greater heating effect from the condenser 3, and the heating element 16 also heats the air. Thus, in the heating mode, the air is heated and to some extent dehumidified.

The heat given out by the condenser is supplied to the main section of the evaporator from the atmosphere, air being sucked into duct 19 containing the main section of the evaporator and into. the passageway 23 via the aperture 27 by means of the extraction fan 6. The air is expelled to the atmosphere via outlet grille 24. See arrows D.

The amount of heat supplied by the electric heating element may be varied. Thus, when the ambient temperature is higher, more evaporation can take place in the evaporator 2, and hence more heat can be supplied from the condenser 3, so that less is needed from the electric heating means.

When the ambient temperature is lower, a greater proportion of the heat supplied by the air conditioning unit can be provided by the electrical heating means.

The heating element 16 may be switched off altogether, and the air conditioning unit now operates in a dehumidification mode (described and claimed in co-pending British Patent Application No. 90 2~7 \o45.. . As explained above, condensation takes place on superheating coil 15 of the evaporator, and the same air is returned to the room at lower humidity. The superheating coil 15 has a by-pass controlled by a solenoid valve (not shown) which is responsive to a room humidity sensor (not shown). When the humidity in the room rises above a predetermined level, the superheating coil is connected in series with the main section of the evaporator. When the humidity is below that level, the upstream and downstream ends of the superheating coil are put into communication with each other, so that the refrigerant flow by-passes the coil.The main reason for this approach is that the latent heat transfer to the superheater section decreases with a decrease in the dew point temperature of the room air.

Thus, when the humidity in the room rises above a preset level, the by-pass path is closed by the solenoid valve, and moisture in the air drawn into the room is condensed onto the surface of the superheating coil. That same air is then returned to the room via the aperture 9 but the air is now drier. When the room humidity has been reduced to below the preset level, the solenoid opens the by-pass path and refrigerant does not flow through the superheating coil. In this condition, moisture is not withdrawn from the air circulating through the air conditioning unit.

The air valve 17 has a small aperture 17a in it so that a certain amount of leakage across the valve takes place from the duct 22 to the passageway 23. The result is that more air is sucked from the room than is returned to the room i.e. there is a slight overall suction from the air conditioning unit. This provides ventilation, since the room air is regularly changed. A typical rate of change for an average room would be an overall air change in a time of the order of two hours.

Typical dimensions for the air conditioning unit are around 400mm in dimension projecting away from the wall, a length along the wall of around 800mm, and a height in a vertical direction of around 300mm. The apertures need be no more than 120mm diameter (4.5"), whereas previous air conditioning units have required a cut out size in the wall of as much as 25" x 18".

The heating capacity could be 3kW at -10C, 1.7kW from the element and 1.3kW from the heat pump action. The output from the heat pump would be higher, say, 1.7kW at 50C ambient.

The cooling capacity could be 1.5kW at an ambient temperature of around 300C.

Of course, variations may be made without departing from the scope of the invention. Thus, for example, the superheating coil 15 of the evaporator 2 could be positioned next to the main section of the evaporator, or could be built into it, or omitted altogether, if dehumidification was not required.

Also, in the heating and cooling mode, the air flow past the condenser could originate from the atmosphere, rather than from the room via the aperture 10 i.e. the aperture 10 could be dispensed with.

Equally, instead of pivoting the air valve 17 to change from the heating mode to the cooling mode, the valve could be fixed permanently in the orientation of Figure 2, i.e. the apertures 18, 21 could be permanently open and the apertures 26, 27 permanently closed. In order to change from the cooling mode to the heating mode, the fans would be reversed in direction so that air was sucked from the room via aperture 9 and heated air blown into the room via aperture 10.

Claims

1. An air conditioning unit for a room, comprising a refrigeration system including an evaporator and a condenser and a valve arranged to permit expansion of vapour through the valve, and respective fans for assisting the flow of air past the evaporator and the condenser, and means for varying the ducting of the airflow through the evaporator and the condenser, so that in use, the room is cooled by fan-assisted airflow via the evaporator or heated by fan-assisted airflow via the condenser.

2. An air conditioning unit as claimed in claim 1, in which the evaporator is located in a duct which, depending on the position of valve means, communicates either with a passageway leading to the interior of the room, or with a passageway leading to a region outside the room.

3. An air conditioning unit as claimed in claim 2, in which the condenser is located in a duct which, depending on the position of the valve means communicates either with a passageway leading to the interior of the room or with a passageway leading to a region outside the room.

4 An air conditioning unit as claimed in claim 3, in which the evaporator duct and the condenser duct communicate with common passageways leading to the interior of the room or a region outside the room, depending on the position of a common valve means.

5. An air conditioning unit for a room substantially as hereinbefore described with reference to the accompanying drawings.

5. An air conditioning unit as claimed in claim 4, in which the valve means is a pivotable flap.

6. An air conditioning unit as claimed in claim 4, in which the valve means is arranged to provide an air bleed from the duct for the condenser to the passageway leading to the region outside the room.

7. An air conditioning unit for a room substantially as hereinbefore described with reference to the accompanying drawings.

Amendments to the claims have been filed as follows CLAIMS

1. An air conditioning unit for a room, comprising a refrigeration system including an evaporator and a condenser and a valve arranged to permit expansion of vapour through the valve, and respective fans for assisting the flow of air past the evaporator and the condenser, an outlet opening and an inlet opening, the evaporator and the condenser being located in ducts which, in one position of valve means, lead from a region outside the room to the outlet opening, for the evaporator duct, and lead from the inlet opening to a region outside the room, for the condenser duct, for cooling of the room, and in another position of the valve means, lead from the inlet opening to the outlet opening, for the condenser duct, and from a region outside the room to a region outside the room, for the evaporator duct, for heating of the room, the inlet opening and outlet opening being adapted to be connected to the outside ends of a pair of openings in an external wall of the room.

2. An air conditioning unit as claimed in claim 1, in which the valve means is a pivotable flap.

3. An air conditioning unit as claimed in claim 1 or claim 2, in which the valve means is arranged to provide an air bleed in use from the duct for the condenser to the duct for the evaporator in the heating mode, to perform an overall suction from the room.

4. An air conditioning unit as claimed in claim 3, in which the valve means has an aperture in it to provide the air bleed.