GB2242261A - Exhaust gas driven air cycle air conditioning system - Google Patents

Exhaust gas driven air cycle air conditioning system Download PDF

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Publication number
GB2242261A
GB2242261A GB9006628A GB9006628A GB2242261A GB 2242261 A GB2242261 A GB 2242261A GB 9006628 A GB9006628 A GB 9006628A GB 9006628 A GB9006628 A GB 9006628A GB 2242261 A GB2242261 A GB 2242261A
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Patent type
Prior art keywords
air
lt
rti
heat
exchanger
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9006628A
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GB2242261B (en )
GB9006628D0 (en )
Inventor
Michael John Atkinson
Peter Hugh Birch
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Aisin Seiki Co Ltd
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Aisin Seiki Co Ltd
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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60HARRANGEMENTS OR ADAPTATIONS OF HEATING, COOLING, VENTILATING, OR OTHER AIR-TREATING DEVICES SPECIALLY FOR PASSENGER OR GOODS SPACES OF VEHICLES
    • B60H1/00Heating, cooling or ventilating devices
    • B60H1/32Cooling devices
    • B60H1/3204Cooling devices using compression
    • B60H1/3205Control means therefor
    • B60H1/321Control means therefor for preventing the freezing of a heat exchanger
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60HARRANGEMENTS OR ADAPTATIONS OF HEATING, COOLING, VENTILATING, OR OTHER AIR-TREATING DEVICES SPECIALLY FOR PASSENGER OR GOODS SPACES OF VEHICLES
    • B60H1/00Heating, cooling or ventilating devices
    • B60H1/00007Combined heating, ventilating, or cooling devices
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24HEATING; RANGES; VENTILATING
    • F24FAIR-CONDITIONING, AIR-HUMIDIFICATION, VENTILATION, USE OF AIR CURRENTS FOR SCREENING
    • F24F5/00Air-conditioning systems or apparatus not covered by F24F1/00 or F24F3/00, e.g. using solar heat or combined with household units such as an oven or water heater
    • F24F5/0085Systems using a compressed air circuit
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B11/00Compression machines, plant, or systems, using turbines, e.g. gas turbines
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B27/00Machines, plant, or systems, using particular sources of energy
    • F25B27/02Machines, plant, or systems, using particular sources of energy using waste heat, e.g. from internal-combustion engines
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F25REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
    • F25BREFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT-PUMP SYSTEMS
    • F25B9/00Compression machines, plant, or systems, in which the refrigerant is air or other gas of low boiling point
    • F25B9/002Compression machines, plant, or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant
    • F25B9/004Compression machines, plant, or systems, in which the refrigerant is air or other gas of low boiling point characterised by the refrigerant the refrigerant being air
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60HARRANGEMENTS OR ADAPTATIONS OF HEATING, COOLING, VENTILATING, OR OTHER AIR-TREATING DEVICES SPECIALLY FOR PASSENGER OR GOODS SPACES OF VEHICLES
    • B60H1/00Heating, cooling or ventilating devices
    • B60H1/32Cooling devices
    • B60H2001/3236Cooling devices information from a variable is obtained
    • B60H2001/3248Cooling devices information from a variable is obtained related to pressure
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60HARRANGEMENTS OR ADAPTATIONS OF HEATING, COOLING, VENTILATING, OR OTHER AIR-TREATING DEVICES SPECIALLY FOR PASSENGER OR GOODS SPACES OF VEHICLES
    • B60H1/00Heating, cooling or ventilating devices
    • B60H1/32Cooling devices
    • B60H2001/3236Cooling devices information from a variable is obtained
    • B60H2001/3255Cooling devices information from a variable is obtained related to temperature
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B60VEHICLES IN GENERAL
    • B60HARRANGEMENTS OR ADAPTATIONS OF HEATING, COOLING, VENTILATING, OR OTHER AIR-TREATING DEVICES SPECIALLY FOR PASSENGER OR GOODS SPACES OF VEHICLES
    • B60H1/00Heating, cooling or ventilating devices
    • B60H1/32Cooling devices
    • B60H2001/3286Constructional features
    • B60H2001/3297Expansion means other than expansion valve
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02ATECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A30/00Adapting or protecting infrastructure or their operation
    • Y02A30/20Adapting or protecting infrastructure or their operation in buildings, dwellings or related infrastructures
    • Y02A30/27Relating to heating, ventilation or air conditioning [HVAC] technologies
    • Y02A30/274Relating to heating, ventilation or air conditioning [HVAC] technologies using waste energy, e.g. from internal combustion engine

Abstract

A compact, exhaust gas driven air cycle air conditioning system comprising an expansion turbine (18), two compressors (12, 14), two heat exchangers (16, 20) and an exhaust turbine (38) is preferably controlled by means of an exhaust gas bypass arrangement (44, 46, 48) and supplies either hot or cold conditioned air, as required, to a load air space (26). Switching between cooling and heating modes is implemented using two-way valves (28, 30) such that the same components may be used, and in all embodiments the conditioning air is supplied from a dry, closed loop. In reverse flow embodiments the working air enters the turbine first. In all embodiments moisture removal devices (22, 32, 62) are incorporated to avoid heat exchanger icing and also control humidity. In addition, de-icing systems may be included for use in those applications where heat exchanger icing is a particular problem. Further embodiments allow control over the temperature at which air is delivered to the load by diverting controlled amounts of hot or cold air, as appropriate, to be mixed with the conditioning air. An extra compressor may be driven by a high speed motor as an additional means of power input under conditions of low exhaust gas energy. <IMAGE>

Description

TITLE OF THE INVENTION Exhaust Driven Air Cycle Air Conditioner.

BACKGROUND OF THE INVENTION Field of the Invention The invention relates to the provision of air conditioning in applications where a source of exhaust gas is readily available, for instance in automotive applications. More specifically, it provides an exhaust gas driven, compact air conditioning system which uses air as the refrigerant medium and in a preferred form is capable of providing both heating and cooling.

Description of the Prior Art Motor driven air cycle air conditioners have been proposed for some years as an alternative to the well-established vapour-compression air conditioners used in residential, or similar, applications (for example, US Patent <RTI>No.4295518</RTI> and European Patent No. EP45144-A2).

This is because they have several advantages over vapour-compression systems, which are known to have a number of disadvantages.

Firstly, because the evaporators of <RTI>vapour-conpression</RTI> devices operate at around 50C the heating capacity of these devices is seriously impaired at low ambient temperatures, since they rely on heat transfer from ambient to the evaporator. Secondly, in cold weather ice forms on the evaporator heat transfer surfaces thereby increasing pressure losses and also reducing evaporator effectiveness. Thirdly, vapour-compression devices use chlorofluorocarbons (CFCs) as the refrigerant which presents manufacturing and maintenance problems with regard to refrigerant leakage, problems which are substantially reduced when air is used as the refrigerant. In addition, CFCs are known to have a harmful effect on the Earth's ozone layer and it is thought that they may also be contributing to global warming caused by the so-called greenhouse-effect.

Despite the advantages, air cycle air conditioning systems have yet to make a significant impact on the markets currently served by CFC based air conditioners. This is largely due to their relatively poor coefficient of performance (C.O.P.) but also because air cycle designs have previously been based on conventional electric motors as prime movers and are therefore relatively low speed, and hence large, devices. Prior art air cycle air conditioners do often incorporate regenerative heat exchangers for claimed improvements in C.O.P. but the improvement is minimal when the increased losses due to the presence of the heat exchanger(s) are taken into account. Such an improvement may also be seen as expendable when offset against the attendant increase in size, complexity and cost of the conditioning system.

A recognised way of significantly improving the C.O.P. of air cycle devices is to operate in reverse flow mode, i.e. the refrigerant air flows through the turbine, rather than the compressor, prior to the heat exchanger. However, this approach is not common in the prior art, probably because the reduced cycle temperatures can create icing problems in the heat exchangers.

In prior art air cycle air conditioners the air delivery temperature is dictated by the <RTI>ambient</RTI> and operating conditions, which may be undesirable in some <RTI>=pplications</RTI> from the point of view of safety and/or comfort. Such air conditioners would therefore be improved by incorporating some means of air delivery temperature control.

SUMMARY OF THE INVENTION The invention is <RTI>intend</RTI> as an alternative to vapour-compression air conditioning systems <RTI>commonly</RTI> used in automotive, or similar, applications. The invention provides an air cycle air conditioning system for cooling a load air space, comprising: an exhaust turbine drivable by a supply of exhaust gases from an engine; an air compressor drivingly connected to the exhaust turbine; a second compressor drivingly connected to an expansion turbine; an expansion air heat exchanger for receiving expanded air from the expansion turbine and delivering it to the two compressors in series for re-compression, the expanded air in the expansion air heat exchanger being in heat exchange relationship with a fan-assisted flow of conditioning air to the load air space for effecting cooling of the load air space.

Advantageously an air conditioner according to the invention can be designed to utilise the same components to deliver cooling or heating to the load air space, depending on the requirements, and which uses air as the refrigerant fluid. Switching between heating and cooling modes is facilitated using a number of two-way valves. It is a particular feature of the invention that the rotating components are preferably designed to operate at high rotational speed in order to produce a compact and light-weight unit.

A number of embodiments are described beginning with the most basic system for heating or cooling a load air space; regenerative heat exchangers have been excluded from all of the embodiments in order to minimise their size, cost end complexity. Reverse flow heating and cooling embodiments are shown since they offer improvements in terms of the coefficient of performance. The potential problem of heat exchanger icing in the reverse flow embodiments is minimised by appropriate use of moisture removers. Despite this, gradual icing of the heat exchanger passages may occur, and of particular interest in the reverse flow embodiments is the possible incorporation of de-icing facilities. Additional embodiments allow control over the conditioning air delivery temperature for both cooling and heating modes in reverse flow and normal flow configurations.

Finally, <RTI>embodimtnts</RTI> are included which incorporate a third air compressor in series with the previously mentioned compressors such that it can contribute to the compression process if required. The extra compressor is drivingly connected to a very high speed, compact electric motor of the type disclosed in British Patent Application <RTI>No.2217118A,</RTI> or some other similar means of power input. These embodiments are arranged such that the motor, and hence compressor, is automatically activated to provide additional power input when there is insufficient energy available in the exhaust gas to operate the air conditioner at or near the design point.

BRIEF DESCRIPTION OF THE DRAWINGS FIG.1 is a schematic diagram of an exhaust driven air cycle air conditioning system according to the invention for cooling a load air space using air in a dry, closed loop.

FIG.2 is a block diagram of the preferred control system for obtaining the required power input to the air conditioning system of <RTI>FIG.1.</RTI>

FIG.3 is a schematic diagram of the air cycle air conditioning system of FIG.1 in heating mode.

FIG.4 is a schematic diagram of an exhaust driven, reverse flow air cycle air conditioning system according to the invention for cooling a load air space using air in a dry, closed loop.

<RTI>FIG.5</RTI> is a schematic diagram of the reverse flow air cycle air conditioning system of <RTI>FIG.4</RTI> in heating mode.

<RTI>FIG.5</RTI> is a schematic diagram of the air conditioning system of FIG.1 modified to incorporate an extra air compressor, driven by a high speed motor, as an additional means of power input for use under conditions of low exhaust gas energy.

FIG.7 is a schematic diagram of the reverse flow air cycle air conditioning system of <RTI>rIG.4</RTI> with the addition of a cooling mode heat exchanger de-icing facility associated with the expansion air heat exchanger.

FIG.8 is a schematic diagram of the reverse flow air cycle air conditioning system of <RTI>FIG.S</RTI> with the addition of a heating mode heat exchanger de-icing <RTI>factlity</RTI> associated with the expansion air heat exchanger.

FIG.9 is a schematic diagram of the air conditioning system of FIG.l modified to allow control over the air delivery temperature.

<RTI>FIG. 10</RTI> is a block diagram of the preferred control system necessary to obtain the desired air delivery temperature from the air conditioning system of FIG.9.

DETAILED DESCRIPTION OF THE INVENTION In the following description those components common to the various embodiments are <RTI>preferred</RTI> to, and shown in the relevant figures, using the same reference numerals.

Figure 1 is a schematic diagram of an air cycle air conditioning system 10 according to the invention in <RTI>cooling</RTI> mode. The working air flows in a closed loop comprising: an initial compressor 12 which raises the temperature and pressure of the air; a second compressor 14 which further raises <RTI>t:e</RTI> working air temperature and pressure; a compression air heat exchanger 16 in which heat is rejected to an ambient air stream; a turbine 18 in which the compressed and cooled air is expanded back to its original pressure; an expansion air heat exchanger 20 in which heat is absorbed from the conditioning air stream; and a moisture removal device 22 positioned between the heat exchanger 16 and the turbine 18 to prevent ice from forming in the heat exchanger 20.

The conditioning air also flows within a closed loop under the action of an electrically driven fan 24. It is drawn from the load air space 26 and passes through the expansion air heat exchanger 20 via a two-way valve 28. Heat is rejected to the working air stream within the heat exchanger 20 and the cooled conditioning air returns to the load air space 26 via the fan 24 and another two-way valve 30.

Conditioning air humidity is controlled by means of a moisture removal device 32 positioned between the load air space 26 and heat exchanger 20.

The ambient air stream is fed through the low pressure side of the compression air heat exchanger 16 by means of a second electrically powered fan 34 and via valve 28. It absorbs heat from the working air stream within the heat exchanger 16 and is then ducted back to ambient via valve 30.

A third moisture removal device 62, between the two-way valve 28 and heat exchanger 20, is not used in the cooling mode of the system but is described below in connection with the system in heating mode.

In passing through the turbine 18 the working air does work which is transferred via a shaft 36 to provide the power requirement of the inital compressor <RTI>12.</RTI> Power input to the system 10 is via the second compressor 14 which is driven by an exhaust turbine 38 mounted on the same shaft 40 as the compressor 14. The exhaust turbine 38 is in turn driven by exhaust gas from a suitable source, for instance a car exhaust. The exhaust turbine 38 is designed to operate at high rotational speed thereby reducing the size of the rotating components for a given duty, and hence resulting in a compact air conditioner 10.

The amount of exhaust gas passing through the exhaust turbine 38 is controlled by means of a bypass duct 42, bypass control valve 44, valve controller 46, <RTI>valve</RTI> actuator 48 and pressure sensor 50 such that operation of the air conditioner 10 is maintained at or near design conditions. The preceding description of the power inputs to the compressors 12 and 14 also applies to each of the embodiments described hereafter.

Figure 2 is a block diagram of the preferred control system for achieving this. The design operating condition is factory-set in terms of a desired compressor outlet pressure which is compared, by a negative feedback summer 52, with the pressure measured by pressure sensor 50 positioned in the compressor outlet duct 54. The summer 52 adjusts the bypass control valve 44 by means of the actuator 48 thereby altering the amount of exhaust gas allowed to bypass the exhaust turbine 38. In this way the power input to the compressor 14 is adjusted until the compressor outlet pressure lies within a factory-set pressure band defined in the feedback circuit 56 by a high/low threshold crossing detector 58. Once the measured pressure lies within this Sand a switch 60 is opened to nullify the feedback and hence maintain the current setting of the control valve 44.When the measured pressure subsequently moves out of the band, for instance due to a sufficient change in car engine condition, the switch 60 is again closed and adjustment of the valve 44 resumes.

The control system described in the preceding paragraph is incorporated in all of the embodiments described hereafter. It will be appreciated by those skilled in the art that a parameter other than compressor outlet pressure, for instance rotational speed or compression ratio, may be used as a measure of the operating condition without departing from the scope of the invention as described. It will also be appreciated that control can be facilitated at less expense using a simple mechanical link between the bypass valve 44 and sensor 50 such as those commonly used in automotive <RTI>turbochergers.</RTI>

However, the valve setting is then limited to only two discrete settings, e.g. fully open and fully closed.

As described for <RTI>figure</RTI> 1, the <RTI>conlitioning</RTI> air circulates in a closed loop. If it is <RTI>a</RTI> requirement that fresh air be supplied to the load air space 26 rather than the recirculated air of the closed loop, then it will be appreciated by those skilled in the art that it is a simple matter for ambient air to be ducted into the expansion air heat exchanger 20 via the moisture removal device 32, and for the air leaving the load air space 26 to be ducted back to ambient. The expansion air heat exchanger 20 ensures that the conditioning air is isolated from the <RTI>working</RTI> air in the event that the working air becomes contaminated cue to ineffective sealing or seal failure between the exhaust turbine 38 and compressor 14.

If required, it is also possible for the working air to flow in an open loop, i.e. for ambient air to be ducted into the initial compressor 12 and <RTI>baciC</RTI> to ambient on leaving the expansion air heat exchanger 20. Hcwever, operation in <RTI>tis</RTI> way is slightly detrimental with regard to cycle efficiency.

Figure 3 is a schematic diagram of <RTI>*he</RTI> air conditioning system of Figure 1 switched to operate in heating mode; this is achieved simply by altering the settings of the two-way valves 28 and 30 as appropriate. The working air closed loop is the same as for Figure 1 except that in this case heat is rejected to the conditioning air stream in the heat exchanger 16, and absorbed from an ambient air stream in the heat exchanger 20. The conditioning air again flows within a closed loop but in this case under the action of the electrically driven <RTI>Q2n</RTI> 34. It is drawn from the load air space 26 and passes through the low pressure side of the compression air heat exchanger 16 via the two-way <RTI>valve</RTI> 28 and fan 34. Heat is absorbed from the working air stream within the heat exchanger 16, and the heated conditioning air returns to the load air space 26 via the two-way valve 30. <RTI>C > nditioning</RTI> <RTI>atr</RTI> humidity is again controlled by means of the moisture removal device 32.

The ambient air strean now flows through the low pressure side of the expansion air heat <RTI>exchanger</RTI> 20 under the action of the fan 24 and via valve 28. It rejects heat to the working air stream within the heat exchanger 20 and is then <RTI>duped</RTI> back <RTI>tt</RTI> ambient via the fan 24 and valve 30. Under <RTI>typis l</RTI> cold weather conditions the temperature of the ambient air leaving the <RTI>het</RTI> exchanger 20 will be sub-zero; a third moisture <RTI>removal</RTI> device 62 is therefore included between the valve 28 and heat <RTI>exchanger</RTI> 20 to prevent ice from forming in the heat exchanger 20.

As in the cooling <RTI>modss</RTI> it fresh rather than recirculated air is required for conditioning, it is a <RTI>single</RTI> matter for the air to be ducted in from <RTI>ambient.</RTI> and <RTI>subsequen*9y</RTI> returned in an open loop.

This is also true of the <RTI>working</RTI> air, with the advantage that in heating mode the cycle efficiency is improved slightly by operating with the working air in an open loop.

In some applications either cooling or heating will be required but not both; for instance, in the automotive industry cooling only is required since heating can be obtained from engine heat loss using well established methods. In such cases it will be appreciated that the air conditioner 10 may be modified o operate in either cooling or heating mode only, thereby simplifying the embodiments of Figures 1 and 3.

Figures 4 and 5 show embodiments of the air cycle air conditioning system 10 in which the majority of the components are the same as for Figures 1 and 3, the <RTI>eein</RTI> difference being that the flow direction of the working air is reversed. This has the effect of significantly improving the coefficient of <RTI>perfozinance</RTI> of the system <RTI>10</RTI> In Figures 4 and 5 the heat exchanger 16 is the expansion air heat exchanger and the heat exchanger 20 is the compression air heat exchanger.

Figure 4 is a schematic diagram of <RTI>the</RTI> reverse flow air conditioner 10 in cooling mode. In <RTI>f)ris</RTI> case, the working air flows in an open loop since this <RTI>substantiatly</RTI> improves the system efficiency relative to operating with a closed loop.The open loop comprises: a turbine 18 which draws the air from <RTI>ambient</RTI> via a two-way valve 64 and a moisture removal device 22, <RTI>a8</RTI> expands it to sub-atmospheric pressure thereby cooling it; an expansion air heat exchanger 16 in which heat is absorbed from the <RTI>con ioning</RTI> air stream; an initial compressor 14 which partially <RTI>re-c~presses</RTI> the air back to ambient pressure; a second compressor 12 <RTI>vhich</RTI> completes the re-compression and exhausts to ambient via <RTI>a</RTI> <RTI>tWC-W</RTI> valve 66. The moisture remover 22 prevents ice from forming in <RTI>t--</RTI> heat exchanger 16.

The conditioning air flows in a closed loop under the action of an electrically driven <RTI>fn</RTI> <RTI>34.</RTI> The air is drawn from the load air space 26 and passes <RTI>trough</RTI> the expansion air heat exchanger 16 via a moisture removal device 32, a two-way valve 28 and the fan 34. Heat is rejected to the working air stream within the heat exchanger 16 and the cooled conditioning air returns to the load air space 26 via a two-way valve 30. The moisture remover 32 is used to reduce conditioning air <RTI>humi8Z*y.</RTI>

As with the embodiment: of Figures 1 and 3, it will be appreciated that fresh ambient air may be used as the conditioning air in an open loop. The heat <RTI>exchanger</RTI> 20 and fan 24 are not used in this embodiment, but are described below in connection with the system in heating mode.

Figure 5 is a <RTI>schematic</RTI> diagram of the air conditioning system of Figure 4 switched to operate in heating mode; this is achieved simply by altering the settings of the two-way valves 28, 30, 64 and 66 as appropriate. The working air circuit is similar to that for Figure 4, except now the loop is closed with the air leaving the second compressor 12 being ducted through the compression air heat exchanger <RTI>2D,</RTI> vie value 66, and back to the turbine 18 via valve 64 and moisture removal <RTI>device</RTI> 22. Heat is rejected to the conditioning air stream within the heat exchanger 20, and is absorbed from an ambient air stream within the expansion air heat exchanger 16.

The conditioning air <RTI>-e-in</RTI> flows in a closed loop, this time under the action of the electrically driven fan 24. The air is drawn from the load air space 26 and passes through the compression air heat exchanger 20 via the <RTI>moisture</RTI> removal device 32 and two-way valve 28.

Heat is absorbed from the working air stream within the heat exchanger 20 and the heated conditioning air returns to the load air space 26 via the fan 24 and valve 30.

The ambient air stream flows through the expansion air heat exchanger 16 under the action of the electrically driven fan 34 and via the valve 28 and fan 34. It rejects heat to the working air stream within the heat exchanger 16, and returns to ambient via the valve 30.

Again, if fresh rather than recirculated air is required for conditioning then it is a simple matter for the air to be ducted in from ambient and subsequently returned in an open loop. This is also true of the working air and can be achieved simply by leaving the valve 64 in the position shown in Figure 4. However, the embodiment of Figure 5 is preferred since operation with the working air in an open loop is slightly detrimental to cycle efficiency in this mode.

As mentioned previously, some applications will require either cooling or heating but not both. In such cases it will be appreciated that the air conditioner 10 may be modified to operate in either cooling or heating mode only, thereby simplifying the embodiments of Figures 4 and 5.

Under certain operating conditions, for instance during idling in automotive applications, the energy available in the exhaust gas will be insufficient to drive the air conditioner 10 at or near the design point. Figure 6 shows the embodiment of Figure 1 modified in order to overcome this problem. An additional compressor 68 is incorporated in the working air circuit as an extra means of power input for use under low exhaust energy conditions. The compressor 68 is driven by an electrically powered high speed motor 70 of the type described in British Patent Application <RTI>No.2217113A.</RTI> Designing for high rotational speed is preferred since it significantly reduces the size of the rotating components relative to those of a similar compressor/motor arrangement powered by a more conventional motor.However, it will be appreciated that alternative methods of providing extra power input, such as a conventional motor or a supercharged compressor, may also be used to achieve the same end.

While sufficient <RTI>exhaust</RTI> energy is available to meet the power requirement of the air conditioner 10, the compressor 68 and motor 70 are not used and the system operates as described for Figure 1.

However, if the <RTI>pressure</RTI> measured by the sensor 50 at the outlet of the compressor 14 fall below a pre-set minimum, and maximum energy is being extracted from the exhaust gas, i.e. the exhaust bypass valve 44 is fully closed, then electrical power input to the high speed motor 70 is initiated by the control electronics 72. The control electronics 72 drive the motor 70, and hence compressor 68, at a speed suitable for the system <RTI>0</RTI> operate at or near design conditions. This continues until such time as the energy capacity of the exhaust gas rises sufficiently for the control electronics 72 to deactivate the motor 70. Two non-return valves, 74 and 76, ensure that the correct working air flow <RTI>dire-tions</RTI> are maintained.

It will be appreciated <RTI>t5.at</RTI> the extra means of power input described for Figure 6 may also be incorporated in all of the air conditioner embodiments described so far.

In the reverse flow embodiments of Figures 4 and 5, sub-zero temperatures are encountered at the expansion air heat exchanger 16 for a wide range of ambient and operating conditions. Therefore, despite the presence of the moisture removal devices 22 and 32, it is likely that gradual icing of the heat transfer surfaces of the heat exchanger 16 will occur, thus impairing its performance.

Figure 7 shows the reverse flow cooling mode embodiment of Figure 4 modified to incorporate <RTI>2</RTI> de-icing facility and thereby alleviate this problem. Under normal circumstances operation of the air conditioner 10 is as described for Figure 4. In this case, however, the pressure drop across the working air side of the expansion air <RTI>Iieat</RTI> exchanger 16 is measured by a pressure difference sensor 78 which communicates with the de-icing control electronics 80; the pressure drop is measured on the working air side since this will be more susceptible to icing.If, due to the <RTI>formation</RTI> of ice, the pressure drop increases to a factory-set level then the control electronics 80 switch the lain cycle off and cause the settings of valves 30 and 82 to be altered <RTI>such</RTI> that air is driven, by the fan 34, from a source of hot air through the heat exchanger 16, via valve 82 and the fan 34, and on to ambient via valve 30. In <RTI>t.is</RTI> way the hot air de-ices the expansion air heat <RTI>exchanger</RTI> 16 <RTI>End</RTI> the resultant water leaves said heat exchanger via a drain 84.The source of hot air will depend on the application, for <RTI>instance</RTI> air <RTI>from</RTI> around the exhaust manifold might be used in an <RTI>tsrotive</RTI> <RTI>splrcstion.</RTI> Operation in de-icing mode continues for a <RTI>actory-se-.</RTI> tire period sufficient to complete de-icing, after which the control electronics 80 switch the system back to normal mode.

Figure 8 shows the reverse <RTI>Clos</RTI> <RTI>heating</RTI> mode embodiment of Figure 5 also modified to <RTI>incorporate</RTI> a de-icing facility. The modifications and operation of the <RTI>facility</RTI> are essentially the same as those described for <RTI>Figure</RTI> 7. However, in this case it is only necessary for valve 82 to be altered when <RTI>sOitc:-ing</RTI> to de-icing mode, and the pressure drop is <RTI>measured</RTI> across the ambient air side of the heat exchanger 16 since in this embodiment it will be most susceptible to icing, being open loop.

Figure 9 shows the <RTI>embodiment</RTI> of Figure 1 modified to allow a greater degree of control over the temperature of the conditioned air. The addition of a control valve 86, valve controller 88, valve actuator 90, temperature sensor 92 and extra duct 94 allows a controlled amount of air to be diverted from the hot stream leaving the ambient pressure side of the heat exchanger 16 and mixed, via the duct 94, with the cold air being delivered to the load air space 26.

In this way the <RTI>tenperature</RTI> at <RTI>which</RTI> the conditioning air is delivered can be adjusted.

Figure 10 is a block diagram of the preferred additional control system for <RTI>implerentleg</RTI> the air delivery temperature control described for the embodiment of <RTI>figure</RTI> 9. The desired air delivery temperature may be input by the user but would normally be factory-set. A negative feedback <RTI>summer</RTI> 96 compares the set temperature with that measured by the temperature sensor 92 positioned in the air delivery duct 98, and adjusts the valve 86 by means of the actuator 90 thereby altering the amount of hot air diverted through the duct 94. The air delivery temperature is adjusted in this way until it lies within a temperature band defined in the feedback circuit <RTI>100</RTI> by a high/low threshold crossing detector 102. Once the measured temperature lies within this band a switch 104 is opened to nullify the feedback and hence maintain the current setting of the control valve 86. If the temperature subsequently moves out of the band, for instance due to a sufficient change in car engine conditions, then the switch 104 is again closed and adjustment of the valve 86 resumes.

It will be clear to those skilled in the art that control of the air delivery temperature in this way may be applied to all of the air conditioner <RTI>embodiments</RTI> described previously, with slight modifications determined by the appropriate point from which hot or cold air should be diverted.

Claims (19)

1. An air cycle air conditioning system for cooling a load air <RTI>space, comprising:</RTI> an exhaust turbine drivable by a supply of exhaust gases from an engine; an air <RTI>compressor</RTI> drivingly connected to the exhaust turbine; a second compressor drivingly connected to an expansion turbine; an expansion air heat exchanger for receiving <RTI>exçxukhed</RTI> air from the expansion turbine and delivering it to the two <RTI>cdmpressors</RTI> in series for <RTI>re-cogpression,</RTI> the air flow generated by the two conpressors in series driving the expansion turbine and the expanded air in the expansion air heat exchanger being in heat exchange relationship with a fan-assisted flow of conditioning air to the load air space for effecting cooling of the load air space.
2. An air conditioning system according to claim 1, which is switchable between cooling and heating modes for cooling or for heating the load air space, further comprising a compression air heat exchanger for receiving fully <RTI>re-compressed</RTI> air from the compressors and delivering it to the expansion turbine, the compressed air in the compression air heat exchanger being in heat exchange relationship with a fan-assisted flow of conditioning air to the load air space when the system is in its heating mode for effecting heating of the load air space, and the expanded air in the expansion air heat exchanger being in heat-exchange relationship with its fan-assisted flow of conditioning air to the load air space only when the system is in its cooling mode.
3. An air conditioning system according to claim 2, wherein the supply of air to the expansion turbine in both the cooling and heating modes is a supply of compressed air from the exhaust turbine driven compressor via the compression air heat exchanger.
4. An air conditioning system according to claim 3, further comprising a first fan for driving the conditioning air through the compression air heat exchanger in the heating mode and for driving ambient air through the compression air heat exchanger in the cooling mode; and a second fan for driving the conditioning air through the expansion air heat exchanger in the cooling mode and for driving ambient air through the expansion air heat exchanger in the heating mode.
<RTI>
5.</RTI> An air conditioning system according to claim 4, wherein the air flows are controlled by two two-way valves operable in unison to switch the system between its cooling and heating modes.
6. An air conditioning system according to claim 3, further comprising a number of moisture removal devices appropriately positioned to inhibit the formation of ice in the expansion air heat exchanger and to control the humidity of the conditioning air.
7. An air conditioning system according to claim 3, further comprising means for temperature control of the load air space by selectively adding a controlled flow of heated air to the cooled conditioning air delivered to the load air space in cooling mode, and a controlled flow of cooled air to the heated conditioning air delivered to the load air space in heating mode.
8. An air <RTI>conditinning</RTI> system according to claim 3, further including a de-icing system for the expansion air heat exchanger, wherein the de-icing system comprises a pressure difference sensor for sensing differences between the entry and exit pressures of at least one of the air flows through the expansion air heat exchanger; a controller responsive to a pressure difference so sensed; a source of heated air; and at least one two-way valve controlled by the controller to direct the heated air in a fan-assisted air flow through the expansion air heat exchanger to melt any ice therein responsible for the pressure difference.
9. An air conditioning system according to claim 3, further comprising an exhaust turbine bypass valve controlled by a control system for automatically adjusting the proportion of the total exhaust gases passing through the exhaust turbine to maintain a desired power input to the system.
10. An air conditioning system according to claim 3, further comprising an extra air compressor driven by a high speed motor, or other suitable means, to provide additional power input to the system whenever the exhaust gas flow is insufficient fully to meet the system power requirement.
11. An air conditioning system according to claim 2, wherein the supply of air to the expansion turbine in the cooling mode is a supply of ambient air at ambient pressure, and the supply of air to the expansion turbine in the heating mode is a supply of compressed air from the expansion turbine driven compressor via the compression air heat exchanger.
12. An air conditioning system according to claim 11, comprising a first fan for driving the conditioning air through the compression air heat exchanger in the heating mode, and a second fan for driving the conditioning air through the expansion air heat exchanger in the cooling <RTI>mode</RTI> and for driving ambient air through the expansion air heat exchanger in the heating mode.
13. An air conditioning system according to claim 12, wherein the air flows are controlled by four <RTI>two-way</RTI> valves operable in unison to switch the system between its cooling and heating modes.
14. An air conditioning system according to claim 11, further comprising a <RTI>number</RTI> of moisture removal devices appropriately positioned to inhibit the formation of ice in the expansion air heat exchanger and to control the humidity of the conditioning air.
15. An air conditioning system according to claim 11, further comprising means for temperature control of the load air space by selectively adding a controlled flow of heated air to the cooled conditioning air delivered to the load air space in cooling mode, and a controlled flow of cooled air to the heated conditioning air delivered to the load air space in heating mode.
16. An air conditioning system according to claim 11, further including a de-icing system for the expansion air heat exchanger, wherein the de-icing system comprises a pressure difference sensor for sensing differences between the entry and exit pressures of at least one of the air flows through the expansion air heat exchanger; a controller responsive to a pressure difference so sensed; a source of heated air; and at least one two-way valve controlled by the controller to direct the heated air in a fan-assisted air flow through the expansion air heat exchanger to melt any ice therein responsible for the pressure difference.
17. An air conditioning system according to claim 11, further comprising an exhaust turbine bypass valve controlled by a control system for automatically adjusting the proportion of the total exhaust gases passing through the exhaust turbine to maintain a desired power input to the system.
<RTI>ls.</RTI> An air conditioning system according to claim 11, further comprising an extra air compressor driven by a high speed motor, or other suitable means, to provide additional power input to the system whenever the exhaust gas flow is insufficient to fully meet the system power requirement.
19. An air conditioning system substantially as described herein with reference to the drawings.
GB9006628A 1990-03-24 1990-03-24 Exhaust driven air cycle air conditioner Expired - Fee Related GB2242261B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
GB9006628A GB2242261B (en) 1990-03-24 1990-03-24 Exhaust driven air cycle air conditioner

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
GB9006628A GB2242261B (en) 1990-03-24 1990-03-24 Exhaust driven air cycle air conditioner
JP26975090A JPH03129267A (en) 1989-10-10 1990-10-09 Air conditioner
US07596657 US5121610A (en) 1989-10-10 1990-10-10 Air cycle air conditioner for heating and cooling

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GB9006628D0 GB9006628D0 (en) 1990-05-23
GB2242261A true true GB2242261A (en) 1991-09-25
GB2242261B GB2242261B (en) 1993-11-24

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Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0690275A3 (en) * 1994-06-27 1996-06-26 Praxair Technology Inc Cooling system employing a primary high pressure closed refrigeration loop and a secondary refrigeration loop
WO2000055550A1 (en) * 1999-03-17 2000-09-21 Daikin Industries, Ltd. Air conditioner
FR2796918A1 (en) * 1999-07-30 2001-02-02 Liebherr Aerospace Gmbh Method and air conditioning system for aircraft cabins
EP1467158A2 (en) * 2003-04-09 2004-10-13 Hitachi Air Conditioning Systems Co., Ltd. Refrigeration cycle apparatus
US7222499B2 (en) 2004-06-26 2007-05-29 Honeywell Normalair Garrett (Holdings) Closed loop air conditioning system
CN100498123C (en) 2006-10-19 2009-06-10 君 何 Internal combustion engine waste gas energy and high speed motor hybrid driven air circulation refrigeration system
US7908766B2 (en) * 2004-12-06 2011-03-22 Lg Electronics Inc. Clothes dryer
US7975398B2 (en) * 2004-07-19 2011-07-12 Earthrenew, Inc. Process and system for drying and heat treating materials
CN103134230A (en) * 2012-11-27 2013-06-05 北京航空航天大学 Two-wheel boosting type air circulation refrigerating system capable of exhausting and acting by cockpit
FR3033290A1 (en) * 2015-03-04 2016-09-09 Valeo Systemes Thermiques motor vehicle air conditioning circuit

Cited By (17)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0690275A3 (en) * 1994-06-27 1996-06-26 Praxair Technology Inc Cooling system employing a primary high pressure closed refrigeration loop and a secondary refrigeration loop
EP1178266A4 (en) * 1999-03-17 2003-06-04 Daikin Ind Ltd Air conditioner
WO2000055550A1 (en) * 1999-03-17 2000-09-21 Daikin Industries, Ltd. Air conditioner
EP1178266A1 (en) * 1999-03-17 2002-02-06 Daikin Industries, Ltd. Air conditioner
US6484525B1 (en) * 1999-03-17 2002-11-26 Daikin Industries, Ltd. Air conditioner
GB2355520A (en) * 1999-07-30 2001-04-25 Liebherr Aerospace Gmbh Air-conditioning system for airplane cabins
GB2355520B (en) * 1999-07-30 2003-09-03 Liebherr Aerospace Gmbh Air-conditioning system for airplane cabins
FR2796918A1 (en) * 1999-07-30 2001-02-02 Liebherr Aerospace Gmbh Method and air conditioning system for aircraft cabins
US6923016B2 (en) 2003-04-09 2005-08-02 Sunao Funakoshi Refrigeration cycle apparatus
EP1467158A3 (en) * 2003-04-09 2004-12-01 Hitachi Air Conditioning Systems Co., Ltd. Refrigeration cycle apparatus
EP1467158A2 (en) * 2003-04-09 2004-10-13 Hitachi Air Conditioning Systems Co., Ltd. Refrigeration cycle apparatus
US7222499B2 (en) 2004-06-26 2007-05-29 Honeywell Normalair Garrett (Holdings) Closed loop air conditioning system
US7975398B2 (en) * 2004-07-19 2011-07-12 Earthrenew, Inc. Process and system for drying and heat treating materials
US7908766B2 (en) * 2004-12-06 2011-03-22 Lg Electronics Inc. Clothes dryer
CN100498123C (en) 2006-10-19 2009-06-10 君 何 Internal combustion engine waste gas energy and high speed motor hybrid driven air circulation refrigeration system
CN103134230A (en) * 2012-11-27 2013-06-05 北京航空航天大学 Two-wheel boosting type air circulation refrigerating system capable of exhausting and acting by cockpit
FR3033290A1 (en) * 2015-03-04 2016-09-09 Valeo Systemes Thermiques motor vehicle air conditioning circuit

Also Published As

Publication number Publication date Type
GB2242261B (en) 1993-11-24 grant
GB9006628D0 (en) 1990-05-23 grant

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Effective date: 19960324