Abstract:
An aircraft air-conditioning system including an air-conditioning unit which is designed to provide cooled process air. A process air line conducts cooled process air provided by the air-conditioning unit into a working area of an aircraft cabin. A cooler supplies cooling energy to a device to be cooled which is provided in the working area of the aircraft cabin. Finally, the aircraft air-conditioning system includes a heat transfer arrangement which transfers waste heat generated by the cooler to process air flowing through the process air line.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of the German patent application No. 102013005596.2 filed on Apr. 3, 2013, the German patent application No. 102013005595.4 filed on Apr. 3, 2013, and the German patent application No. 102013211177.0 filed on Jun. 14, 2013, the entire disclosures of which are incorporated herein by way of reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to an aircraft air-conditioning system and a process for working an aircraft air-conditioning system. 
         [0003]    The cabin of a modem commercial aircraft is normally divided into different air-conditioning zones which are supplied with air-conditioning air as required by an air-conditioning unit of the aircraft. Typical air-conditioning zones of an aircraft cabin are, for example, a first class area, a business class area and an economy class area. The operation of an air-conditioning unit of the aircraft air-conditioning arrangement is normally controlled according to the cooling requirement of the air-conditioning zone with the highest cooling requirement, i.e., the air-conditioning unit provides cooled process air at a temperature which is sufficiently low to cool the air-conditioning zone with the highest thermal load generally the economy class area of the cabin—to a comfortable temperature. For example, the operation of the air-conditioning unit is controlled in such a way that it provides cooled process air at a temperature of 11 oC. 
         [0004]    To also enable a comfortable temperature to be set in air-conditioning zones with a lower thermal load, an appropriate quantity of hot engine bleed air is mixed with the cooled process air provided by the air-conditioning unit before the air is finally blown into the air-conditioning zone. As an alternative to this, the cooled process air provided by the air-conditioning unit can be heated to the desired temperature by means of an electric heating device before being supplied into an air-conditioning zone. These circumstances are described for example in EP 1 701 884 B1 or U.S. Pat. No. 7,802,732, B2. 
         [0005]    Working areas which are provided in the door areas of the aircraft cabin and in which the on-board kitchens, the so-called galleys, of the aircraft are also arranged, are cabin areas with a particularly low thermal load since there are normally only a few people in these areas. Moreover, cooled galley areas, which serve for example for storing foodstuffs provided for distribution to the passengers of the aircraft, give off cooling energy to the environment. Finally, cooling energy is also supplied to the working areas of an aircraft cabin by way of cold interior surfaces of the aircraft doors. The air-conditioning air supplied to the working areas of the aircraft cabin by the aircraft air-conditioning arrangement therefore also normally has to be heated by means of appropriate heating devices, such as those described in EP 1 701 884 B1 or U.S. Pat. No. 7,802,732, to a considerably higher temperature than the temperature of the cooled process air provided by the air-conditioning unit of the aircraft air-conditioning arrangement in order to enable a comfortable ambient temperature to be set in the working areas of the aircraft cabin. 
       SUMMARY OF THE INVENTION 
       [0006]    The object on which the invention is based is to provide an aircraft air-conditioning system and a process for working an aircraft air-conditioning system which enables energy-efficient air conditioning of working areas provided in an aircraft cabin. 
         [0007]    An aircraft air-conditioning system according to the invention comprises an air-conditioning unit which is designed to provide cooled process air. The air-conditioning unit associated with an aircraft air-conditioning arrangement is normally supplied with compressed engine bleed air from an engine or an auxiliary engine of the aircraft. As an alternative to this, the air-conditioning unit may also be supplied with air which is compressed by a separate compressor. Before being supplied to the air-conditioning unit, the compressed engine bleed air or the air compressed by the compressor normally flows through a heat exchanger, a so-called pre-cooler, which cools the compressed engine bleed air or the air compressed by the compressor to a desired temperature. In the air-conditioning unit, the air is further cooled and expanded as it flows through at least one heat exchanger and various compression and expansion units. 
         [0008]    The operation of the air-conditioning unit is normally controlled by a central control device of the aircraft air-conditioning arrangement. For example, the central control device of the aircraft air-conditioning arrangement may control the operation of the air-conditioning unit according to the cooling requirement of a cabin, which is divided into different air-conditioning zones, of an aircraft equipped with the aircraft air-conditioning arrangement. In particular, the central control device of the aircraft air-conditioning arrangement may control the operation of the air-conditioning unit according to the cooling requirement of the air-conditioning zone with the highest cooling requirement. In such a case, the operation of the air-conditioning unit is controlled by means of the central control device of the aircraft air-conditioning arrangement in such a way that the air-conditioning unit provides cooled process air at a temperature which is sufficiently low to cool the air-conditioning zone with the highest thermal load to a comfortable temperature. For example, the cooled process air provided by the air-conditioning unit may have a temperature of approximately 11 oC. 
         [0009]    The aircraft air-conditioning system further comprises a process air line which is designed to conduct cooled process air provided by the air-conditioning unit into a working area of an aircraft cabin. The working area may be arranged for example in a door area of the aircraft cabin, i.e., an area of the aircraft cabin which is adjacent to a door. A galley may be provided for example in the working area. The working area of an aircraft cabin differs from other areas of the aircraft cabin in particular in that there are normally relatively few people in the working area. Moreover, cooling energy can additionally make its way into the working area by way of galley areas which are cooled by way of cold surfaces or the aircraft doors. The working area therefore normally has a lower cooling requirement than other areas of the aircraft cabin, for example, a business class area or an economy class area, in which there are many passengers. Instead, the cooled process air provided by the air-conditioning unit normally has to be heated to a higher temperature before being supplied into the working area of the aircraft cabin in order to enable comfortable ambient conditions to be produced in the working area. 
         [0010]    A cooler, which is designed to supply cooling energy to a device to be cooled, which is provided in the working area of the aircraft cabin, is moreover associated with the aircraft air-conditioning system. The cooler may be for example an air chiller, which supplies cooling energy for example to a galley device to be cooled. The galley device to be cooled may be for example a compartment of the galley which serves for storing foodstuffs provided for distribution to the aircraft passengers. In particular, if the cooler is constructed in the form of an air chiller, the cooler may be designed to operate with a two-phase coolant, i.e., a coolant which is converted from the liquid state into the gaseous state when giving off cooling energy to the device to be cooled. 
         [0011]    The cooler generates waste heat during operation. If the cooler is operated with a two-phase coolant, the two-phase coolant, which is in the gaseous state of aggregation after giving off cooling energy to the device to be cooled, reverts back to the liquid state of aggregation as a result of thermal energy transfer to a corresponding fluid. The fluid serving to absorb the waste heat of the cooler may in turn be in the liquid or gaseous state of aggregation. 
         [0012]    Finally, the aircraft air-conditioning system comprises a heat transfer arrangement. The heat transfer arrangement is designed to transfer the waste heat generated by the cooler to the process air flowing through the process air line. The heat transfer arrangement therefore ensures that the waste heat generated by the cooler can be used to heat the process air flowing through the process air line before it is supplied into the working area of the aircraft cabin. It is therefore no longer necessary to discharge the waste heat generated by the cooler to the aircraft environment with the aid of the aircraft air-conditioning arrangement or an additional cooling system. Moreover, to generate comfortable ambient conditions in the working area of the aircraft cabin, it is possible to forego energy-intensive heating of the process air by means of an additional heating device before it is supplied into the working area of the aircraft cabin. 
         [0013]    Finally, owing to its low temperature of, for example, approximately 11 oC, the process air flowing through the process air line constitutes a heat sink having a comparatively low temperature level for the waste heat to be discharged from the cooler. This means that the cooler may be operated particularly energy efficiently. In particular, with a cooler which is constructed in the form of an air chiller, it is possible to operate a compressor of the air chiller at a comparatively low speed. This enables a reduction in the noise emissions generated by the air chiller, thereby increasing the comfort of people in the aircraft cabin and in particular in the working area of the aircraft cabin. 
         [0014]    The heat transfer arrangement of the aircraft air-conditioning system according to the invention may furthermore be designed to transfer waste heat generated by a heat-generating device of a galley to the process air flowing through the process air line. The heat-generating galley device may be for example an oven, a device for preparing hot drinks or any other galley device which generates waste heat during operation. The only significant factor is that the waste heat of this device does not have to be discharged to the aircraft environment in energy-intensive manner with the aid of the aircraft air-control arrangement or an additional cooling system, but can instead be used to heat the process air flowing through the process air line. 
         [0015]    The heat transfer arrangement preferably comprises a heat exchanger which is designed to bring fluid which is heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley into thermal contact with the process air flowing through the process air line. The fluid heated by the waste heat of the cool and/or the waste heat of the heat-generating device of the galley is preferably a liquid heat carrier medium which is brought into thermal contact with the process air flowing through the process air line in the heat exchanger of the heat transfer arrangement. As an alternative to this, however, it is possible to use a two-phase heat carrier medium, i.e., a heat carrier medium which is converted from the liquid state of aggregation into the gaseous state of aggregation as a result of absorbing thermal energy from the cooler and/or the heat-generating device and then converted back into the liquid state of aggregation again when flowing through the heat exchanger of the heat transfer arrangement. 
         [0016]    The heat exchanger of the heat transfer arrangement may be connectable for example to a heat carrier circuit in which the fluid heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley circulates. A conveyor device, which is constructed for example in the form of a pump and conveys the fluid heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley through the heat carrier circuit, may be arranged in the heat carrier circuit. As an alternative to this, it is also possible to provide natural circulation for conveying the fluid heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley through the heat carrier circuit. The cooler and the heat-generating galley device may be arranged parallel to one another in the heat carrier circuit. 
         [0017]    In a preferred embodiment, the aircraft air-conditioning system furthermore comprises a further heat transfer arrangement which is designed to transfer waste heat generated by the cooler and/or waste heat generated by the heat-generating device of the galley to a cabin air extraction system. The cabin air extraction system normally serves to divert waste heat from heat-generating devices on board the aircraft and/or bad smells from the aircraft cabin into the aircraft environment. The further heat transfer arrangement enables the waste heat of the cooler and/or the heat-generating galley device to be discharged to the aircraft environment, for example if it is undesirable for the process air flowing through the process air line to be heated before being supplied into the working area of the aircraft cabin. This may be the case for example if, on hot days, the aircraft cabin has to be cooled to a comfortable temperature level as quickly as possible during ground operations of the aircraft. 
         [0018]    The further heat transfer arrangement may comprise a further heat exchanger which is designed to bring fluid heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley into thermal contact with cabin exhaust air which flows though a cabin exhaust air line of the cabin air extraction system. In a configuration of this type, the cabin exhaust air flowing through the cabin exhaust air line of the cabin air extraction system therefore absorbs the excess thermal energy of the cooler and/or the heat-generating galley device before the cabin exhaust air is discharged to the aircraft environment by way of the cabin exhaust air line. A conveyor device constructed in the form of a fan may be arranged in the cabin exhaust air line to convey the cabin exhaust air through the cabin exhaust air line. 
         [0019]    The further heat exchanger of the further heat transfer arrangement preferably is connectable to the heat carrier circuit in which the fluid heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley circulates. Like the heat exchanger of the heat transfer arrangement, the further heat exchanger of the further heat transfer arrangement may therefore also have the fluid heated by the waste heat of the cooler and the heat-generating galley device flowing through it. As it flows through the further heat exchanger, the fluid gives off its excess thermal energy to the cabin exhaust air which is brought into thermal contact with the fluid in the further heat exchanger of the further heat transfer arrangement. 
         [0020]    The aircraft air-conditioning system may furthermore comprise a control unit which is designed to control the operation of the heat transfer arrangement and the further heat transfer arrangement according to a set temperature of the process air to be supplied to the working area of the aircraft cabin in such a way that the waste heat generated by the cooler and/or the heat-generating device of the galley is alternatively transferred to the process air flowing through the process air line or to the cabin air extraction system in order to heat the process air flowing through the process air line to the desired set temperature. The control unit may be constructed for example in the form of an electronic control unit and integrated in the central control device of the aircraft air-conditioning arrangement. As an alternative to this, it is however also conceivable to construct the control unit as a separate control unit. Under the control of the control unit, it is always possible to heat the process air flowing through the process air line to a desired set temperature which enables comfortable ambient conditions to be set in the working area of the aircraft cabin. 
         [0021]    The control unit is essentially able to control the operation of the heat transfer arrangement and the further heat transfer arrangement in such a way that the waste heat generated by the cooler and/or the heat-generating galley device is either transferred exclusively to the process air flowing through the process air line or exclusively to the cabin air extraction system. However, the control unit is preferably also designed to control the operation of the heat transfer arrangement and the further heat transfer arrangement so that the waste heat of the cooler and/or the heat-generating galley device is transferred in part to the process air flowing through the process air line and in part to the cabin air extraction system, with the quantity of heat which is transferred to the process air flowing through the process air line in particular being controlled so that the process air is heated to the desired set temperature. 
         [0022]    In particular, the control unit may be designed to control a valve arrangement in such a way that the fluid which circulates in the heat transfer circuit and is heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley is alternatively brought into thermal contact with the process air flowing through the process air line or the cabin exhaust air flowing through the cabin exhaust air line of the cabin air extraction system according to a set temperature of the process air to be supplied to the working area of the aircraft cabin. For example, the control unit may control the valve arrangement in such a way that the heated fluid circulating in the heat carrier circuit is conducted either exclusively through the heat exchanger of the heat transfer arrangement or the further heat exchanger of the further heat transfer arrangement. Under the control of the control unit, however, the valve arrangement may also be controlled in such a way that the fluid flowing through the heat carrier circuit is conducted in part through the heat exchanger of the heat transfer arrangement and in part through the further heat exchanger of the further heat transfer arrangement. The partial volume flows of the heated fluid in the direction of the heat exchanger of the heat transfer arrangement and the further heat exchanger of the further heat transfer arrangement are preferably controlled during this according to the set temperature of the process air to be supplied to the working area of the aircraft cabin. 
         [0023]    In a process according to the invention for working an aircraft air-conditioning system, cooled process air is provided by means of an air-conditioning unit of an aircraft air-conditioning arrangement. The cooled process air provided by the air-conditioning unit is conducted into a working area of an aircraft cabin by means of a process air line. Furthermore, cooling energy is supplied by means of a cooler to a device to be cooled which is provided in the working area of the aircraft cabin. Waste heat generated by the cooler is transferred to the process air flowing through the process air line by means of a heat transfer arrangement. 
         [0024]    The heat transfer arrangement furthermore preferably transfers waste heat generated by a heat-generating device of a galley to the process air flowing through the process air line. 
         [0025]    A fluid, which is heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley, is preferably brought into thermal contact with the process air flowing through the process air line by means of a heat exchanger of the heat transfer arrangement. 
         [0026]    The heat exchanger of the heat transfer arrangement may be connectable to a heat carrier circuit in which the fluid heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley circulates. 
         [0027]    Waste heat generated by the cooler and/or waste heat generated by the heat-generating device of the galley may furthermore be transferred to a cabin air extraction system by means of a further heat transfer arrangement. 
         [0028]    A fluid heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley may be brought into thermal contact with cabin exhaust air flowing through a cabin exhaust air line of the cabin air extraction system by means of a further heat exchanger of the further heat transfer arrangement. The further heat exchanger of the further heat transfer arrangement may be connectable to the heat carrier circuit in which the fluid heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley circulates. 
         [0029]    The operation of the heat transfer arrangement and the further heat transfer arrangement is preferably controlled by means of a control unit according to a set temperature of the process air to be supplied to the working area of the aircraft cabin in such a way that the waste heat generated by the cooler and/or the heat-generating device of the galley is alternatively transferred to the process air flowing through the process air line or to the cabin air extraction system in order to heat the process air flowing through the process air line to the desired set temperature. 
         [0030]    The control unit preferably controls a valve arrangement in such a way that the fluid which circulates in the heat carrier circuit and is heated by the waste heat of the cooler and/or the waste heat of the heat-generating device of the galley is alternatively brought into thermal contact with the process air flowing through the process air line or the cabin exhaust air flowing through the cabin exhaust air line of the cabin extraction system according to the set temperature of the process air to be supplied to the working area of the aircraft cabin. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0031]    A preferred embodiment of the invention is now explained in more detail with reference to the accompanying schematic drawing, in which 
           [0032]    The FIGURE shows a schematic illustration of an aircraft air-conditioning system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    An air-conditioning system  10  shown in the FIGURE comprises an air-conditioning unit  12  to which compressed engine bleed air is supplied from an engine or an auxiliary engine of the aircraft or compressed air is supplied from a compressor. In the air-conditioning unit  12 , the compressed air is cooled and expanded as it flows through at least one heat exchanger and diverse compression and expansion devices. The temperature of the process air exiting the air-conditioning unit  12  is controlled according to the cooling requirement of an aircraft cabin divided into different air-conditioning zones. In particular, the operation of the air-conditioning unit  12  is controlled in such a way that the temperature of the air exiting the air-conditioning unit  12  is sufficiently low to also meet the cooling requirement of the air-conditioning zone of the aircraft cabin with the highest cooling requirement—normally this is an economy class area of the aircraft cabin. For example, the air-conditioning unit  12  generates process air at a temperature of approximately 11 oC. 
         [0034]    The cooled process air generated by the air-conditioning unit  12  is conducted into the different air-conditioning zones of the aircraft cabin by way of a process air line  14 . In  FIG. 1 , a portion of the process air line  14  is shown which serves to conduct the cooled process air generated by the air-conditioning unit  12  into a working area  16  of the aircraft cabin. The working area  16  of the aircraft cabin is situated adjacent to the doors of the aircraft cabin (not shown in  FIG. 1 ). A galley  18  is arranged in the working area  16 . 
         [0035]    Since there are normally comparatively few people in the working area  16 , and the working area  16  is moreover cooled by the transfer of cooling energy from cold surfaces of the aircraft doors and cooled galley devices, the process air flowing through the process air line  14  has to be heated to a higher temperature before being supplied into the working area  16  in order to enable comfortable ambient conditions to be set in the working area  16 . 
         [0036]    A cooler  20  in the form of an air chiller is associated with the galley  18 . The cooler  20  serves to supply cooling energy to areas of the galley  18  which are to be cooled. The galley areas to be cooled may be for example galley compartments which serve to store foodstuffs provided for distribution to the aircraft passengers. The cooler  20  generates waste heat during operation. A heat-generating device  22  is moreover present in the galley  18 . The heat-generating galley device  22  may be for example an oven, a device for preparing hot drinks or any other galley device which generates waste heat during operation. 
         [0037]    The aircraft air-conditioning system  10  further comprises a heat transfer arrangement  24  which serves to transfer the waste heat generated by the cooler  20  and the waste heat generated by the heat-generating galley device  22  to the process air flowing through the process air line  14 . The heat transfer arrangement  24  comprises a heat exchanger  26  through which process air supplied to the heat exchanger  26  by way of the process air line  14  flows on its cold side. On the other hand, a fluid, particularly in the form of a liquid heat carrier medium, can flow through the heat exchanger  26  on its hot side and circulates in a heat carrier circuit  28  which serves to discharge waste heat from the cooler  20  and the heat-generating galley device  22 . 
         [0038]    The cooler  20  and the heat-generating galley device  22  are arranged parallel to one another in the heat carrier circuit  28 . A conveyor device  30 , which is arranged in the heat carrier circuit  28  and is constructed in the form of a pump, serves to convey the heat carrier fluid through the heat carrier circuit  28 . As an alternative to this, natural circulation can also be provided to convey the heat carrier fluid through the heat carrier circuit  28 . The transfer of the waste heat from the cooler  20  and the heat-generating galley device  22  to the heat carrier fluid circulating through the heat carrier circuit  28  takes place by way of the respective heat exchanger  32 ,  34  associated with the cooler  20  or the heat-generating galley device  22 . 
         [0039]    The aircraft air-conditioning system  10  furthermore comprises a further heat transfer arrangement  36 . The further heat transfer arrangement  36  serves to transfer waste heat generated by the cooler  20  and the heat-generating galley device  22  to a cabin air extraction system  38  as required. In particular, the further heat transfer arrangement  36  comprises a further heat exchanger  40  through which cabin exhaust air conducted through a cabin exhaust air line  42  of the cabin air extraction system  38  flows on its cold side. On the other hand, the hot side of the further heat exchanger  40  is connectable to the heat carrier circuit  29  in which the heat carrier fluid heated by the waste heat of the cooler  20  and the heat-generating galley device  22  is guided in a circuit. A conveyor device  43  constructed in the form of a fan serves to convey the cabin exhaust air to be discharged from the aircraft cabin through the cabin exhaust air line  42  of the cabin air extraction system  38 . 
         [0040]    The operation of the heat transfer arrangement  24  and the further heat transfer arrangement  36  is controlled by an electronic control unit  44 . According to a set temperature of the process air supplied to the working area  16  of the aircraft cabin by way of the process air line  14 , the control unit  44  controls a valve arrangement  50  comprising two valves  46 ,  48  in such a way that the heat carrier fluid circulating in the heat carrier circuit  28  is alternatively conducted through the heat exchanger  26  of the heat transfer arrangement  24  or the further heat exchanger  40  of the further heat transfer arrangement  36 . Therefore, the waste heat of the cooler  20  and the heat-generating galley device  22  is optionally transferred either to the process air flowing through the process air line  14  or the cabin exhaust air flowing through the cabin exhaust air line  42  of the cabin air extraction system  38 . 
         [0041]    The valves  46 ,  48  of the valve arrangement  50  have a variably adjustable flow cross-section so that the fluid volume flows which are supplied to the heat exchanger  26  of the heat transfer arrangement  24  or the further heat exchanger  40  of the further heat transfer arrangement  36  can always be controlled so that the process air flowing through the process air line  14  is heated to the desired set temperature before the process air is supplied into the working area  16 . The cabin exhaust air flowing through the further heat exchanger  40  of the further transfer arrangement  36  is discharged to the aircraft environment after it exits the further heat exchanger  40 . 
         [0042]    As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.