Abstract:
The air to be supplied to a room is brought to a desired temperature and a desired humidity through the following process steps:
       making outside air flow as a first air stream through a first line ( 20 ) and making a first portion of exhaust air coming from the room flow as a second air stream through a second line ( 21 ), wherein moisture is exchanged between the first air stream and the second air stream by means of a device for exchanging humidity,   condensing, by means of a dehumidifying and cooling device ( 19 ), moisture in the form of water from the first air stream and/or from the second air stream and/or inside the device for exchanging humidity, and   making a second portion of the exhaust air flow as a third air stream through another line ( 32 ) comprising another dehumidifying and cooling device ( 33 ) and returning said second portion back to the room, wherein in the other dehumidifying and cooling device ( 33 ) moisture is condensed from the third air stream in the form of water.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to a method and a device for preparing air to be supplied to a room, which is designated in technical language as supply air, to a desired temperature and a desired humidity, wherein moisture and heat are exchanged with the exhaust air to be removed from the room. 
       BACKGROUND OF THE INVENTION 
       [0002]    Known from U.S. Pat. No. 6,178,966 is a dehumidifying device, in which fresh outside air to be supplied to a room and exhaust air to be removed from the room are passed through two cavities separated by a water-vapor-permeable membrane in order to transfer both moisture and also heat between the two air streams. Known from EP 1521040 and EP 1748260 are devices in which the outside air and the exhaust air are passed through two separate humidity exchangers, wherein a third intermediary air stream transports moisture from one humidity exchanger to the other humidity exchanger. The third air stream makes it possible to regulate the moisture exchange. These devices are used in winter to transfer moisture and heat contained in the exhaust air to the outside air to be prepared and in summer to transfer cold contained in the exhaust air to the outside air to be prepared and moisture contained in the outside air to be prepared to the exhaust air in order to bring, with the lowest possible energy, the outside air to a desired temperature and a desired humidity, which is perceived as pleasant by persons residing in the room. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0003]    It is the object of the invention to improve the preparation of the supply air. 
         [0004]    The said object is solved according to the invention by the features of claims  1  and  6 . Advantageous embodiments are obtained from the dependent claims. 
         [0005]    The invention relates to a method for the preparation of supply air to a desired temperature and a desired humidity, wherein the supply air comprises prepared outside air and a portion of prepared exhaust air=prepared circulating air, and wherein moisture and heat are exchanged between the outside air and the exhaust air. The method comprises the steps:
       making outside air flow as a first air stream through a first line and making a first portion of exhaust air coming from the room as a second air stream flow through a second line, wherein moisture is exchanged between the first air stream and the second air stream by means of a device for exchanging humidity, e.g., by means of a single humidity exchanger or by means of coupled humidity exchangers, e.g. by means of two humidity exchangers coupled through a closed air circuit or liquid circuit,   condensing, by means of a dehumidifying and cooling device, moisture in the form of water from the first air stream and/or from the second air stream and/or inside the device for exchanging humidity, and   making a second portion of the exhaust air flow as a third air stream through another line comprising another dehumidifying and cooling device, and returning said second portion back to the room, wherein moisture is condensed from the third air stream in the form of water in the other dehumidifying and cooling device.       
 
         [0009]    In this context, the third air stream is designated in technical terminology as circulating air. 
         [0010]    The dehumidification and cooling of the air stream flowing through one of the necessary dehumidifying and cooling devices is preferably accomplished by means of Peltier elements. 
         [0011]    The dehumidification and cooling of the air stream flowing through one such dehumidifying and cooling device can alternatively take place by condensing this air stream by means of a compressor, whereby the air stream is heated to a temperature above the ambient temperature so that the air stream can release heat to the surroundings, and by relaxing the condensed air stream by means of a turbine, wherein the condensed air stream is cooled to a temperature below the dew point so that moisture is separated as water. 
         [0012]    The dehumidification and cooling of the air stream flowing through such a dehumidifying and cooling device can take place according to a further alternative, whereby the second air stream is condensed by means of a compressor and is separated into a warm and a cold air stream by means of a vortex tube, wherein the temperature of the cold air stream lies below the dew point so that moisture is separated as water. 
         [0013]    The invention relates on the other hand to a device suitable for carrying out the method according to the invention. Such a device comprises
       a first line having an inlet via which outside air can be drawn in and an outlet via which supply air can be delivered to the room,   a second line having an inlet via which exhaust air can be drawn in and an outlet via which outgoing air can be released to the surroundings,   a device for exchanging humidity between a first air stream flowing in the first line and a second air stream flowing in the second line,   a dehumidifying and cooling device, which is disposed either in the first line or in the second line or inside said device for exchanging humidity between the first and the second air stream, and   another line having an inlet to which exhaust air can be supplied from the room, and an outlet which opens into the room or into the first line upstream of the outlet thereof, and   another dehumidifying and cooling device, which is disposed in the other line.       
 
         [0020]    The device advantageously comprises another line or other lines through which outside air can be passed to one or both dehumidifying and cooling devices and then back (as outgoing air) to the surroundings, in order to remove heat accumulating in the corresponding dehumidifying and cooling device. If necessary, these lines contain a separate fan. 
         [0021]    The device for exchanging humidity between the first air stream flowing through the first line and the second air stream flowing through the second line is, for example, a single humidity exchanger, advantageously an air-air humidity exchanger, which has two cavities which are separated by a water-vapor-permeable membrane, wherein the two air streams can flow through the two cavities. However, it can also comprise a first and a second humidity exchanger, wherein the first humidity exchanger comprises a first cavity disposed in the first line, which is separated from a second cavity by a water-vapor-permeable membrane, wherein the second humidity exchanger comprises a third cavity disposed in the second line, which is separated from a fourth cavity by a water-vapor-permeable membrane, and wherein the second and the fourth cavity are disposed in a closed air circuit in which an air stream can circulate or in a closed liquid circuit. In this case, a dehumidifying and cooling device can be disposed in this closed air circuit or liquid circuit. 
         [0022]    A water-vapor-permeable membrane is to be understood as any structure which is permeable for water molecules but not for air. 
         [0023]    The invention is explained in detail hereinafter with reference to exemplary embodiments and with reference to the drawing. The figures are schematic and are not drawn to scale. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0024]      FIGS. 1-5  show various exemplary embodiment of a device for the preparation of outside air, 
           [0025]      FIG. 6  shows a schematic functional diagram of a dehumidifying and cooling device, and 
           [0026]      FIGS. 7-10  show various examples for the dehumidifying and cooling device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]      FIGS. 1 and 2  show two different exemplary embodiments of a device  1  for the preparation of outside air to a desired temperature and a desired humidity, in which the outside air exchanges moisture and heat with the exhaust air removed from the room and is supplied to the room as supply air. The device has a first inlet  2  at which the outside air is drawn in, passed as a first air stream to a first outlet  3 , and there released into the room as supply air, and a second inlet  4 , at which the exhaust air is drawn in, passed to a second outlet  5  as a second air stream, and there released as outgoing air. The device  1  comprises a first fan  6 , a second fan  7 , optionally a first filter  8 , optionally a second filter  9 , a heat exchanger  10 , a first humidity exchanger  11  having two cavities designated as cavity  12  and cavity  13 , which are separated from one another by a water-vapor-permeable membrane  14 , a second humidity exchanger  15  having two cavities designated as cavity  16  and cavity  17 , which are separated from one another by a water-vapor-permeable membrane  18 , and a dehumidifying and cooling device  19 . The outside air entering at the first inlet  2  is passed in a first line  20  as a first air stream through the first filter  8 , the heat exchanger  10 , and the cavity  12  of the first humidity exchanger  11  to the first outlet  3 . The exhaust air entering at the second inlet  4  is passed in a second line  21  as a second air stream through the second filter  9 , the cavity  16  of the second humidity exchanger  15 , and the heat exchanger  10  to the second outlet  5 . The device further comprises a closed air circuit  22 , in which a third air stream driven by a third fan  23  circulates through the cavity  13  of the first humidity exchanger  11  and the cavity  17  of the second humidity exchanger  15 . The third air stream preferably flows in counterflow to the first and to the second air stream, as shown by the arrows of the fans  6 ,  7 , and  23  in the figures. The water-vapor-permeable membrane  14  or  18  of the two humidity exchangers  11  and  15  is permeable for water vapor but not for air. The exchange of moisture in the humidity exchangers  11  and  15  takes place in a passive manner, i.e. without supply of energy. The two filters  8  and  9  comprise a coarse particle filter  24  and an electric filter  25 . The coarse particle filter  24  prevents insects or any other larger dirt particles from entering into the electric filter  25 . The electric filter  25  prevents dust and other dirt from entering into the heat exchanger  10  and/or onto the membrane of the humidity exchanger. The heat exchanger  10  is preferably a plate heat exchanger. The electric filter  25  can also be integrated in the heat exchanger  10 , as is described, for example, in WO 2004085946. Waste heat accumulates in the dehumidifying and cooling device  19 . A third line  26  is provided for removing this waste heat to the surroundings, through which outside air is supplied to the dehumidifying and cooling device, which outside air takes up the waste heat and then releases it to the surroundings. The third line  26  opens, for example as shown, upstream of the second outlet  5  into the second line  21 . In this example, a fourth fan  27  is provided in the line  26 , in order to allow the cooling outside air to flow past the dehumidifying and cooling device  19 . The fourth fan  27  can possibly be omitted if the first fan  6  is disposed directly downstream of the first inlet  2 , as in the example according to  FIG. 2 . 
         [0028]    In the first exemplary embodiment shown in  FIG. 1 , the dehumidifying and cooling device  19  is disposed between the cavity  17  of the second humidity exchanger  15  and the cavity  13  of the first humidity exchanger  11  in the air circuit  22 . 
         [0029]    In the second exemplary embodiment shown in  FIG. 2 , the dehumidifying and cooling device  19  is disposed downstream of the second filter  9  but upstream of the second cavity  16  in the second line  21  or a dehumidifying and cooling device  19 ′ is disposed upstream of the first outlet  3  in the first line  20  or both dehumidifying and cooling devices  19  and  19 ′ are disposed at the said locations. 
         [0030]    In the exemplary embodiments shown in  FIGS. 1 and 2 , the heat exchanger  10  is provided to exchange heat between the exhaust air and the outside air and the two humidity exchangers  11  and  15  are provided to exchange moisture with the third air stream. Two further exemplary embodiments are shown in  FIGS. 3 and 4 , in which the two humidity exchangers  11  and  15  not only exchange moisture but also sufficient heat so that no separate heat exchanger is required. 
         [0031]    The first line  20  and the second line  21  are a part of the device, as shown in the figures, on the other hand they are connected to the surroundings or the room by means of additional external lines. 
         [0032]    The devices according to  FIGS. 1 to 4  operate with two humidity exchangers, which are coupled through the closed air circuit  22  so that the exchange of moisture can be regulated.  FIG. 5  shows an exemplary embodiment in which the exchange of moisture between the first air stream and the second air stream takes place by means of a single humidity exchanger  28 , which comprises a cavity  29  disposed in the first line and a cavity  30  disposed in the second line, which are separated by a water-vapor-permeable membrane  31 . However, the use of a single humidity exchanger of this design or another design is possible in all the exemplary embodiments. 
         [0033]    According to the invention, in all the exemplary embodiments, as illustrated for the exemplary embodiment in  FIG. 5 , a first portion of the exhaust air is left to flow as a third air stream through a fourth line  32 , treated, and fed back to the room again. The third air stream is designated as circulating air stream in technical terminology. The treatment of the third air stream is accomplished by means of another dehumidifying and cooling device  33 , which condenses moisture in the form of water from the third air stream. The fourth line  32  has an inlet, optionally a filter  34 , a fan  35 , the dehumidifying and cooling device  33 , and an outlet. The inlet is either directly connected to the room or, as shown, connected directly to the second line  21  downstream of its inlet  4 . The outlet either opens directly into the room or, as shown, directly upstream of its outlet  3  into the first line  20 . The filter  34  advantageously comprises a coarse particle filter and an electric filter. 
         [0034]    According to the invention, such a circulating air stream is also provided in the exemplary embodiments according to  FIGS. 1 to 4 . 
         [0035]    A plurality of fans are required for conveying the various air streams. The number of the fans and their arrangement inside the device  1  can vary according to the specific design. The devices  1  presented are suitable for carrying out the method according to the invention. They are to be understood as exemplary embodiments which can be modified within the scope of the technical knowledge of a person skilled in the art. 
         [0036]    The humidity exchangers shown in  FIGS. 1 to 5  are humidity exchangers, which comprise two cavities separated by a water-vapor-permeable membrane, in which humidity is exchanged through the membrane. Alternatively, humidity exchangers based on other physical principles can also be used, e.g. humidity exchangers with adsorption and desorption processes or those with absorption and degassing processes. 
         [0037]    The devices  1  described are switchable between two operating modes, which are designated as winter operation and summer operation. These two operating modes are now explained in detail. 
       Winter Operation 
       [0038]    The device  1  transfers moisture and heat contained in the exhaust air to the outside air. The first fan  6  conveys outside air into the room and the second fan  7  conveys exhaust air out from the room. The first fan  6  can be disposed anywhere in the first line  20 , the second fan  7  can be disposed anywhere in the second line  21 . The third fan  23  circulates the air stream in the closed air circuit  22 . The dehumidifying and cooling device  19  is switched off, i.e. the air flows through the dehumidifying and cooling device  19  without releasing moisture or heat. 
       Summer Operation 
       [0039]    The device  1  transfers a portion of the moisture contained in the outside air to the exhaust air and transfers a portion of the heat of the outside air to the exhaust air, i.e. the cooler exhaust air is used to cool the warmer outside air. The transfer of the moisture from the outside air to the exhaust air is accomplished by means of the two humidity exchangers  11  and  15  which are interconnected via the closed air circuit  22 . Since the exhaust air cannot absorb as much moisture as is necessary, in the exemplary embodiment according to  FIG. 1 , the air stream circulating in the air circuit  22  is additionally dehumidified, i.e. the dehumidifying and cooling device  19  extracts from the air stream circulating in the air circuit  22  that portion of the moisture which the exhaust air cannot absorb and which must be extracted in order that the supply air has the desired humidity. In the exemplary embodiment according to  FIG. 2 , the exhaust air is additionally dehumidified, i.e. the dehumidifying and cooling device  19  extracts so much moisture from the exhaust air that the moisture extracted from the outside air in the humidity exchanger  11  can be transferred completely to the exhaust air by means of the humidity exchanger  15 . It is also possible to dehumidify both air streams. 
         [0040]    The first fan  6  conveys outside air into the room and the second fan  7  conveys exhaust air out from the room. The dehumidifying and cooling device  19  is operating so that the air at the outlet of the dehumidifying and cooling device  19  is drier and cooler than the air at the inlet of the dehumidifying and cooling device  19 . Air circulates in the closed air circuit  22 , which, depending on the design of the dehumidifying and cooling device  19 , is made to flow either by the third fan  23  or by the dehumidifying and cooling device  19 . 
         [0041]    In addition, that portion of the exhaust air which flows as circulating air through the fourth line  32 , is cooled and/or dehumidified by means of the dehumidifying and cooling device  33  and then returned to the room. The circulating air and the outside air are prepared so that together they supply air of the desired temperature and humidity to the room. 
         [0042]      FIG. 6  shows a schematic functional diagram of the dehumidifying and cooling device  19 , through which an air stream  38  to be treated flows. The dehumidifying and cooling device  19  has a cooling block  36  and optionally a subsequent thermal block  37 . In the cooling block  36  the air stream  37  is cooled to a temperature below the dew point so that at least a portion of the moisture contained in the air condenses out as water. As described above, the heat accumulating there is supplied to the outgoing air at the second outlet  5  ( FIG. 1 ) by means of the air stream conveyed through the line  26 . If the thermal block  37  is present, a portion of the accumulating heat is supplied directly to the outgoing air and the remaining portion of the accumulating heat is supplied directly or via a line  32  to the thermal block  37  and then to the outgoing air in order to heat up again the cold air emanating from the cooling block  36 . 
         [0043]      FIGS. 7 to 10  illustrate various examples for the dehumidifying and cooling device  19 , which also all contain the thermal block  37 . However, the thermal block  37  can also be omitted. In this case, the accumulating heat is supplied to the outgoing air. 
       Example 1 
       [0044]    In the example shown in  FIG. 7 , the cooling of the air stream  38  flowing through the dehumidifying and cooling device  19  in the cooling block  36  is accomplished by means of at least one Peltier element  39 . Two Peltier elements  39 , having a cold wall  40  and a warm wall  41  are shown in the example. The temperature of the cold wall  40  is cooled by supplying electrical energy, wherein at least the last Peltier element viewed in the direction of flow of the air stream  38  is cooled to a value which lies below the dew point of the inflowing air. The air stream  38  flowing along this cold wall  40  is cooled, wherein moisture contained in the air stream  38  condenses out in the form of water at the cold wall  40  as soon as the temperature of the air stream  38  falls below the dew point. The water is supplied via a line  42  to a collecting basin  43  or removed directly to the surroundings. The heat accumulating during cooling of the air stream  38  and during condensation of moisture as well as the electrical energy supplied to the Peltier elements  39 , which is also converted into heat, reaches the warm wall  41 . A portion of this heat is supplied, for example via a line  44 , to the thermal block  37  and transferred in the thermal block  37  by means of a heat exchanger  45  to the air stream  38  in order to heat the air stream  38  in the thermal block  37  to a desired temperature. The remainder of the heat is released to the air flowing through the line  26 . This is possible because the temperature of the warm wall  41  is higher than the temperature of the outside air. 
         [0045]    A particularly advantageous embodiment is shown in  FIG. 8 . The dehumidifying and cooling device  19  comprises a plurality of Peltier elements  39  at which the air flowing past is cooled and dehumidified. The air stream  38  is then passed along the cold side of the Peltier elements  39  and then along the warm side of at least one of the Peltier elements  39 . That is, the thermal block  38  is formed here by the warm side of this at least one Peltier element. 
         [0046]    In winter operation, the dehumidifying and cooling device  19  is usually not operating since the outside air is relatively dry and does not need to be dehumidified. The Peltier elements  39  provided in this example can, however, be used to heat the air stream flowing through the dehumidifying and cooling device  19 . The current flowing through the Peltier elements  39  then flows in the reverse direction so that the wall  40  is now heated and the wall  41  is cooled. 
       Example 2 
       [0047]    In this example shown in  FIG. 9 , the cooling block  36  comprises a compressor  46 , a heat release chamber  47 , a turbine  48 , and a condensation chamber  49 , wherein the drive shafts of the compressor  46  and the turbine  48  are coupled to one another. The compressor  46  compresses the air in a mechanical manner, whereby the air is heated. When the relatively hot air flows through the heat release chamber  47 , the heat release chamber  47  is heated to a temperature which lies significantly above the local ambient temperature so that the heat release chamber  47  can release heat to the surroundings. The accumulating heat is removed by the outside air flowing through the line  26 . The supplied outside air therefore cools the heat release chamber  47 . In this way, heat is extracted from the air stream  38 . When the air stream  38  then flows through the turbine  48 , it drives the turbine  48 . When driving the turbine  48 , the air stream  38  must perform so much mechanical work that it is cooled to a temperature below the dew point. The cold air therefore cools the condensation chamber  49  so that moisture in the condensation chamber  49  condenses in the form of water and is collected via a line  42  in a collecting basin  43  or removed directly to the surroundings. When the air stream  38  leaves the condensation chamber  49 , it is cold and dry. In order to heat up the air stream  38  again, a portion of the heat accumulating in the heat release chamber  47  is supplied to the thermal block  37 , for example, via two heat exchangers  45  and  52  which are interconnected by a line  44 . Since the drive shafts of the compressor  46  and the turbine  48  are coupled to one another, the turbine  48  drives the compressor  46  so that merely the power P=P K −P T  needs to be supplied to the compressor  46  from outside, where the quantity P K  denotes the power required by the compressor P K  and P T  denotes the power delivered by the turbine  48 . 
       Example 3 
       [0048]    In the example shown in  FIG. 10 , the dehumidifying and cooling device  19  comprises a compressor  46  and a vortex tube  53 . The compressor  46  compresses the air stream  38  and thereby increases the pressure of the air so that the air stream  38  flows into the vortex tube  53  at high speed. The temperature of the air stream  38  is thereby increased. A portion of the heat is removed by means of a heat exchanger  54  via the line  26 . The vortex tube  53  separates the air stream into a hot air stream and a cold air stream and is designed so that the temperature of the cold air stream lies below the dew point so that the moisture contained in the cold air stream condenses out in the form of water. The cold air stream and the hot air stream are guided in separate lines  50  or  51 , so that on the one hand the water can condense out and on the other hand, heat can be extracted from the hot air stream, for example, by means of another heat exchanger  55 . The dehumidified cold air stream and the hot air stream are then combined again before they leave the dehumidifying and cooling device  19 .