Abstract:
A device ( 200 ) for the exchange of thermal energy between an interior of a housing, more particularly for a telecommunication apparatus and an environment, in order to convey heat from the housing interior to the outside and, in this case, in order to maintain the internal temperature for the components involved within tolerated limits one heat exchanger block ( 11 ) possesses two fluid duct systems ( 12,16 ) which are separated from each other and that are in thermal energy-transmitting contact with each other, while a first fluid duct system ( 12 ) communicates with the housing interior and a second fluid duct system ( 16 ) communicates with the surroundings and each fluid duct system ( 12,16 ) has allocated to it one fluid pump ( 22,24 ) each for conveying a first working fluid ( 18 ) in the first fluid duct system ( 12 ) and a second working fluid ( 20 ) in the second fluid duct system ( 16 ).

Description:
The invention relates to a device for the exchange of thermal energy between the interior of a housing, more particularly for a telecommunication apparatus and an environment according to the preamble of the claim  1 . 
     BACKGROUND OF THE INVENTION 
     The housing of an electrical apparatus, by way of example a transmission cabinet with radio equipment contained therein for a mobile telephone system, does in particular comprise electric components which generate waste heat. In order to avoid an overheating of the electric equipment, this waste heat has to be eliminated. 
     Since such housings normally are air-tight or hermetically sealed containers, the employment of a simple waste heat extractor fan is not possible. 
     That is why it is the technical problem of the present invention to provide a device of the type stated above, which conveys heat from a housing interior to the outside and maintains the internal temperature for the components involved within tolerated limits. 
     This technical problem is resolved by a device of the above-mentioned type possessing the features characterized in claim  1 . 
     SUMMARY OF THE INVENTION 
     For this purpose, in the air—air heat exchanger according to the invention, a heat exchanger block is provided with at least two fluid duct systems that are separated from each other and which are in thermal energy-transmitting contact with each other, in which case a first fluid duct system communicates with the interior of the housing and a second fluid duct system communicates with the environment and wherein, to each fluid duct system, at least one fluid pump each is allocated for the conveyance of a first working fluid in the first fluid duct system and of a second working fluid in the second fluid duct system. 
     This has the advantage that the heat is eliminated in an indirect manner, thus without the removal of fluid from the housing interior and without an intermingling of fluid in the housing interior, i.e. the first working fluid and the second working fluid, taking place. That is why the device according to the invention can be employed especially with insulated, airtight or hermetically sealed housings. 
     Further developments of the device are preferably described in the subclaims. 
     A particularly simple, effective and maintenance-friendly arrangement is achieved in that the heat exchanger block is mounted externally on the housing and in that pertinant apertures for the inflow of fluid and the outflow of fluid are provided between the housing interior and the first fluid duct system. 
     Expediently, the first and/or the second working fluid is air and, by preference, the fluid pumps are fans, in particular radial fans, axial fans or tangential fans. 
     In a specially preferred embodiment, which permits a particularly good heat exchange to be effected between the interior of the housing, the heat exchanger block comprises a cross reverse flow plate exchanger or counter-current plate exchanger. 
     In order to reduce weight and so as to enhance the corrosion resistance, the heat exchanger is preferably manufactured from aluminum and/or plastic, more particularly polypropylene (PP). 
     In order to ensure a predetermined temperature in the in-interior of the housing or in the first fluid duct, a controller is provided in the interior of the housing, which controls the speed of at least one fan. This controller possesses, in a specially preferred manner, a malfunction reporting output. 
     Expediently, the housing is airtight, more especially, hermetically sealed in relation to the environment. 
     In order to avoid the falling below a dew point of at least one working fluid, in a specially preferred embodiment, provision is made for a heating means, particularly a resistance heating element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the following, the invention is described in greater detail with the aid of the attached drawings. Thus 
     FIG. 1 shows an embodiment of a device for the exchange of thermal energy in a diagrammatical representation; 
     FIG. 2 shows an embodiment of the device in a sectioned view; 
     FIG. 3 shows the device in a side view in the direction of the arrow B in FIG. 2; 
     FIG. 4 shows the device in a view from the top; 
     FIG. 5 shows the device in a rear view, and 
     FIG. 6 shows the device in a further side view in the direction of the arrow A in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The embodiment of a device  100  depicted in FIG. 1 comprises a housing  10  and a heat exchanger block  11  with a first fluid duct system  12  (FIG.  2 ), which communicates with an interior  14  of the housing  10 , and a second fluid duct system  16 , which communicates with an environment. In the fluid duct system  12 , 16 , referred to hereinafter also as internal circuit  12  and external circuit  16 , in each case, air is circulated as working fluid  18 , 20  ny means of fluid pumps in the form of radial fans  22  and  24  (FIG.  3 ). In this case, the radial fan  22  conveys the air  18  in the interior  14  of the housing  10  through the first fluid duct system  12  and the radial fan  24  conveys the surrounding air through the second fluid duct system  16 . 
     The heat exchanger block  11  is constructed in the form of an inverse flow plate exchanger and effects a heat exchange between the air  18  in the interior  14  of the housing  10  and the air  20  of the environment so that thermal energy from the interior  14  is evacuated to the outside. 
     The FIGS. 2 through 6 depict a further embodiment of the device  200 . In this case, as is discernible from FIG. 2, the heat exchanger block  11  is constructed in the form of a cross counterflow plate heat exchanger. Cold ambient air  20  penetrates into the second fluid system  16  and issues again slightly heated via an aperture  30 , whereas warm interior air  18  of the housing enters via an aperture  32  into the first fluid system  12  of the heat exchanger block  11  and issues again cooled via an aperture  34 . 
     A bottom part  36  with pertinent apertures  38  and  40  for the air inlet  28  and the air outlet  30  of the ambient air  20  is depicted in FIG. 4. A cover part  42  with a pertinent aperture  44  for the air inlet  32  of the ambient air  18  becomes apparent from FIG.  5 . 
     The FIGS. 3 and 6 illustrate the inflow and the outflow of the ambient air  20  and interior air  18  into and out of the heat exchanger block  11  via apertures  28 , 30 , 32  and  34 . 
     As results from FIG. 2, a controller  46  is provided in the first fluid duct  12 . This records the temperature of the interior air  18  and, depending on this value, determines a speed for the fan  22  in such a fashion that a maximal interior temperature in the housing is not exceeded. 
     The cross counterflow heat exchanger according to FIG. 2 is preferably comprised of polypropylene and possesses the following advantages: 
     An easy cleaning of the external air path  16  since the plates are deformed simply and can be washed down with a high-pressure steam jet. Since the surface is a smooth closed-pore one, particles of dirt hardly adhere to the surface areas. 
     The weight saving is 15% with the same performance in comparison with aluminum. By means of the constructional principle according to the invention, a simple assembly and disassembly of all components (especially exchanger block  11  and fans  22 , 24 ) is possible, this is especially servicing-compatible. In polypropylene heat exchangers, the plates are preferably bonded, which makes an absolute separation of internal and external circuit  12 , 16  possible (no leakage rate or intermingling). The specification according to IP 54 is surpassed. The selection of the materials (aluminum housing plus polypropylene heat exchanger) results in an extremely corrosion-resistant end apparatus. 
     In this case, the use of aluminum has the following advantages: 
     On account of the constructional principle of the device, a simple assembly and disassembly of all components (especially heat exchanger block  11  and fans  22 , 24 ) is possible; this is particularly servicing-compatible. 
     The design of the housing and of the heat exchanger in aluminum throughout leads to a corrosion-resistant end apparatus. 
     The counterflow plate heat exchanger according to FIG. 11 is comprised preferably of polypropylene and has the additional advantage of a cross counterflow heat exchanger. 
     Due to the exchanger principle, extremely flat structural configurations can be realized. 
     The heat exchanger block  11  is preferably fabricated from a series of aluminum sheets; the corners are alternatingly compressed so as to form  2  sets of narrow air passages  12 ,  16 , one for the surrounding air  20  and one for the circulating air  18 . The warm air stream  18  gives off heat to the cold air stream  20 , however, without any intermingling of the air streams taking place. 
     The mechanical data of the heat exchanger block in an exemplary embodiment are as follows: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Dimensions 
                 300 × 300 × 120 mm 
               
               
                   
                 Weight 
                 50 kg 
               
               
                   
                 Plate spacing 
                 3 mm 
               
               
                   
                 Plate thickness 
                 0.4 mm 
               
               
                   
                 Number of ducts 
                 19. 
               
               
                   
                   
               
             
          
         
       
     
     The fans  22 , 24  are located at the top on the right and on the left on the heat exchanger block  11  as per FIG.  2 . They are radial fans  22 m 24  which, by way of example, are driven by collector-less 48V DC motors. The motors are speed-controlled by means of pulse-width modulation and are speed-monitored (Hall generator). The internal fan  22  runs permanently at 50% minimum and 100% at maximal internal temperature. The external fan  24  runs from 35° C. internal temperature at 50% speed and goes up to 100% at maximal internal temperature. The motors are speed-regulated by means of pulse width modulation at 48V DC and phase sector control at 230V AC. 
     For the dimensioning the following example results: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Fan wheel 
                 190 mm diameter 
               
               
                   
                 Air delivery volume 
                 300 m 3 /h 
               
               
                   
                 External static pressure 
                 100 Pa 
               
               
                   
                 Voltage 
                 48 V DC 
               
               
                   
                 Power consumption 
                 62 Watt 
               
               
                   
                 Full load current 
                 1.3 Amp 
               
               
                   
                 Starting current consumption 
                 4 Amp. 
               
               
                   
                   
               
             
          
         
       
     
     The above-stated specifications apply exemplarily to external and internal fans. 
     Optimally, an external heating means is provided, which, at 7° C., is activated from a controller. 
     A control system used comprises a circuit board with the following connections: 
     Speed control for the fans  22 , 24  by means of a temperature sensor on the circuit board for  2  fans and a 48V output for an external heating relay for an alarm signal (malfunction fan) and excess temperature; potential-free contacts. 
     The temperature sensor measures the temperature of the reconveyed air  18  and adapts the speed of the external and the internal fans  22 , 24  accordingly. The target value is e.g. 45° C. 
     The external fan starts at approximately 35° C. and reaches the highest speed at the target value. 
     The alarm temperature is e.g. 48° C. In the event of a fan failure or a temperature alarm, a potential-free contact is actuated, which can be processed further externally. 
     The following control table results: 
     
       
         
               
               
               
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 Temp. 
                 &lt;0°- 
                 5°- 
                 7°- 
                 25°- 
                 30°- 
                 35°- 
                 40°- 
                 43°- 
                   
               
               
                 ° C. 
                 5° 
                 7° 
                 25° 
                 30° 
                 35° 
                 40° 
                 43° 
                 48° 
                 &gt;60° 
               
               
                   
               
             
             
               
                 Fan 
                 60% 
                 60% 
                 60% 
                 70% 
                 80% 
                 80% 
                 100% 
                 100% 
                 100% 
               
               
                 50% 
               
               
                 Fan 
                 off 
                 off 
                 off 
                 off 
                 off 
                 50% 
                  70% 
                 100% 
                 100% 
               
               
                 Alarm 
                 off 
                 off 
                 off 
                 off 
                 off 
                 off 
                 off 
                 off 
                 on 
               
               
                 Temp. 
               
               
                 Heater 
                 on 
                 on 
                 off 
                 off 
                 off 
                 off 
                 off 
                 off 
                 off 
               
               
                   
               
             
          
         
       
     
     By way of example, the main date of the device are as follows: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Dimensions 
                 460 × 640 × 130 mm 
               
               
                   
                 Weight 
                 14 kg 
               
               
                   
                 Operating temperature 
                 −35° C. to +60° C. 
               
               
                   
                 Maximal internal temperature 
                 55° C. 
               
               
                   
                 Maximal external temperature 
                 40° C. 
               
               
                   
                 Maximum rate of heat extraction 
                 64 W/K 
               
               
                   
                 Voltage 
                 48 V DC 
               
               
                   
                 Power consumption 
                 124 Watt 
               
               
                   
                 Full load current 
                 2.6 Amp 
               
               
                   
                 Starting current consumption 
                 6 Amp. 
               
               
                   
                   
               
             
          
         
       
     
     A servicing of the device is effected as described below: 
     1. Cleaning the fans: 
     Dust, which settles on the fans (particularly in the external fan  24 ) has, for example, to be removed every 6 months in order to ensure a perfect operation as well as to avoid vibration, which leads to bearing damage and reduces the useful service life of the fans. Clean the fan with compresssed air or, in special cases, with a brush and a pH-neutral soap solution (only the external fan). Deposits on the internal fan mean that the switch cabinet or the housing  10  is not airtight or properly sealed. For this, special measures have to be taken. 
     2. Cleaning the heat exchanger block  11 : 
     Dust, which settles on the heat exchanger block  11  (particularly in the external fan circuit  16 ) has, for example, to be removed every 6 months in order to ensure a perfect operation. The heat exchanger block  11  has to be cleaned with compressed air or, in special cases, with a pH-neutral soap solution, which is sprayed on with compressed air (only in the external air circuit  16 ). The fan must not be sprayed with water and solely the external air circuit of the heat exchanger block is to be cleaned. When using compressed air or water spray, care has to be taken that the seals are not damaged. 
     With certain components it can happen that they will have to be replaced in the course of the service life of the device. The following procedures have to be had regard to when replacing spare component parts. 
     Prior to any maintenance operations, the PLL circuit has to be rendered currentness. 
     1. General 
     The fans, the circuit board and the heat exchanger block can be readily reached after the hood is removed. 
     2. Control unit (circuit board) 
     Clamp off all cables. Remove the  4  screws retaining the circuit board. Remove the circuit board. Then clamp on all the cables once more and insert the new circuit board. Check that all the connections have been effected correctly (see connection diagram). Make certain that no cables rest against the fans. 
     3. Internal fan (DC fan) 
     Clamp off the circuit board cables. Remove the four screws retaining the fan supports, remove the four screws on the rear of the fan support, remove the fan. Insert the new fan, fit the screws in reversed sequence as aforetstated, connect cables. Check that all connections have been carried out correctly (see connection diagram) and that no cables are resting against the fan. 
     4. External fan (DC fan) 
     As above—Internal fan) 
     5. Heat exchanger block 
     Detach the clamping fixture located on the separating plate between the two fans and remove the exchanger block  11 . Check the seals! Then insert the new exchanger block and clamp fast the same. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 List of Reference Numbers 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 Device 
                 100,200    
               
               
                   
                 housing 
                 10 
               
               
                   
                 heat exchanger block 
                 11 
               
               
                   
                 first fluid duct system 
                 12 
               
               
                   
                 interior 
                 14 
               
               
                   
                 second fluid duct system 
                 16 
               
               
                   
                 working fluid, internal 
                 18 
               
               
                   
                 working fluid, external 
                 20 
               
               
                   
                 radial fans, internal 
                 22 
               
               
                   
                 radial fans, external 
                 24 
               
               
                   
                 aperture 
                 28 
               
               
                   
                 aperture 
                 30 
               
               
                   
                 aperture 
                 32 
               
               
                   
                 aperture 
                 34 
               
               
                   
                 bottom part 
                 36 
               
               
                   
                 aperture 
                 38 
               
               
                   
                 aperture 
                 40 
               
               
                   
                 cover part 
                 42 
               
               
                   
                 aperture 
                 44 
               
               
                   
                 controller 
                 46.