Abstract:
An electrohydrodynamic (EHD) condenser device includes a condenser installed with an EHD electrode. An electric field is generated upon a fluid of low conductivity inside a compressor device and an enhanced thermal conduction effect is then achieved since the electric field induces current convection, migration and deformity of bubble, increases perturbation and mixture of the flow field and eliminates boiling and delay. With the EHD utilized, size, weight, cost and required refrigerant amount of the condenser device are reduced. Further, thermal conduction efficiency of the alternative refrigerant is improved, making the EHD compensator device in compliance with associated refrigerant regulations made by CFC and achieve the purposes of environmental protection and energy saving.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention pertains to an electrohydrodynamic (EHD) condenser device, and particularly to an EHD condenser device having an enhanced thermal transport efficiency through generating an EHD effect by using of an electrode. 
   2. Description of the Prior Art 
   To improve thermal exchange efficiency of a compressor, increased surface area, a number of compressor tube are generally suggested. For example, threads may be added to an interior wall of the thermal exchanging tube to enhance the thermal exchange efficiency. However, this manner may only increase the thermal exchange efficiency passively with results of limited heat exchange effect, prolonged process time and larger volume and weight of the compressor. Such evaporator may be seen in, for example, R. O. C. patent no. 531630. In this patent, a disclosed compressor is characterized in that one or more compartments are formed vertically in an area where a thermal exchanging tube is disposed in prevention of liquid refrigerant deposited around the thermal exchanging tube and for speeding up a gaseous refrigerant in-flow. 
   In another patent, R. O. C. patent no. 526322, a refrigerant tube of a thermal exchanger is disclosed. This refrigerant tube is characterized in that a plurality of heat sinking pieces are combined so that the refrigerant flown in the tube and air surrounding thereto may thermally exchange with each other. 
   However, this refrigerant tube has the following disadvantages as follows. 
   1. Only a passive improvement in structure is provided and the heat exchange efficiency may not be self-controlled. 
   2. Since the condenser may only be improved in structure, dimension, volume and weight of the condenser may not be efficiently reduced. 
   3. Partial cooling function may not be achieved. 
   4. The amount of the refrigerant required for the condenser may not be reduced. 
   In view of these problems encountered in the prior art, the Inventors have paid many efforts in the related research and finally developed successfully an electrohydrodynamic (EHD) condenser device, which is taken as the present invention. 
   SUMMARY OF THE INVENTION 
   It is, therefore, an electrohydrodynamic (EHD) condenser device capable of actively controlling heat transport efficiency of refrigerant used therein. 
   It is another object of the present invention to provide an EHD condenser device having a reduced dimension, volume and weight. 
   It is yet another object of the present invention to provide an EHD condenser device which may achieve a partial cooling function. 
   It is still another object of the present invention to provide an EHD condenser device having a reduced amount of refrigerant required therefore. 
   The EHD condenser device according to the present invention comprises a condenser being a case having a plurality of openings thereon and a plurality of metal tubes therein, a working fluid being a fluid of low conductivity, a voltage applicable insulator comprising a voltage application end and a voltage applicable insulation seat and inputtable by a high voltage and one or more electrodes disposed in the working fluid and used to generate an electric field. The working fluid is filled between an interior wall of the condenser case and an exterior wall of the metal tube and the electrode is disposed in the working fluid and connected to the voltage application insulation seat at one end, the voltage applicable insulator being installed at an opening of the condenser case so as to be connected to a high voltage power supplying device. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a structural diagram of an electrohydrodynamic (EHD) condenser device according to the present invention; 
       FIG. 1B  is a cross sectional view of the EHD condenser device according to the present invention; 
       FIG. 1C  is a cross sectional view of the EHD condenser device according to the present invention where electrode lines are disposed among alternatively arranged tube nests; 
       FIG. 1D  is a cross sectional view of the EHD condenser device according to the present invention where the electrode lines are disposed circumferentially with respect to the tube nests; 
       FIG. 2  is a schematic diagram illustrating an EHD evaporator iced-water mainframe comprising the EHD condenser device according to the present invention; and 
       FIG. 3  is a relationship plot of an EHD voltage and refrigeration performance of the iced water mainframe according to the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1A , a structural diagram of an electrohydrodynamic (EHD) condenser device according to the present invention is shown therein. The EHD condenser device comprises a condenser  1  being a case  11  having a plurality of openings. These openings are served as an amount 17 for any of a cooling water inlet/outlet, a refrigerant inlet/outlet and a safety valve  16  or a voltage applicable insulator. The case has a plurality of metal tubes disposed therein. In this embodiment, copper tubes  18  are utilized, each having macro-fins having interior threads formed on its interior wall and being smooth on its exterior wall. These copper tubes  18  are arranged in an orthogonal relationship and served as a ground electrode (negative electrode). The condenser is filled with a working fluid of low conductivity, which is refrigerant  2  in this embodiment. A voltage applicable insulator  19  comprises a voltage application end and an insulation portion. In this embodiment, a conducting rod  191  is provided to have a threaded case  192  of Telfon at an exterior wall thereof. The conducting rod  191  has a protrusion mated with an indentation portion of an insulation seat  193  for high voltage application to form the whole body of the voltage applicable insulator  19 . One or more corrugated electrodes (positive electrodes)  3  have refrigerant flowing around and are fixed in position by a Teflon-made insulation seat, which prevents a long and thin electrode from breaking off. Further, the Telfon-made insulation seat may prevent the electrode (positive electrode) and the copper tube (negative electrode) from contacting with each other and thus an electric field may be generated. The voltage applicable insulator  19  amounted at an opening of the condenser case  11  so as to connect to a high voltage power device  4 . 
   In real operation, refrigerant is fed and filled into the condenser between an interior wall of the case  11  and an exterior wall of the copper tube  18  through a refrigerant inlet  15 . Cooling water is instilled into the copper tubes  18  through a cooling water inlet  12 . As such, the cooling water is flown in the copper tubes  18  and outside which the refrigerant is flown. Then, the high voltage power device  4  is turned on so as to provide a voltage to the electrode through a conducting rod  191  of the voltage applicable insulator  19 , an iron-made insulation seat frame  31  and an electrode integration piece  32  (refer to  FIG. 1B , a cross sectional view of the EHD condenser device) so as to achieve the purpose of generating the electric field upon the refrigerant. 
   When a high voltage difference (about 10 to 100 kV) is existed between the electrode  3  (positive electrode)  3  and copper tube (negative electrode)  18 , corona discharge occurs so that gaseous refrigerant between the two electrodes are ionized, in which positive ions transmitted momentum to neutral atoms so that an enhanced convention effect occurs with respect to a flow field of the refrigerant. As such, heat transferred from the gaseous refrigerant to the cooling water is promoted in efficiency, the gaseous refrigerant returns to its liquid form and flows out the refrigerant outlet  14  and the cooling water leaves out the cooling water outlet  13 . With related to the corona discharging, the thus generated gas has a speed of about 2 m/s and a thermal conduction coefficient of about 10 times that of general gas. In summary, since the generated electric field induces convection, perturbation, speedy nucleation and separation between the gaseous form and the liquid form, the purpose of enhanced thermal conduction efficiency is considerably achieved. 
   Alternatively, the electrode may be arranged among alternatively disposed tube nests but not the orthogonally disposed metal tubes. The electrodes  8  of line shape are disposed between adjacent tube lines (refer to  FIG. 1C ) or circumferentially with respect to the tube lines  9  (refer to  FIG. 1D ). 
   Referring next to  FIG. 2 , a schematic diagram of an iced water mainframe refrigeration system according to the present invention is shown therein. The iced water mainframe refrigeration system is composed of an iced-water mainframe refrigerant circulation system  5 , a cooling water circulation system  6  and an iced-water circulation system  7 . When the testing system performs, the cooling water in the condenser receives heat transmitted from the gaseous refrigerant (the cooling water flows within the copper tubes while the refrigerant at the high voltage side flows between outside the copper tubes and the iron case). 
   The 32° C. water  61  is delivered to a cooling water tower  62  by means of a cooling water pumping  61  and cooled down in the water tower  62  as 27° C. cooling water  63  and then returned to the condenser  1 . In this manner, the cooling water circulation system  6  operates. In an EHD evaporator  71 , the iced water transmits heat to the low pressure refrigerant in the evaporator, through which the 12° C. water  72  is reduced in temperature to become 7° C. water  73 . Then, the water is directed to a constant temperature water trough  74  and then drawn into the evaporator  71  by an iced water pumping. Based on this principle, the cooling water circulation system  7  operates. 
   To test refrigeration performance (kJ/h) of the iced-water mainframe when the EHD evaporator is operated under some conditions, parameters associated therewith have to be measured, such as cooling water circulation amount at points a and b in  FIG. 2 , iced water circulation amount (m3/h) at points c and f, temperature (° C.) and temperature difference of the cooling water when entering and leaving the condenser, jet pressure (bar) of the refrigerant from the compressor, temperature of a drawing port of the refrigerant (° C.) at point d in the condenser, temperature of the outlet of the liquid refrigerant at point e in the condenser (° C.), temperature of the inlet of the refrigerant and pressure of the inlet of the refrigerant in the evaporator, among other. 
   Now the description will be made to a measurement operation of the iced-water mainframe performance testing system.
     1. After the mainframe is initialized, the operation of the mainframe is tested. When the mainframe is stably operated with a full load presented, temperature of the cooling water when entering and leaving, temperature of the iced water when entering and leaving, circulation amount of the cooling water, circulation amount of the iced water, consumption power of a compressor and the like are measured and recorded.   2. When the mainframe is operated to the full load being presented, the high voltage power device  4  is enabled and maintained at a specific high voltage. When the high voltage is applied on the iced water mainframe, the operation thereof is observed and the high voltage is adjusted. Further, an upper and lower pressure and the circulation amount of the refrigerant are recorded.   3. Increasing the EHD voltage several times, then recording the associated data until spark discharge occurs.   4. To observe the operation when a partial load is presented, temperature of the iced water at the outlet is adjusted higher or lower. Then, a high voltage is applied and the operation is observed and recorded.   

   Referring to  FIG. 3 , a relationship plot of the EHD voltage and refrigeration tones (RT) is shown therein. As shown, it may be known that the refrigeration performance increases as the input voltage increases when the refrigerant amount is kept constant. When the voltage is up to about 12 kV, the refrigeration tones (RT) reaches to a maximum (an increase of 4%) and then reduces slightly until the voltage reaches 20 kV. 
   The refrigeration tones of the iced water mainframe increases is because the applied EHD voltage makes the condensed liquid refrigerant outside the copper tubes in the condenser easy to come off from the copper tubes and the gaseous refrigerant has an increased condensation area and thus the gaseous refrigerant may rapidly condense. Thus, liquid refrigerant of lower temperature is presented at the outlet of the condenser. The flattened increase rate occurred when the voltage is further increased is because dryness of the refrigerant in the condenser reduces gradually and thus separation of the liquid and gaseous refrigerant becomes lesser. 
   When reaching 20 kV, the inputted voltage may not increases again since breakdown (short circuit) is occurred in the condenser. In conclusion, the refrigeration performance of the iced water mainframe increases as the applied voltage kV increases. Further, when the refrigerant amount increases, the refrigeration performance increases more significantly. 
   As compared to the prior art, the EHD condenser device disclosed in the present invention further has the following advantages.
     1. The structure and installation method of the EHD evaporator device are simpler and power consumption thereof is lesser, compared with other active thermal conduction enhancement technologies.   2. A relatively lower cost is required since only a transformer, a wire and plate electrode and an insulation material is required.   3. The thermal conduction efficiency may be rapidly controlled by adjusting strength of the electric field applied on the EHD evaporator device.   4. Flow field or cooling effect may be partially improved in the delivery tubes.   5. The EHD technology may be used for the CFC refrigerant, other alternative refrigerants, such as R-123, R-134a, and gas (owing to the low conductivity).   6. The EHD evaporator device may be used even in outer space environment where gravity is not existed.   

   While embodiments and applications of this invention have been shown and described, it would be apparent to those skilled in the art having the benefit of this disclosure that many more modifications than mentioned above are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the appended claims and their equivalents.