Patent Publication Number: US-2016238284-A1

Title: Adaptive temperature control system for cooling working fluid

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to temperature control systems and more particularly, to an adaptive temperature control system for cooling working fluid. 
     2. Description of the Related Art 
     Upon testing electronic elements or electronic devices composed of electronic elements, such as wafers, integrated circuits, printed circuits, and so on, it is often important to obtain endurable temperatures of a device under test (hereinafter referred to as the “DUT”). This means the DUT has to be tested at various temperatures throughout a specific temperature range. Therefore, a temperature control system is necessary in the aforesaid testing process to control the temperature of the DUT as accurately as possible. 
     In a conventional temperature control system, a probe head controllable in temperature is adapted to directly contact a DUT disposed on a test socket so as to control the temperature of the DUT. However, only one surface of the DUT is contacted with the probe head, which is usually the top surface of the DUT; therefore, the temperature control system is difficult to provide a uniform temperature to the whole DUT. 
     In another conventional temperature control system, an airstream controllable in temperature is directed to the surrounding of a DUT so as to adjust the temperature of the DUT. Such temperature control system can provide not only a uniform temperature to the whole DUT, but also high stability and accuracy in temperature control, which is resulted from a temperature sensor located close to the DUT for obtaining the ambient temperature of the airstream to feedback control the output temperature of the airstream. However, in such temperature control system a cooling device driven by an AC generator is utilized to cool working fluid, i.e. the airstream, and an electric power with a frequency of 50 or 60 Hz is constantly applied to the cooling device. The electric power is usually not monitored in any parameter or unchangeable in any parameter even if it is monitored. Therefore, it often happens that the refrigerating capacity outputted from the cooling device is higher than demand, thereby causing energy waste. For example, the temperature control system may output working fluid with temperature of −60° C. under the frequency of 60 Hz of the electric power. If a required working temperature of the working fluid is set −20° C., the working fluid with the temperature of −60° C. will need to be heated up by a heater. This consumes much energy. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished in view of the above-noted circumstances. It is an object of the present invention to provide an adaptive temperature control system for cooling working fluid (gas or liquid), which can cool down the working fluid at a target temperature accurately so as to control the temperature of a DUT accurately and uniformly by means of the working fluid, or be applied in another process or system that requires the working fluid with accurate temperature. 
     To attain the above object, the present invention provides an adaptive temperature control system for cooling a working fluid, which flows in a pipe, at a target temperature set by a user. The adaptive temperature control system comprises a cooling device and a controller. The cooling device has a compressor, a condenser, an expander (ex. capillary), an evaporator, a coolant cyclically passing through the compressor, the condenser, the expander and the evaporator in order, and an inverter. The compressor has a motor. The condenser has a fan which helps dissipating heat of the coolant. The motor is electrically connected with the inverter. The coolant in the evaporator is functioned to thermally exchange with the working fluid, thereby cooling the working fluid. The controller has a plurality of input ports for receiving a plurality of system parameters respectively, and a first output port electrically connected to the inverter for enabling the controller to transmit a signal for controlling a rotary speed of the motor of the compressor to the inverter according to the system parameters. The system parameters may comprise the target temperature, a temperature in the evaporator, a mass flow of the working fluid in the pipe, an inlet pressure of the compressor, and an outlet pressure of compressor. 
     Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: 
         FIG. 1  is a simplified block diagram of an adaptive temperature control system for cooling working fluid according to a first preferred embodiment of the present invention; 
         FIG. 2  is a schematic drawing of a cooling device of the adaptive temperature control system, a pipe, a working fluid and a DUT according to the first preferred embodiment of the present invention; 
         FIG. 3  is a schematic drawing of a cooling device of an adaptive temperature control system, a working fluid and a pipe according to a second preferred embodiment of the present invention; and 
         FIG. 4  is a schematic drawing of a cooling device of an adaptive temperature control system, a working fluid and a pipe according to a second preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1-2 , an adaptive temperature control system  10  for cooling a working fluid  60  according to a first preferred embodiment of the present invention primarily comprises a cooling device  20  and a controller  30 . The adaptive temperature control system  10  may, but not limited to, further comprise a power factor corrector  40  (hereinafter referred to as the ‘PFC’), through which the cooling device  20  is electrically connected with a power source  50 . 
     The adaptive temperature control system  10  is adapted for cooling the working fluid  60 , which is gas or liquid flowing in a pipe  70  and directed to a DUT  80 , at a target temperature set by a user. In other words, the working fluid  60  is adapted to adjust the temperature of the DUT  80  after being cooled by the adaptive temperature control system  10 . However, the adaptive temperature control system of the present invention is not limited to be adapted for controlling the temperature of the DUT, but may be applied in another process or system that requires the working fluid with accurate temperature. 
     The cooling device  20  has similar fundamental principle to a conventional refrigeration sys and primarily comprises a compressor  21 , a condenser  22 , an expander  3 , an evaporator  24 , a coolant  25  cyclically passing through the compressor  21 , the condenser  22 , the expander  23  and the evaporator  24  in order, and two inverters  26 ,  27 . For the coolant  25 , commercially available coolants or a mixture of at least two of commercially available coolants can be used depending on usage requirements. 
     The compressor  21  has a motor  212  electrically connected with the inverter  26  and controllable in rotary speed by the inverter  26 . In this embodiment, the inverter  26  is electrically connected with the power source  50  through the PFC  40 . For the PFC  40 , a commercially available integrated circuit capable of correcting power factor can be used. The PFC  40  is capable of receiving input AC power having a wide voltage range, operating in a wide frequency range, and outputting DC power having constant voltage. The PFC  40  is adapted to receive AC power from the power source  50 , which may be, but not limited to, public supply mains used in worldwide areas, and output DC power to the inverter  26  so as to drive the motor  212 . 
     The compressor  21  is powered by the motor  212  to compress gaseous coolant  25  with low temperature and low pressure, thereby outputting gaseous coolant  25  with high temperature and high pressure and driving the coolant  5  to flow cyclically. The condenser  22  is adapted to dissipate heat of the gaseous coolant  25  with high temperature and high pressure by means of a cooling medium, e.g. air, thereby outputting liquid coolant  25  with moderate temperature and high pressure. Besides, the condenser  22  has a fan  222  which helps dissipating the heat of the coolant  25 . The expander  23 , e.g. capillary, is adapted Co depressurize the liquid coolant  25  with moderate temperature and high pressure, thereby outputting liquid coolant  25  with moderate temperature and low pressure, so that the coolant  25  can absorb heat when passing through the evaporator  24  and thereby be vaporized to become gaseous coolant  25  with low temperature and low pressure. The coolant  25  in the evaporator  24  is functioned to thermally exchange with the working fluid  60  passing by the evaporator  24  in the pipe  70 , thereby cooling the working fluid  60 . 
     The controller  30  has a first output port  31 , a second output port  32 , and a plurality of input ports  33 . The input ports  33  are adapted to receive a plurality of system parameters, respectively. The first output port  31  is electrically connected to the inverter  26  for enabling the controller  30  to transmit a signal for controlling the rotary speed of the motor  212  according to the received system parameters to the inverter  26 , The second output port  32  is electrically connected to the inverter  27  for enabling the controller  30  to transmit a signal for controlling the rotary speed of the fan  222  according to the received system parameters to the inverter  27 . It is to be understood that the cooling device  20  may be configured without having such inverter  27 . In this case, the fan  222  that is switchable between several stages of rotary speed may be used. It is to be understood that the controller  30  may be allocated in the inverter  26  and/or the inverter  27 . 
     The system parameters may optionally comprise the target temperature set by the user, a temperature in the evaporator  24 , a mass flow of the working fluid  60  in the pipe  70 , and inlet and outlet pressures of compressor  21 . The usage of the system parameters quantity depends on the actual demand in use of the adaptive temperature control system  10 , and it may be more than or less than and is not limited to the aforesaid system parameters. By means of the system parameters, the controller  30  can adjust the rotary speeds of the motor  212  of the compressor  21  and the fan  222  of the condenser  22  according to the instantaneous situation of the adaptive temperature control system  10 , so that the working fluid  60  can be cooled at the target temperature accurately, and therefore the temperature of the DUT  80  can be accurately and uniformly controlled. The correlation between the aforesaid system parameters and the temperature of the working fluid will be specified in the following contents. 
     The target temperature is the temperature of the working fluid demanded to be outputted from the system to the DUT  80 . If the temperature of the working fluid outputted from the cooling device  20  is close to the target temperature, it needs only a little additional adjustment by a heater (not shown), thereby causing relatively less energy waste to the heater. The optimal condition is that the temperature of the working fluid to be outputted from the cooling device  20  is lower than but very close to the target temperature after a transmission loss, and then the temperature of the working fluid is further adjusted to the target temperature by the heater when the working fluid is outputted. 
     The working fluid is thermally exchanged primarily when passing by the evaporator  24 . Theoretically, after the working fluid passes by the evaporator  24 , the temperature thereof is usually adjusted to be close to the temperature of the evaporator  24 . Thus, the temperature in the evaporator  24  (internal temperature of the evaporator  24 ) should be included in the system parameters to be received by the controller  30  for controlling the temperature of the working fluid  60 . For example, the controller shall speed up the motor  212  of the compressor  21  and the fan  222  of the condenser  22  when the target temperature is lower than the temperature in the evaporator  24  and slow down the motor  212  and the fan  222  when the target temperature is higher than the temperature in the evaporator  24 . 
     When the working fluid outputted from the system is stable in temperature, it will have an increase in its temperature in the event that the mass flow of the working fluid increases because the heat taken away from the working fluid by the evaporator  24  maintains constant. In this condition, the motor  212  of the compressor  21  needs to be speeded up if the temperature of the working fluid outputted from the system is to be maintained to the former level, and vice versa. Thus, the mass flow of the working fluid  60  should be included in the system parameters to be received by the controller, so that the controller  30  can change the rotary speeds of the motor  212  of the compressor  21  and the fan  222  of the condenser  22  subject to the variation of the mass flow of the working fluid  60  so as to achieve the target temperature quickly. 
     When the cooling device  20  is just started, the inlet pressure of the compressor  21  is usually very close to the outlet pressure of the compressor  21 , thereby causing a very large loading to the compressor  21  since the compressor  21  has a specific compression ratio. Therefore, the motor  212  of the compressor  21  should run in a low rotary speed when the cooling device  20  is just started, and be speeded up until the inlet pressure of the compressor  21  drops to a specific value. Thus, the inlet pressure of the compressor should be included in the system parameters so as to prevent the compressor  21  from overload when the system is just started. 
     In general, the cooling device is increased in cooling efficiency and lowered in output temperature of the working fluid subject to the increasing of the rotary speed of the motor of the compressor. However, the cooling device usually has a maximum pressure limitation on safety consideration, and the system is usually shut down automatically when reaching the maximum pressure for safety. Therefore, the outlet pressure of the compressor should be monitored when the motor of the compressor is speeded up. In general, the rotary speed of the motor is increased to a certain level and then kept at that level for a period of time to enable that the outlet pressure of the compressor is stable again or lower than a specific value, and then the motor is continuously speeded up to another level. Thus, the outlet pressure of the compressor should be included in the system parameters so as to enable the system to output working fluid having relatively lower temperature quickly without exceeding a safe operating pressure. 
     A temperature difference between the target temperature and the temperature of the working fluid having passed by and then cooled down by the evaporator  24  may exist. Further, the aforesaid temperature difference may vary according to variation of the mass flow of the working fluid. Thus, the temperature of the working fluid obtained after the working fluid has passed by the evaporator in the pipe should be included in the system parameters so that the working fluid can have a temperature very close to the target temperature when arriving at the DUT  80 . 
     In order to control the temperature of the working fluid  60  more accurately, the system parameters received by the input ports  33  of the controller  30  may, but not limited to, further comprise a temperature of the working fluid  60  obtained after the working fluid  60  has passed by the evaporator  24  in the pipe  70 , such as the temperature obtained at a sense position  72 , a downstream in the pipe  70  relative to the evaporator  24  as shown in  FIG. 2 , a compressor inlet temperature of the coolant  25 , a compressor outlet temperature of the coolant  25 , a current of the motor  212  of the compressor  21 , an inlet temperature of working fluid  60 , a condenser outlet temperature of the coolant  25 , and ambient environment temperature and humidity. Besides, the aforesaid system parameters can be measured and/or detected by means of commercially available temperature sensors, pressure sensors, humidity sensors, and mass flow sensors, which are disposed in specific positions in the system. The correlation between the aforesaid system parameters and the temperature of the working fluid will be specified in the following contents. 
     If the compressor inlet temperature of the coolant  25 , i.e. the temperature of the coolant  25  at the inlet of the compressor  21 , is too low, a liquid phase compression might occur in the compressor, thereby decreasing the lifetime of the compressor. The compressor inlet temperature of the coolant is usually lowered when the motor of the compressor has a relatively higher rotary speed. Thus, the compressor inlet temperature of the coolant  25  may be included in the system parameters and monitored when the motor of the compressor runs in a relatively higher rotary speed in a fast cooling process. 
     If the compressor outlet temperature coolant  25 , i.e. the temperature of the coolant  25  at the outlet of the compressor  21 , is too high, a failure in heat dissipation might happen to the compressor, and a protective shutdown of the compressor might be even adopted by the system. This issue may happen especially when the compressor is in high speed operation. Thus, the compressor outlet temperature of the coolant  25  may be included in the system parameters for controlling purpose, so that the compressor  21  of the cooling device  20  is capable of running in high speed without the problem of overheat. 
     When the cooling device  20  is in operation, the current of the motor  212  of the compressor  21  can&#39;t exceed a rated value so as to prevent the system from overload. Thus, the current of the motor  212  of the compressor  21  may be included in the system parameters so as to prevent the working current of the motor  212  from exceeding the rated value when the motor of the compressor and the fan of the condenser are running in high speed operation. 
     The inlet temperature of working fluid  60 , which means the temperature of fluid at the inlet of the cooling device  20 , may influence the temperature of the working fluid outputted from the system. In general, the temperature of the working fluid outputted from the system is increased subject to the increasing of the inlet temperature of working fluid  60 , and vice versa. Thus, the inlet temperature of working fluid  60  may be included in the system parameters so that the controller can adjust the rotary speed of the motor of the compressor according to the inlet temperature of working fluid. This means the motor is controlled to be speeded up when the inlet temperature of working fluid  60  is increased and slowed down when the inlet temperature of working fluid  60  is decreased. 
     When the condenser outlet temperature of the coolant  25 , i.e. the temperature of the coolant  25  at the outlet of the condenser  22 , is relatively lower, i.e. the coolant  25  stays in an overcooled phase, the coolant will be capable of taking away more heat when passing through the evaporator  24 . In this condition, the motor of the compressor can run in a relatively slower speed while the system maintains a same cooling efficiency. Thus, the condenser outlet temperature of the coolant  25  may be included in the system parameters so that the controller can correspondingly adjust the rotary speed of the motor of the compressor quickly. 
     When the ambient environment temperature around the system is lowered, the thermal exchange of the coolant in the condenser is increased, so that the coolant will be cooled at a relatively lower temperature after passing through the condenser, thereby bringing away more heat when passing through the evaporator  24 . Thus, the ambient environment temperature may be included in the system parameters so that the controller can correspondingly adjust the operation of the system quickly. For example, when the ambient environment temperature is lowered, the rotary speed of the motor of the compressor can be also lowered. 
     In brief, the adaptive temperature control system of the present invention can cool down the working fluid at the target temperature accurately so as to control the temperature of the DUI accurately and uniformly by means of the working fluid. In addition, the present invention has high stability in the temperature of the working fluid outputted from the cooling device, high energy efficiency and thereby low energy waste. Besides, the present invention can provide the required temperature to the working fluid in a relatively shorter time, prevent the compressor from exceeding safe temperature and pressure ranges, and operate under an AC input voltage and a frequency in wide ranges. 
     It is to be understood that the present invention is not limited to the disclosure of the above-mentioned first embodiment. Various modifications and/or improvements may be adopted without departing from the technical features of the present invention. For example,  FIG. 3  shows an adaptive temperature control system for cooling a working fluid according to a second preferred embodiment of the present invention, which is similar in structure to the aforesaid adaptive temperature control system  10  of the first preferred embodiment with the following exceptions. That is, the cooling device  20 ′ in this embodiment further comprises an additional condenser  91  of a dual circuit design, and optionally utilizes a coolant mixture consisting of more than one refrigerant gas. After the gaseous coolant  25 A has been compressed within the compressor  21 , the coolant  25 A flows through the air cooled condenser  22 , where the heat of compression is extracted, thereby allowing some or all of the gaseous coolant  25 A to condense. Then, the coolant  25 A passes through a first circuit  911  of the additional condenser  91 , and via the expander  23  flows into the evaporator  24 , where the condensate expands, thereby extracting heat. After flowing out of the evaporator  24 , the coolant  25 B flows back to the compressor  21  through a second circuit  912  of the additional condenser  91  in a counter-flow direction and still has low temperature close to the temperature of the evaporator  24 , which can further enable condensation of the gaseous coolant  25 A traveling through the first circuit  911  of the additional condenser  91 . 
     In this way, after the coolant  25 A is cooled down by the condenser  22 , the coolant  25 A can be further cooled down again by the additional condenser  91 , such that the coolant  25 A may have a relatively lower temperature when flowing through the evaporator  24 , thereby enabling to cool the working fluid  60  to a relatively lower temperature. Besides, the coolant  25 B flowing backwards from the evaporator  24  to the compressor  21  can be functioned to thermally exchange with the coolant  25 A when flowing through the additional condenser  91 , thereby further cooling down the coolant  25 A, so that the cooling device  20 ′ has relatively better cooling efficiency. Resulted from the aforesaid thermal exchange between the coolant  25 A flowing to the evaporator  24  and the coolant  25 B flowing backwards from the evaporator  24 , the coolant  25 B is raised in its temperature before flowing back into the compressor  21 , which helps the liquid in the coolant  25 B to be transformed into gas before the coolant  25 B flows into the compressor  21 , so that the compressor  21  is prevented from liquid phase compression. 
     In addition, the working fluid  60  flowing in the pipe  70  can be arranged to pass by the additional condenser  91  before passing by the evaporator  24 . In this way, the coolant  25 B in the additional condenser  91  is functioned to thermally exchange with the working fluid  60  passing by the additional condenser  91 , so that the working fluid  60  is pre-cooled before passing by the evaporator  24 , and therefore the working fluid  60  can be further cooled to the required temperature more quickly when passing by the evaporator  24 . 
     Referring to  FIG. 4 , an adaptive temperature control system for cooling a working fluid according to a third preferred embodiment of the present invention is disclosed similar to the aforesaid adaptive temperature control system  10  of the first preferred embodiment with the following exceptions. That is, the cooling device  20 ″ in this embodiment further comprises a first additional condenser  92 , a second additional condenser  95  of a dual circuit design, a liquid/vapor phase separator  93  situated between the first and second additional condensers, and an additional expander  94 . A mixture of at least two different coolant gases would then be desirable, wherein the coolant gas with the warmest boiling point would be selected to fully condense and separate in the phase separator  93 . Any uncondensed coolant gases with colder boiling point would then flow through the phase separator&#39;s gas outlet and enter a first circuit  951  of the second additional condenser  95 . Specifically speaking, the coolant  25 A after flowing out of the compressor  21  flows through the condenser  22  to be cooled down, and then flows through the first additional condenser  92  to be further cooled down, After that, a part of the coolant  25 A with higher boiling point may be transformed into liquid, but the other part of the coolant  25 A with lower boiling point is still in gas phase; therefore, the coolant  25 A is arranged to flow through the phase separator  93  to let the gas and the liquid in the coolant  25 A be separated from each other. After flowing out from the phase separator  93 , the part of gaseous coolant  25 A flows through the first circuit  951  of the second additional condenser  95  and is cooled down once again and transformed into liquid, and then flows through the expander  23 , e.g. capillary or expansion valve, to be depressurized to become gaseous coolant with low pressure, and then flows into the evaporator  24 . After flowing out from the phase separator  93 , the part of liquid coolant  25 A flows through the additional expander  94 , e.g. capillary or expansion valve, to be depressurized to become gaseous coolant with low pressure, and then flows backwards to the second additional condenser  95  for cooling down the gaseous coolant  25 A in the second additional condenser  95  to transform it into liquid. In other words, the liquid coolant out of the phase separator  93  and via the additional expander  94  would return through a second circuit  952  of the second additional condenser  95  in a counter-flow direction with the first circuit  951 , where the expanding condensate would extract heat from uncondensed gaseous coolant traveling through the first circuit  951 , thus enabling condensation of these gaseous coolant with colder boiling point to feed the expander  23  and the evaporator  24 . The coolant  25 A flowing out from the expander  23  is functioned to thermally exchange with the working fluid  60  when flowing through the evaporator  24 . After flowing out from the evaporator  24 , the coolant  25 B flows back to the second additional condenser  95  and the first additional condenser  92 , and then flows back to the compressor  21 . 
     Because of being re-cooled by the additional condensers  92 ,  95 , the coolant  25 A in this embodiment may have a relatively lower temperature when flowing through the evaporator  24 , and therefore the coolant  25 A is able to cool down the working fluid  60  to a relatively lower temperature. On the other hand, the coolant  25 B flowing backwards from the evaporator  24  to the compressor  21  has a very low temperature (usually below −10° C. in the first additional condenser  92  and below −40° C. in the second additional condenser  95 ), such that when the coolant  25 B flows through the second additional condenser  95  and the first additional condenser  92 , it can be functioned to thermally exchange with the coolant  25 A (the temperature of the coolant  25 A at the outlet of the condenser  22  is usually a little bit higher than the ambient environment temperature). Resulted from the aforesaid thermal exchange between the coolant  25 A flowing to the evaporator  24  and the coolant  25 B flowing backwards from the evaporator  24 , the coolant  25 A is further cooled down and therefore the cooling device  20 ″ has relatively better cooling efficiency; besides, the coolant  25 B is raised in temperature before flowing back into the compressor  21 , which helps the liquid in the coolant  25 B to be transformed into gas before the coolant  25 B flows into the compressor  21 , so that the compressor  21  is prevented from liquid phase compression. 
     In addition, the working fluid  60  flowing in the pipe  70  can be arranged to pass by the first additional condenser  92  and the second additional condenser  95  before passing by the evaporator  24 . In this way, the coolant  25 B in the first and second additional condensers  92 ,  95  and the coolant flowing backwards from the additional expander  94  to the second additional condenser  95  are functioned to thermally exchange with the working fluid  60  passing by the additional condensers  92 ,  95 , so that the working fluid  60  is pre-cooled before passing by the evaporator  24 , and therefore the working fluid  60  can be further cooled to the required temperature more quickly when passing by the evaporator  24 . 
     The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.