Atsushi Tsujimori

Heat transport characteristics of the capillary pumped loop for cooling the tower-type computer -2nd report: considering the inclination of the evaporator-

The capillary pumped loop has been widely investigated for a space thermal control device. This cooling device with high reliability and thermal controllability is considered to be suited to cool the electronic device like a tower-type personal computer, because the capillary pumped loop is good for absorbing heat from high heat flux region like a CPU, transporting it and releasing it from the large surface area like a packaging of the tower-type computer. In this study the capillary pumped loop was manufactured as a cooling device for the tower-type personal computer, and the heat transport characteristics was investigated. The experimental equipment consisted of the evaporator, the condenser, the liquid path and the vapor path. The heat transport length was set to 2500mm considering the air-cooled heat release area of the condenser. In the 1st report the effect of the wick dimension, cooling water temperature, evaporator height above the condenser were investigated. In this study, the influence of the inclination of the evaporator on the heat transport characteristics was mainly investigated. In results, this capillary pumped loop was able to work within the inclined angle of 20deg, but the maximum heat transport rate decreased as the inclination increased

Heat transport characteristics of capillary pumped loop with plate-type evaporator

A tube-type evaporator requires capillary force in order to lift liquid refrigerant to circumference direction under a gravity field, which reduces thermal performance. Therefore, a capillary pumped loop with a plate-type evaporator was newly manufactured to improve the performance and reduce the thickness of the evaporator. The plate-type evaporator is flat disk shaped with an effective diameter of 46 mm. The wick with equivalent diameter of 5 mum and 2 mm thickness is embedded in it. The vapor line and liquid line are both 750 mm in length, and the condenser is 1000 mm in length. The condenser is soaked in a water bath set to a constant temperature by the refrigerator. The total heat transport length is 2500 mm. Using HFC134a as the working fluid, the heat transport characteristics were experimentally investigated by changing the heat load to the evaporator from 8 to 24.5 W. The plate-type evaporator achieved a higher evaporative heat transfer coefficient with higher heat flux into the evaporator than the tube-type evaporator.

Dynamic Characteristics of the Capillary Pumped Loop for Cooling the Tower-Type Computer

Capillary pumped loop has been widely investigated for space thermal control devices. This cooling device with high reliability and thermal controllability is also considered to be suited to cool electronic devices like personal computers. Because the capillary pumped loop is good at absorbing heat from high heat flux region like micro-processors, transporting it and releasing it from the large surface for packaging. In this research, the experimental equipment of the capillary pumped loop was manufactured. The experimental apparatus consists of the evaporator, the condenser, the liquid line, the vapor line and the reservoir. In the experiments heat load is applied to the evaporator by a resistance heater. And heat is released from the condenser to the cooling water which is set to be a constant temperature by the refrigerator. The length and the diameter of the evaporator are 150mm and 27mm respectively and the capillary wick with equivalent diameter of 5μm is embedded in the evaporator. These specifications were designed to give 2500mm heat transport distance and to adapt the natural convection heat transfer to the ambient without a cooling fan. As is proposed in the recent study, the inside of the capillary wick was used as the reservoir to simplify the loop. In our previous study, the heat transport characteristics in steady states were investigated when the heat flux, the cooling water temperature and the evaporator height above the condenser changed, and then the effects of enclosed rate of the working fluid in the reservoir and the inclination angles of the evaporator on heat transport rate were investigated. The computer code was also developed to simulate the heat transport characteristics and evaluate the maximum heat transport rate of the tested capillary pump. In the next step, we focus on the dynamic characteristics. The heat loads of the micro-processors in the computers usually change according to the working conditions of the application software and vary hourly. Thus the active thermal regulation accompanied with the change of heat loads is the important factor for cooling devices in the computers. So in this study the heat transport characteristics in the dynamic conditions of the capillary pumped loop were investigated. In the experiment, the start-up and shut-down mode at a given heat load were tested at first. Then heat load were changed in incremental or decremental steps from 30 to 70W. All results show the good thermal controllability.Copyright

Heat Transport Characteristics of the Capillary Pumped Loop for Cooling the Tower-Type Computer

The capillary pumped loop has been widely investigated for a space thermal control device. This cooling device with high reliability and thermal controllability is considered to be suited to cool the electronic device like a tower-type personal computer, because the capillary pumped loop is good for absorbing heat from high heat flux region like a CPU, transporting it and releasing it from the large surface area like a packaging of the tower-type computer. In this study the capillary pumped loop was manufactured as a cooling device for the tower-type personal computer, and the heat transport characteristics was investigated. The experimental equipment consisted of the evaporator, the condenser, the liquid path and the vapor path. The heat transport length was set to 2500mm considering the air-cooled heat release area of the condenser. In the 1st report the effect of the wick dimension, cooling water temperature, evaporator height above the condenser were investigated. In this study, the influence of the inclination of the evaporator on the heat transport characteristics was mainly investigated. In results, this capillary pumped loop was able to work within the inclined angle of 20deg, but the maximum heat transport rate decreased as the inclination increased