Earticle

In this study, the effect of thermal grease and heat sink material of cooler on CPU temperature was measured and compared with LinX(v0.9.6) and HWMonitor.When the computer is booted without thermal grease applied, the CPU temperature rises rapidly, and the CPU temperature reaches 100℃ after 60 seconds for aluminum heat sink and 140 seconds for copper heat sink. The CPU temperature is lower as the thermal conductivity coefficient of thermal grease is higher, and the CPU temperature is lower when the thermal conductivity coefficient of the cooler is higher. In addition, when using a thermal grease and a heat sink with a high coefficient of thermal conductivity, the cooler rpm can be lowered, which is considered to be advantageous in terms of system stability and energy saving.

The performance of louver-finned flat-tube and fin & tube radiators for computer CPU liquid cooling were experimentally investigated. In this study, 7 samples of radiators with different shape and pass number (1, 2, 10) were tested in a wind tunnel. The experiments were conducted under the different air velocity range from 1 to 4 m/s. The water flow rate through a pass was 1.2 LPM. Inlet temperatures of air and water were $20^{\circ}C$ and $30^{\circ}C$ respectively. It was found that the best performance was observed in the louver-finned flat-tube sample considering pressure drop and heat transfer coefficient.

The performance of louver-finned flat-tube radiators for computer CPU liquid cooling were experimentally investigated. In this study, 5 samples of louver-finned flat-tube radiators with different width size (19mm, 24mm), tube hole (1, 9) and pass number (1, 2, 5) were tested in a wind tunnel. The experiments were conducted under the different air velocity ranging from 1 to 5 m/s. The water flow rate through a pass was 1.7 LPM. Inlet temperatures of air and water were $20^{\circ}C$ and $30^{\circ}C$ respectively. The results showed that the best performance in the 24mm sample considering pressure drop and heat transfer coefficient.

The fundamental theory and technical approach to aid design and development of an automotive air-conditioning system are presented. The evaluation methods for transient cooling load transferred to a passenger compartment and simulation of automotive air-conditioning components are outlined. The structure of the computer program, the experiemntal correlations, and the simulation results are also included. The total cooling load of the white-colored car is reduced upto 5% for that of the black-colored car when the car is running. Using the infrared reflectance glass, we can also obtain 5% reduction of the total cooling load for the common glass.

현재의 컴퓨터는 고성능화, 다기능화, 소형화, 경량화 등의 이유로 인해 기기 내부에서 발생하는 열량이 증가하고 있는 추세이다. 컴퓨터의 성능을 높이고 수명을 연장하기 위해서는 발열을 효과적으로 제어할 수 있어야 한다. 본 연구에서는 열전소자를 이용한 열전냉각시스템을 구성하여 컴퓨터에 설치하였고, 실험을 통해 기존의 공기냉각시스템을 사용한 컴퓨터 내부의 온도분포와 열전냉각시스템을 함께 사용한 컴퓨터 내부의 온도분포를 측정한 후, 이를 비교하여 열전냉각시스템의 발열제어 성능을 알아보고자 하였다. 또한, 열전냉각시스템이 기존의 컴퓨터 냉각시스템을 대처할 수 있는 성능을 낼 수 있는지 예측해 보기 위해서 기존의 냉각시스템을 사용한 컴퓨터와 열전냉각시스템만을 사용한 컴퓨터 내부의 온도분포를 수치해석을 통해 예측하고 비교해 보았다.

In recent years, the amount of heat generated inside of the computer has more increased because of high performance, multi-function, miniaturization and light weight. It is necessary to control the effective heat generation to improve performance and life extension of the computer. In this study, thermoelectric cooling system was manufactured using thermoelectric module and was attached to computer in order to control the heat generated inside computer. And the temperature distributions inside computer were experimentally measured and compared with and without thermoelectric cooling system to investigate the effect of cooling system. Also, to estimate the new cooling system which can substitute for the existing computer cooling system, temperature distributions inside computer were calculated by numerical analysis when there was no cooling system and was applied only cooling system to computer.

The increasing heat generation rates in CPU of notebook computers motivate a research on cooling technologies with low thermal resistance. This paper develops a closed-loop two-phase cooling system using a micropump to circulate a dielectric liquid(PF5060). The cooling system consists of an evaporator containing a boiling enhancement microstructure connected to a condenser with mini fans providing external forced convection. The cooling system is characterized by a parametric study which determines the effects of volume fill ratio of coolant, existence of a boiling enhancement microstructure and pump flow rates on thermal performance of the closed loop. Experimental data shows the optimal parametric values which can dissipate 33.9W with a film heater maintained at $95^{\circ}C$.

This study investigates two-phase cooling system of close-loop by using FC-72 and PCM(Phase change material). The cooling system consists of evaporator, cold plate, micro pump, and condenser. The heat input on the performance of evaporator is appreciated by visualizing the boiling on the evaporator. The heat performance of cooling system is investigated to determine the effects of volume fill ratio change at working fluid, pump flow rate change, and volume fill ratio change at PCM in cold plate. Experimental results show the ideal condition when the volume ratio of working fluid, the pump flowing, and the volume ratio of PCM are 60%, 6ml/min, and 60% respectively.

In a numerical study, equations relating the mechanical properties and cooling rate in a casting process have been applied to an AC4CH cast aluminum alloy. Good agreement was found between the measured and predicted material properties. Step-shaped steel blocks were made to comprise a casting mold with a Y-shaped cavity. Thermometers were inserted into each step of the mold to investigate temperature changes. The microstructure and mechanical properties, such as hardness and tensile stress were measured for each cut of piece. The correlation between the cooling rate and SDAS was found by curved fitting. Moreover, both the solidification time and the temperature were simulated using a commercial package, ZCast. The simulation results for yield strength, tensile strength, elongation, and hardness were compared with experimental results. Using the estimated K and n values, the hardness values of a ship propeller were simulated, and the results were similar to those obtained for actual castings.

Recently both high performance and low noise for a cooling fan used in a server computer have been required. In this study, we measured the noise characteristics for a small cooling fan used in a computer or in a server, and compared the computational data to measured ones. SC/Tetra V10 and FlowNoise V4.3 was used for the unsteady flow field and the aeroacoustic analysis, respectively. The aeroacoustic analysis results have the good agreement with measured data within 3% errors in overall SPL. In the noise spectrum, we could find the peak tonal noise at lower frequency than 1st BPF, and confirm that the reason is caused by the asymmetry of bell mouth shape.

In this study, a two-phase closed loop cooling system is desinged and tested for a laptop computer using a FC-72. The cooling system is characterized by a parametric study which determines the effects of existence of a boiling enhancement microstructure, initial system pressure, volume fill ratio of coolant and inclination angle of condenser on the thermal performance of the closed loop. Experimental data show the optium condition when the volume ratio of working fluid is 70%, the pump flowing is 6ml/min, and the inclination angle of condenser is $0^{\circ}$. This research shows the maximum values which can dissipate 33W of chip power with a chip temperature maintained at $95^{\circ}C$.