الفهرس | Only 14 pages are availabe for public view |
Abstract Cooling temperature-sensitive devices, such as electronic components, has recently become necessary to reduce the negative impact of excessive temperature rise on performance. Since passive cooling methods have advantages over other active methods, such as less cost and maintenance, and do not require an electrical source for operation, the current study focuses on passive cooling of electronic devices by using a vapor chamber with a cylindrical cross-section integrated with straight fin heat sink. Steam rooms have many advantages, including that they can be installed in narrow areas without the need to use a pump or an electric fan, and they also work to dissipate excess heat in more than one direction. It can be used in areas with high temperatures. An insulated electric heater with a thick layer of rubber padding was used to simulate heat dissipation from electronic devices without heat loss. The effect of two working fluids (ethyl alcohol and water) inside the vapor chamber was investigated because of the high amount of latent heat for each of them. The vapor chamber was charged with different charging ratios (20%, 25%, 30%, 35%, 45%, 55%, and 65%) for each of the two working fluids and under different heat loads (5, 8, 13, 19.2, 26, 34, and 45 watts), then it was compared to the performance of a straight-fin heat sink without a vapor chamber and also a heat sink that is a solid copper plate with 10mm thickness without fins under the same heat loads. The vapor chamber performance was investigated at different inclination angles ranging from zero to 180 with a rise of 45 degrees and under different heat loads. The results revealed that the use of the integrated vapor chamber straight fins heat sink significantly reduces the average front wall temperature associated with the electronic component when compared to other heat sinks. At heat flux values of 1.4 W/cm2, the temperature of the heat source at steady state in the case of the straight-fin heat sink and the combined heat sink with the vapor chamber filled with 23% pure water are 140 °C and 110 °C, respectively, which are Lower than the temperature with the solid copper plate by about 27% and 43% after 46 minutes and 40 minutes, respectively. Moreover, the results revealed that using pure water has better performance than ethyl alcohol. Whereas, the steadystate temperature of the heat source in the case of the combined heat sink with the vapor chamber filled with 23% pure water and ethyl alcohol at the same charging ratio was 110 °C and 120 °C, respectively. As for the effect of different charge ratios, the working fluid charge ratio has a significant impact on the performance of the vapor chamber, and this enhancement appears more clearly with the increase in heat load. At 34 W convection, the temperature of the heat source using water was 108, 100, 102, 102, 117, 105, and 109 °C at charge ratios of 20%, 25%, 30%, 35%, 45%, and 55% and 65%, respectively. The results also indicate that the inclination angle of the vapor chamber has a significant effect on the cooling performance, as indicated by the variation of heat source temperature and the system’s thermal resistance. At zero inclination angle, the temperature of the heat source is the lowest, which indicates the best performance, and in contrast, the highest temperature of the heat source is reached at an inclination angle of 180°, regardless of the applied heat load or the charging ratio. other additional experiments focused on the passive cooling of electronic devices in a vacuum space environment utilizing a vapor chamber with a cylindrical cross-section that is integrated with a straight fin heat sink. Several experiments were conducted to investigate the effect of two vacuum levels and compared them to the condition of work in the atmospheric pressure. The experiments were performed with pure water as a working fluid at a charge ratio of 25%, one system orientation 0◦, and one distinct heat load value of 1.2 W/cm2 on overall system performance. The results reveal that using the vapor chamber integrated with the straight fin heat sink significantly works better in the atmospheric pressure as is obvious from the evaporator surface temperature. It presented a notable good effect on its cooling performance as indicated by the variation of heat source temperature at two vacuum levels. It reached to the steady state temperatures at atmospheric pressure faster than at low vacuum level, and high vacuum level. |