Air-conditioners used in high-rise residential or office buildings often have outdoor units installed on the side-walls or roofs in the confined space of the buildings.The heat released from the outdoor units causes t...Air-conditioners used in high-rise residential or office buildings often have outdoor units installed on the side-walls or roofs in the confined space of the buildings.The heat released from the outdoor units causes the tem-perature rise in the confined installation space and leads to uncomfortable thermal environment and deteriorative performance of air-conditioners.The factors affecting the performance of air-conditioners are the heat released from the outdoor units,the solar radiation and the ventilation of the confined installation space,which are inves-tigated in this study and simulated by FLUENT using the porous model and discrete ordinates (DO) radiation model.It is proved that the porous model is more reliable than the solid model.The optimal installation distance from the supporting wall is obtained.The average temperature of the exit without wind is 1.18% higher than that with wind.The results show that the heat released from the outdoor units and the ventilation of the confined in-stallation space are the main factors affecting the thermal environment in the confined installation space.The in-fluence of the solar radiation is negligible.展开更多
Efforts to limit CO2 emissions from buildings in the tropics either focus on reducing energy demand, i.e., air-conditioning, or on replacing fossil with renewable sources. The link between energy demand and supply is ...Efforts to limit CO2 emissions from buildings in the tropics either focus on reducing energy demand, i.e., air-conditioning, or on replacing fossil with renewable sources. The link between energy demand and supply is often overlooked, especially the effect of the temperature lift of air-conditioning systems on energy consumption. But while heat and humidity gains define energy demand, operating temperatures of the system define the necessary energy input. We aim to transfer our experience of usin~ the LowEx paradigm for heat pump systems in moderate climates to the tropical climate of Sinsapore. In this paper, we took a systematic overview of a range of heat sinks, to which we refer to as anergy sinks. We analysed their thermal properties and their effect on the performance of air-conditioning systems, expressed as COP. The predominantly used dry air-cooled condenser units performed worst, especially when subject to a stack effect in （semi-）confined spaces. The performance is highest for cooling towers using the wet bulb temperature followed by water body based anergy sinks and the soil. The wide spread of results confirms that the heat rejection temperature is a decisive factor for the performance of the overall cooting system and the input of primary energy.展开更多
设计制作了一种带有自重式热管的散热器,并应用于100 W LED工矿灯。测试了LED工矿灯的光源模组引脚温度以及工作状态下散热器温度的分布。结果表明:自重式热管散热的光源引脚温度要比传统散热方式低4℃,光源表面温度要比传统散热方式的...设计制作了一种带有自重式热管的散热器,并应用于100 W LED工矿灯。测试了LED工矿灯的光源模组引脚温度以及工作状态下散热器温度的分布。结果表明:自重式热管散热的光源引脚温度要比传统散热方式低4℃,光源表面温度要比传统散热方式的光源表面温度低约6℃;散热鳍片温度分布更为均匀,提高了鳍片散热的效率。展开更多
基金supported by National Basic Research Program of China (973 Program)(No.2012CB720406)the Fundamental Research Funds for the Central Universities (No.FRF-AS-10-005B)
文摘Air-conditioners used in high-rise residential or office buildings often have outdoor units installed on the side-walls or roofs in the confined space of the buildings.The heat released from the outdoor units causes the tem-perature rise in the confined installation space and leads to uncomfortable thermal environment and deteriorative performance of air-conditioners.The factors affecting the performance of air-conditioners are the heat released from the outdoor units,the solar radiation and the ventilation of the confined installation space,which are inves-tigated in this study and simulated by FLUENT using the porous model and discrete ordinates (DO) radiation model.It is proved that the porous model is more reliable than the solid model.The optimal installation distance from the supporting wall is obtained.The average temperature of the exit without wind is 1.18% higher than that with wind.The results show that the heat released from the outdoor units and the ventilation of the confined in-stallation space are the main factors affecting the thermal environment in the confined installation space.The in-fluence of the solar radiation is negligible.
文摘Efforts to limit CO2 emissions from buildings in the tropics either focus on reducing energy demand, i.e., air-conditioning, or on replacing fossil with renewable sources. The link between energy demand and supply is often overlooked, especially the effect of the temperature lift of air-conditioning systems on energy consumption. But while heat and humidity gains define energy demand, operating temperatures of the system define the necessary energy input. We aim to transfer our experience of usin~ the LowEx paradigm for heat pump systems in moderate climates to the tropical climate of Sinsapore. In this paper, we took a systematic overview of a range of heat sinks, to which we refer to as anergy sinks. We analysed their thermal properties and their effect on the performance of air-conditioning systems, expressed as COP. The predominantly used dry air-cooled condenser units performed worst, especially when subject to a stack effect in （semi-）confined spaces. The performance is highest for cooling towers using the wet bulb temperature followed by water body based anergy sinks and the soil. The wide spread of results confirms that the heat rejection temperature is a decisive factor for the performance of the overall cooting system and the input of primary energy.
文摘设计制作了一种带有自重式热管的散热器,并应用于100 W LED工矿灯。测试了LED工矿灯的光源模组引脚温度以及工作状态下散热器温度的分布。结果表明:自重式热管散热的光源引脚温度要比传统散热方式低4℃,光源表面温度要比传统散热方式的光源表面温度低约6℃;散热鳍片温度分布更为均匀,提高了鳍片散热的效率。
