Temperature Distribution of Ｈeat Source in a Confined Space with Reflective Surface

• Main Authors: Bor- Ren Chen, 陳博仁
• Other Authors: Muh-Rong Wang
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/95829300864435128305

碩士 === 國立成功大學 === 航空太空工程學系 === 88 === Investigation on the heat-transfer phenomena from a heat source in a confined space is conducted in this research program. The confined space is covered by reflective surface with one opening. The heating and burning out process of the reflective surface under the heat source is first investigated to confirm the relationship of its thermal damage with temperature. Analysis of the thermal loading on the reflective surface is carried out by measuring the input and output energy of the confined space. The radiation energy from the reflective surface is measured by the Delta Model-Hd9221 radiometer. The temperature distribution of the confined space is measured by the K-type thermocouple as well as Inframetrics Model-760 IR-imager to analysis the heat-transfer mechanisms of the heat source. The temperature distribution of the flow field above the heat source is also measure by the K-type thermocouple. Results show that the thermal damage of the reflective surface under an 70W heat source takes place in 15 min after turning on the power because the temperature of the base material of the confined surface reaches the melting point. Further distortion of the surface takes place after 22 min because the heat transfer rate of the surface is not enough to cool it down. Hence the designer should consider the thermal loading to the surface. Proper design of the heat transfer mechanisms and the selection of the proper surface material are important. Measurement also shows that the highest temperature on the surface is above the heat source and is dependent on the height of the surface to the heat source. An empirical formula is derived to express the relationship between the temperatures to the height. Analysis on the thermal loading on the reflective surface indicates that about 89% of the heat input is absorbed by the surface. The rest of the input energy is transferred to the radiation energy from the opening. Results show that only 1.6% of the radiation energy is in the visible light range and the rest is the IR radiation. Measurements of the temperature distribution of the flow field above the heat source and the temperature on the reflective surface justify that the heat transfer from the heat source to the surface is mainly due to the nature convective heat transfer mechanism from the hot flow above the heat source. It is also found that the thermal loading to the upper surface increases if a reflection plate is placed under the heat source. It implies that the radiation heat transfer mechanism becomes important in this case.