| Summary: | 碩士 === 國立屏東科技大學 === 機械工程系 === 93 === The phenomenon of secondary flow can be created by the curved pipe and it can obtain a better heat transfer than in a straight tube. Therefore a suitable curved tube can mix the flow better chaotically. The purpose of this study was to analyze the property of a carevd tube, which creates chaotic, mixing and the properties of a regular helical tubes. The two types of tube (shell and tube, and tube-in-tube) were used in the heat exchanger system to analyze properties of heat transfer. The results were found the chaotic mixing created the so-called chaotic tube which can increase heat transfer rate and well mixed temperature on flow. The shell and tube heat exchanger system had a higher total heat transfer rate, but the flow pressure were also increased relatively. The selection of the way for the working fluid was very important. The counter flow could achieve higher heat transfer efficiency in shell and tube helical tube than that of in chaotic tube. The temperature was more stable and well mixed in counter flow, and the thermal stress concentration was hardly found in the heat exchanger system. Thus, counter flow can reduce the probability that the tube is broken by thermal stress concentration.
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