An assessment of fin-tube thermal contact resistance in round-tube-plain-fin heat exchangers

Contact resistance;Fin-tube heat exchanger

Cortes, Maria

关键词: Contact resistance;    Fin-tube heat exchanger;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/78523/CORTES-THESIS-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Fin-and-tube heat exchangers are used in a wide variety of applications. Heat exchangers with expanded tubes are economical, but a drawback is the potentially large contact resistance between tubes and fins. Previous studies have investigated this topic under the exclusion of air-side convection. The present work is more realistic, because the contact resistance is evaluated in the presence of air-side convection. The goal of this experimental work is to determine the contribution of the contact resistance to the overall heat transfer resistance in round-tube-plain-fin heat exchangers. The four samples have copper tubes with two different expansion ratios and aluminum fins with collars of two different lengths. The heat exchangers were examined in a wind tunnel under dry and frosted conditions to determine the contact resistance. The frosted heat exchangers are used as a baseline, because frost growth bridges the gaps between fins and tubes. The contact resistance was much higher for the unexpanded heat exchangers – about 30-60% of the overall resistance, whereas expanded heat exchangers exhibited a contact resistance of about 10-30% of the overall resistance.