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Experimental and numerical investigation of using pulsating heat pipes instead of fins in air-cooled heat exchangers

Jafari Mosleh, Hassan, Bijarchi, Mohamad Ali, Shafii, Mohammad Behshad
Energy conversion and management 2019 v.181 pp. 653-662
air, air flow, case studies, convection, heat exchangers, heat transfer coefficient, pipes, temperature
The goal of this study is the experimental and numerical investigation of using pulsating heat pipes (PHPs) as substitutes for fins in a typical air-cooled heat exchanger. Due to the small temperature difference between the cooling air and internal airflow in the case study, it was necessary that appropriate PHPs with the capability to work in small temperature difference conditions be investigated and an appropriate working fluid be selected. After reviewing various studies, R134a was selected as the best working fluid from the heat transfer standpoint. Afterward, a testing device was designed and fabricated. Additionally, in order to predict the behaviors of the main tubes with pulsating heat pipes and also finned tubes, the computational fluid dynamics was used and pulsating heat pipes and fins were simulated and compared. Different tests were performed with various air flow rates and temperatures. The results indicated that using pulsating heat pipes as fins have a significant effect on improving the heat transfer. In free convection (without external flow over the tubes), using the heat pipes resulted in a better performance in comparison to fins and in the best case, the overall heat transfer coefficient was improved by 310%. This improvement was approximately 263% for the forced convection condition.