Experimental Investigation on the Application Potential of Finless Heat Exchanger with Mini-Diameter Tubes Utilized as Air Heater or Air Cooler

Abstract

Increasing the ratio of the internal and external surface areas of heat exchangers is ordinarily considered to be an effective way of improving performance. In this paper a novel finless heat exchanger with mini-diameter tubes used as air heater or air cooler is proposed. In order to fully understand the performance of this novel type of heat exchanger, a test bench was established. The heating and cooling performances were tested according to relevant standard specifications. Furthermore, the heat exchanger was compared with seven conventional heat exchangers. This novel heat exchanger has excellent surface heat transfer temperature difference uniformity. Relative to the seven traditional heat exchangers examined, this novel design demonstrated remarkable heat transfer enhancements, registering gains of at least 173% as an air heater and a staggering 277% as an air cooler. However, it also exhibited elevated water-side flow resistances. Critically, conventional empirical heat transfer equations proved suboptimal for this system, necessitating modifications that yielded new coefficients: C=0.0839 and n=0.992.