Experimental Study on Frosting Characteristics and Heat Transfer Performance of Circular Tube Surface in a Confined Space

An experimental study on the frosting process in a confined space through a horizontal tube frosting visualization test bed is conducted to optimize the structure of the heat exchanger and improve its defrosting performance. The growth rule of frost layer thickness along the length of a tube, the variations of frost accumulation and heat transfer rate with time are evaluated. The influences of wet air initial flow rate, temperature, relative humidity and wall temperature on the frost accumulation and heat transfer rate on the surface of the tube are analyzed. Experimental results show that the thickness of the frost layer gradually increases along the length of the tube at the beginning of frosting. Then, the frost layers are the thickest in the middle of the round tube, and the lowest near the inlet, respectively. Frosting begins at the outlet of the air flow passage. The frost accumulation shows an increasing trend with time passing, while the heat transfer rate increases first and then decreases. Higher wet air flow rate, wet air temperature and relative humidity and lower wall temperature correspond to larger amount of frosting and heat transfer rate, among which the wall temperature has less influence on the frost accumulation and heat transfer rate. The resulting characteristics of frosting and heat transfer rate have certain reference value for heat exchanger design. © 2020, Editorial Office of Journal of Xi'an Jiaotong University. All right reserved.