An experimental study on the frosting characteristics of multi-tube heat exchanger with spraying condensable additive at the temperature of 77 K and 240 K

Abstract

In this paper, the effect of condensable additive on frost resisting under different operating conditions was investigated through an established visualization experimental system. The physical parameters including the thickness of frost layer, heat transfer coefficient, and the pressure drop were observed, measured, and calculated during the course of frosting formation. The characteristics of fluid flow and heat transfer were studied under various testing conditions. In order to analyze the effect of condensable additive on the process of frosting, different spraying ratios were utilized to estimate the frost resisting results under various humidity, air velocities and coolant liquid temperatures. It has been found that the increasing of condensable additive results in high heat transfer coefficient and low pressure drop. It is also indicated that air velocity, humidity, and coolant liquid temperature play a significant role in the frost growth. The capacity of heat transfer is enhanced under higher air velocity, higher humidity, and lower coolant liquid temperature. The frosting process of anti-frosting with condensable additive has been investigated in detail, compared with pure water, the compound frost layer with condensable additive has higher density and slighter thickness, which decreases the heat resistance of heat exchanger. In addition, condensable additive reduces the freezing point of compound fluid, which makes it difficult to freeze under this circumstance, and the freezing process is prolonged.