Condensation of refrigerant R450A inside a mini-channel of rectangular cross section with an internal longitudinal groove

Abstract

The increase in jeopardizing the natural life and environmental resources together with high rates of energy consumption are still in focus of international agencies and scientific communities. For this issue, global awareness has been oriented to uncover alternatives to harmful species and to magnify effectiveness of thermal systems. For the present study, the refrigerant R450A was investigated as a potential substitute to R134a during condensation inside two mini-channels which are rectangular cross section channel (SRC) and a modified channel (MRC). The latter was characterized by an internal longitudinal groove. Wall subcooling, vapor superheat, and mass velocity were considered while the condensing temperature was kept constant. Numerical CFD simulation was realized for the condensation inside the channel using ANSYS-CFX 15.0 with additional user defined expressions to describe condensate layer thickness inside the channel, which in turn was utilized for the condensation heat transfer coefficient (HTC). Predicted data was compared with experimental one in terms of HTC and flow patterns. The predicted data of HTC showed an average deviation by about 6.6% compared to experimental data for R134a.The refrigerant R450A resulted in lower condensation HTC than R134a. The MRC resulted in an average enhancement in the HTC by about 55.7% and a reduction in the pressure drop by about 10.4% compared to the SRC. The enhancement of the MRC in HTC was remarkable at high degree of superheat, low mass velocity, and low wall subcooling. Accordingly, the novel MRC represents a successful potential design for condensation of refrigerants in mini-channels.