Experimental Investigation of Evaporative Heat Transfer Characteristics for R-22 and R-407C Using Thermochromic Liquid Crystal

Evaporative heat transfer coefficients of R~22 and R-407C (R-32/125/134a, 23/25/52 wt%) in a horizontal smooth tube have been measured. Heat was transferred to theJefrigerant at the test section by applying electric current directly to the stainless steel tube. Saturation temperature of refrigerant was calculated from the measured pressure. The inner wall temperatures were calculated by one dimensional heat conduction equation from the measured outer wall temperatures by an imaging technique using thermochromic liquid crystal (TLC). The RGB values of TLC were calibrated by neural network theory. Experiments were conducted for heat flux of 3.6 kW/m, mass flux from 100 kg/ms to 300 kg/ms, and quality from 0.1 to 0.7. Results show circumferential variation of heat transfer coefficients for R-22 was greater than that for R-407C.