Pressure Drop of Refrigerant R22 Inside a Horizontal Spirally Grooved Steel Tube

The experiment on the pressure drop of evaporating refrigerant R22 was performed using a internal grooved micro-finned steel tube. The test tube used in the present study was configured with 12 mm in the average inner diameter, 0.4 mm in fin height, 32 in the fin number and 15 degree in the helix angle and was made of STB-340-S-C steel. The measured pressure drop gradients showed 60～70% lower than that of R123 at high vapor quality conditions. The measured values were compared with some available correlations. Homogeneous model is also used in the comparison with the liquid viscosity as the two phase viscosity and with Carnavos equation to estimate the friction factor for the micro-fin tube. At low mass velocity condition, the values predicted by the homogeneous model were better agreement with the measured values than the other correlations. The Murata correlation predicted the measured values within ±20% at high mass velocity condition