Pressure Drop Prediction of R-134a Two Phase Flow inside Evaporators

The pressure drop of refrigerant R-134a flow boiling inside a horizontal tube has been investigated experimentally. The test set-up which was used in this investigation is a well instrumented vapor compression refrigeration system. These instruments are thermocouples, flow meter, pressure gauges and the pressure drop measuring apparatus. This system consisted of three electrically heated evaporators called as pre-evaporator, test evaporator and after evaporator, respectively. The empirical pressure drop data for two phase flow boiling of R-134a inside a horizontal tube of 7.5mm internal diameter has been collected. The ranges of mass velocities and vapor qualities are 54-136 kg/m2s and 0.2-1, respectively. The collected data were compared with the predicted pressure drop values by seven different correlations. Finally, a new correlation was developed to predict the pressure drop of two phase flow inside evaporators.