Evaporator performance enhancement by pulsation width modulation (PWM)

In this work, the effects of pulsation width on heat transfer coefficient and pressure drop in an air-to-refrigerant evaporator is studied experimentally. The pulsation width can be controlled to a minimum period of 2 s. A general model is also developed to predict heat transfer performance and pressure drop. The overall heat transfer coefficient, refrigerant side heat transfer coefficient, and pressure drop are measured and compared to a baseline without pulsating flow. The results show that the overall and refrigerant-side heat transfer coefficients have improved about 27% and 123%, respectively, with pulsating flow. The refrigerant mass flux and pulsation period have an important effect on the heat transfer enhancement. The average pressure drop of the pulsating flow differs little from that of continuous flow, but the temporal pressure drop of pulsating flow is quite different and varies with mass flux and pulsation period.