Heat Transfer in Film Boiling With Pulsating Pressures

The purpose of this exploratory experimental investigation was to determine the effect on the heat-transfer rate when a pulsating pressure is applied to a stable film boiling system. The test section used consisted of a 0.030-in-dia horizontal platinum wire. The boiling medium was monofluorotrichloromethane, C Cl3F, commercially available in high purity as Refrigerant 11. A boiling curve was obtained at atmospheric pressure. In addition, pulsating tests were conducted for various pulsing rates and for three different test wire temperatures. Periodic pressure pulses of approximately 100 psi were applied to the system. The initial results thus far obtained in this investigation show a substantial increase in the heat-transfer rate for pulsing frequencies ranging from 11.3 cps to 25.8 cps. The improvement is noted to be from 59.5 percent to 103 percent above the heat-transfer rate for film boiling at atmospheric pressure at the same temperature difference between the test wire and the fluid. It was also found that the heat-transfer rate achieved was higher than the average of the heat-transfer rate for atmospheric pressure film boiling and that for subcooled film boiling at the peak pressure achieved in pulsing. For the higher pulsing frequencies, the heat-transfer rate was found to be even greater than that for subcooled film boiling at the peak pressure.