EHD-based load controllers for R134a convective boiling heat exchangers

The objective of this study is to investigate the application of high voltage DC waveforms as a mechanism of load control for convective boiling systems. Electrohydrodynamics (EHD) induces flow pattern redistribution, which directly influences the system performance. EHD can provide a low power (<1 W), fast responding method of enhancing two phase flow systems such as heat exchangers. This study compares the use of EHD for load control with control via changing the refrigerant side flow rate in terms of required power, response time and effect on flow parameters. It was found that EHD responds faster and requires less power when a constant exit condition is required for the heat exchanger. Two EHD based controllers; PI controller and a Smith predictor were established using LabVIEW and compared in terms of their response time and regulation behaviour subject to dynamic loading. The Smith predictor resulted in less overshoot and approximately a 50% reduction in settling time in response to dynamic loading. It has been shown that this EHD based controller can regulate subject to ±25% deviation in load from the designed steady state load condition.