Heat Transfer in a Liquid Convective Diode

Abstract

The dynamic behavior of a liquid convective diode for space heating of passive solar buildings is analyzed and explained by experiments and theory. The experiments include flow visualization and temperature measurements obtained for a diode installed in the laboratory and temperature measurements obtained for three diodes installed in a test cell during the winter. We present a first-principles analytical model to predict diode time-temperature histories and performance. A comparison of predicted temperatures and solar energy contribution with data obtained for the test cell experiment showed excellent agreement. The good agreement indicates that the model contains the elements necessary to accurately predict site-specific diode performance and temperatures. The thermal efficiency of the diode system installed in the test cell is calculated. The data show that the diode system outperforms all other non-phase-change passive solar heating components. A thermal efficiency of 50 percent over a three-month winter period is obtained for the diode. We suggest and discuss improvements to present-day diode designs that may increase performance to as high as 65 percent.