In an experimental study of the performance of a unidirectional two-phase air-to-air thermosiphon loop heat exchanger it was found that for an R-11 copper interface, a hot duct to cold duct temperature difference of 16 C to 17 C was required to initiate boiling for operating pressures between 1.2 and 1.6 bars. Once initiated, however, boiling was sustained until the air-to-air temperature difference decreased to 4 C. This hysteresis behavior was exhibited when operating with temperature differences below 50 C. Upon reheating, in this region, a portion of the nucleation sites previously made inactive reactivated easily whereas others were completely quenched. The experimental system was simulated. Good agreement with the experimental results in the hysteresis region could be achieved by using a simple quench-dormancy model.

Units: Dual