Abstract
Noncondensable gas (NCG) in a loop heat pipe (LHP) results in degradation of its performance. In an LHP operating on the ground with low pressure working fluids, atmospheric air entering into it acts as NCG. The goal of this paper is to estimate the NCG mass in an LHP with flat evaporator with a low-pressure working fluid based on the pressure and liquid volume measurements inside the compensation chamber (CC) and study its effect on deprime (i.e., dry out or capillary limit). An LHP with flat evaporator was tested with acetone for various heat inputs till deprime for two sink temperature, namely, −20 °C and 0 °C, by allowing entry of atmospheric air into the LHP through an intentionally fixed defective gasket. The NCG mass is estimated at various heat inputs based on the CC pressure measured using an absolute pressure transducer and the CC liquid volume measured using a capacitance gauge. Comparison of the test results with the results of previous tests without the NCG shows that the NCG causes increased operating temperature and decreased heat transport. Analysis of the test results at the maximum heat input prior to deprime reveals that the capillary pressure developed in the pores of the wick in the LHP with the NCG is less than that without the NCG and the radius of evaporating meniscus in the pores of the wick with the NCG is more than that without the NCG.
Published Version
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