Operational Characteristics of the Oscillating Heat Pipe with Noncondensable Gas

Abstract

In this study, the effects of noncondensable gas on the behavior of oscillating heat pipes were investigated. The oscillating heat pipe was made of capillary copper tube, and its turn number was 16. The working fluid used was ethanol, and argon gas was used as noncondensable gas. Experiments were conducted using four different noncondensable gas volume ratios. The temperature and inner pressure of the oscillating heat pipe were measured over a heat input range from 40 to 180 W. The results of this study suggest that the operating characteristics of the oscillating heat pipe were affected by noncondensable gas. In particular, the thermal resistance of the oscillating heat pipe increased with lower heat input as the amount of noncondensable gas increased. In addition, the thermal performance rapidly deteriorated with a large amount of noncondensable gas after local dryout. With higher heat input, the thermal resistance increased even with small noncondensable gas amounts. Nomenclature A = amplitude,°C, kPa m = mass, kg P = pressure, kPa Q = heat input, W R = gas constant, J∕kg mol R th = thermal resistance, K∕W T = temperature,°C, K V = volume, m 3 α = charging ratio, % β = inclination angle, deg ρ = density, kg∕m 3 σ = surface tension, N∕m Subscripts c = cooling section f = working fluid g = noncondensable gas h = heating section l = liquid phase max = maximum min = minimum v = vapor phase