Effects of mass of charge on loop heat pipe operational characteristics

Experimental results on a loop heat pipe, using R134a as the working fluid, indicates that the liquid inventory in the compensation chamber can significantly influence the operating characteristics. The large liquid inventory in the compensation chamber, under terrestrial conditions, can result in loss of thermal coupling between the compensation chamber and the evaporator core. This causes the operating temperature to increase monotonically. This phenomenon, which has been experimentally observed, is reported in this paper. A theoretical model to predict the steady-state performance of a loop heat pipe with a weak thermal link between the compensation chamber and the core, as observed in the experiment, is also presented. The predicted and the experimentally determined temperatures correlate well.

Saturated liquid viscosity correlations for alternative refrigerants

This article presents dimensionless equations for the temperature dependence of the saturated liquid viscosity of R32, R123, R124, R125, R134a, R141b, and R152a valid over a temperature range of engineering interest. The correlation has the form Phi(D)(n)=A+BTD where Phi(D) is the dimensionless fluidity (1/eta(D)) and T-D is a dimensionless temperature. n, A, and B are evaluated for each of the above refrigerants based on a least-squares fit to experimental data. This equation is found to provide an improved fit over those existing in the literature up to T-D=0.8.