Mathematical Modeling for Predicting Steady State and Transient Characteristics of Reservoir Embedded Looped Heat Pipe (RELHP)

This paper presents the heat transfer characteristics of a Reservoir Embedded Looped Heat Pipe (RELHP) with stainless steel porous wick with pore diameter of 1μm and working fluid of ammonia. The core of evaporator is used as a liquid reservoir to enhance operational reliability. Mathematical models for predicting static and transient heat transfer characteristics of RELHP were developed. Evaporative heat transfer coefficient in wick and heat transfer between vapor phase and liquid puddle in reservoir are taken into consideration in these models. Experiments using the reservoir visual inspection model and practical RELHP were conducted and compared with the prediction. The evaporator of the practical model has the length of 1000mm and diameter of 38mm and the total loop length is 11.5m. The practical RELHP model has the same configuration, as that will be experimented in ETS-VIII. Natural convection but nucleate boiling was observed in the liquid puddle in the reservoir of the visual inspection model. The practical RELHP model showed larger heat transport capacity than specified 1kW. The steady state and transient simulations of RELHP approximated to the experimental results.