Optimizing the design for a two-phase cooling loop heat pipe: Part A: Numerical model, validation and application to a case study

Abstract

High-power light-emitting diodes can dissipate several times more heat power than conventional lighting devices, while keeping the junction temperature below a security value, in order to assure reliability and low light decay. No fans are usually permitted, so the heat dissipation solution should adopt new technological advances that are required in the form of lighter, shape-embedded heat-sink devices. The present study addresses the implementation of a special heat-dissipation technology, known as a loop heat pipe, consisting of an evaporator, a condenser, a compensation chamber, and vapor and liquid lines for cooling particular types of devices, such as light-emitting diodes, through the phase-change cooling method. In this paper a new algorithm to simulate this loop heat pipe is presented. This mathematical model is based on steady-state energy balance equations for each main component. Finally, a validation procedure through a fully monitored experimental test is performed to show the effects of different key parameters on the heat load such as radius and length of the vapor line, wick thickness and condensing temperature. It produces an effective optimization of the original design, representing an innovative tool for design assessment, to determine the influence of these key performance parameters for each particular application. Finally, a case study is presented for the optimization of a loop heat pipe design, applied to the cooling of an 80 W street lamp.