Sharif Digital Repository

In this paper, two models are developed to predict liquid pressure drop and velocity profile in the wicks of concentric annular heat pipes. A steady-state incompressible laminar flow is modeled in the wicks based on velocity and pressure mean values by the extended Darcy-Brinkman model. The corresponding one- and two-dimensional governing equations are solved analytically and numerically, respectively, in the range of low to moderate radial Reynolds numbers. It has been found that there is a difference, about 12% in the worse case, between the total pressure drops of the two models. Whereas, the predicted total pressure drop by the one-dimensional model and that of the Darcy model are in... 

A detailed description of a concentric annular heat pipe (CAHP) operation is presented in low to moderate temperature ranges (50-200°C). The steady-state response of a CAHP to various heat fluxes in the evaporator and condenser sections are discussed. Two-dimensional mathematical modeling of the fluid flow and heat transfer in the annular vapor space and the wicks are described. The fundamental aspects and limitations of the operation of a CAHP are also discussed. Previously used numerical and experimental approaches for the analysis of the CAHPs and some related concepts are reviewed. The Navier-Stokes and similar equations are recommended for the simulation of fluid flow and heat transfer... 

A numerical method based on the SIMPLE algorithm has been developed for the analysis of vapor flow in a concentric annular heat pipe. The steady-state response of a concentric annular heat pipe to various heat fluxes in the evaporator and condenser sections are studied. The fluid flow and heat transfer in the annular vapor space are simulated using Navier-Stokes equations. The governing equations are solved numerically, using finite volume approach. The vapor pressure and temperature distributions along a concentric annular heat pipe are predicted for a number of symmetric test cases. The vapor flow reversal and transition to turbulence phenomena are also predicted. The results are compared...