Numerical analysis on heat transfer of a complete anti-gravity loop-shaped heat pipe

Anti-gravity loop shaped heat pipe (AGLSHP) with continuous step-graded sintered wick is useful for enhancing the effective heat transfer in the anti-gravity direction. In this work, a complete steady state model has been presented to investigate in the thermal performance and hydraulic behavior of the AGLSHP. The governing equations for the heat and mass transfer are developed for the loop operation, with specific attention given to the evaporator region. By comparing the numerical simulation with the experimental data, the heat transfer mechanism is revealed. The liquid/vapor velocity and pressure distribution in the evaporator are discussed, and the temperature distribution along the transport line is also analyzed. The numerical results indicate that with the increase of the heat load, the maximum velocity and pressure value of the liquid and vapor increase as expected. The highest temperature position occurs at the outlet of evaporator surface. Providing the capillary pressure for the circulation of working fluid, the wick in the liquid line is paid more attention. Moreover, the longer condensation length is more effective in decreasing the temperature at the outlet of condenser and improving the heat transfer capacity of the AGSLHP.