The theoretical analysis and experimental investigation of a flexible, lightweight radiator with micro heat pipes

In order to develop a flexible, lightweight radiator for long term space missions, a micro heat pipe radiator made of two thin aluminum sheets and aluminum wires is proposed, designed and fabricated. Experimental facilities were set up to verify this concept in both convection and radiation environments. Three aluminum-acetone micro heat pipe arrays were fabricated, tested, and the results presented. The experimental results indicted that the maximum transport capacity, effective thermal conductivity and radiation efficiency of the micro heat pipe radiator increased with the increases in wire diameter and operating temperature before dryout occurred. Comparison of the micro heat pipe radiators with an uncharged test article indicated that the micro heat pipe radiators developed herein could obtain more uniform temperature distributions and higher radiation efficiencies, especially at higher heat fluxes. Using these devices, the overall radiator size and weight can be reduced, thereby meeting or exceeding the baseline design requirements for longterm space missions.; A one-dimensional analytical model, which took into consideration the variation of the cross-section areas and vapor-liquid interaction, was developed to predict the maximum heat transfer capacity, mass distributions and optimum charging volume in both convection and radiation environments. The predicted results indicated that the optimum charging volume decreases with increases in heat flux and more working fluid is needed in a radiation environment than in a convection environment. In addition, evidence was found that there exists an optimum operating temperature at which the maximum heat transport capacity reaches maximum. Comparison of the predicted results with experimental results indicated a good agreement.; Using the effective thermal conductivity of the micro heat pipe arrays obtained from the experiments conducted in a convection environment, a two-dimensional conduction model coupled with radiation was proposed and solved to predict the temperature distribution on the radiator in a radiation environment. Comparison of the numerical results with the experimental results indicated that the predicted temperature distributions were quite comparable to the experimental results, and the average temperature along the heat pipe radiator was also in good agreement. The numerical radiation model can be used to predict the temperature distribution and radiation efficiency in space environment within a reasonable degree of accuracy.