Numerical Simulation And Experimental Studies On Loop Heat Pipe Radiator For Electronic Device Cooling

With increase in heat output and miniaturization of electronic device, the problem of heat dissipation has more and more influence on its performance,reliability and working life. In this paper, a series of explorative research on loop thermosyphon for the cooling of electronic devices have been carried on to meet the heat dissipation demand of electronic devices with high heating flux and ensure their working in normal temperature range. The loop thermosyphon doesn't have capillary structure. Working substance transfers heat with its boiling and condensing and is circumfluent by its own gravity. The loop thermosyphon is simple in structure and easy to make, therefore it becomes one of the most effective way to solve heat dissipation of electronic devices with high heating flux.By analyzing the structure of loop thermosyphon heat sink and the complexity of flow in tube, the boiling heat transfer inside the evaporator is emphasizely simulated numerically. The theory calculation model about the heat transfer characteristic of thermosyphon heat sink has been founded. The determination of control equation,boundary condition and physical parameter as well as their implementation methods in software have been analyzed detailedly. The influence of those main design parameterssuch as evaporation saturation temperature t_s,heat dissipated power Q and charge ofworking fluid L on the temperature distribution of evaporation's bottom and boiling heat transfer inside the evaporation has been calculated and analyzed concretely. The method that uses channels to enhance boiling heat transfer of evaporation's bottom has also been analyzed and calculated preliminarily. The results of numerical simulation provide theoretical basis for the thermosyphon heat sink to avoid the blindness of experiment and inaccuracy of experimental theory.Through simulating electronic apparatus with a heating copper block and operating working conditions, an experimental equipment of loop thermosyphon heat sink on heat transfer character was set up. Experiments on heat transfer character of loop thermosyphon were carried on under different heat dissipated power and different inlet temperatures of cooling water in condensation. Trough the comparison to verify the results of numerical simulation calculation and based on the reliability of experimental results, the parameter correlation formula of average boiling heat transfer coefficient h of loop thermosyphon evaporation has beenobtained. h = C₁t_s^3.520Q^0.119L^0.662 , where C₁ = 4.730×10^-4W^0.881/mm^2.662·°C^4.520.A performance testing system of thermosyphon heat sink and an experimental equipment of loop thermosyphon heat sink on heat transfer character were set up as good experimental basis for the further research. The designed optimization design software of loop thermosyphon heat sink solves the complicated influence relation between many design parameters and performance of radiator. Experiments show that the designed loop thermosyphon heat sinks can meet the cooling demand of small computer server. The four thermosyphon heat sinks of different structure have become the basis of development and design of new product of relative enterprises.