Development And Thermal Properties Study Of Bi-porous Wicks Of Dual-Evaporator Loop Heat Pipe

Loop heat pipe is a kind of device which is in the use of two-phase change to achieve heat transfer,widely used in cooling of aerospace equipment and electronic components.The wick is the key component of loop heat pipe,which provides power for the entire loop.With high-power radiating element,multi-source development trend,pore characteristic using a single capillary structure has been unable to achieve the overall op timization of the capillary structure,and wick with bi-porous distribution has excellent capacity of heat transfer.Through orthogonal experimental design,the paper carried bi-porous distribution of nickel wicks sintering.The porosity,permeability,capillary pumping height and effective thermal conductivity of wick samples were measured and calculated.Reasonable sintering parameters were selected,including pore former particle size,pore former content,compacting pressure,sintering temperature and holding time,in order to study the effects of these five sintering parameters on the wick key performance parameters of porosity,permeability,capillary pumping height and effective thermal conductivity.The relationship between the primary and secondary of the influence of various factors to the performance of wicks was obtained.The greatest impact on the performance of wicks is the content of the pore former,followed by the pressing pressure and sinter ing temperature,to a lesser extent the holding time and the size of pore former.Meanwhile,the optimal wicks were found to be sintered at 650°C,with pore former content 30% by volume using a 400 mesh size or more,the molding pressure at 5MPa and holding time of 30 min,which is very important for porous wick to achieve low-cost manufacturing in laboratory and mass production of industrial applications.Single factor multi-level control experiments were used to study the effect of pore former content and sintering temperature on the porosity,permeability and effective thermal conductivity of wicks,and the pore former particle size on the nickel wick microstructure,by correlation between sintering parameters and key performance parameters of bi-porous wicks.The effective thermal conductivity of bi-porous nickel wicks has been studied and the experimental values are compared with the calculated values from 11 effective thermal conductivity computation models of porous medium.The result shows that it helps to obtain a high porosity and permeability,and low effective thermal conductivity of the wick at the condition of lower sintering temperature and high pore former content.When the pore former size is 400 mesh size or more,we could obtain the superior bi-porous structure distribution.In the porosity range of 0.5-0.7,the average calculated values of C hernysheva&Maydanik model and C haudhary&Bhandari model are best fit with the experimental values,which provides a method for ETC estimate of bi-porous nickel wicks.The calculation of compensator volume,filling volume and pressure drop checking,leak detection and assembly of the loop heat pipe,vacuum and filling and other key issues were taken into account and it was produced a dual-evaporator loop heat pipe with a compensator separately.Using methanol as the working fluid,it was tested that the startup characteristic for the loop heat pipe with dual-evaporator.When the thermal load was applied 30 W on the two evaporators simultaneously,the system started successfully.