Research On The Mechanism Of High Temperature Heat Pipes Used In Leading Thermal Protection Structures

The existing thermal protection system couldn’t satisfy the thermal protectionrequirement which hypersonic vehicle encountered in high-speed flight. Leadingthermal protection system which is different from traditional ablative thermal protectionand active cooling thermal protection system transmits aerodynamic heat from hightemperature region to low temperature region through heat pipes.This paper studies themechanism of high temperature heat pipes and application of high temperature heat pipein leading thermal protection structures and does numerical simulation of this kind ofthermal protection structure.Heat pipe is a high performance passive heat transfer components. Its equivalentthermal conductivity is more than a thousand times of copper’s. The high thermalperformance is from heat pipe’s unique working principle. Because of the huge phasechange heat generated by the evaporation and condensation of the heat pipe workingfluid, heat can be quickly transmitted from high-temperature region to low-temperatureregion. With the help of capillary force, heat pipe can recycling work.This paper introduces the working principle and structure of heat pipe, makes anoverview of high temperature heat pipe’s application in the leading thermal protectionsystem. A mathematical model is established to predict the grooved wick heat pipe’sthermal properties. The model takes the shear force of the gas-liquid interface, thecontact angle and the amount of liquid filled into account. The axial wall temperaturedistribution and the evaporation and condensation rates are considered by solving theone dimensional conduction equation and the augmented Young-Laplace equation.Based on the high temperature heat pipe’s working condition, this paper poses areasonable hypothesis and builds a model for horizontal axial symmetry hightemperature heat pipe. The numerical results calculated from the model agree with theexperimental results well. So the numerical model and method is reasonable. Thismodel can simulate the flow and heat transfer process of the heat pipe, and reveals theflow and heat transfer law clearly. So it can be used to predict the performance of heatpipe, and the flow and heat transfer characteristics inside the heat pipe. Furthermore,this paper calculates the performance of wing leading edge structured heat pipes usedleading thermal protection system and builds an integrative model for the structure.Under certain heat conditions, the two-dimensional simulation results are comparedwith no heat pipe state. Comparative results show that, heat pipes used leading thermalprotection system can effectively reduce the temperature of the stagnation zone, andraise the temperature of the wing surface area, so as to flatten the temperaturedistribution of the entire structure. So the structure’s radiation cooling is enhanced andthe requirement of thermal protection material is reduced.