喷雾冷却表面瞬态热流密度计算方法研究

Methodology for Prediction of Time-Varying Heat Flux During Pulsed Spray Cooling

瞬态喷雾冷却过程中,表面热流密度是衡量表面冷却效果的重要参数。本文以环氧树脂为冷却基体,分别采用直接与间接两种方式测量冷却表面瞬态温度,通过构建新的传递函数,将Green函数法成功拓展至半无限大多层平板导热反问题的热流密度计算。对比分析了Duhamel定理、顺序函数法(SFSM)与Green函数法在不同测温方法下计算表面瞬态热流密度的有效性与适用性,结果表明,在表面温度直接测量方式下,三种方法均能较准确计算出表面瞬态热流密度。在间接测温方式下,Duhamel法忽略了测点和表面之间材料的散热影响,因此无法准确计算出瞬态表面热流密度,SFSM在温度快速变化阶段计算结果有一定失真,而利用Green函数法求解表面热流密度最为准确。

Surface heat flux plays a crucial role in the evaluation of heat transfer performance during pulse spray cooling. This paper employed direct and indirect methods to measure transient surface temperature of epoxy resin.A new transfer function was constructed, and thus the Green function method was extended to solve multi layer, semi-infinite inverse heat conduction problems. The accuracy of several algorithms, i.e. Duhamel＇s theorem, sequential function specification method （SFSM） and Green function method were analyzed under different temperature measurement methods. It was found that all algorithms were able to predict surface heat flux well based on the direct measurement of surface temperature. However, Duhamel＇s theorem was unsuitable for predicting surface heat flux under condition of in direct measurement of surface temperature, since it did not take into consideration of heat dissipation between measurement point and surface layer. The result predicted by SFSM appeared a noticeable discrepancy during the period when surface temperature changed extremely fast. Green function method can always predict an accurate surface heat flux.