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1、产品的热设计Thermalintrodu,1,Introduction of Thermal,GGT/RE Environment Test Team,产品的热设计Thermalintrodu,2,Primary Mechanic of Heat Transfer,Thermal energy transport: cause by temperature difference, high T - low T Conduction Heat transferring by solid medium Convection Transferring energy between solid sur
2、face and fluid Mass transport Natural (free) convection Forced convection Radiation Heat transferring by electromagnetic waves,产品的热设计Thermalintrodu,3,Conduction,Fouriers Law Q= -KA T/L Q: heat transfer rate A: cross-sectional area of heat flux T/L: temperature gradient K: thermal conductivity (W/mk)
3、 Ex. Al = 230 Cu = 380 Mylar = 1.8,产品的热设计Thermalintrodu,4,Convection,Newtonian cooling Law Qc = hc As (Ts Ta) Qc: convection heat transfer rate As: surface area Ts: surface temperature of solid Ta: tmperature of ambient hc: heat transfer coefficient, f(flow type, body geometry, physical property, te
4、mperature, velocity, viscosity) Natural convection 太小, 噪音上升.,W: 作為風道, 盡量大,Single fan,Double fan,Parallel,CFM,Pressure,Pressure,CFM,Single fan,Double fan,Series,TIM: thermal interface material 考慮將散熱器固定於發熱器件的方法時, 重要的是要使二者之間界面熱傳到處效率最大. 也應考慮其他要求, 如介電特性, 電導性, 附著強度和再次安裝的可能性. 發熱組件和散熱器之間界面的熱傳輸效率取決於空氣殘留, 填充物類型和黏合曾的厚度等參數.,