接觸熱導
Multi tool use
接觸熱導（thermal contact conductance）是指二個固體在有熱接觸時的热传导。接觸熱導係數（thermal contact conductance coefficient）hc{displaystyle h_{c}}
是有二個相接觸的固體之間的熱導率，也表示其導熱的能力。接觸熱導係數的倒數稱為接觸熱阻（thermal contact resistance）。
定義
當二個固體相接觸（例如圖1的A和B），熱會由較高溫的物體流到較低溫的物體。二個固體的溫度分佈大致如圖1所示。在接觸面上有明顯的溫度落差，這就是二個接觸面之間接觸熱阻造成的影響。接觸熱阻定義為溫度差和介面平均熱流的比例[1]。
依照傅立葉定律，兩物體之間的熱流如下式所示：
q=−kAdTdx{displaystyle q=-kA{frac {dT}{dx}}}
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(1)
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其中q{displaystyle q}
為熱流，k{displaystyle k}
為熱傳導率，A{displaystyle A}
為截面積，dT/dx{displaystyle dT/dx}
是延著熱流方向的溫度梯度。
考慮能量守恆，兩物體之間的熱流可以用以下方式計算：
q=T1−T3ΔxA/(kAA)+1/(hcA)+ΔxB/(kBA){displaystyle q={frac {T_{1}-T_{3}}{Delta x_{A}/(k_{A}A)+1/(h_{c}A)+Delta x_{B}/(k_{B}A)}}}
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(2)
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可以看出熱流和兩物體的熱傳導率kA{displaystyle k_{A}}
和kB{displaystyle k_{B}}
，接觸面積A{displaystyle A}，以及接觸熱阻1/hc{displaystyle 1/h_{c}}
有關。而接觸熱阻的倒數即為接觸熱導係數hc{displaystyle h_{c}}。
參考資料
^ Holman, J. P. Heat Transfer, 8th Edition. McGraw-Hill. 1997.
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