課程名稱︰熱傳學
課程性質︰
課程教師︰馬小康
開課學院：工學院
開課系所︰機械系
考試日期（年月日）︰2010/10/26
考試時限（分鐘）：100
是否需發放獎勵金：是
（如未明確表示，則不予發放）
試題 :
(30%)(1) Consider ac ubic block whose side are 5 cm long and a cylindrical
block whose height and diameter are also 5 cm. Both blocks are
initially at 20℃ and are made of granite (k=2.5 W/m.℃ and α=
1.15*10^(-6) m^2/s). Now both blocks are exposed to hot gases at
500℃ in a furnace on all of their surfaces with a heat transfer
coefficient of 40 W/m^2.℃. Determine the center temperature of each
geometry after 10, and 60 min.
(參考習題4-82)
(30%)(2) A 5-mm-diameter spherical ball at 50℃ is covered by a 1-mm thick
plastic insulation (k=0.13 W/m.℃). The ball is exposed to a medium
at 15℃, with a combined convection and radiation heat transfer
coefficient of 20 W/m^2.℃.
Please (a) write down the rate of heat transfer and the total thermal
resistance Rtotal.
(b) determine if the plastic insulation on the ball will help
or hurt heat transfer from the ball.
(參考習題3-90)
(10%)(3) For one-dimensional transient conduction in Cartesian coordinates in
a semi-infinite medium, what is the similarity variable η? and why?
(30%)(4) A slab insulated on both sides. Assume k and other properties are
constant. Please solve T(t,x) by the separation variable method when
Initial condition T(0,x)=f(x). Also, the special case when f(x)=T0=
constant.
│ │
│ k │
│ │
insulated-->│ │<--insulated
│<----->│
│ L │
└>
x=0
--
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