Unformatted text preview: PROBLEM 3.2] KNOWN: Thickness, overall temperature difference, and pressure for two stainless steel
plates. FIND: (a) Heat flux and (b) Contact plane temperature drop. SCHEMATIC:
9' pressure 1 661'
T 7.3 .
5,: L R" _L_ y 7;: '32.: 400 C
F f“ k T53 Sfainfcas safe-e! ASSUMPTIONS: (l) One-dimensional heat transfer, (2) Steady-state conditions, (3)
Constant properties. PROPERTIES: Table A—1, Stainless Steel (T a: 400K): k = 16.6 WEm-K.
ANALYSIS: (a) With REC 2:: 15X 10—4 m2 - KIW from Table 3.] and L & = 6.02x10_4m2A tow, k 216.6 me-K it follows that 11:0, = 2(Uk)+ REC re: 27x10‘4m3.K,«w, hence q"— M — 100 C —3.T0xlO4me2. < Riot 27x 10'4m2 - 10w (b) From the thermal circuit, ATC _ Ric _15x10_4m2-KHW _0556
T5,1'Ts,2 Rlot ZTXIOJ‘lmZ-KJ’W
ATC = 0.556(T,,] 4,52) = 0.556(100°C] = 556°C. < COMMENTS: The contact resistance is signiﬁcant relative to the conduction resistances.
The value of Ric would diminish, however, with increasing pressure. Note that there is considerable uncertainty in the answer since the thermal contact resistance can take on a wide
range ofvalues. ...
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- Spring '10
- Heat Transfer