(1)calculate the overall heat transfer coefficient from air to a product packaged in 3.2mm of solid cardboard and 0.1mm of celluloid if the surface air heat transfer coefficient is 11Jm
-2s
-1¡É-1
solid cardboard ºÎ·Ï¿¡ º¸´Ï±î 0.07(¿Àüµµµµ)
celluloid 0.21 (¿Àüµµµµ)
1/u=0.0032/0.07+0.0001/0.21=0.0457+0.00047=1/0.0462 u=21.65·Î Çغôµ¥ ´äÀÌ ¾Æ´Ï¾î¼¿ä.
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(2)calculate the thermal conductivity of uncooked pastry. measurements show that with a temperature difference of 17
¡Éacross a large slab 1.3cm thick, the heat flow is 0.5JS
-1 through an area of 10cm2 of slab surface.
0.5=x(¿Àüµµµµ?)/0.013*17*0.001
=0.013/(17*0.001)*0.5
°è»êÇؼ 0.38jm
-1s
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