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Radiation Midterm Exam ME 3345 Heat Transfer Fall 2008 Hesketh CLOSED BOOK MIDTERM EXAM TIME ALLOWED 55 MINUTES Name: Grade: Question 1 (30 pts): Calculate the angle factor F12 for the geometries shown bellow: FPOM /Y/~/MF~~Y fix= Fr3 =o \ Ei +- +jz-t &- - I -. 2&,.=- l F L L = aJ Page 1 r

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Radiation Midterm Exam ME 3345 Heat Transfer Fall 2008 Hesketh QQ Question 2 (Sts): Consider a cylindrical furnace with diffuse gray surfaces, 0.3m long and 0.3m in diameter. One end is maintained at 400K with emissivity 0.4 and the other at 500K with emissivity 0.5, the walls include a heater element is black, and maintained at a temperature of 800K. Cy'indri& Heater (a) Sketch the equivalent thermal circuit (b) Estimate the heat transfer from the heating element and from each ends of the furnace.

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Unformatted text preview: Page 2 Radiation Midterm Exam ME 3345 Heat Transfer Fall 2008 Hesketh Question 3 (38pts) A thin sheet of glass sheet covers a solar collector which is transparent to visible radiation. The irradiation solar flux is 1100 w/m2, and the irradiation from the sky is 3 15 w/m2 Estimate the temperature of the glass. Assume the emissivity of the solar collector is equal to unity. Given the external convection heat transfer is 10 w/m2 K and the outside air temperature is 20 O C and the temperature of the surroundings is 0 O C. Properties of glass are: Transparent for wavelength less than 1 Sum (absorptivity is zero), and absorptivity equal to 1 for wavelength greater than 1 Sum. [Hint: carry out an energy balance on the glass and neglect convection inside the collector]...
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