solution.midtermts.fa10

solution.midtermts.fa10 - 5 o C and the convection heat...

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MAE 4071 Thermal System Design Midterm Exam (11/4/10) Fall 2010 Name: I.D.# 1. Geothermal water ( c p = 4250 J/kg o C) at 75 o C is to be used to heat fresh water ( c p = 4180 J/kg o C) at 17 o C at a rate of 1.2 kg/s in a double-pipe counter-flow heat exchanger. The heat transfer surface area is 25 m 2 , the overall heat transfer coefficient is 480 W/m 2 o C, and the mass flow rate of geothermal water is larger than that of fresh water. If the effectiveness of the heat exchanger is desired to be 0.823, determine the mass flow rate of geothermal water and the outlet temperatures of both fluids. 10 points
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2. Solar radiation is incident on the front surface of a thin plate with direct and diffuse components of 300 and 250 W/m 2 , respectively. The direct radiation makes a 30 o angle with the normal of the surface. The plate surfaces have a solar absorptivity of 0.63 and an emissivity of 0.93. The air temperature is
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Unformatted text preview: 5 o C and the convection heat transfer coefficient is 20 W/m 2 o C. The effective sky temperature for the front surface is -33 o C while the surrounding surfaces are at 5 o C for the back surface. Determine the equilibrium temperature of the plate. 10 points 3. A furnace is of cylindrical shape with a diameter of 1.2 m and a length of 1.2 m. The top surface has an emissivity of 0.70 and is maintained at 500 K. The bottom surface has an emissivity of 0.50 and is maintained at 650 K. The side surface has an emissivity of 0.40. Heat is supplied from the base surface at a net rate of 1400 W. Determine the temperature of the side surface and the net rates of heat transfer between the top and the bottom surfaces, and between the bottom and side surfaces. 10 points...
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This note was uploaded on 03/07/2012 for the course MAE 4071 taught by Professor Dr.mitra during the Spring '12 term at FIT.

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solution.midtermts.fa10 - 5 o C and the convection heat...

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