课程名称︰热传学 课程性质︰必修 课程教师︰陈炳辉 开课学院：工学院 开课系所︰机械系 考试日期（年月日）︰2017.01.13 考试时限（分钟）：150 试题 : 1.(20%)Consider a water flow at one atmosphere over a flat plate without the pressure gradient. If the free steam temperature is 10°C, the free steam velocity is 0.1m/s. The wall temperaturedistribution is given by as follows: 10°C for x = 0m to x = 0.1m, 50°C for x = 0.1m to x = 0.2m, and 90°C for x > 0.2m. Please calculate(a)(10%)the heat flux at x = 0.15m, (b)(10%)the heat flux at x = 0.22m. 2.(20%)Consider a water flow through an in-line tube bank with NL = 17,NT = 10, ST = 0.3m, ST/SL = 2, tube length, L, of 1m, and tube diameter, D, of 0.1m. The tube surface temperature is 80°C and the inlet water temperature with an upstream velocity of 0.1m/s is 20°C. (a)(10%)Please determine the heat flow transported from the tube bank into the water flow. (b)(10%)Please determine the required pumping power for driving the water flow through the tube bank. 3.(20%)Consider a developing water flow in a circular pipe with a constant wall temperature of 90°C and diameter of 0.02m. The water flow has an inlet temperature of 10°C and a uniform velocity of 0.05m/s. Please determine the heat flow from the tube into the water for the pipe from x = 0 to 0.6m. 4.(20%)Consider a heated vertical cylinder in an atmosphere with a temperature of 20°C. The cylinder has a temperature of 80°C, a length of 0.1m and a diameter of 0.2m. Please determine the heat flow from the cylinder to the surrounding air. 5.(20%)(送分)One can reduce radiation heat flux between two disks, shown in figure, by placing a highly reflective thin disk between these two disks. Note that there is a boundary, 3, connecting disks 1 and 2. The emissivity of disk 1, disk 2, and boundary 3 is 0.9. The temperature of disk 1 is 600K. Temperature of disk 2 is at 300K and boundary 3 is insulated. A highly reflective thin disk 4 is placed between two disks and it has an emissivity of 0.05 on the surface facing disk 1 and with an emissivity of 0.2 on the other surface facing disk 2. The diameter of all three disks is 1 m and the distance between disk 1 and disk 2 is 2m. (1)Please determine the reduction percentage of heat flow from disk 1 to disk 2 if the disk 4 is placed at midpoint between disk 1 and 2. (2)Please determine the location at which the disk 4 is placed for having the maximum reduction on the heat flux from disk 1 to disk 2 if the disk is placed between two disks 1 and 2. The equation for determining the view factor between two parallel, equal, coaxial disks is F12 = [X-(X^2-4)^0.5]/2, X = (2R^2+1)/R^2, R = d/2x where d is the disk diameter and x is the distance between two disks. http://imgur.com/oovPFPs --

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