MEM 345 Final Spring 10-11 - NAME Drexel University...

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NAME__________________________ Drexel University MEM 345 Mechanical Engineering and Mechanics Heat Transfer (Spring 2010) Final Exam (Open book and closed notes) Note: Per university regulations, all forms of academic dishonesty will be addressed in a strict manner. The student may be given an “F’ grade if found to cheat or plagiarize. 1. The temperature of a gas stream is to be measured by a thermocouple whose junction can be approximated as a 1-mm-diameter sphere. The properties of the junction are: thermal conductivity k = 35 W/m, density != 8500 kg/m3, and specific heat cp= 320 J/kg.K, and the convection coefficient between the junction and the gas is h = 210 W/m2.K. (a) Determine if the problem can be analyzed via the “lumped capacitance method”. (b) Determine how long it will take for the thermocouple to read 99 percent of the initial temperature difference. 302. Consider a thin-walled, stainless steel pipe of diameter D = 20 mm. The surface of the pipe is maintained at 70°C. Water flows through the pipe at the rate of = 0.01 kg/s. The water

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