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# HW4_Solutions.pdf

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University of Michigan - Ann Arbor

Mechanical Engineering

MECHENG 235

Donald Siegel

Winter

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THE UNIVERSITY OF MICHIGAN
Department of Mechanical Engineering
ME 235 Thermodynamics I / Winter 2014 / Section 002
HW 4 Solutions
Due date: Feb. 11 2014
3.34 Airplane takeoff from an aircraft carrier is assisted by a steam driven pistowith ander device
average pressure of 1250 kPa. A 17500 kg airplane should be accelerated from zero to a speed of 30 m/s
with 30% of the energy coming from the steam piston. Find the needed piston displacement volume.
3.55 Air goes through a polytropic process fro m 125 kPa, 325 K to 300 kPa and 500 K. Find the
polytropic exponent n and the specific work in the process. 3.57 Consider a piston cylinder with 0.5 kg of R -134a as saturated vapor at -10°C. It is now compressed
to a pressure of 500 kPa in a polytropic process with n = 1.5. Find the final volume and temperature, and
determine the work done during the process. 2
3.61 A 2-m window has a surface temperature of 15°C and the outside wind is blowing air at 2°C across
it with a convection heat transfer coefficient of h = 125 W/m K. What is the total heat transfer loss?
3.65 A pot of steel, conductivity 50 W/m K, with a 5 mm thick bottom is filled with 15°C liquid water.
The pot has a diameter of 20 cm and is now placed on an elect

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