Study Guides (238,085)
United States (119,672)
Midterm

# ME235_Exam1_F11.pdf

4 Pages
60 Views

School
University of Michigan - Ann Arbor
Department
Mechanical Engineering
Course
MECHENG 235
Professor
Donald Siegel
Semester
Winter

Description
ME 235 EXAM I , Oct 19, 2011 K. Kurabayashi and D. Siegel, ME Dept. Exam Rules: Open Book and one page of notes allowed. Name: __________________________________ I have observed the honor code and have neither given nor received aid on this exam. Signature:____________________________________________ 1. [30 points] Determine the phase of the following substances and find the values of the unknown quantities. (a) Water, P = 400 kPa, T = 40°C, v = ?, u = ? (b) Nitrogen, T = 120K, h = 60 kJ/kg, P = ?, u =? (c) R-410a, T = -20 °C, v = 0.0648 m /kg, P = ?, u = ? (d) Water, P = 500 kPa, u = 2802.91 kJ/kg, T = ?, v = ? 2. [30 points] Carbon dioxide (ideal gas) in a piston cylinder is at 300 kPa, 300K with a volume of 0.2m (State1). It is now compressed via a polytropic process with PV = constant (n ≠ 1) to a final temperature of 500K (State 2). The work done during the process is -80 kJ.You may use a constant specific heat to solve this problem C v0= 0.653 kJ/kg -K (a) What is the mass of carbon dioxide? (b) Find the value of n (c) Find the heat transfer in the process (e) Show the P-v diagram for the process 3. [40 points] A 500 Watt heater is used to melt 2 kg of solid ice at −10ºC to liquid at +5ºC at a constant pressure of 150 kPa. a) Find the change in the total volume of the water. (Note that “water” = ice + liquid) b) Calculate the work done on the water during this process. c) Find the energy the heater must provide. d) Find the time the process will take assuming uniform T in the water. 1. (a) Table B.1.2 T < T = 143.63°C at 400kPa => compressed liquid. sat Approximate properties by saturated liquid same T. v = v (40°C) = 0.001008 m /kg … 3 f u = u (40°C) = 167.53 kJ/kg … f (b) Table B.6, h < v atg120K = 74.30 kJ/kg => saturated liquid + saturated vapor. At T = 120 K, P= P sat= 2513 kPa, x = (h − h)/f = fg8444 u = u fx×u = 4fg29 kJ/kg
More Less

Related notes for MECHENG 235

OR

Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Join to view

OR

By registering, I agree to the Terms and Privacy Policies
Just a few more details

So we can recommend you notes for your school.