Name:
ME 220a.01 Thermodynamics I
Midterm Exam II
There are four problems. Try to attack each problem since the problems are NOT arranged according
to their difficulties.
Problem 1. Fundamentals of thermal efficiency, coefficient of performance, and rever
Announcements
Midterm #2: in-class, Tuesday (04/01) at 8:10 AM
Additional office hour: Monday (03/31) at
3:00-4:30 PM
Policy: the same as midterm I
Thermal Reservoirs and Heat Engines
Thermal Energy Reservoirs: A thermal reservoir is a special
kind of sys
0tIA,'+t ts^
Name:
ME 220 A.01 Thermodynamics I
Midterm Exam 2
Problem 1. Fundamentals of thermal efficiency, coefficient of performance, and reversible
steady-flow work. (15 points)
(a) An inventor claims to have developed a refrigerator that maintains t
1515.9 An egg is dropped into boiling water. The amount of heat transfer to the egg by the time it is cooked
and the amount of entropy generation associated Twith this heat transfer process are to be determined.
Assumptions 1 The egg is spherical in shape
139 An insulated rigid tank contains a saturated liquidvapor mixture of water at a specified pressure. An
electric heater inside is turned on and kept on until all the liquid Ttaporized. The entropy change of the
water during this process is to be determi
Name: 5-b C ct+^ rn1
ME 220a.01 Thermodynamics i
Midterm Exam 1
There are four problems. Try to attack each problem since the problems are NOT arranged according
to their difficulties.
Problem 1. Complete the following table for H2O. Solve for the quality
(b) Heat Pumps are preferred than direct electric resistance heaters since they Will save energy. If
a house needs an electric resistance heater to produce 1200 kWh to keep warm in a winter
month. how much electric power will be saved 1f the home owner sw
531 Air is accelerated in a nozzle from 30 m-"s to 131] The mass ow rate, the exit temperature, and
the exit area of the nozzle are to be determined.
Assumptions 1 This is a steady-ow process since there is no change with time. 2 Air is an ideal gas with
Name: SO l WH O11
ME2203.01 Final Exam
Spring 2007
Problem 1. Answer each question concisely. (total: 18 points)
(a) Fill out the following table for water. Find the quality only when it is applicable to do so (6
points).
Pressure Temperature Specic volum
HW#3 Solution
1. A pistoncylinder device contains 0.15 kg of air initially at 2 MPa and 350C. The air is first
expanded isothermally (temperature is constant) to 500 kPa, then compressed polytropically
with a polytropic exponent of 1.2 to the initial pres
System, Surroundings, and Boundary
A THERMODYNAMIC SYSTEM (SYSTEM), is defined as a quantity of
matter or a region in space chosen for study.
Everything external to the system is considered to be part of the
systems SURROUNDINGS. Or simply, The matter or
'.-'-1 15. Liquid. Twater is to be plunped b)? a 25-kW pump at a specied rate. The highest pressure the water
can be pumped to is to be determined.
Assumptions 1 Liquid Twater is an incompressible substance. 2 Kinetic and potential energj.r changes are
ne