MER 439, Fall 26, Take home Quiz #1
Hodgson
This Quiz is due prior to the START of class on Friday 9/11. It must be written up FORMALLY
(neat, use words, include a sketch, STATE ASSUMPTIONS, DISCUSS Results… I assume you
know how to do a good homework write up.)…W.R.T. Role playing: assume that I am your boss
at your first job and I asked you to do this … what would you want to hand to your boss?
!! You must NOT WORK WITH OTHER STUDENTS ON THIS ASSIGNMENT!!
!! You may not look at any pre-existing solutions to this problem (I know they are out there)!!
!! You must write and sign the honor pledge on the assignment that you turn in (or it will
not be graded). Doing so means that you have read, understood, and obeyed the previous two
points!!
As we discussed in class, you should allow yourself minimal use of AI tools. For example, you
should not copy the problem statement into a model. Document exactly how you use AI tools and
submit that as part of your discussion.
An ideal vapor compression refrigeration system operates with Refrigerant 134a as the working
fluid. Refrigerant enters the compressor at 2.2 bar, -5 oC with a volumetric flow rate of 0.6 m3/min
and is compressed to 9.2 bar. Saturated liquid exits the condenser at 9 bar. Determine:
(a)
(b)
(c)
(d)
the compressor power
the rate of heat rejected in the condenser
the rate of heat absorbed in the evaporator
the coefficient of performance
Now modify the problem to have an isentropic compressor efficiency of 75% and let the
temperature of the liquid leaving the condenser be 32 oC. Determine:
(e) the compressor power
(f) the rate of heat rejected in the condenser
(g) the rate of heat absorbed in the evaporator
(h) the coefficient of performance
Assume that cooling water is available at a flow rate of 1.1 kg/s and a temperature of 25 oC
(i) How much temperature rise will the cooling water experience?
(j) What would happen if the cooling water were available at 56 oC instead of 25 oC?
(k) Suppose you wanted to use this cycle to cool a process gas (in the evaporator) to 10oC. Can you do it with this cycle? Why or why not?
Use EES or CATT to aid your analysis unless you really like to interpolate!
Additional Homework (NOT part of the Quiz, NOT to be turned in, just designed to get you
thinking) Think about the design issues relative to the problem posed in design project 1. (You
will have to wait until Thursday to start this…but I want you to have these questions in your head
when I introduce the project so I am putting them here.)
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What are the fixed variables?
How will you specify each state?
What assumptions will you have to make?
How do you choose a refrigerant?
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