ENGI 2334, Intro to Thermrodyna

Exam I June ?.4,2OL4

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OPEN BOOK OPEN NOTES (your notes, your book, no

INDICATE CLEARLY IF VOU WORK ON THE IIACK OF A P

State all assumptions and show allyour work. You will lose credit for clearly outlining yourapproach to the solution, even if you combine several steps of caand arrive at the correct answer. A correct final answer does not

on your calculatorfull credit without

the supporting work shown. For problems that require interpolation -

table that are closest to your known parameters (i.e. if the pressure isfrom the table).

There are FIVE questions.

the values in thekPa, use 100 kPa

1) 20 points - Saturated steam (vapor) at l00oC is heated to 300oC. F:ind the heat required if100 kg of steam undergo this temperature rise through

a. A constant pressure process, orb. A constant volume process.c. What is the physical significance of the difference or "sameness" of the answers?

2) 10 points totala, 3 points - Define heat capacity and what is it er function of?

b. 4 points -

When is it safe to apply the ideal gas law?

c. 3 points -

How many kg of air are there in a nnole of air? And how do you comeby this number?

3) 20 points - A rigid vessel of 0.50 m3 is filled with saturated steam (vapor) at 1500 kPa. Ifthe vessel is cooled untrl25o/o of the steam is condensrld, how much heat is transferredand what is the final pressure.

4) 25 points - Refrigerant 134a is to be cooled in a horizontal heat exgtunger that will act asa complete condenser. The refrigerant enters the condenser with a firass flow rate of 6kg/min at I MPa and 70oC and leaves at 35oC. On therother side of the heat exchanger,cooling water enters at 300 kPa and l5oC and leaves at25oC. Findl he mass flow rate ofwater required and the heat exchanged.Heat exchangers such as these are isobaric and the fluid velocities do not change. In heatexchangers, the fluids do not mix, they are separated by a wall.

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s) 25 points - A process consists of a tank connected to an air line,two. The tank is initially filled with air at2soc at a pressure of 10supplies air at 45oC and 1500 kPa, constant. When the valve is ofilled with more air urtil the pressure in the tank is equal to that oslow enough such that the temperature in the tank remains at 25oCftansfened. Cv = (5/2)R or Cp = (712)R

th a valve between the.33 lcPa. The air linened, the tank is slowlythe air line. The fill isFind the heat

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