Description
I am studying for my midterm exam and this problems are really weird to me.
1. In order to save some money, I am going to stop buying humidifier filters and instead run my shower for a while every day. I crank up my water heater to the maximum allowed 140?F and then open the tap, which causes the shower to make a fair amount of steam as the water pressure drops from 50 psia in the pipe down to atmospheric (14.7 psia). If the total flow rate is 1 lb/s, what is the flow rate of water vapor coming out of the shower?
2. One of the oldest cycles in continuous use is the Stirling cycle, which goes back to the XVIII century. In this cycle, air in a cylinder is first heated at constant volume, then expanded isothermally, then cooled at constant volume, and then brought isothermally to the initial state. We make a prototype with the following parameters: initial state 0.5 liters at 10 bar, 300 K, temperature after heating 600 K, volume after expansion 2 liters. You are asked to find the pressure and temperature at each main state, the heat and work for each process, and the overall cycle efficiency. Don’t forget to make a p-V diagram. It is okay to assume constant specific heat with Cp = 1 kJ/kgK
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Explanation & Answer
Please ignore the first file I sent :). used the second file, that is the final answer :).
MMAE 320
Thermodynamics
6/11/18
1
1st Midterm Exam
Problem 1:
Solution:
#1. Given
Tmax = 140oF
P1 = 50 psia
P2 = 14.7 psia
Mass flow rate overall = 1 lb/s
Required of the problem:
Mass flow rate of the steam
When tap is opened water flows from 50 psia to 14.7 psia. This process can be assumed to be
isentropic process ( It is throttling process as there is no enthalpy loss with decrease in pressure).
Knowing that:
In State 1 =>
𝑃1 = 50 𝑃𝑠𝑖𝑎, 𝑇1 140°𝐹
In State 2 =>
𝑃2 = 14.7 𝑃𝑠𝑖𝑎
50 Psia
T
14.7 Psia
1
2
S
MMAE 320
Thermodynamics...