HVAC · Practice-Exam-2 · Problem 20PDFSolution in PDF ↓
HVAC · Practice-Exam-2 · Problem 20
Problem & Solution
Video Synthesis
Problem: Our refrigeration cycle using R123 operates between 75 PSIA and 220 PSIA with no sub-gling.
Approach: So that's reassuring and that'll go from 3 to 4 to some low pressure condition and then we go through the evaporator, which we need not concern oursel...
Key step: And our goal is to find the difference in entropy as we go from state 3 to state 4.
Watch out: So let's remind ourselves on a pressure enthalpy diagram, what that expansion process looks like and we don't have to draw the whole refrigeration cyc...
Result: It gives us 0.003 BTO per pound degree rankin.
✅ Answer: (not detected)
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Student questions asked in live office hours about this problem
OH 98: HVAC: Full Practice Exam #20
Q: I interpreted the reversible heat engine to mean that they were asking for the refrigeration COP on a heat pump with a reversing valve that's performing refrigeration.
A: So a heat engine and compasses all devices that move heat from one reservoir to another. So there's really only two devices that come to mind in that realm which is the air conditioner and the heat pump and really an air conditioner is a heat pump that only does cooling but that's more practical reality. In theory land there's two types of heat engines.