TFS · Practice Exam 2 · Problem 17PDFSolution in PDF ↓
TFS · Practice Exam 2 · Problem 17
Problem & Solution
Video Synthesis
- Problem: A refrigeration cycle using R123 operates between 30 PSIA and 125 PSIA with no sub cooling and isynthopic expansion.
- Key values: 30 PSIA, 125 PSIA, 30 psi
- Reference: steam table
- Result: And that gives us a quality of 0.378.
- ✅ Answer: D
Office Hours
1
Student questions asked in live office hours about this problem
OH 81
Q: In a refrigeration cycle without isentropic expansion, shouldn't the quality be saturated?
A: No—the problem statement meant 'no sub-cooling' AND 'isentropic expansion occurs.' In refrigeration cycles, isentropic expansion is almost always assumed; without it, you couldn't locate state 4 confidently. With isentropic expansion, state 4 lies in the two-phase region closer to the liquid side (quality between 0 and 1, typically < 0.5), never at the saturated vapor boundary.