TFS · Thermodynamics · Problem 4PDFSolution in PDF ↓
TFS · Thermodynamics · Problem 4
Problem & Solution
Video Synthesis
- Problem: Amispheric Air at 77 degrees undergoes isentropic compression to 100 psi and 478 degrees.
- Approach: So there's a useful formula we can use if you search for isentropic process which at first might not seem to do it but we can adapt it and make it wor...
- Key step: This is going to be p2 times v2 and this is little v specific volume and the two signifies that it's the state after the compression.
- Watch out: So there's a useful formula we can use if you search for isentropic process which at first might not seem to do it but we can adapt it and make it wor...
- Result: So now we have p little v equals rt and we can solve for specific volume little v that's rt over p and now that's an expression that must hold true on...
- ✅ Answer: (not detected)
Office Hours
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Student questions asked in live office hours about this problem
OH 85
Q: How do we know if this is a closed system or an open system? The work equation is different in each case.
A: Look for whether mass crosses the system boundary: an open system has mass flowing in or out (like a compressor with inlet and outlet flow rates), while a closed system doesn't (like a piston-cylinder with a fixed amount of gas). This problem involved drop-in compression of air with no mass flow rate or volume flow rate information given — that's a signal it's closed-system behavior. For an isentropic closed-system process, work is W = (P₂V₂ – P₁V₁)/(1 – n), whereas an open system uses steady-flow work = ṁ × (h₂ – h₁).