Closed System
Piston-cylinder energy balance: Q − W = m(u₂ − u₁). Pick the process, fill two properties per state, and the calculator closes the states from the property tables and solves Q, W and boundary work.
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Process
Frequently asked
- What sign convention does the closed-system calculator use?
- Q is positive into the system; W is positive as work done BY the system. The energy balance is Q − W = m(u₂ − u₁), the standard Cengel & Boles convention.
- Which processes are supported?
- Isothermal (T constant), constant volume, constant pressure, polytropic (P·Vⁿ constant — enter n, or leave it blank to solve n from P₁V₁P₂V₂), and general processes where Q or W is given.
- How is boundary work computed?
- Polytropic: Wb = (P₂V₂ − P₁V₁)/(1 − n), with the isothermal limit Wb = P₁V₁·ln(V₂/V₁) when n = 1. Constant pressure: Wb = P·(V₂ − V₁). Constant volume: Wb = 0. General: the trapezoidal estimate ((P₁+P₂)/2)·(V₂−V₁).
- Can it handle saturated mixtures?
- Yes. Enter P and quality x (or T and x) and the calculator fills v, u, h, s from the saturation tables. If T exceeds Tsat it switches to the superheated tables automatically.