Reversible Isothermal Specific Entropy Change
Relate reversible heat transfer to entropy change at constant absolute temperature.
Try this formula
Calculate change in specific entropy or choose another supported quantity.
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Try this formula
Calculate change in specific entropy or choose another supported quantity.
Use decimals or scientific notation, such as 1.2e3. Calculations update as you type.
Change in specific entropy
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Use a reversible path at a constant, strictly positive absolute temperature. Heat is positive into the system, and all quantities use the same mass basis. For an irreversible actual path, do not set system entropy change equal to actual heat divided by one temperature; account for entropy generation.
Difficulty
Intermediate
Read time
5 min
Prerequisites
Basic algebra and introductory thermodynamics
Source
Teng-Jui Lin — CHEM E 326 — Chemical Engineering ThermodynamicsReference equation: Isothermal/Isoenergetic process — Entropy change. FormuLab wrote new explanations, assumptions, applications, and numerical examples. Kept heat positive into the system and made the reversibility, constant-temperature, and mass-specific basis explicit.
Adapted from Teng-Jui Lin, Equation Sheets — Mechanical Engineering Expansion, under CC BY 4.0.
Adapted standard equations and added original lesson text, variables, SI examples, and assumptions. Kept heat positive into the system and made the reversibility, constant-temperature, and mass-specific basis explicit.
Definition
Entropy transferred by reversible heat equals that heat divided by the absolute boundary temperature. Heat addition increases the system’s entropy along this path, while heat removal decreases it.
Variables & Units
| Symbol | Meaning | Units |
|---|---|---|
| Change in specific entropy | ||
| Reversible heat transfer into the system per unit mass | ||
| Constant absolute temperature |
Real-World Applications
Reversible phase change
Relate latent heat to entropy change at a saturation temperature.
Entropy balances
Evaluate a constant-temperature reversible reference path.
Worked Example
Problem
A reversible isothermal process transfers 60,000 J/kg of heat into a system at 300 K. Find its specific entropy change.
Given
Solution
Final Answer
Contents
Info
Tools
Source & review
Reference equation: Isothermal/Isoenergetic process — Entropy change. FormuLab wrote new explanations, assumptions, applications, and numerical examples. Kept heat positive into the system and made the reversibility, constant-temperature, and mass-specific basis explicit.
Adapted from Teng-Jui Lin, Equation Sheets — Mechanical Engineering Expansion, under CC BY 4.0.
Adapted standard equations and added original lesson text, variables, SI examples, and assumptions. Kept heat positive into the system and made the reversibility, constant-temperature, and mass-specific basis explicit.
Assumptions
- • Use a reversible path at a constant, strictly positive absolute temperature.
- • Heat is positive into the system, and all quantities use the same mass basis.
- • For an irreversible actual path, do not set system entropy change equal to actual heat divided by one temperature; account for entropy generation.
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