Thermodynamics Cycles Simulator

The Thermodynamics Cycles Simulator lets you explore the four most important ideal thermodynamic cycles: the Carnot cycle, Otto cycle, Diesel cycle, and Brayton cycle. Each cycle is visualised on an interactive pressure-volume (PV) diagram with colour-coded process lines, state points, and a shaded area representing net work output. An animated piston on the right side of the canvas steps through the cycle processes, connecting the abstract PV diagram to physical motion.

This tool covers the first law and second law of thermodynamics, entropy, enthalpy, heat engine efficiency, and the Carnot limit. It is designed for mechanical engineering students studying power cycles, automotive engineers learning about internal combustion engines, aerospace students studying gas turbines, and instructors teaching thermodynamic cycles and energy conversion. Four modes provide simulation, concept exploration, practice, and quizzes.

The simulator opens in Simulate mode with the Carnot cycle selected, T_hot = 800 K, T_cold = 300 K, and a compression ratio of 8. The canvas shows the PV diagram on the left with two isotherms and two adiabats forming the cycle, and an animated piston on the right. Readout cards display efficiency η, net work W_net, heat input Q_in, heat rejected Q_out, the active ratio (compression or pressure), temperatures, and reverse COP.

Each slider has a companion numeric input box for precise values — type a number and the slider snaps to it. Use the SI / Imperial unit toggle at the top to convert all temperature and energy readouts (K ↔ °F, kJ ↔ BTU). Switch Cycle Types (Carnot, Otto, Diesel, Brayton) using the pill tabs; each cycle reveals different PV shapes and different controlling parameters. Use the Presets (Ideal Carnot, Car Engine, Truck Engine, Jet Engine) to load realistic configurations quickly.

The PV diagram is the primary analysis tool. Colour-coded process lines distinguish isothermal (constant temperature), adiabatic (no heat transfer), isochoric (constant volume), and isobaric (constant pressure) processes. The enclosed area represents the net work per cycle — a larger area means more work output. Toggle Show Process Labels to see annotations on each process, Show Energy Flow to see arrows indicating heat in/out, Show State Values to display P/V/T at each numbered state point, and Show Eq. Overlay to draw the cycle's defining efficiency equation with live values on the canvas.

The animation bar gives you a play/pause button, reset, and a speed slider (0.1× to 3×) for the piston animation. Click Show Calculations at the canvas corner to open a step-by-step derivation modal showing how η, W_net, Q_in, and Q_out are computed in SI units. Use Export CSV to download the four cycle state points (P, V, T) and Export PNG to save the canvas as an image. Right-click the canvas for a quick-action menu (copy efficiency, export, toggle labels, reset).

Below the controls, four collapsible Learning panels deepen your understanding. The Live equations panel shows the active cycle's efficiency formula in classical KaTeX notation with current values substituted. The State table lists P, V, and T at each of the four state points (1, 2, 3, 4) in SI or Imperial. The T−s diagram plots the same cycle on temperature-entropy axes — useful for visualising heat transfer as the area under the curve. The What-if coach offers contextual hints based on current parameters (e.g. "increase r to raise η", "Carnot bound exceeded? — not possible by Second Law").

Use the Expand all / Collapse all buttons to manage screen space on mobile. The T−s diagram inside a collapsed card redraws automatically when you open it.

Switch to Explore mode to browse 12 concept cards across Laws, Cycles, and Applications. Each card shows a description, key formula, mini-diagram, and worked example. Practice mode generates randomised thermodynamics problems (Carnot η, Otto η, Diesel η, work, heat rejected, COP, compression/pressure ratios, entropy change, Brayton η) with full solution steps shown after you submit. Quiz mode presents 5 mixed conceptual/numerical questions per session.

Keyboard shortcuts: press Enter to submit your answer in Practice or numeric Quiz questions. Use the Tab key to move between numeric inputs and sliders.

• The Carnot efficiency η = 1 − T_C/T_H sets the absolute maximum for any heat engine operating between the same temperatures. No real engine can exceed this limit — use it as a benchmark.
• On the PV diagram, the enclosed area equals the net work. A fatter cycle loop means more work per cycle.
• For the Otto cycle, efficiency depends only on the compression ratio r and the heat capacity ratio γ = 1.4 for air. Higher r means higher efficiency, but real engines are limited by knock (detonation).
• The Diesel cycle always has lower efficiency than the Otto cycle at the same compression ratio. However, Diesel engines use higher compression ratios (14–22 vs 8–12), making their actual efficiency competitive.
• Use the SI / Imperial unit toggle to compare textbook values across reference systems. All internal calculations stay in SI; the toggle is display-only.
• Watch the energy flow arrows to visualise where heat enters and leaves the cycle. The second law requires that Q_out > 0 for any real cycle.
• Use this simulator alongside the Refrigeration Cycle Simulator to see the same principles in reverse.