Model real heat engines using multiple calculation methods. Switch units and see efficiency instantly here. Save your results, print summaries, and compare cycles easily.
| Case | Qin (kJ) | Qout (kJ) | Work W (kJ) | Efficiency η (%) |
|---|---|---|---|---|
| 1 | 1200 | 800 | 400 | 33.333 |
| 2 | 1500 | 900 | 600 | 40.000 |
| 3 | 900 | 540 | 360 | 40.000 |
| 4 | 2200 | 1400 | 800 | 36.364 |
| 5 | 500 | 300 | 200 | 40.000 |
A heat engine converts a portion of absorbed heat into useful work. This calculator estimates work output using three common data sets: heat-in and heat-out, heat-in and efficiency, or average power over time. These options match typical lab sheets, plant logs, and classroom problems.
For a cyclic engine, the net work per cycle equals the difference between heat absorbed from the hot reservoir and heat rejected to the cold reservoir. If Qin = 1200 kJ and Qout = 800 kJ, then W = 400 kJ. That work can be compared across operating points.
Thermal efficiency is reported as η = W/Qin. Many practical systems fall between 0.20 and 0.45 depending on technology and conditions. Small educational engines may be lower due to friction and heat leakage. High-performance combined-cycle systems can exceed 0.55 under favorable conditions.
Work output scales with cycle size. Doubling Qin at the same η doubles W. Engineers often normalize by fuel energy or by unit mass flow to compare designs. When you keep units consistent, this tool helps you evaluate whether performance changes come from higher heat input or improved efficiency.
When heat data is unavailable, plant monitoring may provide average shaft power. With W = P×t, 2.5 kW sustained for 60 s yields 150 kJ. This method links directly to electrical generation logs, dynamometer readings, and test stand measurements, especially during steady runs.
The calculator converts energies internally and can display results in J, kJ, MJ, Wh, kWh, cal, kcal, or BTU. For reporting, choose one unit across cases to avoid confusion. The CSV export produces a clean table for spreadsheets, while PDF export is useful for quick documentation.
If Qout exceeds Qin, the computed work becomes negative, which indicates inconsistent inputs or a device operating as a refrigerator or heat pump rather than an engine. Very low η often signals high heat rejection, poor insulation, or measurement error.
This calculator evaluates energy balance and efficiency from supplied values. It does not model entropy generation, pressure-volume diagrams, or temperature-dependent properties. For an upper bound, compare η to the ideal Carnot limit, ηC = 1 − Tc/Th, using absolute temperatures in kelvin.
It is the net usable energy produced by the cycle, equal to heat absorbed minus heat rejected. It represents the mechanical or electrical energy you can extract from the engine.
Qin is the absorbed heat that drives the cycle. A non‑positive value cannot represent a working heat engine cycle and makes η = W/Qin undefined or misleading.
Yes. Select “Percent (%)” and enter values like 35 for 35%. The calculator converts it internally to a fraction before computing W and Qout.
Use it when you know average output power over a time interval but do not have heat-flow measurements. It is common for generators, motors on test stands, and monitored industrial equipment.
Negative work means your inputs imply more heat is rejected than absorbed, or the device is not acting as an engine. Recheck units, signs, and measurement values for Qin and Qout.
Pick a unit that matches your data source, such as kJ for thermodynamics problems or kWh for electrical energy reports. Keep the same unit across cases to compare results reliably.
No. Carnot efficiency requires hot and cold reservoir temperatures in kelvin. You can compute ηC separately and compare it to your measured η to judge irreversibilities and losses.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.