Phase Change Simulator Calculator

Sensible heating or cooling:

Q = m · c · ΔT where m is mass (kg), c is specific heat, and ΔT is the temperature change (°C or K).

Phase change (temperature stays constant at the boundary):

Q = m · L where L is latent heat of fusion (Lf) at melting or latent heat of vaporization (Lv) at boiling.

Constant-power time estimate (optional):

t = |Q| / P where P is power in watts and Q is energy in joules. The simulator distributes points using your time step.

• Choose a substance preset, then enter mass and temperatures.
• Enable constant-power simulation if you want time and a table.
• Adjust melting/boiling points and heats if your scenario differs.
• Click Simulate to compute segments and totals.
• Use the download buttons in the results panel for CSV or PDF.

1) What this simulator computes

This tool estimates energy needed to move a sample from an initial temperature to a final temperature while crossing melting and boiling boundaries. It breaks the path into sensible segments plus constant-temperature phase plateaus. Optional constant-power mode estimates time and generates a step table.

2) Sensible heating and cooling segments

Between boundaries, temperature changes and the calculator applies Q = m·c·ΔT. Separate heat capacities are used for solid, liquid, and gas. The water preset is about cp_s 2.090, cp_l 4.186, and cp_g 2.080 in kJ/(kg·K).

3) Latent heat plateaus at Tm and Tb

At Tm and Tb, temperature stays constant while energy changes phase. The calculator adds Q = m·Lf at melting/freezing and Q = m·Lv at boiling/condensing. For water, Lf ≈ 333.55 kJ/kg (0 °C) and Lv ≈ 2256 kJ/kg (100 °C).

4) Heating versus cooling sign conventions

The simulator detects direction. Heating gives positive energies (added heat) and cooling gives negative energies (removed heat). Latent terms keep the same magnitude but flip sign, so melting and freezing are easy to compare.

5) Presets and custom property control

Presets are starting points, but properties vary with purity, pressure, and composition. Override Tm, Tb, heat capacities, and latent heats to match your source. Keep units consistent: °C, kJ/(kg·K), and kJ/kg.

6) Constant-power time estimate

With time simulation enabled, each segment uses t = |Q|/P, where P is watts and Q is joules. Example: 500 W is 0.5 kJ/s, so 100 kJ takes about 200 s. Losses are not included.

7) How to read the segment and time tables

The “Energy segments” table lists each interval, its phase/process, and heat contribution. The “Simulation table” expands segments into time points using your step size and holds temperature flat during plateaus. The cumulative heat column shows where energy concentrates.

8) Practical scenarios and interpretation

Use the simulator to size heaters, estimate cool-down time, or teach phase diagrams with clear energy accounting. Try 1 kg of water from −10 °C to 120 °C to see two plateaus. For metals, enter custom Tm/Tb and compare latent versus sensible energy. Export CSV to archive runs and build lab worksheets, or use PDF to share a compact summary.

1) Why does temperature stay constant during melting or boiling?

During a phase change, energy is used to reorganize the material’s structure rather than increase kinetic energy. That energy is captured by latent heat, so the temperature remains at Tm or Tb until the phase transition completes.

2) What if my material does not melt at a single temperature?

Many mixtures and alloys melt across a range. Approximate the behavior by using an effective melting point and latent heat, or run multiple passes with different boundaries to bracket results. For detailed modeling, use phase-fraction data from your source.

3) Why are my results negative?

If the final temperature is lower than the initial temperature, the simulator treats the process as cooling. Energies become negative to represent heat removed. The magnitude still represents how much energy must be extracted to reach the target state.

4) Does the time estimate include heat losses to the environment?

No. The time model assumes constant delivered power goes entirely into the sample. Real systems may lose heat through convection, conduction, and radiation. To approximate losses, reduce the effective power or add a safety factor to your required time.

5) Which units should I use for specific heat and latent heat?

Enter specific heats in kJ/(kg·K) and latent heats in kJ/kg. Mass is in kg. The calculator outputs total heat in kJ, J, and kWh. Consistent units are essential for meaningful results and comparisons.

6) How can I simulate pressure effects on boiling point?

Set a new boiling point Tb for your pressure condition and adjust Lv if your reference provides it. The model uses your entered boundaries directly, so it can represent high-altitude boiling or pressurized conditions.

7) Why does the simulation table have many rows?

Rows are generated by dividing each segment’s duration by your chosen time step. Smaller steps create more points and smoother traces but larger output. Increase the step size to reduce rows while keeping the same total energy and time estimates.