For iPhone and iPad
Sketch Heat
Draw a part, see where the heat flows.
An educational app for learning heat transfer. Draw a part, heat it and cool it, pick a material, and see the temperature and where the heat flows as you draw.
Requires iOS or iPadOS 16.4 or later. In English.
Draw it
Draw lines, rectangles, circles, curves, freehand strokes, and dimensions in mm, with snapping, undo, and redo. Type a dimension to resize a side.
Give each part a role: the solid part and its holes, where heat comes in and goes out, and the joints between solids. Each solid has its own material.
Put a heat source or a probe at a single point, such as a small chip: with the Line tool, tap the point twice.
Model a plate of set thickness, the section of a long part per unit depth, or the section of a round part (axisymmetric).
The part
- Solid
- Hole
Heat in and out
- Temperature
- Heat flux
- Heat source
- Convection
- Radiation
- Fluid stream
Joints and edges
- Contact
- Insulated
- Symmetry
Analyze it
The solver works while you draw and edit. A quick result shows at once, and a finer one replaces it when you stop.
- Temperature °C
- Heat flux W/m²
- Liquid fraction %
- Concentration kg/m³
- See isotherms, heat flux arrows, the melt front, and the temperature along each fluid stream.
- Type h for a convection edge, or have it worked out from the fluid and how it moves: still or moving air, water, or oil.
- Play a run over time back with the time slider, and read when a probe reaches a temperature.
- Read probes at a point, along a line, or over an area, and the heat into the part at each edge.
- Work in SI units (mm, W, °C) or US units (in, BTU/h, °F).
Four analyses
- Steady The temperature, the heat flux, and the heat through each edge, with the heat balance.
- Over time How fast a part warms up or cools down from its starting temperature.
- Melting and freezing The melt front and the liquid fraction, as ice melts or a casting freezes.
- Diffusion Moisture, salt, or a gas spreading through a solid.
Learn with the examples
Each example has notes on what to look for, the theory value where there is one, and what to try next. Every example runs without a subscription, in every analysis.
Pick from metals, plastics, building and insulation materials, soils and rocks, and materials that melt, such as aluminum 6061-T6, copper, brick, mineral wool, ice, and paraffin, each with its properties and their sources. Air, water, glycol mixtures, and engine oil serve convection and fluid streams, and a list of surfaces gives emissivities for radiation.
The examples menu
- Getting started Heat sink
- Checks against theory Heat through a wall; Composite wall; Insulated pipe; Cooling fin; Pin fin, round; Sudden heating of a block; Cooling a small sphere; Center of a slab over time; Corner of a wall; Two parallel plates radiating; A radiation shield; Ice melting; Counterflow heat exchanger
- Electronics CPU cold plate; LED on a board; Chip on a circuit board
- Radiators and exchangers Car radiator section; Finned tube; Double-pipe heat exchanger; Plate heat exchanger
- Buildings and insulation Window frame thermal bridge; Wall with a timber stud; Slab edge; Insulated tank
- Radiation Vacuum flask; Spacecraft radiator panel; Solar collector absorber
- Melting and freezing Phase-change wall; Casting solidifying
- Diffusion Drying a timber board; Salt into a concrete wall; Hydrogen through a steel plate
- Everyday Cooking a steak; Soldering iron tip; Mug of coffee cooling
Compare with theory
Thirteen examples follow cases with a known answer from heat transfer textbooks. When the run is done, the Results tab shows the theory value beside the app’s own value, and whether they agree within the stated tolerance.
Change the part and see how far the answer moves: make a fin longer, a wall thicker, or the insulation on a pipe thicker.
Theory in the notes
- Heat through a wall A straight-line temperature drop and one heat flux through the wall, from Fourier’s law.
- Cooling fin The tip temperature and the fin’s efficiency, from the fin equation.
- Insulated pipe The critical radius of insulation, k/h: below it, more insulation lets more heat out.
- Corner of a wall The heat through the corner per unit depth, kΔT((ℓ₁ + ℓ₂)/t + 0.55873), where ℓ₁ and ℓ₂ are the walls’ inside lengths, t is their thickness, and 0.55873 is the corner’s own shape factor.
- Cooling a small sphere The whole sphere cools at one temperature, within 1% of the starting temperature difference, while h·r/k is 0.03 or less.
- A radiation shield One shield with the plates’ emissivity halves the radiation between wide plates.
- Counterflow heat exchanger The effectiveness and the log-mean temperature difference, from the ε–NTU relations.
- Ice melting The position of the melt front over time, from Neumann’s solution.
Free and Sketch Heat Pro
Free
- Run and explore every example, in every analysis.
- Draw your own outline and holes in a plate of aluminum 6061-T6 or copper, with a hot edge and a cooled edge, in steady heat.
- Coarse and Medium meshes.
- Projects, files, units, and the help.
- View the sample paper drawing.
Sketch Heat Pro adds
- Every condition: heat flux, heat sources, radiation, fluid streams, contact and symmetry, and probes.
- Every material, and your own materials.
- Heat over time, melting and freezing, and diffusion.
- Convection worked out from the situation: still or moving air, water or oil.
- Fine meshes for more detail.
- Edit the examples.
- Import your own paper drawings from a photo.
- Reports with the model settings and probe readings.
Sketch Heat Pro is an auto-renewable subscription, monthly or yearly, with a free trial for eligible new subscribers. If your subscription ends, your sketches still open and run. See the prices, the subscription terms and the questions about Sketch Heat Pro.
On your device
Drawing and calculation run on your iPhone or iPad. Your sketches stay on your device.
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Works offline
Drawing and the calculation need no connection.
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No account
Open the app and start. There is nothing to sign up for.
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No ads
The app shows no advertising.
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Apple Pencil
Apple Pencil draws while your fingers pan and zoom. A keyboard, trackpad, or mouse works on iPad.
Educational use only
Sketch Heat is for education and learning only. Its results are estimates from a simplified two-dimensional model. The calculation is verified against published exact solutions and benchmark cases, such as a plane wall, a cooling fin, and a suddenly heated block, but it has not been validated against measurements or tested in real-world scenarios. It is not a substitute for professional engineering analysis, testing, or applicable codes and standards. Do not use it to design, rate, or approve any real part or building, or for safety-critical, medical, or compliance decisions. You use the results at your own risk; to the extent the law allows, Journey On is not responsible for any loss or decision based on them. See the Terms of Use.
Sketch Heat for iPhone and iPad
Learn how parts warm up, cool down, melt, and freeze by sketching. Requires iOS or iPadOS 16.4 or later.
Questions? Email support@journeyon.co or read the support page.