Sketch Heat Terms of Use

Last updated: November 6, 2026

These Terms of Use (“Terms”) are an agreement between you and Omnis Dragon LLC, doing business as Journey On (“Journey On”, “we”, “us”). They cover the Sketch Heat app for iPhone and iPad (“Sketch Heat” or “the app”), the Sketch Heat web app once it is available, and the Sketch Heat Pro subscription. Please read them in full, and especially section 4 (Educational use only), section 11 (No warranty) and section 12 (Limitation of liability). By downloading or using the app, you agree to these Terms. If you do not agree, do not use the app.

1. Who we are

Sketch Heat is made by Omnis Dragon LLC, a Tennessee limited liability company doing business as Journey On, 116 Agnes Rd, Ste 200, Knoxville, Tennessee 37919-6306, United States. Email: support@journeyon.co.

2. Apple’s license agreement and these Terms

You get the app from Apple’s App Store. Your license to use the app comes from Apple’s Licensed Application End User License Agreement (the “Standard EULA”, https://www.apple.com/legal/internet-services/itunes/dev/stdeula/), with Journey On as the licensor. These Terms add terms that are specific to Sketch Heat. They do not replace the Standard EULA, and you should read the two together. If they conflict, the Standard EULA governs your license to the app, and these Terms govern everything else.

Apple’s Media Services Terms and Conditions govern your Apple Account, payments, renewals and refunds.

3. Who may use the app

• You may use the app if you can form a binding contract where you live. If you are under the age of majority where you live, use the app and buy a subscription only with the permission of a parent or guardian. That parent or guardian agrees to these Terms for you and is responsible for your use.
• You may not use the app if you are in a country that is subject to a U.S. Government embargo or that the U.S. Government has designated as a “terrorist supporting” country. You may not use it if you are on any U.S. Government list of prohibited or restricted parties.
• If you use the app for an organization, such as a school or a company, you agree to these Terms for that organization as well.

4. Educational use only

4.1 What Sketch Heat is for. Sketch Heat is an educational tool. Use it to learn how heat moves through parts, how they warm up, cool down, melt and freeze, how moisture, salt or a gas spreads through a solid, and how the finite element method works: draw a part, then see its temperature and where the heat flows. Use it for education, learning, teaching and exploring ideas only.

4.2 Not a substitute for professional work. Sketch Heat does not replace any of the following:

• a qualified engineer or other professional;
• physical testing and measurement;
• three-dimensional analysis with validated engineering software;
• the codes, standards and regulations that apply to your work. These include those for buildings and their energy use, insulation, condensation and moisture, heating, ventilation and air conditioning (HVAC), electrical and electronic equipment, boilers and heat exchangers, fire resistance, the durability of concrete and steel, food safety, and product safety.

4.3 Never use it for safety-critical, medical, food-safety or compliance decisions. Do not use Sketch Heat or its results to design, size, rate, approve, certify or operate any real part, building, product or system. Do not use them to decide whether a part, building, product, food or process is safe, stays within a temperature limit, or meets a code, standard or regulation. This covers, for example:

• surfaces hot or cold enough to hurt someone who touches them;
• electrical and electronic equipment, batteries, and anything that can overheat or catch fire;
• heaters, ovens, furnaces, boilers, heat exchangers, pipes and tanks;
• buildings: heat loss, insulation, condensation, moisture and fire resistance;
• cooking, food storage and food safety;
• the corrosion of steel in concrete, and hydrogen taken up by steel;
• any medical or health matter.

The temperatures, heat flows, U-values, times to reach a temperature and the other results that Sketch Heat shows come from typical material, fluid and surface values, published correlations and a simplified model. They are not the ratings, declared values or limits of any code, standard or product.

Some built-in examples show situations that involve safety: Cooking a steak, Soldering iron tip, CPU cold plate, Window frame thermal bridge, Salt into a concrete wall and Hydrogen through a steel plate. They are teaching examples. They do not show that any real part, building, product or food is safe.

4.4 You are responsible for how you use the results. You decide whether and how to use anything Sketch Heat shows, and you bear the risk of that decision. If you share results, reports or sketches with others, do not present them as validated, certified or professional engineering results.

4.5 No warranty, limited liability. Sketch Heat and its results are provided “as is”, without warranty of any kind, including any warranty of accuracy (section 11). To the maximum extent permitted by law, Journey On is not liable for any loss, damage, injury or claim that results from using or relying on Sketch Heat or its results (section 12). These sections add to the “No Warranty” and “Limitation of Liability” sections of Apple’s Standard EULA and are consistent with them.

5. Accuracy and limits of the model

5.1 Results are estimates from a simplified model. Sketch Heat calculates with a simplified two-dimensional model, the finite element method with quadratic triangular elements. A plane model is a plate of a set thickness whose two faces are insulated. A per-unit-depth model is the section of a long part that is the same all along its length. An axisymmetric model is a round part whose conditions are the same all the way around. Real parts are three-dimensional, so results can differ from real behavior by a large amount.

5.2 What the model leaves out or simplifies.

• Three-dimensional heat flow, and any physics other than heat.
• Fluids. A convection edge uses a heat transfer coefficient (h), typed or worked out from a published correlation; the flow of the fluid is not calculated. Correlations match experiments only within their own scatter, which can reach 20% or more, and that scatter is part of every h they give. A fluid stream carries heat along its channel in one dimension: it stores no heat of its own over time, and it leaves out recirculation, mixing and the flow pattern. Its pressure drop is an estimate for smooth walls.
• Radiation. Surfaces are gray and diffuse, each with one emissivity that does not depend on wavelength. Gases that absorb radiation, such as flames and furnace gases, are not modeled, and neither is sunlight passing through glass. Radiation to the surroundings assumes that an edge sees nothing but its surroundings, and that they are large compared with the part. Radiation between surfaces is worked out only in per-unit-depth models, mirrored across one symmetry line at most.
• Contact. A joint between two solids is a resistance that stores no heat. Solids that touch are joined unless a contact line runs along the joint.
• Materials. Each material has one thermal conductivity, a table of conductivity against temperature, or a conductivity along and across one direction. Density and specific heat do not change with temperature, except over a melting range. A conductivity table that changes steeply can make results depend on the number of steps and on where the calculation starts.
• Material, fluid and surface values. The library holds typical values from published sources and makers’ data sheets, each with the temperature and condition its source gives. Real parts, fluids and surfaces vary with the grade, the supplier, the finish and the manufacturing process, 3D-printed parts especially. Some values have no checked source and are shown as “not set”, and a material without them cannot be used for the analyses that need them.
• Melting and freezing. One density serves both phases, so the change of volume on melting is left out. Melting takes place over a narrow range of temperature, 0.1 K unless the material sets another, which adds a small error to the front and to the melted amount. Heat crosses the melted liquid by conduction only; flow in the liquid is not modeled.
• Diffusion. Each material has one diffusivity, and the concentration does not jump between two materials, or between a solid and the air or water around it.
• Singular points. At a point heat source the temperature, and at a sharp inside corner the heat flux, are not finite in theory. The values shown there depend on the mesh and keep rising as the mesh gets finer; the heat totals do not.
• The mesh. Every result is an approximation on a mesh of a set fineness. The app shows an estimate of the error, which is itself an estimate.
• Time steps. Results within the first few steps after a sudden change are less accurate, and a long run needs more steps.

Help and shortcuts > Model in the app describes the model in more detail.

5.3 Verified against exact solutions and benchmark cases, not validated against the real world. The calculation has been verified against published exact solutions and benchmark cases. Its results were compared with published values, and each comparison had to fall within a set tolerance: 0.5% for exact temperatures and heat flows, and for radiation; 1% for peak heat fluxes on curved edges, for temperatures over time (as a share of the temperature change), and for times to reach a temperature; 2% for published formulas that are themselves approximations, and for the position of a melt front. The published correlations were checked against their printed forms and ranges, not against experiments. The cases are:

• heat conduction through plane walls, with convection and with a heat source, a hollow cylinder, a cooling fin, a suddenly heated block, a slab cooled by convection, a point heat source, and the time to reach a temperature: Lienhard, J. H. V and Lienhard, J. H. IV (2024), A Heat Transfer Textbook, 6th ed.;
• radiation: a body cooling or heating by radiation alone, two parallel plates, a radiation shield, and the view factors between surfaces, with and without blocking: Howell, J. R. and Siegel, R. (1969), Thermal Radiation Heat Transfer, vol. II, NASA SP-164; Howell, J. R., A Catalog of Radiation Heat Transfer Configuration Factors; and Lienhard and Lienhard (2024);
• convection correlations for still and moving fluids, banks of tubes, and flow inside tubes, channels and annuli: Lienhard and Lienhard (2024), and Lundberg, R. E., Reynolds, W. C. and Kays, W. M. (1963), NASA TN D-1972;
• a contact resistance between two solids, and a conductivity that changes with temperature or direction: Lienhard and Lienhard (2024), and Toptan, A. et al. (2020), Journal of Verification, Validation and Uncertainty Quantification 5, 041002;
• fluid streams along a heated wall, counterflow and parallel-flow heat exchangers, and the pressure drop in tubes and channels: Lienhard and Lienhard (2024), and Colebrook, C. F. (1939), Journal of the Institution of Civil Engineers 11, 133–156;
• melting and freezing: Neumann’s solution, as Tarzia, D. A. (2011) states it, in Advanced Topics in Mass Transfer, InTech, 439–484;
• diffusion into a solid from a surface held at a set concentration: Lienhard and Lienhard (2024);
• patch tests that each element must pass exactly, a hollow cylinder on finer and finer meshes, and the balance of heat in every case.

These checks show that the model’s equations are solved as intended for those cases. They do not show that the model represents any real part, building or product. Sketch Heat has not been validated against measurements, physical tests or certified engineering software, and it has not been tested in real-world scenarios. The checks were run on a computer with the same calculation code, which gives identical results in the JavaScript engine of iPhone and iPad.

6. Your content

• Your sketches and pictures stay on your device. Sketches, projects, settings, custom materials and background images are stored and processed on your device. We do not receive them. The Privacy Policy (https://sketchheat.journeyon.co/privacy) says more.
• What you make is yours. We claim no ownership of the sketches, reports or files you create or export. When you save or share a file, it goes where you send it, under the terms of the service you choose (for example, iCloud Drive, Mail or AirDrop).
• Files from others. If you open a sketch file someone else made, it is your responsibility that you may use it.
• Files you send us. If you send us a sketch, report, picture or screenshot with a support request, you allow us to use it only to answer that request.
• Feedback. If you send us ideas or suggestions, we may use them without any obligation to you.
• Backups are your responsibility. Deleting the app deletes the projects stored in it. Keep copies of work that matters with Menu > Projects and files > Save as a file.

7. Acceptable use

You agree not to:

• use the app in breach of any law, or of the rights of others;
• copy, modify, reverse-engineer, decompile, or try to extract the source code of the app, except as the Standard EULA, the license of an open-source component, or the law allows;
• get around, disable, or interfere with the subscription check or the limits of the free features;
• resell, rent, or redistribute the app, or offer it as a service to others;
• present results from the app as validated, certified, or professional engineering results, or use them in place of the professional work described in section 4.2;
• use the app for any purpose that section 4.3 rules out.

8. Free features and Sketch Heat Pro

8.1 Free features. Without a subscription you can:

• open and run every built-in example, in every analysis, change what it shows, and read its results;
• draw your own outline and holes in a plate of aluminum 6061-T6 or copper, with a hot edge and a cooled edge, change the hot edge’s temperature, the cooled edge’s h and fluid temperature, and the plate’s thickness, and see its steady temperatures at the Coarse or Medium mesh;
• use projects, save and open files, switch between SI and US customary units, and read the help;
• view the sample paper drawing.

8.2 What 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.
• Per-unit-depth and axisymmetric models.
• 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.

Sections 8.3 to 8.12 cover Sketch Heat Pro bought in the app through the App Store. Section 8.13 covers Sketch Heat Pro bought on our website.

8.3 Plans and prices. Sketch Heat Pro is an auto-renewable subscription with a monthly plan and a yearly plan. The app and the App Store show the price, the period, and any free trial before you confirm a purchase. Prices are set in each country’s currency, may include taxes, and differ between countries.

8.4 Free trials. A plan may include a free trial for eligible customers. Apple decides eligibility; usually an Apple Account gets one free trial for Sketch Heat Pro. When the trial ends, the subscription starts and you are charged, unless you cancel at least 24 hours before the trial ends. If you buy a subscription while a free trial is running, any unused part of the trial is forfeited.

8.5 Automatic renewal. Payment is charged to your Apple Account when you confirm the purchase, or when a free trial ends. The subscription renews automatically for the same period at the then-current price unless you cancel it at least 24 hours before the end of the current period. Apple charges the renewal within the 24 hours before the current period ends.

8.6 Canceling. Cancel in Settings > your name > Subscriptions, or with Manage subscription in the app (Menu > About Sketch Heat). Canceling stops the next renewal; Sketch Heat Pro stays active until the end of the period you have paid for. Deleting the app does not cancel a subscription.

8.7 Refunds. Apple handles all payments and refunds. We cannot issue refunds, and we never see your payment details. To ask for a refund, go to https://reportaproblem.apple.com. Nothing in these Terms limits any right to a refund that the law gives you.

8.8 Other devices and Family Sharing. Sketch Heat Pro works on every iPhone and iPad signed in to the same Apple Account. Use Restore purchases in the app to turn it on there. Family Sharing is not available for Sketch Heat Pro.

8.9 Without a connection. Buying, restoring, and the first check of a subscription need an internet connection. After that, Sketch Heat Pro stays active without a connection, based on the last check.

8.10 When a subscription ends. You keep everything you made. All sketches and projects still open and run. Changing a design beyond the free features (section 8.1) needs Sketch Heat Pro again.

8.11 Changes to prices and features. Apple tells subscribers about price increases and asks for their agreement where its rules or the law require it. We may add, change, or remove features of the app, free or Pro. We describe significant changes in the app’s update notes.

8.12 Offer codes. Codes for Sketch Heat Pro are redeemed through Apple (Redeem a code in the app) and follow the terms shown with the code.

8.13 Buying on the web. Once the Sketch Heat web app is available, Sketch Heat Pro can also be bought on our website.

• Our order process is conducted by our online reseller Paddle.com. Paddle.com is the Merchant of Record for all orders on our website: it sells the subscription to you, takes the payment, issues the receipt, and handles sales tax, VAT, and refunds. Paddle’s Buyer Terms (https://www.paddle.com/legal/buyer-terms) apply to the order.
• The checkout shows the price, any tax, the billing period, and any free trial before you confirm the order.
• A free trial needs a payment method. When the trial ends, the subscription starts and you are charged, unless you cancel before the trial ends.
• The subscription renews automatically for the same period at the then-current price until you cancel. You can cancel at any time with the link in your order email or by emailing us. Sketch Heat Pro stays active until the end of the period you have paid for.
• Refunds follow our Refund Policy: a full refund within 14 days of your first payment and of each yearly renewal.
• A subscription bought on the web is billed separately from one bought in the App Store.

9. Services and terms of others

• Apple. Apple runs the App Store, your Apple Account, and the payment for Sketch Heat Pro, under Apple’s own terms and privacy policy.
• Paddle. Paddle.com sells Sketch Heat Pro bought on our website, as our reseller and Merchant of Record, under its own Buyer Terms and privacy notice.
• Subscription service. The app checks your subscription with a service provider that works for us. The Privacy Policy says what it receives.
• Your network provider. You must follow the terms of your mobile or internet service, and you are responsible for any data charges when the app connects.
• Links. Links in the app (for example, to these Terms or to the App Store) open in Safari or the App Store. We are not responsible for websites or services we do not run.

10. Our rights and third-party software

The app, its examples, help texts, material library, fluid and surface data and design belong to Omnis Dragon LLC or its licensors. They are protected by copyright and other laws, and all rights not granted to you are reserved. The app includes open-source software and fonts under their own licenses, listed in the app under Menu > Third-party notices. For those components, their licenses apply. “Sketch Heat” and “Journey On” are names of Omnis Dragon LLC. The published works named in the app and in section 5, and the sources of the material, fluid and surface values, belong to their authors and publishers; naming them does not mean they endorse Sketch Heat. Material names such as “6061-T6” and “Ti-6Al-4V” name grades, not suppliers.

iPhone, iPad, and Apple Pencil are trademarks of Apple Inc., registered in the U.S. and other countries and regions.

11. No warranty

You use the app and its results at your sole risk. To the maximum extent permitted by applicable law, the app, its results, its material, fluid and surface values, and any services provided through it are provided “as is” and “as available”, with all faults and without warranty of any kind. Journey On disclaims all warranties and conditions, whether express, implied, or statutory. These include any warranty or condition of merchantability, satisfactory quality, fitness for a particular purpose, accuracy, quiet enjoyment, and non-infringement. In particular, we do not warrant that results match real-world behavior, that any part, building or product reaches or stays within the temperatures shown, that material, fluid and surface values match any real material, fluid or surface, or that the app will be uninterrupted or free of errors. No advice or information from us creates a warranty. Some jurisdictions do not allow the exclusion of implied warranties or limits on statutory rights of consumers, so some of these exclusions may not apply to you.

12. Limitation of liability

To the maximum extent permitted by applicable law, Omnis Dragon LLC, its members, managers, employees, and contractors are not liable for:

• personal injury or damage to property;
• incidental, special, indirect, consequential, exemplary, or punitive damages;
• loss of profits, revenue, data, or goodwill, or business interruption.

This applies to any of these arising out of or related to your use of, inability to use, or reliance on the app or its results, however caused and under any theory of liability, even if we were told they were possible. Our total liability to you for all claims is limited to fifty U.S. dollars (US$50), as in the Standard EULA, except where the law requires otherwise. These limits apply even if a remedy fails of its essential purpose. Some jurisdictions do not allow these limits, so some of them may not apply to you. Nothing in these Terms limits liability that cannot be limited by law, such as liability for fraud, or where the law does not allow it, for death or personal injury caused by negligence.

13. Indemnity

To the extent the law allows, you agree to defend, indemnify, and hold harmless Omnis Dragon LLC and its members, managers, employees, and contractors from any third-party claim, loss, or cost (including reasonable legal fees) that arises from:

• your use of the app’s results in any design, part, building, decision, product, service, report, or advice you give to others;
• your breach of these Terms;
• content you import, open, or share;
• your breach of any law or of the rights of others.

14. Apple

You and Journey On agree to the following:

• Parties. These Terms are between you and Journey On only, not with Apple Inc. (“Apple”). Journey On, not Apple, is solely responsible for the app and its content.
• Maintenance and support. Journey On is solely responsible for any maintenance and support of the app, as described in these Terms or required by law. Apple has no obligation to provide maintenance or support for the app.
• Warranty. Journey On is responsible for any product warranty, express or implied by law, to the extent it is not effectively disclaimed. If the app fails to conform to an applicable warranty, you may notify Apple, and Apple will refund the purchase price, if any, to you. To the maximum extent permitted by law, Apple has no other warranty obligation for the app. Any other claims, losses, liabilities, damages, costs, or expenses from a failure to conform to a warranty are Journey On’s responsibility.
• Product claims. Journey On, not Apple, is responsible for addressing any claims by you or any third party relating to the app or your possession or use of it. These include product liability claims, claims that the app fails to conform to a legal or regulatory requirement, and claims under consumer protection, privacy, or similar laws.
• Intellectual property. If a third party claims that the app, or your possession and use of it, infringes that third party’s intellectual property rights, Journey On, not Apple, is solely responsible for the investigation, defense, settlement, and discharge of that claim.
• Legal compliance. You represent that you are not in a country that is subject to a U.S. Government embargo or that the U.S. Government has designated as “terrorist supporting”, and that you are not on any U.S. Government list of prohibited or restricted parties.
• Third-party terms. You must comply with applicable third-party terms when you use the app, such as your network provider’s terms.
• Third-party beneficiary. Apple and Apple’s subsidiaries are third-party beneficiaries of these Terms. Once you accept these Terms, Apple has the right, and is deemed to have accepted the right, to enforce them against you as a third-party beneficiary.
• Contact. Journey On’s name, address, and contact details for questions, complaints, or claims about the app are in sections 1 and 20.

15. Export and sanctions

You may not use, export, or re-export the app except as U.S. law and the law of the place where you obtained it allow. You may not use it for purposes U.S. law prohibits, including the development, design, manufacture, or production of nuclear, missile, chemical, or biological weapons.

16. Changes to the app and to these Terms

We may update the app and these Terms. When we change these Terms, we post the new version at https://sketchheat.journeyon.co/terms with a new “Last updated” date. If a change materially affects you, we say so in the app’s update notes or in the app before it takes effect. If you keep using the app after a change takes effect, you accept the new Terms. If you do not accept them, stop using the app and cancel any subscription.

17. Ending these Terms

You may end these Terms at any time by deleting the app and canceling any subscription. Your rights under these Terms end automatically if you breach them. Sections 4, 5, 6, 10, 11, 12, 13, 14, 18, and 19 continue to apply after these Terms end.

18. Governing law and disputes

These Terms are governed by the laws of the State of Tennessee, United States, without regard to its conflict-of-laws rules. The United Nations Convention on Contracts for the International Sale of Goods does not apply. Before you start a legal claim, email support@journeyon.co and give us 30 days to try to resolve it. Any claim not resolved that way goes to the state courts in Knox County, Tennessee, or the U.S. District Court for the Eastern District of Tennessee, and you and we consent to their jurisdiction. If you are a consumer, you keep any protection that the mandatory law of your country of residence gives you, including the right to bring a claim in your local courts where that law provides it. The governing-law clause of the Standard EULA continues to apply to the license it grants.

19. General

These Terms, the Standard EULA, and the Privacy Policy are the whole agreement between you and us about the app. If a court finds part of these Terms unenforceable, the rest stays in effect, and that part is enforced as far as the law allows. If we do not enforce a right, we do not give it up. You may not transfer your rights under these Terms. We may transfer ours to a company that takes over Sketch Heat. These Terms are written in English, and the English version controls.

20. Contact

© 2026 Journey On