Preliminary engineering calculator
Thermal Oil Heater Sizing Calculator
Useful heat duty · design margin · efficiency · fuel input
Convert the process requirement into a preliminary thermal oil heater rating. The calculator exposes its assumptions so a buyer can compare quotations on the same basis.
Calculation, not final designFinal selection must still verify operating temperature, thermal-fluid properties, circulation flow, pressure drop, fuel and safety architecture.
Interactive sizing basis
From useful process duty to preliminary heater rating
Enter the useful duty required by the process. Add only a defensible margin for startup, distribution loss and operating variability; excessive margin can reduce turndown quality and increase cost.
Use the contracted fuel analysis: the defaults are illustrative, not universal fuel properties. Gas heating value and metered volume must use the same normal reference conditions. This preliminary non-condensing heater estimate accepts LHV efficiency below 100%. It uses 1 kW ≈ 860 kcal/h; changing the unit preserves the physical duty.
Calculated preliminary basis
What the calculator cannot decide
Six checks still control the real thermal fluid system
The result is only the heat-duty line of an RFQ. The system remains incomplete until these engineering constraints are resolved.
Supply and return temperature
Confirm bulk-fluid and film-temperature limits with the selected heat-transfer fluid.
Circulation flow and pressure drop
Use fluid density, viscosity, system resistance and process-user requirements at operating temperature.
Check local tube bore, downward runs and parallel-flow distribution with JIELI’s coil diameter and gas-pocket guide; a calculated heat rating alone does not establish adequate heated-wall cooling.
Fuel condition and turndown
Gas pressure, liquid-fuel properties or biomass moisture and size change combustion design.
Expansion and deaeration
Tank volume, elevation, venting, pump suction and storage arrangement must work as one loop.
Review JIELI’s expansion tank, deaerator and expansion pipe drawings when defining the circulation-loop layout.
Include the filling and venting procedure in the agreed supply scope. JIELI’s cold-filling and pump-cycling notes explain why the actual vent routes, pump preparation and motor-start limits matter; a calculated heater rating does not establish that a circulation loop is ready for heat-up.
Permissives and trips
Minimum circulation, temperature, level, pump status and combustion shutdown logic are project-specific.
Emissions and supply scope
Stack, heat recovery, controls, piping interfaces and destination-country requirements affect the package.
Calculation formulas
Keep the assumptions visible
01 / Unit conversion
QMW = Qkcal/h ÷ 860,00002 / Design duty
Qrated = Quseful × (1 + margin)03 / Fuel input
Qinput = Qrated ÷ efficiency04 / Fuel estimate
Fuel rate = Qinput (kcal/h) ÷ fuel LHVImportant: Enter margin and efficiency as percentages; the formulas use their decimal values. Fuel estimates use lower heating value and steady-state arithmetic. Real consumption depends on fuel analysis, excess air, heat recovery, load profile, startup, ambient conditions and verified system efficiency. Gas volume flow is Nm³/h; diesel mass flow is kg/h. Do not mix HHV efficiency with LHV fuel data.
Worked example: a 4,000,000 kcal/h thermal oil heater duty
With a stated 10% margin, preliminary rated output is 4,400,000 kcal/h (about 5.12 MW). At an illustrative 92% LHV efficiency, required fuel energy is 4,782,609 kcal/h. Divide by gas LHV of 8,600 kcal/Nm³ for about 556 Nm³/h, or diesel LHV of 10,200 kcal/kg for about 469 kg/h. These are alternative fuel scenarios, not simultaneous fuel use or JIELI performance guarantees.
If the contracted gas LHV is 8,000 kcal/Nm³ instead, the same heat duty and efficiency need about 598 Nm³/h. This is why two supplier offers cannot be compared by fuel volume alone. Match useful output, efficiency basis, gas reference conditions and supply boundary in the thermal oil heater quotation comparison.
Thermal-fluid flow is a separate calculation. Use JIELI THERMAL’s flow and pipe-size method with fluid heat capacity, density and supply/return temperatures. For process steam, use the steam boiler selection inputs; heater MW does not directly specify steam tonnes per hour.
Calculation questions
Thermal oil heater sizing FAQ
How do I calculate thermal oil heater capacity?
Start with the maximum useful process heat duty, add justified startup or design margin, and express the result in kcal/h, kW or MW. Fuel input is higher than useful output because heater efficiency is below 100 percent.
Is heat duty enough to select a thermal fluid heater?
No. Final selection also requires supply and return temperatures, thermal-fluid properties, circulation flow, system pressure drop, fuel data, emissions limits, controls and complete supply scope.
How many MW is one million kcal per hour?
One million kcal per hour is approximately 1.163 MW of useful thermal duty.
Convert calculation into selection
Send the result with temperature, flow, fuel and project country.
Copy your current calculated duty and assumptions into the draft, then add fuel, temperatures and project country. Review the thermal oil heater quotation-comparison checklist to separate heater-only pricing from pumps, tanks, controls and site work. Drafts do not send automatically; calculated values are not transferred automatically.
Compare the result with JIELI THERMAL's published gas/oil-fired model data and biomass model data. Match the fuel, oil temperatures and circulation requirements before treating a calculated duty as a model selection.