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.

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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.

Calculate duty Review all selection inputs

Biomass thermal oil heater system with reciprocating grate and conveyor

Capacity must be connected to fuel handling, circulation and site conditions

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.

Useful process duty Design margin% Expected heater efficiency%

Calculated preliminary basis

Useful process duty4.65 MW4,000,000 kcal/h

Duty with margin5.12 MW4,400,000 kcal/h

Required fuel input5.56 MWAt entered efficiency

Natural-gas estimate556 Nm³/hUsing 8,600 kcal/Nm³ LHV

Diesel estimate469 kg/hUsing 10,200 kcal/kg LHV

Nominal selection band≈ 5.1 MWConfirm against available series and project conditions

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.

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.

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 conversionQMW = Qkcal/h ÷ 860,000

02 / Design dutyQrated = Quseful × (1 + margin)

03 / Fuel inputQinput = Qrated ÷ efficiency

04 / Gas estimateVgas = Qrated ÷ efficiency ÷ 8,600

Important: 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.

Convert calculation into selection

Send the result with temperature, flow, fuel and project country.

We will check the preliminary duty against the heater, circulation system, combustion equipment and full supply boundary.

Request sizing review