Adiabatic Temperature Rise Calculator for Exothermic Batch Reactions
If cooling fails mid-batch, how hot does the reactor get? This calculator gives the adiabatic temperature rise from the heat of reaction, the charge and the heat capacity of the mass, then compares the result to your boiling point or decomposition onset.
Your numbers
Heat released per mole of limiting reactant. Enter a positive number for an exothermic reaction.
Amount of limiting reactant that can react in the batch.
Water is 4.18, many organic solvents are 1.7 to 2.4.
Use the lower of solvent boiling point (at relief pressure) and the onset temperature from your thermal screening.
0 means total loss of cooling (adiabatic). 100 means all heat is removed.
Your results
Screening estimate only. It assumes constant cp and all heat released with no accumulation effects. It does not replace calorimetry (RC1, ARC, DSC) or a formal process hazard analysis.
Final temperature vs share of heat removed by cooling
Sweeps Heat removed by cooling from 0 to 100, holding your other inputs fixed.
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How to use it
Enter the heat of reaction per mole of limiting reactant, the kilomoles that could react, the total mass in the vessel and its mean specific heat. Set the cooling slider to 0 percent for the worst case, a complete loss of cooling. The margin output shows how many degrees remain before the limit you entered. The chart sweeps cooling duty so you can see how much removal is needed to stay below the limit.
The formula behind it
The energy balance is simple: delta T = (delta H x n) / (m x cp). Heat released is the heat of reaction times moles reacted. The mass absorbs it according to mass times specific heat. This is the standard first screening step used before more detailed work such as reaction calorimetry and time to maximum rate studies.
- Delta H in kJ per mol times kmol times 1000 gives kJ
- Mass times cp gives the thermal capacity in kJ/K
- Add delta T to the starting temperature for the final value
- Compare the result with the lower of boiling and decomposition onset
Common mistakes
The most frequent error is using only the solvent mass when the charge also contains solids or a heel from the previous batch. Another is ignoring accumulation: if a semi-batch feed is added faster than it reacts, unreacted reagent can release heat all at once. Use the total reactant that could be present at the same time, not just the hourly feed rate.
- Do not use cp of pure water for an organic mixture
- Remember the vessel metal also absorbs heat, a small credit in your favour
- A positive margin is not proof of safety if a secondary decomposition exists
- Re-run the numbers whenever batch size or concentration changes
Frequently Asked Questions
Is adiabatic temperature rise the same as runaway temperature?
No. It is the temperature the mass reaches from the main reaction alone with no cooling. A runaway may continue past it if a secondary decomposition starts, so compare the result with the measured onset temperature of that decomposition.
Where do I find the heat of reaction?
Use reaction calorimetry results, literature enthalpies of formation, or your process development report. Heats of reaction are typically tens to a few hundred kJ per mole. Measured values are always preferred over estimates.
What cp should I use for a mixture?
Use a mass-weighted average of the component specific heats, or a measured value. For a quick check, 1.7 to 2.4 kJ/kg.K suits many organic solvent mixtures and 3.5 to 4.2 suits aqueous ones.
Does this work for semi-batch reactions?
Yes, if you enter the maximum amount of unreacted limiting reactant that could be present together in the vessel. Enter the accumulated amount, not the total of the whole feed, and use the mass at that point in the feed.
If batch records and reactor charges live in your ERP, Netray can help you pull charge quantities directly into checks like this. Ask us for an expert review of the setup.
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