Blog

Estimating Cooling Capacity for Reactors and Exothermic Loads

Why chiller sizing determines scale up success

When scaling chemical reactions, cooling capacity becomes a limiting factor. Undersized chillers lead to:

• runaway temperature spikes
• poor reaction control
• safety risks
• inconsistent product quality

This guide provides a practical approach to estimating chiller capacity for:

• glass reactors
• jacketed vessels
• exothermic chemistry

The core equation (conceptual)

Cooling load is driven by:

1. heat generated by the reaction
2. heat removed via the jacket
3. temperature difference between reactor and coolant

In simplified terms:

Cooling kW ≈ Heat generation rate (kJ/s) ÷ 1000

While exact calculations require detailed thermodynamics, engineering estimates are often sufficient for equipment sizing.

Step 1: Estimate heat of reaction (ΔH)

For scale-up, determine:

• reaction enthalpy (if known)
• reaction mass per hour
• expected conversion rate

If literature values are unavailable:

• use calorimetry data (preferred)
• estimate from lab data
• apply conservative safety factors

Exothermic polymerizations and nitrations, for example, demand aggressive cooling margins.

Step 2: Account for reactor volume and fill level

Cooling demand scales with:

• batch size
• concentration
• reaction rate

A 20L reactor rarely needs 4× the cooling of a 5L system—it depends on:

• kinetics
• dilution
• heat transfer efficiency

Always evaluate heat generation rate, not just volume.

Step 3: Consider jacket efficiency

Not all jackets are equal.

Cooling performance depends on:

• jacket design (single vs dimple vs coil)
• coolant flow rate
• turbulence
• thermal fluid type

Poor jacket flow reduces effective cooling capacity even if the chiller is powerful.

Step 4: Temperature delta (ΔT) matters

Cooling power increases when:

• larger temperature difference exists between reactor and coolant

However:

• very low coolant temperatures may cause viscosity issues
• condensation or freezing risks
• inefficient compressor operation

Balance performance and practicality.

Practical rule-of-thumb sizing

While every process is unique, many engineers use:

Moderate exotherms:
~0.5–1 kW per 10–20L reactor volume

Strong exotherms:
1–3+ kW depending on reaction heat

These are starting points—not substitutes for calorimetry.

Safety factor: always oversize for scale-up

For pilot plants:

• 1.5×–2× safety margin is common
• allows future chemistry flexibility
• prevents scale-up surprises

Chillers rarely fail because they’re too big—only too small.

Other real-world factors

Ambient conditions

Warm facilities increase chiller load.

Multi-reactor setups

Shared chillers must handle peak combined load.

Continuous vs batch operation

Continuous reactions may require sustained cooling rather than short bursts.

Buying used chillers for reactors

Evaluate:

• rated kW at relevant temperatures
• compressor condition
• fluid compatibility
• pump head and flow rate
• service history

Industrial chillers often have long service life when maintained. Explore our inventory.

FAQ

Should I size based on reactor volume alone?
No. Heat generation rate is the critical variable.

Is oversizing inefficient?
Not significantly for pilot plants—and it adds flexibility.

Get expert help
Tell HiTechTrader your reactor size, chemistry type, and temperature targets. We can help estimate chiller capacity and recommend systems suited for scale-up environments. Contact us today.