How to Size a New Chiller for Your Project or Process

Choosing the right chiller size is essential for ensuring efficient cooling performance, energy savings, and long-term reliability of any industrial or commercial process. Whether you’re designing a new system or replacing an old unit, proper chiller sizing ensures your operation stays within optimal temperature control—without overpaying for capacity you don’t need.

This blog post will guide you through the key steps, formulas, and considerations for selecting the right chiller size for your specific project or process.

What Is Chiller Sizing?

Chiller sizing refers to determining the cooling capacity required to remove a specific amount of heat (measured in BTU/hr, kW, or tons) from a process or environment over time. This depends on the process load, ambient conditions, and desired temperature setpoints.

Key Factors Influencing Chiller Sizing

1. Cooling Load

The total amount of heat to be removed. This includes:

Heat from process equipment
Heat from lighting and electronics
Heat generated by people in the space
Environmental or ambient heat gain

2. Process Fluid

Different fluids (e.g., water, glycol, oil) have different thermal properties.

Specific heat capacity affects cooling energy required
Viscosity and flow rate impact pump and chiller selection

3. Temperature Differential

The required drop in fluid temperature across the chiller:

Delta T (∆T) = Fluid Inlet Temp – Fluid Outlet Temp

4. Flow Rate

Measured in LPM (liters per minute) or GPM (gallons per minute), the flow rate directly impacts how much heat is moved.

5. Ambient Temperature & Installation Location

High ambient temperatures reduce chiller efficiency and capacity. Consider:

Indoor vs. outdoor installation
Ventilation and cooling airflow
Local climate (temperature and humidity)

Basic Chiller Sizing Formula

Metric Units (kW)

Q = m × Cp × ∆T

Where:

Q = cooling load (kW)
m = mass flow rate (kg/s)
Cp = specific heat of fluid (kJ/kg·°C)
∆T = temperature difference (°C)

For water:

Q (kW) = 4.2 × Flow rate (L/s) × ∆T (°C)

Imperial Units (Tons of Refrigeration)

Cooling Load (Tons) = (Flow Rate in GPM × ∆T × 500) / 12,000

Where 500 is a constant for water (8.33 lbs/gallon × 60 minutes).

Step-by-Step Chiller Sizing Example

Scenario: A cooling process requires reducing water from 30°C to 20°C at 100 LPM.

Step 1: Convert Flow Rate to L/s

100 LPM ÷ 60 = 1.67 L/s

Step 2: Apply Formula

Q = 4.2 × 1.67 × (30 – 20) = 70.14 kW

Step 3: Add Safety Margin

Recommended: +10% to 20%
Final sizing = 70.14 × 1.2 ≈ 84 kW

Result: Choose a chiller rated for at least 84 kW cooling capacity.

Additional Sizing Considerations

1. Redundancy & Backup

For critical processes, consider:

N+1 configuration (one standby unit)
Modular chillers with shared loads

2. Heat Rejection Type

Air-cooled chillers: Simpler, easier to install, but less efficient in hot climates
Water-cooled chillers: Higher efficiency, but needs cooling tower, water treatment

3. Seasonal Load Variation

Chillers should be able to operate efficiently at partial load or in variable load conditions.

H2: 4. Integration with BMS

Ensure chillers can communicate with the building management system (BMS) or SCADA for control, alarms, and energy monitoring.

5. Energy Efficiency

Check EER/COP ratings. Higher values mean better efficiency.

COP (Coefficient of Performance): Cooling output ÷ power input
EER (Energy Efficiency Ratio): BTU/hr ÷ watt

Mistakes to Avoid

Oversizing: Leads to short cycling, wear and wasted energy
Undersizing: Fails to meet demand, process failures
Ignoring ambient conditions
Skipping safety margin
Not accounting for future expansion

Conclusion

Proper chiller sizing is not just a matter of capacity—it’s a critical engineering decision that affects process stability, energy use, equipment lifespan, and project ROI. By carefully calculating your cooling load, understanding the process requirements, and considering installation conditions, you can select a chiller that’s both right-sized and future-ready.

If you’re unsure, always consult with a certified HVAC or process engineer to verify your calculations and ensure long-term reliability.

Right size. Right efficiency. Right results.

Share The Post :