Cooling Load Calculator — Milk Chilling & Refrigeration Tonnage
Calculate refrigeration load (cooling duty) in TR and kW for chilling milk in dairy plants. Free online cooling load calculator for dairy engineers.
What is Cooling Load in a Dairy Plant?
Cooling load is the rate at which heat must be removed from milk (or other dairy products) to reduce its temperature from the incoming temperature to the storage/processing target temperature.
It is expressed in:
- kW (kilowatts of heat removal)
- TR (Tonnes of Refrigeration — 1 TR = 3.517 kW)
Correct sizing of the chilling system ensures milk reaches safe temperatures quickly, preventing bacterial growth and quality loss.
How to Use This Calculator
- Enter the milk flow rate (litres/hour or litres/batch)
- Enter the inlet temperature of incoming milk (°C)
- Enter the target outlet temperature (°C)
- The calculator gives cooling duty in kW and TR
Formula
Q (kW) = ṁ × Cp × (T_in − T_out)
Where:
- ṁ = mass flow rate (kg/s)
- Cp = specific heat of milk (≈ 3.9 kJ/kg·K)
- T_in = inlet temperature (°C)
- T_out = target outlet temperature (°C)
Refrigeration Tons (TR) = Q (kW) / 3.517
Add 15–20% safety margin for system losses and peak load variation.
Common Dairy Chilling Scenarios
| Scenario | Inlet Temp | Target Temp |
|---|---|---|
| Village collection chilling | 30–37°C | 4°C |
| Post-pasteurization cooling | 72°C | 4°C |
| UHT product cooling | 135°C | 25°C (aseptic) |
| Cream storage | 10°C | 4°C |
| Butter chilling | 20°C | 8°C |
Example Calculation
Chill 20,000 litres/hour of raw milk from 35°C to 4°C:
- ṁ = 20,000 / 3600 × 1.030 = 5.72 kg/s
- Cp = 3.9 kJ/kg·K
- ΔT = 35 − 4 = 31°C
Q = 5.72 × 3.9 × 31 = 691 kW
TR = 691 / 3.517 = 196 TR
With 20% margin: 235 TR → select a 250 TR chiller
Refrigeration System Types in Dairy
| System Type | Application | COP Range |
|---|---|---|
| Vapour compression (ammonia) | Large dairy plants > 100 TR | 3.5–5.0 |
| Vapour compression (Freon/HFC) | < 100 TR, small plants | 2.5–4.0 |
| Ice bank system | Peak demand management | 2.0–3.0 |
| Glycol chiller | Indirect cooling, hygiene-sensitive | 2.8–4.2 |
Energy Efficiency Tips
- Pre-cool with bore well water: Reduce load by 30–50% using 20–25°C groundwater
- Maintain condenser cleanliness: Fouled condenser raises power consumption 10–15%
- Optimise suction temperature: Each 1°C rise in suction = 1% energy savings
- Night-time chilling: Lower ambient reduces compressor head pressure
- Leak-free system: Refrigerant leaks reduce COP significantly