Calculate blast freezer refrigeration capacity from product mass, temperatures, freezing time, and safety factor, or batch capacity from rate and time.
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Blast Freezer Capacity Formula
The calculator runs in two modes. Each mode uses its own formula.
Freezer sizing mode calculates the refrigeration capacity needed to pull a product from its starting temperature down to the target temperature within a set freezing time.
- m = product mass per batch (kg)
- Cp_above = specific heat above freezing (kJ/kg°C)
- Cp_below = specific heat below freezing (kJ/kg°C)
- L = latent heat of freezing (kJ/kg)
- Ti = initial product temperature (°C)
- Tf = final product temperature (°C)
- Tf_point = product freezing point (°C)
- t = freezing time (hours)
- SF = safety factor or allowance (%)
Batch capacity mode multiplies a known freezing rate by a freezing time to give total throughput per cycle.
- Rate = freezing rate (kg/hour or lb/hour)
- Time = freezing time (hours)
Sizing mode adds three heat loads: sensible heat to cool the product to its freezing point, latent heat to convert water to ice, and sensible heat to bring the frozen product to the target. The result is divided by time and multiplied by the allowance to give kW. Batch mode skips the thermodynamics and just gives mass output for a planned cycle.
Typical Product Properties and Sizing Allowances
The values below are the defaults used in the product dropdown. Use them as starting points or override them with custom values.
| Product | Cp above (kJ/kg°C) | Cp below (kJ/kg°C) | Latent (kJ/kg) | Freeze point (°C) |
|---|---|---|---|---|
| Meat / poultry | 3.2 | 1.7 | 250 | -1.5 |
| Fish / seafood | 3.6 | 1.9 | 270 | -1.0 |
| Vegetables / fruit | 3.8 | 1.9 | 300 | -1.0 |
| Bakery / prepared | 2.7 | 1.4 | 180 | -2.0 |
| Water / ice | 4.18 | 2.1 | 334 | 0 |
The output of the sizing mode is the product heat load only. Adding allowances covers items the calculator does not model directly.
| Allowance | Typical range | What it covers |
|---|---|---|
| Light | 10% | Well-insulated room, infrequent door use |
| Standard | 15 to 20% | Fans, lights, packaging, normal door cycles |
| Heavy | 25 to 30% | Frequent loading, warm ambient, racks and trolleys |
Worked Example
You need to freeze 500 kg of meat from +5°C down to -18°C in 8 hours, with a 15% allowance.
Sensible heat above freezing: 500 × 3.2 × (5 − (−1.5)) = 10,400 kJ
Latent heat: 500 × 250 = 125,000 kJ
Sensible heat below freezing: 500 × 1.7 × (−1.5 − (−18)) = 14,025 kJ
Total heat removed: 149,425 kJ
Base capacity: 149,425 ÷ (8 × 3600) = 5.19 kW
With 15% allowance: 5.19 × 1.15 = 5.97 kW required refrigeration capacity.
FAQ
Why does the calculator split heat load into three parts?
Freezing is not a linear process. Removing sensible heat above the freezing point, removing latent heat to form ice crystals, and cooling the frozen mass each take different amounts of energy per degree. Latent heat is by far the largest of the three for most foods.
Does the result include room and infiltration loads?
No. The sizing output covers product load plus the safety factor you enter. Door openings, wall transmission, fans, lights, and people loads should be added separately for final equipment selection.
When should I use batch capacity mode instead?
Use batch mode when the manufacturer has given you a freezing rate in kg/hour or lb/hour and you want to know the total mass per cycle. Use sizing mode when you know the product, mass, and temperatures and need to find the kW capacity.
What freezing time should I use?
Blast freezing typically targets a product core temperature of -18°C within 4 to 24 hours depending on product thickness and packaging. Thin items like burger patties freeze in under 2 hours; thick blocks of meat or fish can take 12 hours or more.
