Cold Storage Tonnage Calculator

Inputs

Enter geometry, temperatures, insulation, airflow, and operational loads.

Example Data Table

Sample values for a medium freezer room with moderate traffic.

Formula Used

• Transmission: Q_trans = U·A·ΔT for walls, ceiling, and floor; summed and converted to kW.
• Infiltration (ACH method): ṁ = ρ·V·ACH/3600, then Q_inf = ṁ·(h_out − h_in).
• Moist air enthalpy: h = 1.006·T + w·(2501 + 1.86·T), with humidity ratio w from RH and saturation pressure.
• Product sensible: Q = (m·c_p·(T_in − T_s)) / (t·3600).
• Optional freezing: Cool to freezing point, add latent heat, then cool below freezing point.
• Total load: Q_total = ΣQ components; apply safety factor: Q_sf = Q_total·(1 + SF).
• Tonnage: TR = Q_sf/3.517. Design TR = TR / efficiency factor.

This is an estimating tool. Final design should follow applicable standards and manufacturer data.

How to Use This Calculator

1. Enter room length, width, and height to define volume and surface areas.
2. Set inside, outside, and slab temperatures to determine temperature differences.
3. Provide U-values for walls, ceiling, and floor based on insulation selection.
4. Choose ACH and humidity values to estimate infiltration heat and moisture load.
5. Add daily product throughput and entry temperature; set pull-down hours.
6. Include internal loads like lighting, fans, equipment, and people activity.
7. Apply safety and efficiency factors, then press Submit for results.
8. Use CSV or PDF downloads to share the calculation summary.

Technical Notes

Load Drivers in Cold Rooms

Cold storage capacity is driven by heat entering the space and heat generated inside it. The calculator aggregates transmission through walls, roof, and floor, plus infiltration, product cooling, internal equipment, people activity, and defrost energy. Each component is expressed in kilowatts to keep units consistent across construction inputs and operating assumptions.

Envelope Heat Transfer Inputs

Transmission depends on surface area, U-value, and the temperature difference. Better insulation lowers U and reduces tonnage significantly. Floor heat gain may differ from wall heat gain, so slab temperature is handled separately. Accurate dimensions and realistic insulation values are essential when comparing panel thickness options or planning retrofits.

Air Infiltration and Moisture Impact

Door openings can dominate refrigeration load, especially in busy facilities. The ACH method estimates the mass flow of incoming air using room volume and air changes per hour. Enthalpy is then calculated from temperature and relative humidity to capture both sensible and latent effects. Lower ACH, tighter seals, and air curtains typically reduce required tonnage.

Product Pull-Down and Throughput

Product load reflects energy removed as warm goods cool to storage temperature. Higher daily throughput, larger temperature drop, and shorter pull-down time increase instantaneous capacity needs. For freezing applications, the optional phase-change term adds latent heat and below-freezing cooling, which can noticeably raise tonnage for meats, seafood, or prepared foods.

Interpreting Tonnage Results

The tool reports total load with and without safety margin, then converts to refrigeration tons using 3.517 kW per ton. The efficiency factor can represent real-world derating, part-load behavior, or conservative selection. Use the breakdown table to identify the largest drivers, then iterate on insulation, traffic, and product handling to optimize system sizing.

Where possible, validate inputs with as-built drawings, panel datasheets, and local climate design conditions. If multiple rooms share a corridor, model each room separately and then consider diversity. For quick checks, adjust ACH and product pull-down first, then refine U-values. Document assumptions in the PDF to support review later.

FAQs

1) What does “tonnage” mean in refrigeration?

It is refrigeration capacity expressed in tons of refrigeration. One ton equals 3.517 kW of cooling. The calculator converts total load in kW into tons to support quick equipment sizing decisions.

2) Why is infiltration load sometimes very high?

Frequent door openings introduce warm, humid air. That adds sensible heat and moisture that must be removed. Lower ACH, better door management, vestibules, or air curtains can reduce this component.

3) How should I choose U-values?

Use panel or insulation datasheets whenever possible. If unknown, start with typical cold-room ranges and refine later. Small U-value changes can shift tonnage noticeably, especially for large surface areas.

4) When should I enable the freezing option?

Enable it when product crosses the freezing point and storage temperature is below that point. The model adds latent heat and below-freezing cooling. Keep it off for chilled rooms where product stays unfrozen.

5) What does the efficiency factor represent?

It is a practical adjustment for derating, part-load behavior, or conservative selection. Using a value below 1.0 increases recommended tonnage. Set it closer to 1.0 when design conditions and equipment performance are well defined.

6) Is this result enough to select compressors and evaporators?

Use it as a sizing estimate. Final selection should consider evaporator temperature difference, suction conditions, defrost strategy, product stacking, and controls. Always verify with manufacturer data and applicable standards.