❄️ How to Calculate Refrigeration Load for a Cold Store
Designing and operating a cold storage facility requires accurate calculation of the refrigeration load. This ensures that the refrigeration system is properly sized to maintain the desired storage temperature, prevent product spoilage, and optimize energy efficiency.
In this Blog, we’ll walk through a step‑by‑step calculation example for a cold store, highlighting the different components of heat gain and how they contribute to the total refrigeration load.
🔹 Cold Store Example
- Dimensions: 10 m × 10 m × 5 m = 500 m³ volume
- External surface area: 385.75 m²
- Storage temperature: –20 °C
- Maximum ambient temperature: 35 °C
- Insulation thickness: 250 mm (polystyrene, conductivity = 0.033 kcal/h·m·°C)
- Occupancy: 2 men working inside the cold room
🔹 Step‑by‑Step Refrigeration Load Calculation
1. Insulation Heat Leak (Walls, Floor, Roof)
Q =(A * Delta T * k)/d
Where:
- A = surface area = 385.75 m²
- ΔT = temperature difference = (35 – (–20)) = 55 °C
- k = conductivity = 0.033 kcal/h·m·°C
- d = thickness = 0.25 m
Q = 2800 kcal/hr
2. Product Load
For fresh fish at –20 °C:
- Heat load = 5.5 kcal/kg
- Daily load = 25,000 kg
Q = (25000 * 5.5)/24= 5729 kcal/hr
3. Fan Load
Two fans at 200 W each:
Q = 400 kcal/hr
4. Air Change Load
- Store volume = 500 m³
- Average air changes = 2.5 per 24 h
- Heat gain per m³ (35 °C, 60% RH) = 40 kcal
Q = (500 * 2.5 * 40)/24 = 2083 kcal/hr
5. Lighting Load
- 1000 W lighting = 860 kcal/hr
6. Occupancy Load
- 1 man at –20 °C = 370 kcal/hr
- 2 men = 740 kcal/hr
7. Defrost Heat
- 8000 W for 1 h, recovered over 6 h
Q = (8000 *0.86)/6= 1142 kcal/hr
🔹 Total Refrigeration Load
Q{total} = 2800 + 5729 + 400 + 2083 + 860 + 740 + 1142
Q{total} = 13,754 kcal/hr
Thus, the total refrigeration load for the cold store is 13,754 kcal/hr.
🔹 Why Accurate Load Calculation Matters
- Energy Efficiency: Prevents oversizing or undersizing of refrigeration equipment.
- Product Safety: Ensures consistent storage temperature for perishable goods.
- Cost Savings: Reduces unnecessary power consumption and maintenance costs.
- System Reliability: Helps in selecting compressors, condensers, and evaporators correctly.