Calculating the capacity of a chiller is essential for determining the cooling needs in specific applications, whether for air conditioning or industrial processes like machinery cooling. This guide explains how to perform these calculations manually and how to use automated tools to simplify the process.
Basic Formula for Chiller Capacity Calculation
The capacity of a chiller can be calculated using the formula:
Chiller Capacity (Kcal/h) = 1000 × Ce × Q × (Te – Ts)
Where:
- Ce: Specific heat of water (1 Kcal/Kg°C).
- Q: Water flow rate.
- Te: Water inlet temperature to the chiller.
- Ts: Water outlet temperature from the chiller.
This formula serves as the foundation for determining capacity in various applications.
Chiller Calculation for Air Conditioning
When the chiller is used for air conditioning, it is crucial to determine the thermal load of the space to be cooled. Key factors include:
- Room dimensions: length, width, and average height.
- Maximum number of occupants.
- Internal heat sources: such as equipment or lighting.
- External thermal conditions: roofs, walls, or windows exposed to direct sunlight.
The calculation can be supported by automated tools to determine the requirements in:
- BTU/h
- Kilocalories (Kcal/h)
- Refrigeration Tons (TRF)
- Kilowatts (KW)
Chiller Calculation for Machinery Cooling
For industrial processes, the primary requirements are:
- Water flow rate: Measured in liters/minute, gallons/minute, or cubic meters/hour.
- Water temperature: At the inlet and outlet of the chiller.
Example Calculation (International System of Units):
- Initial data:
- Water flow rate: 18 m³/h (5 L/s)
- Water inlet temperature: 14°C
- Water outlet temperature: 8°C
- Step 1: Calculate the temperature difference.
ΔT = Te – Ts = 14°C – 8°C = 6°C - Step 2: Determine the total heat required.
Total Heat (Kcal/Kg) = Ce × ΔT = 1 × 6 = 6 Kcal/Kg - Step 3: Calculate the mass flow rate of water.
Mass Flow Rate = 5 L/s × 1 Kg/L = 5 Kg/s - Step 4: Calculate the chiller power.
Power (Kcal/s) = 6 × 5 = 30 Kcal/sConvert to conventional units:- 108,000 Kcal/h
- 427,680 BTU/h
- 35.7 TRF
- Step 5: Apply a safety factor (20%).
Final Power = 35.7 TRF × 1.2 = 42.84 TRF
Pump Calculation for Chiller Systems
The pumps in a chiller system are categorized as:
- Primary pumps: Feed water directly to the chiller.
- Secondary pumps: Distribute water to the application.
Key parameters to consider include:
- Minimum and maximum water flow rates.
- Minimum and maximum pressure.
- Efficiency at different operating points.
Tools and Training
To simplify calculations, there are automated chiller calculators that perform quick conversions between units and include safety factors. Additionally, specialized training programs are available for technicians to deepen their knowledge of the design and operation of chilled water systems.
