1. Determine the Cooling Load

The cooling load is the amount of heat that needs to be removed to maintain the desired temperature. It can be calculated by considering the following factors:

  • Heat Gain from Equipment: Calculate the heat generated by machinery, computers, and other equipment. This can be measured in BTUs (British Thermal Units) or kW (kilowatts).
  • Heat Gain from Lighting: Account for the heat generated by lighting systems.
  • Heat Gain from People: Consider the heat produced by occupants. Each person typically adds around 100-400 BTUs per hour.
  • Heat Gain from Outside: Factor in the heat gained through walls, windows, and roofs from outside temperatures.
  • Internal Heat Sources: Include any additional sources of heat like ovens or production processes.

2. Convert Heat Load to Chiller Capacity

The cooling load is often measured in tons of refrigeration. To convert from BTUs or kW to tons of refrigeration:

  • BTUs to Tons: 1 ton of refrigeration = 12,000 BTUs per hour.
    • Formula: Tons=Total BTUs/hour12,000\text{Tons} = \frac{\text{Total BTUs/hour}}{12,000}
  • kW to Tons: 1 ton of refrigeration = 3.517 kW.
    • Formula: Tons=Total kW3.517\text{Tons} = \frac{\text{Total kW}}{3.517}

3. Account for Safety Margins

Include a safety margin to accommodate peak loads and future expansion. This is usually around 10-20% more than the calculated cooling load.

4. Select Chiller Size

Based on the calculated cooling load and safety margin, select a chiller with the appropriate capacity. Chillers are available in various sizes, so choose one that matches or slightly exceeds your requirements.

5. Consider System Efficiency

Consider the efficiency of the chiller and associated components. The efficiency can impact the overall performance and operational cost.

Example Calculation

  1. Calculate Cooling Load:
    • Equipment: 50,000 BTUs/hour
    • Lighting: 20,000 BTUs/hour
    • People: 10 people × 200 BTUs/hour/person = 2,000 BTUs/hour
    • Total Cooling Load = 50,000 + 20,000 + 2,000 = 72,000 BTUs/hour
  2. Convert to Tons:
    • Tons=72,00012,000=6\text{Tons} = \frac{72,000}{12,000} = 6 tons
  3. Include Safety Margin:
    • Safety Margin = 20% of 6 tons = 1.2 tons
    • Total Required Capacity = 6 + 1.2 = 7.2 tons
  4. Select Chiller:
    • Choose a chiller with a capacity of at least 7.2 tons.

By following these steps, you can accurately determine the required capacity of a chiller plant to ensure it meets your cooling needs effectively.