The cooling capacity of an industrial chiller refers to its ability to take away heat, while the load we often refer to is the amount of heat that needs to be taken away by the cooled equipment or process. If the cooling capacity of the equipment is less than the load, it will make it difficult to lower the temperature, and if it exceeds the load, it results in energy waste. So, how to determine the cooling capacity of a chiller?

Key factors that affect chiller cooling capacity

Before calculating the cooling capacity of a chiller, we need to know what factors will affect it.
 
• ΔT (Delta T)
Delta T is the temperature difference between the coolant when it enters and leaves the chiller. The greater this difference, the more heat the coolant can absorb and carry away.
 
• Flow Rate
The flow rate of a coolant affects its heat exchange. The larger the flow rate, the more contact the coolant has with the equipment that needs heat exchange, thereby taking away more heat.
 
• Chiller fluid
Different types of chiller fluid have different specific heat capacities. Under the same mass, the larger the specific heat capacity of the coolant, the more heat is required for heating or cooling. Let’s take water and copper as an example. The specific heat capacity of water is about 4.186 kJ/kg·℃, and the specific heat capacity of copper is 0.385 kJ/kg·℃. If both rise by 1℃, water consumes 4.186 kJ of heat, while copper only consumes 0.385 kJ of heat. This is why metals heat up faster than water under the sun.

How to calculate the cooling capacity of a chiller

In order to facilitate calculations for people using different units, we introduce the cooling capacity calculation methods under the International System of Units and the Imperial System of Units.

SI Units

A process chiller uses water as a coolant. It is known that the flow rate of water in the equipment is 0.0975 m³/s, the water inlet temperature is 20℃, and the water outlet temperature is 15℃. So, what is the cooling capacity of this equipment?
 
The cooling capacity calculation formula is Q= ṁ×Cp×ΔT.
 
• Q: Cooling capacity (kW or kJ/s)
• Cp: Specific heat (kJ/kg·℃)
• ṁ: Mass flow (in kg/s) = water density p × volume flow (m³/s)
• ΔT: inlet and outlet temperature difference (℃)
 
Calculation process is as follows:
Known:
• Flow rate = 0.0975 m³/s
• Water density = 997 kg/m³
• Water specific heat = 4.186 kJ/kg·℃
• Temperature difference ΔT = 20℃ – 15℃ = 5℃
 
Calculation:
• ṁ = water density × flow rate = 997 kg/m³ × 0.0975 m³/s = 97.0575 kg/s
• Q = ṁ × Cp × ΔT = 97.0575 kg/s × 4.186 kJ/kg·℃ × 5℃=2,030.43 kJ/s=2,030.43 kW
 
So, the cooling capacity of this chiller is 2,030.43 kW.

Imperial units

Let’s convert the above example into imperial units and calculate it again.
 
A process chiller uses water as a coolant. The water flow rate in the equipment is 345 ft³/hr, the water inlet temperature is 68°F, and the water outlet temperature is 59°F. So, what is the cooling capacity of this equipment?
 
• ΔT=68°F – 59°F = 9°F
• Specific heat capacity of water ≈ 1.0 BTU/lb·°F
• Density of water ≈ 62.4 lb/ft³
• ṁ = density of water × flow rate = 62.4 lb/ft³ × 345 ft³/hr = 21,528 lb/hr
• Q = ṁ × Cp × ΔT= 21,528 lb/hr × 1.0 BTU/lb·°F × 9°F = 193,752 BTU/hr

Schlussfolgerung

If you still have questions about how to determine the cooling capacity of the chiller or match the load, the LNEYA team is happy to help you. We not only provide customized equipment with various performances, but also technical support services. Welcome to contact us at any time!