Result
Preliminary calculation: This tool is for quick sizing and information. In real projects, load calculation, selection and commissioning require engineering calculations and a site survey. Results are approximate values.
Formula
Q [kW] = ρ [kg/m³] × V̇ [m³/h] / 3600 × cp [kJ/kgK] × ΔT [K]Taking ρ ≈ 998 kg/m³ and cp ≈ 4.18 kJ/kgK for water gives Q ≈ 1.163 × V̇ × ΔT. For the same capacity, the smaller the ΔT, the higher the required flow rate; this increases pipe diameter, pump power and operating cost.
Typical values
- Commonly used ΔT for a cooling circuit: about 5 K (7/12 °C)
- In a hot water circuit, ΔT is usually larger
- Glycol affects capacity and flow rate requirement
- Reducing ΔT increases pump energy
For pipe selection by flow rate, use the pipe diameter calculator; for glycol ratio, use the glycol calculator.
Frequently asked questions
How is chiller flow rate calculated?
Divide the capacity (kW) by 1.163 and by ΔT to get the approximate flow rate in m³/h (for water).
Why does glycol reduce capacity?
The specific heat of a glycol mixture is lower than that of water and its density is higher; a larger flow rate is needed for the same capacity.
Why is a ΔT of 5 K common?
It is a common design value in cooling circuits because it gives a balanced flow rate, pipe diameter and efficiency; it may vary by project.