How to size a chiller - chiller cooling capacity caculation

Jul 06, 2021

The calculation method of chiller cooling capacity and the calculation summary of chiller selection

(1) How to choose the most suitable industrial chiller and screw chiller? In fact, there is a simple selection formula:

Cooling capacity = chilled water flow * 4.187 * temperature difference * coefficient

1. The flow rate of chilled water refers to the flow rate of chilled water required when the machine is working, and the unit needs to be converted into liters/second;

2. The temperature difference refers to the temperature difference between the water in and out of the machine;

3. 4.187 is quantitative (specific heat capacity of water);

4. When choosing an air-cooled chiller, multiply the coefficient by 1.3, and when choosing a water-cooled chiller, multiply it by 1.1;

5. Select the corresponding machine model according to the calculated cooling capacity.

It is generally customary to use HP to calculate how much the chiller needs to be equipped, but the most important thing is to know the rated cooling capacity. Generally, the air-cooled cooling capacity is 9.07KW and the 3HP chiller is selected, and so on. Therefore, the most important thing in the selection of industrial chillers is to obtain the rated cooling capacity.

(2) The calculation method of the cooling capacity of the chiller

How to calculate the cooling capacity of the chiller

1. Volume (liter) X number of temperature rise / heating time (minute) X 60 / 0.86 (coefficient) = (W)

2. Volume (tons or cubic meters) X number of temperature rise / heating time / 0.86 (coefficient) = (KW)

(3) Selection method of chiller

Energy conservation law Q=W in-W out

Q: Heat load (KW) W in: Input power (KW) example: 8KW, W out: Output power (KW) example: 3W

Example: Q=W in-W out=8-3=5 (KW)

Time heating method Q=Cp.r.V.ΔT/H

Q: Heat load (KW) Cp: Specific heat at constant pressure (KJ/kg.℃)……4.1868 KJ/kg. ℃,

r: Specific weight (Kg/m3)………1000 Kg/m3 V: Total water volume (m3) Example: 0.5m3

ΔT: water temperature difference (℃)…… ΔT= T2-T1 example: 5℃ H: time (h) example 1h

Example: Q=Cp.r.V.ΔT/H=4.1868*1000*0.5*5/3600=2.908 (KW)

Temperature difference flow method Q=Cp.r.Vs.ΔT

Q: Heat load (KW) Cp: Cp: Specific heat at constant pressure (KJ/kg.℃)……4.1868 KJ/kg. ℃,

r: Specific weight (Kg/m3)…….1000 Kg/m3 Vs: Water flow rate (m3/h) Example: 1.5m3/h

ΔT: water temperature difference (℃)…… ΔT= T2 (outlet water temperature)-T1 (inlet water temperature) Example: 10°C

Example: Q=Cp.r.Vs.ΔT=4.1868 * 1000 * 1.5* 10/3600 = 17.445 (kw)

Common plastic method: Q=W* C*ΔT * S

Q=the required frozen water energy kcal/h W=the weight of plastic raw materials KG/H Example: W=31.3KG/H

C=Specific heat of plastic raw materials Kcal/KG ℃ Example: Polyethylene PE C=0.55 Kcal/KG℃

ΔT= is the temperature difference between the melting temperature and the product film, ℃ generally (200℃)

S = safety factor (take 1.35-2.0) Generally take 2.0

Example: Q= W* C*ΔT * S=31.3 * 0.55 * 200 * 2.0 = 6886 (kcal/h)

When you need a chiller, Here is the Necessary info to quote.

1.What is your cooling capacity?_____    Kcal/hr  or   _____KW or _____RT?
2. What's your power supply? For example: 380V-50Hz-3N (N=Phase )
3.What refrigerant type do you require? R22 or R134a or R407c?
4. What's your ambient temperature?

And what is your chiller inlet and outlet water temperature?
5. Which industry do you use the chiller in?

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