Calculation method of air compressor cooling tower selection

Calculation method of air compressor cooling tower selection

More and more air compressors use water cooling, but when it comes to calculating the size of the cooling tower, people often don't know where to start. After years of accumulated experience, Gengchuang Cooling Tower Company summarized the following methods in addition to air compressor selection. The user only needs to calculate according to the following method to ensure that the cooling tower can be selected.

To choose a cooling tower for an air compressor, you need to know at least two parameters:

Free displacement m3/min

Exhaust pressure Pa

The conversion of air compressor from mechanical energy or electrical energy to heat is divided into two processes:

Gas compression. This process is an adiabatic process, and the calculation formula is:

Calculation method for air compressor cooling tower selection

T 2——The absolute temperature of compressed air K

T 1-the absolute temperature of the air before compression K

P 2——The pressure of that gas after compression (exhaust pressure) Pa

P 1——The pressure of the air before compression Pa

K——The adiabatic index of air, K=1.4

2. The heat dissipation of compressed air is an equal pressure process, and the calculation formula is:

Calculation method of air compressor cooling tower selection

Where:

Q-Heat dissipation KJ during compressed air cooling

ρ——The density of inhaled air Kg/m3, which is 1.237Kg/m3

V——The volume of intake air (free exhaust volume) m3

C p——Constant pressure specific heat of air, take C p=1.005KJ/(Kg℃)

t 2——Air temperature before cooling (T 2－273 calculated by the above formula)℃

t 0——air temperature after cooling (10°C higher than ambient temperature)

Note: The calculated Q is the heat dissipation per minute (because V is the suction volume per minute), and Q×60 is the heat dissipation per hour. Knowing the heat dissipation of the air compressor, it is simple to calculate the water flow of the cooling tower. Generally, the water temperature drop of cooling tower design is 5℃, and the flow rate m can be calculated according to Q=CMΔt.

For example: an air compressor with a free exhaust volume of 45m3/min and an exhaust pressure of 7.5×105 Pa, an ambient temperature of 20°C, and an atmospheric pressure of 9.8×104 Pa.

According to calculations, it can be concluded that the compressed air temperature is 265℃, and the cooling heat dissipation per hour is 788800KJ. According to Q=CMΔt, m=Q/(CΔt)=788800/(4.2×5)=37562Kg can be calculated.

That is equivalent to 38 tons of cooling water per hour can completely take away the heat generated by the air compressor. This value is slightly enlarged, and a 50-ton cooling tower is sufficient.