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How to calculate the air volume of the cooling fan required by the product?

How to calculate the air volume of the cooling fan required by the product?

  • Time of issue:2021-04-12
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How to calculate the air volume of the cooling fan required by the product?

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  • Time of issue:2021-04-12
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For customers, manufacturers are obliged to assist them in how to choose a cooling fan with appropriate air volume. Now the calculation method of air volume demand is introduced as follows:
First, we must first understand some known conditions:
1. 1 calorie is equal to the heat required for 1g of water weighing 0°C to increase its temperature by 1°C.
2. 1 watt of power work for 1 second is equal to 1 joule.
3. 1 card is equal to 4.2 joules
4. Air constant pressure (10mmAq) specific heat (Cp)=0.24(Kcal/Kg℃) 
5. Standard air: humid air with a temperature of 20℃, atmospheric pressure of 760mmHg and humidity of 65% is standard air. At this time, the unit body
      The weight of accumulated air (also known as specific weight) is 1200g/M*3
6. CMM and CFM both refer to the volume of air discharged per minute. The unit of the former is cubic meter/minute; the unit of the latter is cubic feet/minute.
Second, formula calculation
1. Know that: the total heat discharged by the fan (H) = specific heat (Cp )× weight (W)× allowable temperature rise of the container (△Tc)  
              Because: weight W=between units (per second) volume multiplied by density
              i.e. weight W=(CMM/60) ×D 
              i.e. weight W=(CMM/60)•1200g/M*3
              i.e. weight W=(Q/60) ×1200g/M*3 
              So: total heat (H)=0.24(Q/60) •1200g/M*3•△Tc 
2. Electrical heat (H)=( P[power] t [sec] )/4.2
3. Known from one and two: 0.24(Q/60) •1200g/M*3•△Tc=(P•t)/4.2
              Solution: Q=(P×60)/1200•4.2•0.24•△Tc
              Solution: Q=0.05P/△Tc…………………………………&hellip ;………… (CMM)
              Solution: Q=0.05•35.3 P/△Tc=1.76 P/△Tc……………………… …(CFM)
4. Converted to Fahrenheit (the temperature difference is equal to 1.8 Fahrenheit for every 1 Celsius temperature):
              Q=0.05•1.8 P/△Tf=0.09 P/△Tf………………………(CMM)
              Q=1.76•1.8 P/△Tf=3.16 P/△Tf…………………………( CFM)
Three. Examples
Example 1: A computer consumes 150 watts of power and a fan consumes 5 watts. When the summer temperature reaches 30°C, the CPU is allowed to work at 60°C, and the fan is required. The calculation is as follows:
                   Q=0.05×155/30=0.258CMM=9.12CFM (air volume required for work)
Example 2: A SWITCHING power supply consumes 250 watts and a fan consumes 20 watts. The local summer temperature is up to 55°C. Set the supply to allow working at 95°C. The required fan air volume is calculated as follows:
 &Nbsp;       P=250W+20W=270W;△Tf=95-55=40
 &Nbsp;       Q=0.09×270/40=0.6075CMM=21.44CFM (air volume required for work)
In this way, the main parameter of the air volume of the cooling fan required by the product can be confirmed, and then the cooling fan that fits the customer's product can basically be selected through other parameters. (Recommended to read "Introduction to Wind Tunnel Laboratory and How to Choose a Cooling Fan")

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