# Introduction

##### Technical Information of Fan Motor

#### Measurement of Air Volume and Static Pressure

In our Company we have been measuring the air volume using the Multi-nozzle Chamber Air Volume Measuring Device of Automatic recording type, which is in conformity with the highly reliable AMCA specifications (USA).

The error rate is below 1% theoretically (based on AMCA). Also it is possible to measure the characteristics of the suction side as well as the blowing side. The values in catalog show the characteristics of the blowing side.

**Operation Principle of Measuring Device** (in the case of blowing characteristics)

#### Principle of Measurement

Determine the internal capacity of the chamber so that the speed of the air inside the chamber becomes less than 1m/sec, and let the air inside the chamber become stationary and measure the static pressure of Room A (difference of atmospheric pressure with the static pressure: (+) Impressing pressure; (-) suction pressure) and the pressure difference between the front and the back nozzles (for air volume), and by means of the computing section output the result on the coder.

#### Computation Formula

Air Volume= 60xcx / 4D2 2g / r Δ Pn (m^{3}/min)

But C= Flow coefficient (variable due to wind speed) of nozzle

D= diameter of nozzle

r= air density= 1.293 x 273 / 273+1 x P / 760Kg/m^{3}

(t=temperature °C, P=air pressure mmhg)

g=9.8m / sec^{2}

ΔPn=Nozzle differential pressure mm-H_{2}O

Stationary Pressure ΔP=PA-P

mm-H_{2}O (PA=Air pressure in chamber A P=Atmospheric pressure)

Conversion formula of Air Volume and Stationary Pressure

P(inch-H_{2}O)=0.0394P(mm-H_{2}O)

Q(CFM)=35.31Q (m^{3} / min)

Q(I/S)=16.67Q (m^{3} / min)

#### Guide to Research of Fan Motor

**Computation of required Draft Volume:**

It becomes necessary to determine the draft volume when we force the equipment to be aircooled. Although it is advisable to obtain the air volume required for actual cooling by experiment, an approximate standard however, can be derived from the following formula:

Q=50 x HW / T... (1)

Q= Required Draft Volume m^{3} / min

HW= hat value of heat source tw

ΔT= T2-T1

(T1= Air temperature at air inlet)

(T2= Air temperature at air outlet)

ΔT= Allowable temperature rise

It is safe to assume ?T =8 °C, so from Formula (1)

Q= 6.25 x HW m^{3} / min.