How do you calculate air handling unit capacity?

In plain English, we’re changing CFM into Cubic Feet per Hour (CFH). Then we calculate the volume of the room by multiplying the room height times the width times the length. Then we simply divide the CFH by the volume of the room.

How do you change the speed of a pulley?

By changing the diameter of the pulley wheels, speed can be changed. A smaller pulley turning a larger pulley results in the larger one moving more slowly but with more shaft power.

How is Ahu performance calculated?

Typical AHU requires a flow rate of 2.4 gallons/ton. So, the flow rate should be 24 gpm for the AHU capacity of 10 TR. A typical AHU will have a Δt of 10° F, hence we assumed the AHU coil outlet temperature as 54° F. Refer water system cooling load calculations for formulae and derivations.

How is air fan speed calculated?

You measure the velocity at a points in the duct and find the average velocity in the exhaust duct is 400 FPM. Multiply 400 Feet per Minute times the area of the duct, which is . 35 square feet, to find 140 CFM exhaust fan airflow. Each fan manufacturer publishes fan performance tables for each fan.

How is fan capacity calculated?

Calculating the size of fan needed Calculate the volume of the room in cubic meters by multiplying its length x width x height. Then multiply the room volume by the required number of air changes per hour, i.e. Example.

Which pulley will turn faster?

A larger pulley turning a smaller pulley results in the smaller one turning faster but with less shaft power. For example, a truck in high gear would have a slower turning engine but faster turning wheels, resulting in a faster truck.

How do you calculate CFM to TR?

TR is tonnage of refrigeration which means amount of heat extracted to produce one ton of ice. Generally we take 1 TR = 400 CFM.

Does a fan increase air pressure?

A fan increases the static pressure on it’s outlet and can also decrease the static pressure on the inlet slightly. Even though very slight in comparrison, a fan is technically a compressor. The static pressure rise is usually in the order of inches of water.

How do I know what RPM My fan is?

It is very easy. Just place the sticker on fan base which is facing the down side. And start your fan just stand below the fan and use tachometer and press the measure button while facing the tachometer to the sticker on the fan. Volla, u will get the RPM.

How to calculate the pulley size of a fan?

The math required for Fan Law One is quite simple. Simply divide once, and then multiply once to find the new pulley size needed for the fan to move the required airflow. Example: Suppose we have a 5.5-in. adjustable motor pulley and the fan is currently delivering 5100 CFM on a 15-ton system that requires 6000 CFM.

How is air velocity measured in HVAC equipment?

air velocity measured in feet per minute or liters or meters per minute is also critical for some HVAC equipment design and testing. Examples of components for which air velocity (speed through the device) is particularly important are given in the HVAC Air Velocity table below. More air bypasses at higher velocities.

How to calculate air velocity in cubic feet per minute?

Once the average air velocity is know, the air flow rate in cubic feet per minute is easily computed using the formula: Q = AV Where: Q = Quantity of flow in cubic feet per minute .

How does a pulley belt work in an ahu?

In this article we’re going to be looking at some pulley belt calculations with worked examples. As shown in the image below, an induction motor is connected via a belt to drive two pulleys which will move centrifugal fan. This is this fairly typical of what you might find to in an Air Handling Unit or AHU.

How to calculate the velocity of standard air?

CFM =Duct area sq ft x Velocity Standard Air=70F @ 29.92” HG (Mercury) 1 cubic foot of standard air =0.075 pounds 13.3 cubic feet of standard air= 1 pound

Which is the correct formula for air flow?

Air Flow formulas CFM =Duct area sq ft x Velocity Standard Air=70F @ 29.92” HG (Mercury) 1 cubic foot of standard air =0.075 pounds 13.3 cubic feet of standard air= 1 pound FAN LAWS: Remember RPM is interchangeable for CFM

How to air balance an ahu air handling unit?

Air Balancing For AHU AIR HANDLING UNIT Set the fan rpm to provide design total air quantity within acceptable limits. Fan speed shall not exceed the maximum allowable rpm as established by the fan manufacturer. Set all the main duct & branch duct dampers and outlet dampers at full open position.