How do you calculate air flow velocity?

Determining Flow Velocity The easiest way to determine Flow Velocity is to measure the Velocity Pressure in the duct with a Pitot Tube Assembly connected to a differential pressure sensor. The Pitot Tube Assembly includes a Static Pressure Probe and a Total Pressure Probe.

How does air velocity affect heat transfer?

Velocity Affects Thermal Transfer higher the turbulence — and the higher the turbulence, the more efficient the thermal transfer. As turbulence falls, the film on the walls of the heat exchanger increases. Called the “film coefficient,” as it increases, the thermal transfer efficiency is reduced.

How is airflow measured?

An anemometer, a test instrument that measures air velocity is used to determine the average air speed in the duct. Then the average feet per minute is multiplied by the area of the duct in square feet to determine the airflow moving through the duct.

How do you measure air flow temperature?

A Hot Wire Anemometer is an instrument for measuring velocity and direction of fluid (in this case air) by measuring heat loss of an electrically-heated wire placed in the air stream. When placed in an air stream the heat is transferred from wire to the air and the temperature of wire reduces.

What is the normal velocity of air?

The study also identified an acceptable air velocity range from 0.3 up to 0.9 m/s under the experimental conditions.

Does heat transfer increase with velocity?

Generally Heat transfer coefficient of fluid increases with the increase in Reynolds number or velocity of fluid when it flows through a pipe.

What is airflow rate?

Airflow rate means the actual volume of air passing through the device per unit of time, expressed in cubic-feet-per-minute, to three significant figures.

Why is 400 cfm a ton?

Air quantities (cfm): 400 cfm per ton of cooling is needed for normal comfort applications, 500 cfm per ton of cooling for heat pump and high sensible heat applications, and 350 cfm per ton of cooling for high latent heat applications. This number is based upon an averaged heat load calculation for comfort cooling.

What is the temp rise formula?

Subtract your beginning temperature from your ending temperature to find the rise in temperature. In the example, 80 degrees minus 76 degrees equals a 4-degree rise in temperature.

How is the effective heat transfer coefficient measured?

This measurement is based on extracting the average heat transfer coefficients from time-depen- dant temperature curves as a function of velocity and bypass. The measured effective heat transfer coefficient is then scaled by mass, volume, weight or height.

How is the convective heat transfer of a fluid calculated?

A fluid flows over a plane surface 1 m by 1 m. The surface temperature is 50oC, the fluid temperature is 20oC and the convective heat transfer coefficient is 2000 W/m2oC. The convective heat transfer between the hotter surface and the colder air can be calculated as

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 the air velocity of a hot radiator?

The air flow velocity at the top of a hot (80oC) radiator with height 1 m in a room with temperature 20oC can be calculated as The air flow volume (for radiator with width 1 m) can be calculated as Q = 0.019 [ (9.81 m/s2) ( (80 oC) – (20 oC) / ( (273 K) + (20 oC))]0.4 (1 m)1.2 Sorry to see that you are blocking ads on The Engineering ToolBox!