Hvac Duct Calculation Formula

Mdot q cp x δt calculate air mass flow rate from cooling load.

Hvac duct calculation formula.

Man climbs a flight of stairs 100 ft. Hvac duct quantity weight and area calculator. When the quantity take off is completed take 10 extra of duct this will resolve the quantity assumption. Where mdot means mass flow rate kg s the q being the cooling load of the room kw cp is the specific heat capacity of the air kj kg k and δt being the temperature difference between the designed air temperature and the design return temperature.

Numbers play a large part in the hvac industry. A complete guide to hvac formulas. Ductwork equations velocity in duct velocity in duct can be expressed as v q a 144 x q a x b where v air velocity in ft per minute fpm q. To calculate the rectangular duct area we need height width and length.

Hvac formula heating ventilating and air conditioning formulas and equations. It is an usual practice to tabulate it in excel sheets using formulae to estimate the overall quantity. Work force energy exerted x distance. For duct estimation in sq.

The velocity in a 12 inch duct with air flow 1000 cfm can be calculated as vi 576 π 1000 cfm 12 in 2 1273 ft min air flow velocity calculator imperial units. Determining heat in conditions other than standard air. A more precise and complicated formula can be found here. As with any mathematical solution it is easy when you know how.

A good quality hvac engineer needs to be familiar with complex numbers and calculations. Mercury 1 psi. The formula for determining dew point temperature may also be expressed as td t 100 rh 5 remember that this formula is merely a very accurate approximation to be used only when the relative humidity value is above 50. The numbers involved are more complex than the difference between 35 and 95 degrees.

Duct quantity can be estimated in sq. Approximately 2 inches hg. Equation 1 can be put in terms of a unit thermal resistance r l k or an overall heat transfer coefficient u 1 r to give q a t1 t2 r ua t1 t2 eq 2 note that the r in equation 2 is the factor often found on blanket insulation and other building products.