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Hanan February 14, 2000 12:25

Pressure drop calcs
Hi everyone,

I need to calculate the pressure drop for an air duct with 2 or more bends at various locations of interest. The flow is turbulent with one inlet and one outlet. From what I know, there are two way to approach this problem: (1) to solve for the volume- (or area-) weighted average of total pressure, or (2) to solve for the mass-weighted average of total pressure at the plane of interest.

Which pressure drop calculation would you recommend and why? Are there better ways to approach this problem?



John C. Chien February 14, 2000 12:46

Re: Pressure drop calcs
(1). The pressure drop normally is referred to the static pressure drop. (2). For the total pressure, we normally called it the total pressure loss. (3). The averaged total pressure at a particular section or station of the duct can be calculated by using either the area-average or the mass-average. (4).Most of the time, the mass-averaged total pressure at a particular station is used. The total pressure is in a way related to the energy, therefore, it is related to the mass flow rate.

Chris February 16, 2000 11:36

Re: Pressure drop calcs
You ask :"which pressure drop calculation would you recommend and why?". This is similar to asking :"what car should I buy" my respons would be : "what do you want to do with your car, drive from and to work, transport your family, tour Africa?"

As John remarked there are static and total pressures, total pressure at a cross-section in the flow field is related to the "mechanical energy" of the flow, provided you express the 3 dimensional kinetic energy correctly (I assume you need this pressure drop in a 1-dimensional analysis of some sort). So, where will you use this pressure drop?

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