LMNO Engineering newsletter - gas flow

This one is MUCH more relevant to us piping types than Ken's last newsletter, "Gas Flow in Open Culverts".

;)

Paul

• Original Message --------

Newsletter. Vol. 7, No. 2. March 17, 2005

Weymouth and Panhandle Equations for Compressible Gas Flow http://www.LMNOeng.com/Flow/weymouth.htm

Three equations are often used for modeling the flow of natural gas. They are the Weymouth, Panhandle A, and Panhandle B equations. These three equations are not just for natural gas, however. They are valid for most other compressible gases as well. Our calculation page includes a drop-down menu for you to choose which of the three equations to use and the gas (air, natural gas, nitrogen, oxygen, butane, carbon dioxide, propane). You may select the last option in the gas drop-down menu, which allows you to enter the specific gravity for an unlisted gas. The drop-down menu also allows you to select which variable to compute (flowrate, pipe diameter, length, or pressure) as well as a variety of units. Actual and standard volumetric flowrates are shown.

Background

The Weymouth, Panhandle A, and Panhandle B equations were developed to simulate compressible gas flow in long pipelines. The Weymouth is the oldest and most common of the three. It was developed in 1912. The Panhandle A was developed in the 1940s and Panhandle B in 1956 (GPSA, 1998). The equations were developed from the fundamental energy equation for compressible flow, but each has a special representation of the friction factor to allow the equations to be solved analytically.

The Weymouth equation is the most common of the three - probably because it has been around the longest. The equations were developed for turbulent flow in long pipelines. For low flows, low pressures, or short pipes, they may not be applicable. If the pressure drop in a pipeline is less than 40% of upstream gage pressure, then our Darcy-Weisbach incompressible flow calculation ( http://www.LMNOeng.com/DarcyWeisbach.htm ) may be more accurate than the Weymouth or Panhandles for a short pipe or low flow. The Darcy-Weisbach incompressible method is valid for any flowrate, diameter, and pipe length, but does not account for gas compressibility.

Reference:
GPSA (Gas Processors Suppliers Association). Engineering Data Book. 11ed. 1998.

LMNO Engineering's previous newsletters can be viewed at http://www.LMNOeng.com/Newsletters/newsletter7.htm Received on Thu Mar 17 19:35:00 2005