Estimate Flow Rate

[mtewolde]

Hello,

I am looking for very rough estimation help for a paper I am writing. Say you have gas supplied to a home at 0.5 psi, measured at the meter. I have looked up the pressure drop table and have decided to use 1"W.C drop per 100 ft of pipe length. Ignore all other pressure losses for now.

What I want to know is, lets say you have 2 appliances using 50 CFH gas, at the same location, meaning similar pipe configuration. When you turn one on, you see 50 CFH in the meter. When you turn the other one on, you don't see (50+50)CFH but a slight reduced value. How can you estimate what the combined load would be based on conditions I provided?

Your help is much appreciated.

 

[quark]

It all depends on the pressure difference between source and user. If you are maintaining constant pressure at source and since user is at atmospheric (ultimately), there is a certain maximum flowrate, for a fixed pipe sizing and a constant pressure difference (which is pressure drop in the system).

Initially, when you are using a sinlgle appliance, your system can be able to provide more flow than 50 CFH but you throttle it to maintain overall losses to correspond to 50 CFH. When starting second applicance, your pipe is not big enough to give you 100 CFH flow. So, the flow reduces as losses corresponding to 100 CFH flow will be higher than the pressure difference between source and users.

If you have a pressure drop calculation for particular gas, freeze the values of available pressure difference and pipe size and you will get your revised flow rate.