Air Pressure Drop across Pump
Air Pressure Drop across Pump
(OP)
We intend to put a number of pumps in our plant in lay-up state for a period of time. During this time we blow dry air thru piping system into these pumps from dehumidifier units. The air static pressure out of dehumidifier Unit is limited to 5" W.C. How much pressure drop one should expect air flowing thru each pump? Any rule of thumb /thoughts? Thanks for your inputs





RE: Air Pressure Drop across Pump
RE: Air Pressure Drop across Pump
Upstream pressure, downstream pressure, gas temperature, pipe size and length, pipe roughness, inserted elements (like pump impellers), and gas composition (including viscosity) determine a flow rate exactly. If you have a max upstream pressure of 0.5 inH20, flowing to atmosphere at a known temperature, then you get a flow rate. If that is more than your blower will put out then upstream pressure will drop. If it is less than your blower is putting out, then upstream pressure will try to rise (until you run out of blower hp). If you add more pumps and piping in parallel then your blower discharge pressure will drop. I don't think it can drop to the point where you get zero dP and zero flow, but it can get awfully close.
The lower the pressure, the more water vapor air can carry and the more liquid you can evaporate. If I was doing this, I would look at putting the blower on the outlet and letting the pressure fall as low as it could (maybe several inH2O of vacuum) by pulling air through the dehumidifier instead of pushing the air.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: Air Pressure Drop across Pump
I know it seems a little strange, that's just how I would start.
RE: Air Pressure Drop across Pump
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: Air Pressure Drop across Pump
Forcing 450 CFM through 10 linear feet of 3-Inch diameter galvanized pipe has a head loss of about 5" W.C.
Forcing 135 CFM through 100 linear feet of 3-Inch diameter galvanized pipe has a head loss of about 5" W.C.
Forcing 2800 CFM through 10 linear feet of 6-Inch diameter galvanized pipe has a head loss of about 5" W.C.
Forcing 850 CFM through 100 linear feet of 6-Inch diameter galvanized pipe has a head loss of about 5" W.C.
RE: Air Pressure Drop across Pump
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way
RE: Air Pressure Drop across Pump
RE: Air Pressure Drop across Pump
Possibly David's suggestion re "sucking" instead of pulling could well be the solution.
It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)
RE: Air Pressure Drop across Pump
My motto: Learn something new every day
Also: There's usually a good reason why everyone does it that way