3 replies to this topic

[CHEMSTRONG]

Dear All,

 

I want to convert compressor diff pressure into compressor differential head in meters. I have compressor inlet gas as hydrogen and methane . I have compressor capacity, speed and inlet density available also.

 

Can you please advice how to convert diff pressure into diff head.

 

 

 

Best Regards,

Chetan Chavan 

[serra]

for liquids (assuming constant volume) it's easy head = (p2-p1)/(rho*g) -> dP*Vs/g

with compressors (volume not constant) head is normally defined as the work required (which can be espressed with different units as N-m/kg , ft-lbf/lbm etc.)

if you know inlet and outlet conditions it is possible to calculate the head directly,

or you can solve a compression stage and obtain the head as result.
 

Edited by serra, 28 February 2018 - 10:14 AM.

[CHEMSTRONG]

Dear sir,

 

Can you please tell me the equation to calculate it. Will it be polytropic process ?

 

Regards,

Chetan Chavan

[serra]

you need the initial and final conditions then the actual work (head) = H(out) - H(in),

do not confuse polytropic head (the sum of isentropic heads) with the actual work,

some software defines a head (h1) as work = h1 * g where g is gravity and h1 has units of meters, feets etc. you can calculate h1 from actual work (head) and gravity,

yes, you can model the compressor with a generic polytropic model,

note that for efficiency = 1.0  polytropic -> isentropic then you can adopt a polytropic model in most cases...

there are many threads at cheresources discussing how to model a compression stage...

Edited by serra, 01 March 2018 - 02:49 AM.