capacity curves Howden 255 and 321

[mpivision]

Hi,

I need technical information for Howden compressors 255 and 321, capacity curves with ammonia refrigerant.

thanks.

[Brian_UK]

It's amazing what you can find when you try the manufacturers' website. ;)

http://www.howden.com/NR/rdonlyres/74E03188-5DE7-485F-841E-A26591A7B584/0/Rotarytwinscrewcompressors.pdf

[mpivision]

thanks Brian but,
I've read this PDF before write in this forum... in page 7 is the curve "ammonia capacity" for WRV.. but is general curve.
with this curve what's the refrigeration capacity for screw compressor Howden 255/1.65 at -5C/35C?? :mad: ;)

[Dacosta]

The long answer…

Page 8 has the swept volume

Assume a volumetric efficiency for the compressors (typically 90%).

Multiply your swept volume by the volumetric efficiency.
This is your suction volumetric capacity.

From your ammonia thermodynamic tables look up your vapor density. (add superheat for more accurate numbers).
Divide your suction capacity by the vapor density.
This is your mass flow rate.


From your ammonia thermodynamic tables look up liquid enthalpy and vapor enthalpy.
Subtract the liquid enthalpy from the vapor enthalpy.
This is your refrigeration effect.

Multiply your refrigeration effect by the mass flow rate.
This is your total compressor capacity. (correct for the units!)


I get about 2500KW for the 255 and about 5000KW for the 321.