Heat Transfer Coefficients for CO2 compression intercooling

[Camarena]

Hi all;

I'm simulating CO2 compression with intercooling.
I'm using and 8 stage compressor.
I'm using water as refrigerant on the shell side (30-40ºC)

At the cooling stages there is some water condensation and as the pressure goes up, gas density (kg/m3) increases as follow:

3.3 6.2 12.1 23.2 42.8 65.2 159.9 231.6

Discharge Pressure (bara)

2.4 4.4 8.5 15.8 27.4 48.2 84.6 148.8


My question is wich Heat Transfer Coefficients (kcal/h·m2 ºC)or (Btu/ft2·°F·h) should I use for the diferent cooling stages.

Thanks in advance

 

[srfish]

The presence of water vapor complicates the estimates. I could give you an estimate if the waqter vapor could be ignored.

 

[Camarena]

Dear srfish;

I enclose estimated vapor fractions for coolers. As you can see Stg 5 and Stg7 won't have cooling and cooling after Stg 8 will liquified CO2.

I don't know if with this vapor fractions, water vapor condensation could be ignored.

Discharge Pressure (bara)
St1 St2 St3 St4 St5 St6 St7 St8

2.4 4.4 8.5 15.8 27.4 48.2 84.6 148.8

Estimate Vapor fraction after cooler

St1 St2 St3 St4 St6 St8

0.975 0.986 0.992 0.996 0.997 0

 

[Latexman]

You are already working in metric units, use kcal/h•m2 ºC. If you have data/correlations in the other units, get the HTC in those units, then convert units.

Good luck,
Latexman

 

[srfish]

Following are the estimated overall heat transfer coefficients for a shell-and-tube exchanger expressed in Btu/hr-ft2-F. They are based on a pressure drop of 1 to 2 psi and a total tube travel of 40 ft and 3/4" tubes.

The effect of the small amount water vapor was ignored by assuming the downward deflection of the condensing curve would be offset by the increase in heat transfer.

St1 St2 St3 St4 St6

23.8 30.7 39.9 51.35 75.9

St8 was not calculated because I don't have the physical properties of liquid CO2.