Refrigeration cycle

[Kayla9696]

I am trying to design refrigeration cycle with propylene refrigerant. I am planning to use heat exchanger for subcooling of liquid and superheating of vapor. I choose centrifugal compressor and water-cooled type of condenser. Evaporating temperature is -38C. It is needed to cool down light hydrocarbons from -26C to -35C. Could you please check the datas I wrote?
In Pressure-Enthaply
A - after condenser (0.62 MPa , 5C)
A* - after subcooling HE (0.62MPa, -10C)
B - after throttling valve (0.16MPa, -38C)
C - after evaporator (0.16 MPa, -38C)
C* - after superheating HE (0.16MPa, -14C)
D - after compressor (0.62 MPa, 50C)
E - condenser (0.62 MPa, 5C)

 

[apetri]

normally (industrial plants) evaporator and condenser have sections for supeheating and subcooling, you can estimate in/out operating points for the different units with Mollier, a table or some software (for example Prode or Refprop)... start with dP (in condenser and evaporator) < 0.5 Bar, then optimize with available data for the different units (exchangers, piping, compressor, valve)

 

[Kayla9696]

I could not download Reprop, so I am trying to use Coolpack software. Is dP is pressure drop across evaporator or condenser?

 

[apetri]

of course there are free versions but the prices for commercial versions of Refprop, Prode Properties etc. are in the 200 .. 300 dollars range... if you get some money from your work that is not a large expense...
yes, you can adopt 0.5 bar dP as initial guess for condenser and evaporator, then you can optimize...

 

[chicopee]

Isn't it of those chemicals that's ban from being used as a refrigerant by virtue of its flammable property?

 

[PaoloPemi]

yes, all refrigerants identified as flammability Class 3 in ANSI / ASHRAE Standard 34 – 2013

 

[georgeverghese]

The condensor temp of 5degC is unusually low for a water cooled HX - typically it would be 40-45degC, depending on the cooling water supply temp at this location, which could go as high as 30degC in summer in many locations. Agreed, you should account for the dp across each HX also.
You should also look at the recycle case for this compressor to see how process parameters change, and that refrigeration capability is still maintained over the entire recycle flow range ( 0-100% recycle) - this will tell you what additional equipment is required / and how the recycle is to be enabled.