calculating Mass flow rate

[Andrew072]

Hello,

I am a new mechanical engineering graduate and have just started a graduate program for plant engineer at an abattoir. They have started me on the refrigeration system which is fairly complex compared to uni textbook examples. they would like me to do the system calculations.
I have determined to try and figure out the mass flowrate of the system. I thought i would start with the work in from the compressor. and get the COP. I have the kW rating of the motor suction and discharge pressures and the tables to get enthalpy entropy. We use R717. does this seem lik a viable option?

Thank you people

[Brian_UK]

I'm not a great theory guy but maybe the CoolPack software might be useful to you in your endeavours.

https://www.ipu.dk/products/coolpack/

[cricri]

I Andrew,
some questions before answers:
- I suppose that you are operating a system with ammonia direct expansion in coils?
- single stage without économiser?
- what kind of expansion device between HP and LP. HP float valve, solenoid with throttle valve, ICM+ICAD....?

[GrantD]

Hi Andrew,

I would start the other way around. You don't know what the C.O.P is currently - only the power absorbed.

You need to find out the swept volume of the compressors (Make, Model and Speed with manufacturer). You then need to establish the operating conditions and then plot this on the pressure enthalpy chart.

If there is no P&ID drawing for the site start by drawing one up so that you fully understand the full process and where to enter the pressure enthalpy chart.

Enjoy the exercise.

[RANGER1]

Andrew,
Do you know what will the information be actually used for?
Does your company have a relationship with a refrigeration company, as they would, or should help you if you requested.
Australia a bit slow, only last couple of years thinking about power savings.
If compressors old then numbers will be inaccurate anyway, probably need flow meters, but pointless unless you have a benchmark.
What brand & size compressors do you have?
What conditions do they run, suction, interstage, discharge pressures
Any VSD compressors?