Refrigeration Compressor Data

[mvh18]

Hi all

I am a process engineer currently working on a project involving heat recovery from a refrigeration system. As part of my work I require information on the capacity of the compressors in the system, and how this changes with suction and discharge temperature/pressure. The refrigeration system is two staged and uses R717 refrigerant. There are six compressors used in the Intermediate pressure stage, and three compressors used in the low pressure stage. I'm currently searching for databooks on each of the compressor capacity specifications, having collected most of the compressor serial and model numbers, however this is proving difficult. Is this type of information readily available, and where is the best place to obtain such information?

Any help is much appreciated

[mad fridgie]

"Employ" a refrigeration engineer. This is what we are "trained" to do.

[RANGER1]

What compressors are they under what conditions do they run ?
Someone may be able to help .

[US Iceman]

If the compressors are refrigeration duty but used in a process refrigeration system you can contact the manufacturer. The manufacturer should e able to provide performance data for each model number.

If the compressors are process duty (some special compressors are rated to specific operating conditions only. This typically falls into the region of gas compression.) you would have to ask the manufacturer to provide a range of performance data.

If this is a process refrigeration system you may be limited on the range of suction pressures you can operate at. Why? Because if you change the suction pressure you are also changing the saturation temperature of the refrigerant in the evaporator. If you increase the evaporating temperature the LMTD on the exchanger will decrease resulting in a lower capacity at a higher suction pressure. In effect, you loose cooling capacity at a more efficient point of operation.

Sort of defeats the purpose...

[mvh18]

"Employ" a refrigeration engineer. This is what we are "trained" to do.

I am in regular contact with a post grad food techy, specializing in ammonia refrigeration. I have a good idea of the information I need and how to use it, it's just a matter of finding it.

He showed me a particular compressor manual which had tables of shaft power % vs refrigeration capacity %, capacities and shaft power requirements at different suction and discharge pressures, and other similar information. Yet, upon trying to find similar data for the compressors in this particular refrigeration system, I've stuggled. Howden sent me a manual for the WRV series but it doesn't really have the type of information I'm looking for. I can't find anything for the Sabroes and Mycoms on the net.

[mvh18]

What compressors are they under what conditions do they run ?
Someone may be able to help .

3 Howden Screw compressors of the same model. WRV 321/165 series.

3 Mycom Screw Compressors. One being a 250 VSD model, 335kW, the other two being 335kW 250 SG-LX models.

3 Sabroes, 16 cylinder recip, 110kW, SMC 60243.

LP suction of approx 10kPaG, IP suction of approx 100kPaG, IP discharge of 1000kPaG. (Two stages, "Low Pressure" and "Intermediate Pressure".)

[Frank Day]

Hi mvh18,

From what I understand the 6 screw compressors are operating on the high stage and the 3 Sabroes are operating on the low stage.

At what speed are the compressors running?

Rgds

Frank

[RANGER1]

The Sabroe's also need model
eg SMC 116 L OR S ?
Like Frank says what duty are each running and what you want to achieve , maybe different conditions .

Interstage of 100kpa is slightly unusual , is there a reason ?

100kpa NH3 = approx -19 deg C

10kpa NH3 = approx -31 deg C

[mvh18]

Sorry, have been on holiday.

Hi mvh18,

From what I understand the 6 screw compressors are operating on the high stage and the 3 Sabroes are operating on the low stage.

At what speed are the compressors running?

Rgds

Frank

No, the low stage compressors are the three howden screws. The high stage compressors are the three sabroes and the three Mycoms. The speed I am not so sure about. I could possibly try to take these measurements on my next visit (in a week) if you think it would aid in me finding the information I require.

The Sabroe's also need model
eg SMC 116 L OR S ?
Like Frank says what duty are each running and what you want to achieve , maybe different conditions .

Interstage of 100kpa is slightly unusual , is there a reason ?

100kpa NH3 = approx -19 deg C

10kpa NH3 = approx -31 deg C

I will try find these model numbers upon my next visit. I'm not sure of the exact reasoning behind the interstage pressure, why is it unusual?