View Full Version : Relative Power / Capacity data

01-08-2002, 11:57 AM
Can any of my erudite colleagues world-wide help me with this one?

I am trying to establish some broad benchmarks for energy consumption across a range of compressor types on air cooled A/C systems to illustrate the relationships between power input, cooling or heating output plotted against a reduction in capacity and then to compare system types.

This reduction can be either reducing condensing temperature simulating intermediate seasonal performance or the result of incremental unloading.

It would be particularly helpful if this could relate to VRF systems also that use a continually variable capacity control through a VSD.

The compressors I have in mind are:

Twin Rotor screws

The reason is that almost all the available manufacturer's information is captured at full rating conditions, at full speed. usually at ISO T1 and it doesn't follow that a reduction of 50% capacity will give a corresponding reduction in input - in reality, far from it. In addition, systems never run at their design or rated condition in real life.

Does any of this information exist on the web? Assuming, of course, that the work has been done in the first place!

I hope I've chosen the right forum, but at the least it?s the one with one of the biggest readerships.

Best regards
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01-08-2002, 02:24 PM
Copeland publishes tables in it's "Compressor performance" literature which (I believe) indicates exactly what you are interested in. A curve is imposed on the table in relation to power consumption at varying suction and discharge conditions. :)

01-08-2002, 04:25 PM
Hi, Argus:)
The nearest data I can think of is the selection programs by Bitzer and Grasso, you can vary the head and suction to see what happens at differing ambients, as for rated speed there is some options available especially with the open drive screws and recips on the Grasso selection.
This software can be down-loaded at.

I hope this is of help.
Regards. Andy:cool:

01-08-2002, 09:11 PM
Many thanks to both. I'm looking into it now.
You definitely have money in the bank.
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