Strange increase of efficiency

[John McGru]

Some time ago i had creating graphs of compressor's volume efficiencies. I noted unusual (in my opinion) behaviour of VE curves for Bitzer's semihermetic recipes (all the range, that exclude the probablity of data misprint), at temp[eratures of evaporation -10..-15.C, for example:


I'm interested - is there any reasons that change (even brake!) the steadiness of decreasing of efficiency dependence on Tev?

[Prof Sporlan]

If the Bitzer data is strictly empirical, then the measurements will be subject to some "noise" if you will. The Prof would suspect the Bitzer engineers elected not to do any extensive smoothing of their data which, of course, will show up in less than perfect curves.

But this data seems reasonable enough to estimate compressor efficiencies.

[John McGru]

I saw such behaviour of VE on all the range of Bitzer's semihermetic recipe compressors.
I think that "noise" would lead to dispersion of the curves, but pictures show systematic change (increase) of volume efficiency.

Having VE's differences of 15% at Pc/Pev~4.6 i cannot choose apropriate compressor for Tev=-10..-15C (automatically).