Exercises

 

 



 

 

 

 

 

 

 

 

 

 

 

 

 

'New' Refrigerants

 Up until the signature of the celebrated Montreal protocol in September 1987, most refrigeration engineers were relatively happy people. They had been using the refrigerants then available for a number of years, and generally understood them well.

In commercial refrigeration, R12 and R502 were the most commonly used refrigerants.  In air conditioning, R22 was the most widely used material.

Then at Montreal we were told that R12 and R502 (as well as R11, R113, R114, R115 and R500) were CFCs (chlorofluorocarbons) that were destroying the ozone layer, and that these refrigerants were to disappear from use within the next ten years!   

This cut-off date seemed a long way away, and the use of CFCs in most refrigeration applications actually increased, especially as there were no real replacements available, except where new systems were designed to use R22 (where this was possible).

And today...

An engineer who was unfamiliar with new refrigerants could think that the superheat is high even though the compresser is taking in liquid, or even that the subcooling is OK when it is actually zero.

Great care must be taken with these refrigerants until adequate experience in using them has been gained!

EXERCISE : what do you make of the superheat value opposite ?

 And what do you think about the sub-cooling value ? 

(Solution : Refrepair Manual pages 405 to 417)

Previous exercise