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Abe
13-03-2002, 10:18 PM
Could someone care to explain what the term refrigerant glide means.

No, Im not looking sheepish asking, I favour the adage, better to ask then remain ignorant

Gary
13-03-2002, 11:16 PM
Zeotrope blends mix refrigerants which can separate from each other, unlike azeotropes which mix together to become one.

Zeoptropes often blend refrigerants with different boiling points (saturation temps), where one will change from liquid to vapor before the other as they go through the evaporator.

The glide is the difference between the lowest boiling point and the highest boiling point. If they are 3 degrees apart, for example, the blend has a 3 degree glide.

frank
13-03-2002, 11:35 PM
I've just been to a 'REFRIGERANT SEMINAR' tonight sponsored by the East Midlands Refrigeration Societyand this very question was asked during the Q & A session.

The knowledgeable chap fron Danfoss spoke on the subject, the basis of which was " glide is the temperature range within which the different chemical components of the refrigerant evaporate at the same pressure".

R404a has a glide of 0.5K whereas R407c has a glide of between 5 and 6K. The 4 basic chemicals that make up the majority of HFC's, R134a, R32, R125 (and 1 other which escapes my recollection at this late hour) are stand alone refrigerants in their own right, however, to overcome the inherant problems of each stand alone fluid they are combined to make the further well known refrigerants that are more stable. It is the individual boiling points of these fluids that causes what is commonly known as glide.

One thing that was pointed out by our knowledgeable speaker was of interest and had not been considered by my self before tonight - if a chiller is operating on R407c with a water leaving temperature of 3deg C there may be parts of the evaporator that are below freezing due to glide!;)

Gary
14-03-2002, 12:26 AM
I'm wondering if they had to paint the walls at Heathrow after Marc left. Vandal or hero?...you decide...LOL

Gary
14-03-2002, 01:49 AM
My netscape won't link to it, Marc. :(

herefishy
14-03-2002, 02:03 AM
CUT THROUGH THE CARP!!!!!!!!!!!!!!!

The refrigerant glide is the difference between the saturation temperatures at a given pressure, of the different elements (refrigerants) in a blend.

The reason it is important to understand is that, when determing superheat, you want to make sure that the element (refrigerant) with the "Highest" saturation temperature is evaporated.

And when determining sub-cooling, you want to make sure that the element (refrigerant) with the "Lowest" saturation temperature is condensed.

In both instances, the corresponding element is different. That's why on the blends you see "Dew" point, and "Bubble" point indicated seperately on "PT" charts!


.....The Fish

Gary
14-03-2002, 02:11 AM
Also use the "bubble point" for off cycle defrost cut-in.

herefishy
14-03-2002, 06:17 AM
Originally posted by Fridgetech

This is a (n over) simplification.[/B]

Indeed, as was my intent.:D

Abe
14-03-2002, 08:05 PM
Im slowly "eschewing the contents of this one, you know what, Im fast becoming an expert on refrigeration matters...........Frank, I was going to attend the seminar last night at Basford Hall in Nottingham. I set off at 5 pm and straight away faced these huge traffic jams. I got so fed up I told the driver ( my partner) to turn around and head back home. I really wanted to meet John Knutton, my old lecturer, ( I dont mean "old, old" only ....ahh it doesnt matter.
John Knutton is one of the most super guys I have had the honour of being a student of.....( have I said that right??? ) Sorry could not meet you last night Frank.
Would have being great if Marc could have come to the seminar, only problem is that I bet he would have HIJACKED the talk, and taught the speakers a thing or two!!!! ( No disrespect to you Marc, Im only acknowleaging your superior knowledge of refrigeration)

Got to pick up the kids from school ( night school) so gotto rush, but will go through the glide stuff later.

frank
14-03-2002, 09:10 PM
Ayuib

Likewise it would have been nice to meet up. Lots of old faces there and some new ones too!

Maybe in the future ?

Are you a member of the EMRA?