bubble point

[rix870]

does that mean the temperature at which a vapor is saturated liquid?

[basser]

I'll try this one. Yes to answer your question. But.....

Think of 134a, this is a single component refrigerant (not a mixture). Here the bubble point would be the saturation point and also the dew point.

Now think of a blend, let's say 401A. This is a blend a three different refrigerants to make one. Each of these three refrigerants in this blend have slightly different bubble (boiling) points and dew points. Look at 36 psig and the bubble point is 30°. That means of the three refrigerants in this mixture the one with the lowest boiling point will bubble at 30°. Also look at 36psig and the dew point is 40°. This means the one with the highest boiling point bubbles at 40° (which is called dew point). So at 36psig, saturation would be present between 30° and 40°. This has to do with the different boiling points of the individual refrigerants of this blend. The difference between 30° and 40° is 10°, this is called glide.

Hope this helps some without being to confusing.

[jayguy]

i think basser said it real nice.

bubble point is the temp/pressure where all components are pure liquid and any change in pressure down (or temp up) would cause a bubble. dew point is the opposite where all components are pure vapor and any change in pressure up (or temp down) would cause a dew drop to form. since we only care to measure from the pure liquid saturation point or the pure vapor saturation point, these are the names that are used.

the glide is also not consistant across all temps/pressures for the same refrigerant. for instance, R402a (MP80) at 0 psig has a temp glide of 3.80F. at 200 psig it has a temp glide of 1.88F. i have seen some of the "drop in" refrigerants have a temp glide of over 10F! this would mean that some components would have 10F superheat while others would have saturation...talk about compressor cooling starvation!