Effect on design evaporator by using R507 instead of R22

[lappee]

Akzo Nobel Engineering is at this moment working on an extension project. In this project ice-machines occur, which freeze sulphuric acid. The existing ice-machines are connected to cooling machines, which use R22 as refrigerant. In the Netherlands it is since January 2001 forbidden to use R22 in new equipment. Therefore we looked for another type of ***** and from a rough study we have chosen R507 as the best alternative.
The ice-machine (= the evaporator) is custom-made and is a result of 15 years experience, so we don’t want to redesign this.
I wonder what will be the result of using R507 on the behavior of the ice-machine (due to different velocities for example). Or in general: what is the result on the design of an evaporator when you compare the use of R22 with R507?

Who can help me?

[Prof Sporlan]

I wonder what will be the result of using R507 on the behavior of the ice-machine (due to different velocities for example).

Using refrigerant manufacturer's thermodynamic data, and figuring a 0°F evaporator and 100°F liquid entering the expansion device as representative of an ice machine, to achieve one ton refrigeration, one would need to flow 3.07 lb/min R-22, and 4.67 lb/min R-507. The two phase flow densities for each refrigerant can be assumed to be roughly the same, one then concludes refrigerant velocity and pressure drop across a given evaporator to be greater for R-507.

Certainly, the expansion device will need to be changed when going from R-22 to R-507. And the compressor will likely have to be changed. The effect of this change on evaporator performance, however, would be difficult to determine empirically, even if one had a decent mathematical model for the evaporator coil.

If you were not hesitant about using a refrigerant with a temperature glide, which may pose a problem for an ice machine, ICI's R-407A has thermodynamic properties which are quite similar to R-22.

[Derek]

I'd check your pressure relationships especially with regard to instrumentation.

You will probably be running with mineral oil so a change to synthetic is almost essential. Material compatability seals etc best source of leaks.

I'd have a word with Isceon about R417A Isceon 59 by-pass the sales people and see if they will try your load conditions on their test rig or share their test data (sorry Neil).

You could look at R410A (azeotropic blend) but the pressure really ramps up.

If you have contraflow heat exchangers then any zeotropic blends or close azeotropes could give glide problems. Some one will say if I got that round the wrong way. A chemist I aint.

Hydrocarbons out of the question?