R407c

[binman54]

We have been using R407c lately as a replacement for
R22. Typically we are cooling water so temperatures are above 5C and we use direct expansion evaporators made by a reputable firm. I understand glide and now it is more important in low pressure drop DX chiller than higher pressure drop brazed plate. Our component suppliers are good with R407c except the evaporator manufacturer. He is asking if we what the vessels sized on bubble point, dewpoint or an average. I would think that the average properties should be used.
Does anyone know why he would be concerned with this?
Has anyone else been asked this question?

Binman54

[Andy]

We have been using R407c lately as a replacement for
R22. Typically we are cooling water so temperatures are above 5C and we use direct expansion evaporators made by a reputable firm. I understand glide and now it is more important in low pressure drop DX chiller than higher pressure drop brazed plate. Our component suppliers are good with R407c except the evaporator manufacturer. He is asking if we what the vessels sized on bubble point, dewpoint or an average. I would think that the average properties should be used.
Does anyone know why he would be concerned with this?
Has anyone else been asked this question?

Binman54

Until better advised I would say select on bubble point and set up the system using dew point

Any other views on this

Kind Regards Andy

[Pooh]

Surely the bubble point should be used when sizing evaporators as this is the lowest temperature which will give you the evaporating temp you are aiming for as I understand it. If you take an average your actual evaporating temperature will be lower than required. If you are setting up the TEV superheat you will need to set up from the Dew point.

Ian

[binman54]

Thanks for the response.
We do use dew point to set up the TX valves.

Binman54