R404A Pressure-Enthalpy Diagram Properties VS Pressure-Temp Chart Properties

[milen_d]

Hey guys, I need some clarification between these 2 data sets.

I was studying a refrigeration system that uses R404A. I graphed the refrigeration cycle on a P-H Diagram to get a better idea of what was going on. After that, i looked up a Pressure-Temp Chart for R404 and noticed things were not adding up. On the PH Diagram R404 is at 0*F at a pressure of about 50psia, however according the Pressure-Temp Chart for the same refrigerant, @ 0*F P=33.5 psig. Am i missing something here?

Thanks in advance!

[Brian_UK]

Only missing about 2.5 psi so not too bad.

[milen_d]

haha actually it turns out it was a little more than 2.5, more like 14.7 psi. I think i have found the discrepancy and it all boiled down to units. The Pressure-Temp table is in psig and the P-H graph is in psia.

[Brian_UK]

haha actually it turns out it was a little more than 2.5, more like 14.7 psi. I think i have found the discrepancy and it all boiled down to units. The Pressure-Temp table is in psig and the P-H graph is in psia.Exactly hence my answer.

[Rob White]

.

:)

pH charts are always in absolute.
So they will always be 1 atmosphere
higher than gauge.

1 atmosphere = 1 bar = 14.7 psi

Rob

.

[milen_d]

Cool thanks for the help guys! Just one more example of why units are our friends :p!