# Calculate refrigerant temp inside evaporator based on exit temp and pressure

• bobboviking

#### bobboviking

Hi guys,

I'm stuck on some thermodynamic calculations and I would really appreciate some help!

I'm trying to calculate the refrigerant temperature inside of an evaporator (two-phase lumped parameter model) based on the exit temperature of the evaporator and the pressure.
I've understood that the refrigerant temperature in phase 1 (fluid) may be expressed as
Tr1 = T(Pe) (temperature as a function of evaporator pressure)

and the refrigerant temperature in phase 2 (vapor) may be expressed as
Tr2 = T(Pe,he2) (temperature as a function of evaporator pressure and enthalpy in the second region)

But I'm not quite getting how to do that after measuring the exit temperature and evaporator pressure (I'm assuming constant pressure in the evaporator). I've got a refrigerant table (see attachment) but I'm not sure how to use it.

I would really appreciate if you could point me in the correct direction!

#### Attachments

• Suva407C (2).pdf
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Last edited:

If you know the exit temperature and pressure coming out of the valve, then you know the enthalpy. From the 1st law of thermodynamics, there is no change in the enthalpy of the vapor in passing through the valve. So you know the enthalpy of the vapor in the evaporator and you know that it is saturated. So you go to the saturated tables and look up the temperature and pressure of the refrigerant at which this is the enthalpy.