determining refirgerant temperature

[kellogs]

For a given outside temperature range, refrigerant type and weight, pipe length between inside and outside units, and (air conditioner) compressor power, are there any formulas for determining refrigerant temperature, in heating mode, as it enters the heat exchanger at the inside unit ? What else do I need to know ? Thanks!

 

[EnergyProfessional]

is this homework?

Start with this.

 

[nuuvox000]

My first thought would be to start with a Pressure vs Enthalpy curve for the refrigerant in question and then go from there. At that point it's heat transfer but I'm not aware of any all-encompassing equation for this. It's probably manufacturer specific with how much heat comes for the compressor.

 

[kellogs]

Hello again,

I could not figure any way to compute the numbers with the date I got, but, after some research online, I now think that the refrigerant temperature, in heating mode, ought to be about 50 deg C (122 deg F) when outside ambient temperatures are at 7 deg C (45 deg F)

Just took some measurements with a K-thermocouple device I have put together.
Outside ambient temp: 15 C (59 F)
Probe temp (photo 1): 50 C (122 F)
Probe temp (photo 2): 60 C (140 F)

Should I surmise that the refrigerant temperature as it enters the indoor unit will be a bit over 60 C (140 F) in this case ?

 

[ProcessHVAC]

Hopefully this is not homework, but here is a hint: knowing the refrigerant type, find the compressors working pressures. The rest should be easy if you know your thermodynamics.

 

[kellogs]

Well, that's the main issue i guess, don't know the working pressure. Someone in my area suggested that it ought to be in the 29.5 - 30 bar range for the usual AC units around here having my specs, which corresponds to about 50 degrees C -

http://www.csgnetwork.com/r410apresstempconv.html

P.S. why do you guys keep mentioning "homework", is this forum anti-homework ? It is not, btw, I am past homework age.

 

[LittleInch]

"I could not figure any way to compute the numbers with the date I got, "

That's because you didn't know pressure or temperature of the chiller section.

Yes we're anti homework type questions and the style of the question was a bit suspicious.

But glad you've found the answer by some practical measurement.

Differential temp of 45 C sounds about right. Most A/C system struggle to reject heat once you go past about 50C air temp to deliver 10C cool air so the reverse looks right as well.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[kellogs]

Got it!

And thanks for the confirmation as well