superheat

[lana]

hello guys i am new in this field of refrigeration . is there any formula to calcute asuperheat in low pressure. i know is to do with the expansion valve . do u need any special tools to mesure superheat . thank u guys.

Hi there,

Superheat is one of the basic definition you need in this field.
The simple explanation is this : When a liquid is boiling in a constant temperature (boiling point), say 5°C - and after a while all the liquid converts to gas and the gas temperature reaches to a higher temperature, say 12°C, then superheat is 12-5=7°C. In other word , the gas is heated 7°C more than the boiling temperature.

In the evaporator the same happens.

I suggest you study from basic principles until you can measure the superheat.
It is not difficult but you have to know the pressure-temperature relationship first.

Good luck

[marco blanco]

thank you for effort lana.
i would to know how to work out superheat on the system .. let say system is running with r404 . suction pessure is about 3 bar. is there any calculation needed

[lana]

Hi Marco,
To measure the superheat do the followings:
1- Take the suction pressure.
2- Go to refrigerant pressure and temperature chart and find the evaporating temperature (Te). Be careful about the pressure readings. The pressure you read from the gauge is 'gauge pressure". if your chart is absolute pressure then you have to convert the reading.
3- With a thermometer measure the suction line temperature neat the TEV bulb. (T2)
4- The superheat is T2-Te.

If you have Zeotropic refrigerant then there is a glide. For R404A the glide is 0.5°C so there isn't so much difference.
For other Zeotropic there are two temperatures for each pressure. You take the DEW POINT temperature as (Te).

Hope this helps.
Cheers