Temperature measurement of compressed air

[freefallingbody]

I am trying to estimate the temperature of compressed air at 7 bar g., stored in a receiver of 1 cubic metre volume. I have measured the surface temperature of the receiver by using a surface temperature probe and thermocouple. The probe was properly covered using insulation during the measurement.

I do not have facility to directly insert a probe into the receiver. I also don't have thermowells on the receiver.

How can I derive a relationship between the receiver surface temperature and the actual air temperature inside? (Assuming there is no airflow into/from the receiver during the measurement).

 

[TD2K]

If you've taken the temperature measurement up against the vessel wall, under the insulation and allowing sufficient time for the thermocouple to reach equilibrium, that is essentially the air temperature in the drum.

Unless the air is high temperature or there is something unusual about your setup, I would not worry about the temperature drop across the inside air film.