I am trying to explain (or even better to find a relationship describing) the gas temperature increase in the scraper-trap of a natural gas pipeline system, when it is filled with gas (from 0 bar to 50 bar) wich is supllied from a 50 bar underground (at steady temperature of aprox. 8 deg C) pipeline.

At the end of the filling proccess, the wall of the above-ground scraper-trap was aprox 35 deg C (aprox. 40 on the upper section of the diameter, and aprox. 20 on the lower section of the diameter)

Length of scraper-trap : 20 m
Diameter of scraper-trap : aprox. 1 m
Ambient air temperature : 6