So, I've recently carried out an experiment to find the volumetric efficiency of a singular reciprocating compressor. During the experiment, there are sub questions asking you to find the value of n and then whether the process is isothermal, poly tropic or adiabatic. Well, n is found to be very close to 1 so the process is isothermal. However, the temperature in the receiver (where the compressed gas is stored) does change by about 3K from t= 0s until t = 180s (when the compressor switches off). Why is that? And, is this therefore not an isothermal process? Or, am I just not properly understanding what's happening? Thanks.