refrigeration of a wagon: effect of the number of passengers

Hi,

I am modeling the refrigeration system of a wagon. One of the parameters that I want to evaluate is the "number of passengers", for that end I add a knob in the subsystem 'Control panel' in order to control it while the simulation is running.

However, the simulation seems to work well just until 5 passengers, but when I use values higher than it, the temperature of the wagon never decrease when the refrigeration system is working (i.e., with the compressor in mode 'on').

Do you have some idea which parameter(s) of some block(s) I should change in order to obatin a good simulation for higher number of passengers? I have tried the number of tubes of the evaporator and condenser and the mass flow rate in the compressor.

Thanks in advance for your kind attention and reply.

Regards,

P.S.: I am attaching the simulink model 'Cooling_system_new.slx' and the parameters data 'Cooling_parameters_new.m'.