Why does temperature drop near outlet when DeletionPatch is used?

[PrikMushi]

Hi I am working on a case where I define gas entering a hollow cylinder through some orifices. At the inlet mass flow rate is defined with 300 K temperature, and the walls are at 500 K temperature with diffuse relection condition. For the outlet I only use deletion patch. When I view the temperature results it shows that at exit the gas temperature is 300 K, which is unphysical considering collisions with 500 K walls before reaching outlet. Can someone explain me what could be an issue here?

I have also tried absorptionpatch for outlet and here the temperature is correct to 500 K at outlet, but velocity is way lower than maxwellian velocity to make any sense.

Any advice or suggestions?