Mass flow rate vs temperature.

Hi, I used Comsol to model a really simple problem. A pipe with 50mm diameter and 25m long with an inlet temperature of 20°C and 0.5kg/s of mass flow rate. Also, the pipe´s wall temperature was 150°C. I used a parametric sweep to increase the mass flow rate with a step of 0.15 until 2kg/s. The fluid was engine oil and in laminar flow.

When I made the plot of temperature vs mass flow rate, it behaves as a parable in which at a point near 1.4 kg/s the temperature begins to increase instead of decrease as it´s expected.

Do you know what is the explanation for this?

Thanks