[yamifm0f]

I am using a simple example to see the temperature behaviour in starccm+

my geometry is pipe 1m longe with a a diameter on 0.016 m
the boundary conditions are
**velocity inlet ; velocity is about 0.039 m/s (calculated using field function 0.008 mass flow) and temperature 298.15 K.
**pressure outlet; pressure is 101325.0 Pa (atmosphere pressure) and temperature is also 298.15 K.

In physics
I use single phase liquid water with IAPWS-IF97
I use segregated flow solver and segregated Fluid temperature
gravity is in the flow direction (outlet)
implicit unsteady

run time is for 50 s
with a time step of 0.1
40 Iterations

Temperature values are not as expected using both laminar model and turbulent realizable k-e two-lay (all y+ wall treatment)

based on a simple analytical solution the outlet surface average temperature should be 39.9 C
the analytical solution is (Tout-Tin = (q*L)/(cp*m))
Tin is 25 C, q is 500 w, cp is 4180, m is 0.008, and l is 1m
Re starts at 715 at inlet and ends at around 980 at outlet

This is Laminar case but with laminer as you can see in the attached file the temperature value at outlet increases to about 38.5 C and then falls to 36.4 C
with a jump at the temperature values in the first part of the pipe. the temperature jump is then decrease and becomes linear as it should from the start (the jump is unknown to me)

using turbulent realizable k-e two-lay (all y+ wall treatment) I get better temperature values at outlet but still not the hoped ones (I get 40.7 C). I also get a jump at the temperature values in the first part of the pipe. the temperature jump is then decrease and becomes linear as it should from the start (the jump is unknown to me)

I have tried decreasing the time step to 0.01 and 0.001 but no change and also have tried different mesh but still nothing.

Can you please help me with this?