Matching simulation results with experimental measurements for a simple heat transfer and laminar flow problem

Hi,

I am trying to model a simple heat transfer problem with laminar flow. My 3-D model has a silicon block with 1W power source at the bottom. At the top of the Si-block, liquid is flowing at a certain speed. I simulated this problem in COMSOL and here are my observations:

surface-average temperature at the top of the Si-block: T1 = 0.8731 K (w.r.t fluid inlet Temp)
volume-average temperature of the fluid domain: T2 = 0.0097 K (w.r.t fluid inlet Temp)
h = P/(A*dT), where dT = T1-T2 = 0.8634 K and A = 14e-3*12e-3 m^2 and P=1W

The heat transfer coefficient obtained from the above calculation is about 6894 W/m^2.K.

However, when we perform the real experiment, and compute the heat transfer coefficient, we obtain an 'h' value of almost 10 times higher than what we get in COMSOL. I know the experimental details are not provided here, but I am pretty confident that my flow-rate, temperature, etc. measurements are quite accurate. If needed, I could provide more details about my setup.

Any general comments to match simulation results with experimental results are appreciated. I am attaching my model (build using version 4.2.0.150) herewith.

Thanks,
Kapil