[sargordan]

hi
i know this is kind of crazy , but i have problem in modeling nanofluid in rectangular microchannel with single phase model. i use vahja and das model,and maxwel model , etc and by using all these model i still don't have enhancement in heat transfer!!!
my boundary condition is constant temperature at walls and Re=400 and temperature of inlet flow is 300 and Twall=340 .
i use integral of wall flux( total heat transfer) for all walls. and compare them for different nanoparticle volume fraction.
when i increase Volume fraction of nanofluid from 0% to 4% , total heat transer of all four walls is decreasing !!!!!!
the following is my calculation for nanofluid properties. i really need help
. i have no idea why i can't get the reasonable result!i appreciate if you help me.

fluid Rho Cp K mu
water 992.22 4178.5 0.631 0.0006532
particle 3970 765 40
0.01 1021.9978 4045.900938 0.649272499 0.0007602
0.025 1066.6645 3860.883847 0.677293572 0.001023323
0.04 1111.3312 3690.739196 0.706149661 0.001581281