Double Precision Solver
 

Its a convective heat transfer problem. I have water flowing through a channel of dimensions 0.2x0.1x12.5mm, with constant heat flux applied on the walls of channel. The inlet and outlet faces are 0.2x0.1mm. Should i use double precision solver ?

It depends on other details of the setup than you gave.

Is there a large difference between the extent of the smallest and the biggest cell in your grid, for example because you are resolving the boundary layer with Y+ < 1?

Or is there any need to account for very small values of a variable?

If in doubt, go for double precision. It is just the amount of memory usage that will be doubled, the computational time will increase only slightly.

thanks flotus1
The cells are of uniform size.
I was worried because channel walls are of silicon with thermal conductivity of 148W/m.K, while that of water thermal conductivity is 0.6W/m.K (ratio of thermal conductivities is high). Also, the cross section of channel is much smaller compared to its length.