This paper investigates experimentally and numerically the effect of maximum density on laminar water pipe. flow solidification. To Visualize the secondary flow patterns and ice morphology experimentally; the water was seeded with a small amount of mercurochrome solution. The numerical analysis employs the large Prandtl number assumption and considers a gradual variation of solid shell in the streamwise direction. The experimental parameters cover the ranges of the dimensionless axial length from 0.008 to 0.32, the inlet water temperature from 5 to 20 degrees C; the wall temperature from -12 to 0 degrees C and the Rayleigh number from 10(4) to 3 x 10(6). The comparison of the measured and calculated heat transfer rates are in good agreement for wide ranges of operating parameters.