| Abstrakt: |
The influence of rolling on the heat transfer in ship tanks filled with liquid has been investigated in the paper for the case of turbulent flow of liquid in the boundary layer. Experimental investigations were carried out in a model tank of dimensions 0.4 x 0.3 x 0.5 m made of organic glass. The tank was subjected to harmonic rolling through angles from 0–10 deg. range at frequencies of 0.3–1.5 Hz. Distilled water and oh were the liquids used. The level of liquid in the tank, position of rotation axis of the tank and thermal conditions in the tank were varied during the investigations. The results obtained have been presented in the form of correlations of nondimensional criterial numbers. Two methods for presenting the results were adopted: 1) global approach where the entire tank was regarded as a single heat exchanging system, 2) decomposition of the system into the vertical and horizontal wall of the tank (ship side and bottom). For the first case, when all the tank walls participated in the heat transfer, oscillations intensified the global transfer by 40–100% compared to that without oscillations. For the vertical wall a slight increase of the Nusselt number, amounting to 5–15% was observed whereas for the horizontal wall an extremely strong influence of oscillations on the heat transfer was ascertained. The Nusselt number increased 5–7 times compared to that for heat transfer associated with a free convection i.e. for the wall at rest. It was found that the parameter (Gr)/(Re)2·(Pr)1/3may serve as an important criterion in studies of mixed convection, allowing to distinguish between the regions of free or forced convection predominance. |
