Parametric study on the thermal gradient of a small stratified domestic oil storage tank
A simplified one dimensional model for a small stratified domestic oil storage tank is used for a parametric study on the thermal gradient in the storage tank. The model is validated with experimental results and reasonably good agreement between experiment and simulation is obtained. The effects of measurable and physically adjustable parameters of the average charging flow-rate, the inlet charging temperature and the heat loss factor on the thermal gradient are investigated with the model.
Effects of a porous manifold on thermal stratification in a liquid storage tank
Abstract A numerical model for a porous manifold has been developed to study its effects on thermal stratification in a typical storage tank. The tank considered has a capacity of 300 l and a height-to-diameter ratio of 2. The numerical model employs a transient stream function-vorticity formulation to predict the development of flow and temperature fields in a charging process. The Reynolds number of the inlet flow is fixed at 200 and a wide range of the Richardson number (0.01≤Ri≤100) is considered. Other parameters considered include the Biot number (i.e. heat loss from the tank), the Darcy number (permeability of the porous manifold), the location of baffle, and the thickness of the porous tube. The results show that all these factors should be taken into account for a better design of a thermal storage tank. In addition, the results provide an envelope for these design parameters.
Turbulent boundary layer wall‐pressure fluctuations downstream from an abrupt change in surface roughness
Spectra of wall‐pressure fluctuations beneath a turbulent boundary layer have been investigated immediately downstream from an abrupt change in surface roughness, from slightly rough to very rough. Over the measurable frequency band (400 Hz to 7 kHz), the spectra in the first 150 mm scale on wall variables. This indicates that the motions responsible for the pressure fluctuations measured in this region are very close to the wall. Farther downstream this scaling procedure breaks down. It is suggested that the initially thin internal layer behaves independently of the flow external to it until it has grown appreciably and only then interacts with the outer boundary layer. It was found that, for all frequencies measured, the dimensional spectral level decreases initially then rises to a maximum at 250 mm from the roughness change before decreasing once more. The position of the maximum is close to where the internal layer ceases to have a distinct edge.