低質油, COMなどの超高粘度油のタンク加熱における自然対流熱伝達

概要

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Natural convection heat transfer is investigated for high viscosity fluids including a Coal Oil Mixture [COM], a low grade heavy fuel oil and a heavy crude oil to clarify the problems on heating of these kind of fluids storaged in ships tanks. In the investigation, a heating tube in a tank is assumed to be a single horizontal heated cylinder embedded in the fluid. A model test and a theoretical calculation were carried out to predict both the heat transfer coefficient of heating tubes and the temperature distribution in a tank. A coal oil mixture indicates high viscosity below the normal temperature range. Natural convection flow is weak and the heat transfer rate from the cylinder to a COM is much lower, compared with the case of a conventional heavy fuel oil. A formula is given to calculate the heat transfer coefficients for this case. A low grade fuel indicates solid state below the temperature about 40°C. Melting natural convection phenomenon is observed when the oil heated by a heated cylinder. The heat transfer coefficients are also given for this case. A heavy crude oil includes low temperature boiling substances. Subcool boiling phenomenon is observed when the oil heated by a horizontal cylinder, then the heat transfer coefficient around the cylinder increases much more than that of natural convection cases.