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 ship's 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.

View full abstract

A method of one dimensional analyses on unsteady gas flow in exhaust and scavenging manifold is developed, in which specific heat ratio is a function of gas temperature and gas mixture. The two-step Lax-Wendroff' s method is used at inner points in pipe and the characteristic method of semi-ideal gas is applied to boundary condition of pipe.
The simulation by this method conserves energy flow integrated over one engine cycle better than conventional simulation assuming that specific heat ratio is constant, while there is practically no difference between the predicted pressure waves in pipes by two methods.

View full abstract

Experiments and attempts for practical use of the fluidized bed combustion, which has many advantages such as fuel flexibility, improved heat transfer, less maintenance cost, environmentally clean combustion, etc., are being world-widely carried out.
In the land service field, a fluidized bed combustion boiler is already in the process of being put to practical use, but in the marine service field, there is nothing but a few papers on a fundamental study and application of this boiler to a marine propulsion plant.
We made an experimental research of fluidized bed combustion for its marine use to cope with the recent trend to using low quality fuels such as coal and heavier fuel oil.
In the experiments, we used a 500 mm^_??_ vertical furnace and a 500 mm^_??_ inclined furnace adjustable in angles (0°, 10°, 15°and 22.5°) as test furnace, coal from Australia for test fuel, and silica sand for bed material, and we found relation for marine use between combustion factors (bed temperature, heat release, combustion air ratio, bed height, free board height in furnace) and combustion efficiency, change of bed temperature after coal feed cut, relation between ash recycle ratio and combustion efficiency, relation between furnace inclined angle and combustion efficiency, and measures to prevent unfluidized bed caused by inclined furnace.
On the basis of this research, we developed a marine fluidized bed combustion boiler and a marine propulsion plant, “Kawasaki-UNI Plant”, with the marine fluidized bed combustion boiler and a repeat steam turbine.
We will report about these developments on other papers.

View full abstract

The hot-water flash power generating plant recently developed by Mitsubishi Heavy Industries for diesel ship application far exceeds the conventional economizer-steam power generating plant in terms of waste heat recovery rate, and hence can adequately do its job even with the limited waste heat energy available from the lean exhaust of the increasingly fuel-efficient marine diesel engines which are also smaller for the ship size than hitherto and which are frequently run at part loads for slow steaming. Thus, it is believed that the hot-water flash power generating plant will prove especially worthwhile for ships powered by diesel engines 12, 000 PS and above in output, all these ships now finding it almost practically impossible to employ the conventional economizer-steam power plant.
Mitsubishi's hot-water flash power generating plant comes in two types; MARK-N1 and MARK-N2. The former recovers the engine exhaust gas energy all with pressurized water in the exhaust-gas economizer and produces steam by flashing pressurized hot water to drive its generator turbine: The latter, though also equipped with the economizer, recovers high-temperature engine exhaust gas energy as steam and heat of low-temperature exhaust gas and scavenging air with pressurized water to drive the generator turbine with both superheated steam and flash steam.

View full abstract