Variability With Depth of Some Physico-Chemical and Biological Parameters of Atlantic Ocean Water in Part of the Coastal Area of Nigeria

Results of in-situ measurements of some physico-chemical and biological parameters (temperature, electrical conductivity, density, dissolved oxygen, turbidity, pH, and salinity) of Atlantic Ocean water at various depths are presented. It is shown that temperature and dissolved oxygen vary significantly with depth, while variations of the other parameters with depth are minimal. Temperature, dissolved oxygen, electrical conductivity, density, pH, and salinity vary in the ranges: 3.6\ub0C\u201328.32\ub0C, 1.8mg/l\u20138.4mg/l, 3 . 29 \u3bcs/cm \u2013 4 .71 \u3bcs/cm, 1017 .34 kg//m3 \u20131036 .61 kg//m3 , 7.1\u20138.4, and 34.52ppt \u201335.8ppt respectively. Turbidity is less than 1.0NTU, indicating that the water is clear and transparent

How ions distribute in a drying porous medium: A simple model

Salt crystallization at surfaces is an important problem for buildings and monuments. We do not consider the formation of salt crystals as such, but focus on transport properties of ions in a drying porous medium. We deal with the first phase of the drying process, where the water is still uniformly distributed throughout the medium. An approximate model is presented, which accounts for both convection and diffusion. It is shown that the key parameter is the Peclet number at the evaporating surface, PehL/D, where h, L, , and D are the drying rate, sample size, porosity, and diffusion constant, respectively. When Pe1 (diffusion dominates over convection) the ions remain uniformly distributed throughout the system. Strong accumulation at the evaporating surface occurs for Pe1 (convection dominates over diffusion). Crossover behavior is found for Pe1. Therefore, it is likely that the first crystals will be formed both in the bulk and at the interfaces of the material when Pe1. For high values of Pe the density peak at the evaporating surface will reach the saturation concentration long before it is reached in the bulk of the material. As a consequence, the salt starts to crystallize at the interfaces

Performance evaluation of heat-transfer co-efficients for constant-rate period of drying during tape casting

Ceramic suspensions for tape casting are known to dry in two stages; the first stage is called the constant-rate period, and the second stage is the falling-rate period. The drying rate in the constant-rate period can be characterized by mass-transfer coefficient or heat-transfer coefficient. A general model is presented that predicts the heat-transfer coefficient at a given temperature and different ambient humidity in the constant-rate period. An average value of the heat-transfer coefficient for a temperature range from 298K to 328K, and a range of relative humidity from 40% to 90%, during drying of water-based alumina suspension for tape casting is calculated using this model to be. A model developed for the water-based suspension is also presented that predicts the heat-transfer coefficient as a function of temperature. Predicted drying rates based on heat-transfer coefficients obtained from the two models are compared with experimental data and good agreement is obtained. The average value of the coefficient for the suspension is shown to be inadequate. Keywords: Modelling; Drying; Tape casting; Suspension; Ceramics; Heattransfer CoefficientJournal of Modeling, Design and Management of Engineering Systems, Vol. 3 (1) 2005: pp. 25-3

Variability With Depth of Some Physico-Chemical and Biological Parameters of Atlantic Ocean Water in Part of the Coastal Area of Nigeria

Results of in-situ measurements of some physico-chemical and biological parameters (temperature, electrical conductivity, density, dissolved oxygen, turbidity, pH, and salinity) of Atlantic Ocean water at various depths are presented. It is shown that temperature and dissolved oxygen vary significantly with depth, while variations of the other parameters with depth are minimal. Temperature, dissolved oxygen, electrical conductivity, density, pH, and salinity vary in the ranges: 3.6°C–28.32°C, 1.8mg/l–8.4mg/l, 3 . 29 μs/cm – 4 .71 μs/cm, 1017 .34 kg//m3 –1036 .61 kg//m3 , 7.1–8.4, and 34.52ppt –35.8ppt respectively. Turbidity is less than 1.0NTU, indicating that the water is clear and transparent

Six-lump kinetic modelling of adiabatic plug-flow riserreactor in an industrial FCC unit

A six-lump kinetic model is presented that describes the catalytic cracking reactions taking place in an industrial riser-reactor. In this scheme, C3’s (propane and propylene gases) and C4’s (butane and butylenes gases) components of liquefied petroleum gas are predicted independently, as well as gasoline, dry gas, and coke. The riser-reactor is modelled as a plug-flow reactor operating adiabatically. Model-predicted yields of gasoline, C3’s, C4’s, fuel gas, coke, and riser-reactor outlet-temperature, agree reasonably well with plant data obtained from an operating industrial riser-reactor. Sensitivity analysis carried out on the riser-reactor indicates that inlet-temperature of gas-oil (feed), catalystto-gas oil ratio, and mass flowrate of gas-oil, are important process variables that affect the operation of the riser-reactor. It is shown that the minimum catalyst-to-gas oil ratio required for maximum conversion of gas-oil is 3. Simulation results using catalyst-to-gas oil ratio of 6.5, inlettemperature of gas-oil of 505K, and mass flowrate of gas-oil of 67.8 kg/s, give yields of 45.81 % gasoline, 6.32 % C3’s, 10.68 % C4’s, 5.42 % fuel gas, 5.11 % coke, and 26.66 % of unconverted gas-oil