Effects of Surge Tank Geometry on the Water Hammer Phenomenon: Numerical Investigation

A surge tank, as one of the most common control facilities, is applied to control head pressure level in long pressurized pipelines during the water hammer occurrence. The cost-effective operation of surge tank is highly affected by its characteristics (i.e., surge tank diameter and inlet diameter of surge tank) and can effectively reduce the repercussion of water hammer. This investigation utilized the method of characteristics (MOC) in order to simulate the behavior of transient flow at surge tank upstream and head pressure fluctuations regime for hydraulic system of a hydropower dam. The various types of boundary conditions (i.e., sure tank, reservoir, branch connection of three pipes, series pipes, and downstream valve) were applied to numerically investigate the simultaneous effects of the surge tank properties. In this way, all the simulations of water hammer equations were conducted for nine various combinations of surge tank diameter (D) and inlet diameter of surge tank (d). Results of this study indicated that, for the surge tank design with D=6m and d=3.4m, head pressure fluctuations reached minimum level in the large section of pipeline here is surge tank upstream. Additionally, occurrence of water hammer phenomenon was probable at the initial section of pipeline.

COMPARISON STUDY OF VERTICAL CYLINDER TANK DIAMETER MEASUREMENT BETWEEN STRAPPING AND OPTICAL METHOD

Vertical Cylinder Tank is used as a storage area or as a measuring tool. Liquids are used in the form of Fuel oil, Liquid Natural Gas, vegetable liquids, and other chemical liquids. The tank calibration results are in the form of a volume per height table that is used as a reference by Automatic Tank Gauging. There are two tank calibration methods, namely: the strapping method and the optical method. The process of measuring the inside or outside diameter of the tank becomes very important in the tank calibration process—the measurement of tank diameter by the strapping method using steel meters manually. At the same time, the optical method uses theodolite or total station. For tank diameters ≤ 5 m, the strapping method has smaller diameter measurement results with a difference of 0.7% compared to the optical method. In further research, a prototype can be developed that can accelerate the calibration process using the strapping method (for example, a vertical track measuring robot) or a low-cost prototype theodolite

Investigating Mass Transfer Phenomena in Batch Solvent Extraction of Rice Bran Oil

In this study, we will point out the correlation of critical parameters in designing scale-up of process equipment for commercial rice bran oil extraction with different types of rice paddy, solvent, and physicochemical condition. Advantageously, this research was also intended to enhance the discoveries of novel sustainable production method for resilient agro-based food, energy, and chemical industries. In our experiment, the extraction of rice bran oil was organised in a batch agitated vessel and showed a profile of first order system. The most important factors which profoundly contributed towards the yield of rice bran oil from Saigon I and PadiBesar variety are temperature (T), impeller speed (N), ratio of bran to solvent (s/L), and ratio of impeller’s height-off bottom to tank diameter (h/d). For the mass transfer constant and the rate of extraction as consequence, factors that significantly influenced the correlation were temperature (T), impeller speed (N), ratio of impeller diameter to tank diameter (d/D), and ratio of impeller’s height-off bottom to tank diameter (h/d). For the dimensionless yield, generalised equation is provided with coefficient of determination 0.95, while that of the mass transfer equals to 0.63, reflecting the yield correlation to be more accurate in predicting further experimental results. These correlations are furthermore unique for different rice varieties, of which in this case belongs to Saigon I. Application for other rice species is relevant as by inserting additional correction factor which also exemplified in this research for PadiBesar. Keywords: rice bran oil; batch extraction; storage time; mass transfer, rate, yield

A Recipe for Optimum Mixing of Polymer Drag Reducers

Preparation of large-scale homogeneous solutions of drag reducing polymers requires an appropriate mixing procedure to ensure full disentanglement of the polymer chains without chain scission due to over-mixing. The latter is known as mechanical degradation and reduces the performance of drag reducing polymers. The dominant large-scale mixing parameters including time, impeller type, impeller speed, and impeller-to-tank diameter ratio are investigated to obtain a recipe for maximum mixing with minimum polymer degradation. Three water-based solutions of 100 ppm Superfloc A-110 (flexible structure), Magnafloc 5250 (flexible structure), and Xanthan Gum (XG) (rigid structure) are considered. The performance of the mixing parameters for each polymer is evaluated based on the solution viscosity in comparison with the highest viscosity (i.e., optimum mixing) obtained by 2 h of low-shear mixing of a small-scale polymer solution using a magnetic stirrer. The results demonstrate that optimum large-scale mixing is obtained at mean and maximum shear rates of ∼17 s−1 and ∼930 s−1, respectively, after 2–2.5 h of mixing for each of the polymers. This shear rate is obtained here using a three-blade marine impeller operating at 75 rpm and at impeller-to-tank diameter ratio of 0.5. The resulting polymer solution has the highest viscosity, which is an indication of minimal degradation while achieving complete mixing. It is also confirmed that chemical degradation due to contact with a stainless steel impeller is negligible.

Thermal Stratification in Spherical Tanks

Spherical tanks have the potential for cost reduction in sensible thermal energy storage (TES) systems, by using less tank building material and insulation. The current CFD study compares the Thermal Efficiency (TE) of a thermocline storage system in a spherical tank to a cylindrical tank of the same volume. A parametric study is then performed on a spherical tank during the discharge process to determine the flow parameters that govern the thermocline formation and entrainment. The following parameters are used: tank diameter to inlet diameter ratio D/d = 10, inlet velocity (0.02–0.1 m/s), and ΔT (10–70° C), leading to an inlet Froude number (0.4–3), inlet Reynolds number (500–7500), and tank Richardson number (2–100). The results show a significant correlation between the inlet Reynolds and inlet Froude numbers, and the tank TE, in addition to a weak correlation between the tank Richardson number, based on the tank diameter, and the tank TE. The parametric study also shows a maximum tank TE at a Froude number equal to 0.5, and a proportional decrease of TE as the Reynolds number increases.

New Correlations of Volumetric Liquid-Phase Mass Transfer Coefficients in Gas-Inducing Agitated Tank Reactors

Volumetric liquid-phase mass transfer coefficient (kLa) is one of the most important parameters for the evaluation of the performance of a gas-inducing agitated tank (GIAT). In this paper, two equations in terms of power input per unit liquid volume (P/VL) and relative gas dispersion parameter (NI/Ncd), respectively, are developed according to data in literature. They can correlate existing kLa values within ±20% of measured ones for bladed impellers with different impeller submergence to tank diameter ratios in the range of 0.5 -1.23. In order to validate these equations, the liquid phase mass transfer coefficients in a continuous GIAT equipped with a 4-blade straight impeller were measured by removal of oxygen from water. It was found that the equation in P/VL criterion could correlate kLa values within ±12% of the experimental data, and the equation in NI/Ncd criterion could correlate kLa values within ±15.6% with an exception of 26.8% for NI = 16.7 Hz.