Vortex- and Wake-Induced Vibrations of a Circular Cylinder Placed in the Proximity of Two Fixed Cylinders

Purpose This study aims to understand the vibratory response of a circular cylinder placed in proximity to other fixed bodies. Methods A circular cylinder model was placed in a circulating water channel and was supported elastically to vibrate in the water. Another two circular cylinders were fixed upstream of the vibrating cylinder. The temporal displacement variations of the vibrating cylinder were measured and processed by a frequency analysis. Results When the inline spacings were small, two amplitude peaks appeared in the reduced velocity range 3.0–13.0. When the inline spacings were large, the amplitude response showed a single peak. Conclusion For small inline spacings, the first peak was attributed to high-amplitude vibrations forced by Karman vortex streets shed from the upstream cylinders. The second peak arose from interactions of the wakes of the upstream cylinder with the vibrating cylinder. When the inline spacing increased, the vortex-induced vibrations resembled those of an isolated cylinder.

Development and Application of Internal Circulating Water-cooled Electromagnetic Separator

For dusty and explosive use environment, especially in coal mines, mostly self-cooled and water-cooled electromagnetic iron separators are used. This article introduces the application of water cooling internal circulation technology to electromagnetic separator equipment for the first time, the advantages and disadvantages of the three cooling methods as well as the development process and application prospects of the internal circulating water-cooled electromagnetic separator are introduced and analyzed respectively.

New bacilli-based probiotic for aquaculture: efficacy study on Macrobrachium rosenbergii

The data on the study of the effectiveness of a new probiotic based on strains B. toyonensis B-13249 and B. pumilus B-13250 when growing shrimps are presented. The experiments were carried out on a private farm in Kazakhstan. The control group of shrimps, which did not receive the probiotic, completed the molting process on the 28th day of the experiment, and the experimental group – 10 days earlier. It was also found that the probiotic has a positive effect on the hydrochemistry of water in recirculating aquaculture system (RAS). The concentration of ammonium (NH3/NH4 +), nitrite (NO2) and nitrate (NO3-) nitrogen in the experimental group did not reach the limit value, in contrast to the control. Based on the obtained results, this probiotic can be recommended for greening aquaculture. The dosage of the probiotic when applied with brine shrimp as feed for shrimp is 1 g/100 g of dry cysts. The dosage of the probiotic when the RAS is added to the water is 5 g/600 l of circulating water once a week.

Design and feasibility verification of regenerative system of electric thermal storage boiler for peak shaving in summer in power plant

During the heating period, the thermal storage electric boiler helps the thermal power units to participate in the deep peak regulation by converting the electric energy into heat energy for heating users, but in the non-heating period, the thermal storage electric boiler can not operate because there is no heat user, as a result, the thermal storage electric boiler is shut down in summer, and can not assist the thermal power unit to participate in the deep peak regulation. Therefore, this paper designs an electric thermal storage boiler regenerative system for peak shaving in summer. In this regenerative system, electric boiler is used to heat circulating water in heating period, and electric boiler is used to heat condensed water in non-heating period, and in the non-heating period, the number of low-pressure heaters can be adjusted according to the load and heat storage capacity of the units, so that the electric boiler can assist the thermal power units to participate in the deep peak regulation throughout the year, taking a 350MW unit with 70MW regenerative electric boiler as an example, the heat exchange capacity is calculated to verify the feasibility of the regenerative system. In this paper, a new method of heating condensate by regenerative electric boiler in non-heating period is proposed to solve the problem that the new energy can not be used and the energy is wasted in summer.

Pembuatan Westafel Otomatis dengan Memanfaatkan Kondensasi AC sebagai Sumber Air

The problem of Coronavirus disease (COVID-19) has not stopped. It was necessary to implement the Covid-19 protocol to avoid spreading, one of which is to wash hand regularly using and circulating water. Based on these reasons, it was still necessary to develop automatic hand washing equipment which is currently a primary need in public places, offices, and educational facilities. This study aims to modify the automatic sink using the Arduino Uno R3 microcontroller as a data processor and Ultrasonic HC-SR04 as a sensor; testing the function of the tool, namely automatic soap and water faucet, hand dryer, piezoelectric buzzer as an air level alarm, by utilizing the results of AC condensation as an water source. The results of this automatic sink modification can meet Covid-19 standards and can be used by all groups, especially schools and offices that have started to be active, so that with this tool it can reduce the spread of Covid-19. In addition, it is that the source of water from the condensation can be used as an alternative to water to save the current increasing use of PDAM water.

Heat Transfer of Turbulent Gaseous Flow in Microtubes with Constant Wall Temperature

Experiments were conducted with nitrogen gas flow in two microtubes with constant wall temperature, made of stainless-steel and copper with diameters of 524 and 537 micrometers, to measure the total temperature at the inlet and outlet and quantitively determine the heat transfer rates. The temperature differences between the inlet and the wall were maintained at 3, 5 and 10 K by circulating water around the inlet and the wall. The stagnation pressures were controlled such that the flow with atmospheric back pressure reached Reynolds numbers as high as 26000. To measure the total temperature, a polystyrene tube with thermally insulated exterior wall containing six plastic baffles, was attached to the outlet. Heat transfer rates were obtained from the gas enthalpy difference by using the pressures and the total temperatures measured at the inlet and outlet. Heat transfer rates were also compared with those obtained from the ideal gas enthalpy using the measured total temperatures and from the Nusselt number for incompressible flow. It was found that the measured total temperature at the microtube outlet was higher than the wall temperature. Also, the heat transfer rates calculated from the total temperature difference were higher than the values obtained from the incompressible flow theory.

Improving the Performance of Solar Heat Collector Using Molten Salts

An individual solar collector and two partly freight cylinders filled with molten salts embedded storage tank were connected to each other and forced circulated water by electric pump to improve the thermal performance of residential solar hot water tank. Multi flow rates of 25, 50 and 70 l/h. used to achieve an appropriate flow rate of circulating water. The calcium nitrate tetra hydrate Ca(NO3)2-4H2O and magnesium nitrate hex hydrate Mg(NO3)2-6H2O were mixed to form cheap binary molten salts base on different weight ratios. These molten salts combined could be used as both sensible heat materials and latent heat storage materials, besides they can directly use as heat transfer fluid due to freezing temperature. Six samples of different mixing ratio of molten salts had tested to assess the thermal analysis of each sample. The result indicated that the mixture 60%Ca(NO3)2+40%Mg(NO3)2 had the best performance for thermal storage tank with melting point of 38°C and the thermal value is 8.7 mW, and thermal stability of molten salts were noticed by DSC 60 SHIMADZSU devise.

MEASURED LOADING RESPONSE OF MODEL MOTION CONTROL STERN TABS

Active trim tabs are commonly used as part of the ride control systems of high-speed craft. This paper investigates the lift characteristics of rectangular stern tabs that are commonly fitted to INCAT wave-piercer catamarans. A test apparatus was developed to enable the testing of a model scale trim tab in a circulating water tunnel in the University of Tasmania hydraulics laboratory. The magnitude and location of the lift force produced by the tab were measured over a range of tab angles and flow velocities. From this the lift coefficient of the tab was calculated and the performance of the tab under varying conditions was analysed. The lift force produced by the tab was shown to increase with velocity and tab angle as expected, with the lift coefficient of the tab increasing linearly with tab angle and remaining relatively constant with increases in flow velocity. The magnitude of the measured lift coefficient was lower than had been previously estimated in shallow water tests and the force was found to act forward of the tab hinge, indicating that much of the lift force generated by the tab is due to the increased pressure on the underside of the hull forward of the tab.

Wastewater treatment from washing agricultural machinery by electroflotation and sorption on activated carbons

Wastewater from car wash stations of agricultural machinery is contaminated with mechanical impurities, oil products, pollution generated by exhaust gases, fertilizers and processing agents used in agriculture, as well as a large amount of surfactants. Purification of this wastewater to the quality required for their reuse allows organizing a circulating water supply scheme, which significantly reduces not only the negative impact on the environment, but also the need for clean tap water. This article describes the results of wastewater treatment from car wash stations of agricultural machinery on an electroflotator and post-treatment by filtration through various filter media, incl. through a sorbent made of modified rice straw - agricultural waste.