Advanced Materials Research Vols. 875-877

Abstract: This study discussed the feasibility of developing a system to circulate the heat loss from the coil and iron core of the power transformer equipped for buildings during power supply to the heat recovery unit. This study affixed a copper tube into the transformer insulating oil, allowing the water to circulate at normal temperature in the coil tube, and absorb the heat energy generated by the transformer coil and iron core. The heat energy was then recovered and stored. A low tension power transformer (7.5 KV) was used in the experiment. The operation was carried out in transforming power supply mode to seek for the most suitable recovery unit for various occasions. The test results showed that if the hot water recovery efficiency is 50%, in the course of producing hot water, the mean temperature of 17.5 L normal temperature water can be increased from 20°C to 50°C, thus producing 12.5 kJ heat only spends about 34 min. The results proved that the recovery unit for the heat from the power transformer can benefit from heating, prolong the transformer's lifetime, increase the power supply efficiency, and reduce the air conditioning load to save energy and to reduce global warming.

Abstract: This study developed an oxygenase system with horizontal-axis wind turbine driving the oxygenation device by belt pulley for aquaculture, and verified the feasibility of the system in conditions of Taiwan’s average wind speed. The experimental system is consisted of a horizontal wind turbine, a reciprocating compressor, and water channels. At the first stage of the experiment, the reciprocating compressor oxygenase system was measured according to the power supply standards in terms of power consumption, air displacement and oxygen production, in case of various rotating speeds and the compliance with aquaculture standards. At the second stage of the experiment, the wind turbine was used to directly drive the reciprocating compressor oxygenase system. According to the experimental results, regarding the test of the compressor oxygenase system, when power supply rotating speed is 406.7 rpm, power consumption is 234.5 W and the oxygen production is 7.48mg/L, which is above the level of amount of dissolved oxygen of aquaculture at 5.5mg/L. In case of driving the oxygenation device by wind power, when wind speed is 5.06 m/s and the wind turbine rotating speed is 140 rpm, the average dissolved oxygen in the water is 5.9 mg/L, which meets the aquaculture standards. Even in case of unstable wind speed, good oxygen production effects can be achieved. Moreover, the system is directly driven by wind power and does not require electric power.

Abstract: Thermal conduction capability of metal hydrides can be enhanced by 400 ~ 500% through pelletizing the metal hydride powder after a well-controlled copper-coating treatment. In this paper, pelletized LaNi5 metal hydride is studied to evaluate its heat transfer performance and hydrogen absorption rate. In order to analyze the transient heat transfer and hydriding reaction, numerical simulations are carried out based on a multiple-physics modeling. The reactor temperature variation and the dimensionless mass of absorbed hydrogen are plotted for different hydrogen gas supply pressures. The results are compared with the conventional powder-type metal hydride reactor.

Abstract: In this paper, we develop the overall model of the wind energy conversion systems (WECS) structure based on induction generator (IG). The goal of this paper is to control the power generated by the WECS and transmitted to the grid. We propose a new control strategy based on fuzzy logic in order to control the power of the WECS. The main drawback is that the WECS is highly nonlinear. An adaptive Fuzzy-PI power controller is proposed to overcome this problem. A Simulation study is done to validate the strategy used in power control.

Abstract: A laboratory-scale ESP with new electrode configuration was established to investigate the electric field characteristic. Eight teeth prick line and prick plate with the length of 20mm were employed as discharge electrodes, respectively. The effects of discharge electrode type and electrode gap on V-I characteristic and surface current density were studied. The results showed that the optimum electrode gaps were 350-400mm for eight teeth line and 300-350mm for prick plate, which could obtained higher average current density and lower variance.

Abstract: Biodiesel from a high free fatty acid (FFA) mixed crude palm oil (MCPO) can be produced to high fatty acid methyl ester (FAME) conversion by a two-step process. The first process is an acid-catalyzed esterification to reduce FFA in oil followed by a base-catalyzed transesterification process to produce biodiesel from esterified oil. In this study, the transesterification of esterified oil with methanol in the presence of potassium hydroxide (KOH) was performed in a 1,000 W ultrasonic homogenizer at a low frequency of 18 kHz. The use of high-intensity ultrasound to accelerate the reaction, the high surface power density of 1.62 W.mm-2 and the volumetric acoustic energy of 20 W.mL-1 were fixed. The objective of this study was to determine the various parameters (methanol concentration, KOH concentration, and initial temperature of oil) to produce the FAME conversion. The results showed that over 98 wt.% of FAME could be achieved with 5 g KOH/liter of oil, 15 vol.% of methanol, the total residence time of 20 seconds, and temperature of 30 oC. Moreover, the glycerides were rapidly converted to the FAME within reaction time of 10 seconds when the base-catalyst of 10 g KOH/liter of oil, and 20 vol.% of methanol were used. Consequently, the use of high-intensity ultrasonic irradiation can minimize the chemical cost, electricity cost, and reaction time.

Abstract: This paper describes a mathematical model of heating hot water for indirectly heated hot water heater. Using the established mathematical model was carried out simulation of the device to change its geometrical parameters. Based on the results of simulations was carried out optimization of indirectly heated hot water heater for hot water. Subsequently been made CFD simulations of the device, and those were compared with a mathematical model to verify the accuracy of the proposed mathematical model of heating hot water for indirectly heated hot water heater. Computational methods based on finite volume methods (CFD method) have proved very useful in optimizing indirectly heated hot water heater.

Abstract: In order to study the influence of fabrication accuracy on the transmission performance of photonic cystals, the resin molds with inverse diamond structure with the same size were fabricated in different forming angle (30°,60°,90°) by stereolithography (SL). The alumina PCs with diamond structure were obtained combining the molds and gel-casting. The results showed that different forming angle of three kinds molds resulted in the change of the size and relative angle of their cells, and the PCs fabricated were also. The transmission properties of PCs had an obvious change in the width and smoothness of the band gap, which displayed that the resin molds by SL resulted in fabrication errors would affect the transmission properties of PCs. In the practical fabrication of diamond-structure PCs, fabrication errors caused in the different forming angle needed to be considered when SL technology was utilized to fabricate the molds, which also fit complex molds.

Abstract: The limestone collected from the Ji county of Tianjin was investigated in this study. The characterization of the limestone dissolution in wet FGD system is carried out by sulfuric acid titration. The results indicate that A lower PH value is benefit for the limestone dissolution, which causes high dissolution rate within short time. Smaller particle size results in higher dissolution rate. The addition of inorganic salt and organic acid significantly affect the limestone dissolution. The limestone dissolution rate increases with the increase of organic acid concentration. In all the inorganic salt, it is obvious that Na⁺ has an positive effect while CI^- plays a negative role on the limestone dissolution. However, the addition of composite additive of adipic acid plus MgO to the limestone slurry is greatly better than using the adipic acid or MgO only.

Abstract: The existing high-speed railway in China is erected on the viaduct. The traction power supply system of high-speed railway consists of catenary with auto-transformer (AT). The catenary above the rails is supported by towers besides the rails. As the increase of the height from top of towers to ground, the probability of the pilot discharging of lightning to catenary will increase. And the pilot striking distance to ground always remains constant. So the horizons shielding effects for catenary will decrese, and the whole catenary naked in the atmosphere extremely easily struck by thunderbolt. In the important places, e.g., substation and areas of frequent lightning, the lightning arrester is installed to limit lightning overvoltage. But the lightning arrester can limit local overvoltage only. In fact, high-speed railway struck by lightning has affected the safety of power supply system in China. So more reasonable lightning protection measures for Chinas high-speed railway will be studied in this paper.