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A new instrument, an averaging bidirectional flow tube (BDFT), is proposed to measure single-phase flow rates. This averaging BDFT has unique measuring characteristics foremost among which is the capability to measure bidirectional flow and insensitivity of the fluid attack angle. Single phase calibration tests were conducted to demonstrate the performance of the averaging BDFT. Likewise, to enhance the applicability of the averaging BDFT on various flow conditions, flow analyses using CFD code were performed focusing on design optimization of the BDFT. The calibration test results indicated that this averaging BDFT has a linearity within 0.5 % in the Reynolds (Re) number range of above 10,000 where it is meaningful in terms of application. The flow analyses results demonstrate a good linearity of the averaging BDFT with various design features. Therefore, averaging BDFT can be applied for measurement of flow rates within a wide range of flow conditions.

Abstract The effects of the ejector geometry (nozzle diameter and mixing chamber) and the operating conditions (liquid circulating rate, liquid level in column) on the hydraulic characteristics in a rectangular bubble column ( 0.22 × 0.26 × 1.3 m 3 ) with a horizontal flow ejector were determined. The gas phase holdup increases with increasing liquid circulating rate but decreases with increasing liquid level in the column. In the multiphase CFD simulation with the mixture model and the experiments, the gas suction rate increases with increasing liquid circulating rate. However, the gas suction rate decreases with increasing the liquid level in the column and nozzle diameter. The predicted values from the CFD simulation are well accord to the experimental data.

Production and utilization of producer gas from mixed plastic wastes were investigated in a pilot-scale moving-grate gasification process. A 500 kWth moving-grate gasifier was developed, including ...

Uniformly distributed carbon-coated Sn92Co8 nanoalloys with a particle size of 50 and 10 nm were prepared using a butyllithium and naphthalide solution at 500 and 700°C, respectively. The samples annealed at 500°C were covered with an amorphous carbon layer with a thickness of about 40 nm, but its thickness was shrunk to 8 nm when annealed at 700°C. The first charge capacity increased with increasing annealing temperature and exhibited 380 and 662 mAh/g at 600 and 700°C, respectively. This is due to enhanced ordering of the carbon layer structure and full decomposition of the butyl ligands that limited Li-ion intercalation/ deintercalation. The capacity retention of the nanoalloys annealed at 500 and 700°C was 76 and 54% after 30 cycles at a rate of 0.3 C =210 mA/g, while that of bulk Sn92Co8 alloy was 15%. Much improved capacity retention of the carbon-coated nanoalloys is associated with the thicker carbon layer on the particle surface that acts as a more effective buffer layer for volume expansion during lithium alloying/dealloying than that of the bulk alloy.

The current study aims to forecast and analyze wind data such as wind speed at a test site called “Urumsill” on Deokjeok Island, South Korea. The measured wind data available at the aforementioned test site are only for two years (2015 and 2016), making it impossible to analyze the long-term wind characteristics. In order to overcome this problem, two measure-correlate-predict (MCP) techniques were adopted using long-term wind data (2000–2016), measured by a meteorological mast (met-mast) installed at a distance of 3 km from the test site. The wind data measured at the test site in 2016 were selected as training data to build the MCP models, whereas wind data of 2015 were used to test the accuracy of MCP models (test data). The wind data at both sites were measured at a height of 10 m and showed a good agreement for the year 2016 (training period). Using the comparison results of the year 2016, wind speed predictions were made for the rest of the years (2000–2016) at the test site. The forecasted values of wind speed had maximum relative error in the range of ±0.8 m/s for the test year of 2105. The predicted wind data values were further analyzed by estimating the mean wind speed, the Weibull shape, and the scale parameters, on a seasonal and an annual basis, in order to understand the wind behavior in the region. The accuracy and presence of possible errors in the forecasted wind data are discussed and presented.

This paper presents the cooling performance of a water-to-refrigerant type ground heat source heat pump system (GSHP) installed in a school building in Korea. The evaluation of the cooling performance has been conducted under the actual operation of GSHP system in the summer of year 2007. Ten heat pump units with the capacity of 10 HP each were installed in the building. Also, a closed vertical typed-ground heat exchanger with 24 boreholes of 175 m in depth was constructed for the GSHP system. To analyze the cooling performance of the GSHP system, we monitored various operating conditions, including the outdoor temperature, the ground temperature, and the water temperature of inlet and outlet of the ground heat exchanger. Simultaneously, the cooling capacity and the input power were evaluated to determine the cooling performance of the GSHP system. The average cooling coefficient of performance (COP) and overall COP of the GSHP system were found to be ∼8.3 and ∼5.9 at 65% partial load condition, respectively. While the air source heat pump (ASHP) system, which has the same capacity with the GSHP system, was found to have the average COP of ∼3.9 and overall COP of ∼3.4, implying that the GSHP system is more efficient than the ASHP system due to its lower temperature of condenser.

AbstractIn order to meet the increasing demand of wind energy utilization, wind turbines (WTs) are developing toward the trend of large size and large capacity. In such a trend, various advanced yaw control strategies have been proposed to improve large WTs' comprehensive performance, but the analysis and summary of these strategies are still lacking. Therefore, it is necessary to have a review of yaw control, which not only enables readers to understand the current status of yaw control research but also promotes the development of wind energy technology. This paper presents a review of the current situation of yaw control for WTs, focusing on the mechanical/aerodynamic parts. The mechanical part is concerned with the WT yaw system and its effect on the fatigue load of the WT, and the aerodynamic part involves the wind energy capture and wake redirection to reduce the impact on adjacent WTs. In this review, the existing yaw control methods are classified in term of three control objectives: (1) increasing the wind energy capture of a single WT, (2) reducing the fatigue load of a single WT, and (3) maximizing the total power production of the whole wind farm and optimizing the wind farm fatigue load. On this basis, the control mechanism, the control algorithm, and the results are presented and analyzed in detail. Meanwhile, the advantages and disadvantages of the existing achievements are discussed. In addition, in a conclusion of the review, the future research direction has been identified.

This study investigates the performance of the “green refurbishment” of existing buildings. Two ordinary rooms in an existing building were chosen for examination. Refurbishment measures such as additional insulation, high-performance glazing, and air-tightening were applied to the control room. Temperature and electricity use were monitored to identify heating performance in winter and then compared with a baseline. The results of the field tests showed that green refurbishment significantly improved heating performance. Lowered heating load and electricity use with increased airtightness were also verified through building performance simulations. The empirical investigation suggests a predictive model to obtain indoor minimum temperatures as a function of outdoor temperature swings.

The tourism industry has received increasing attention as it has become one of the fastest developing business sectors around the world. Service quality in tourism has come to be regarded as an important impetus for economic growth; however, the focus on tourism service quality has not yet been satisfactorily or comprehensively reviewed. Therefore, we conducted a systematic literature review combining bibliometric, citation network and keyword network analysis. We selected the top five tourism journals from the SCOPUS database and then collected papers according to their keywords. Our results revealed the critical issues, topics, and changes over time regarding research on tourism service quality. The critical issues included the important impact of service quality on tourist behavior and service quality evaluation, and topics comprised (1) tourist satisfaction, (2) sustainable issues in tourism, (3) value of service quality for customers, (4) restaurant service quality, (5) customers’ perceptions of tourism, (6) service quality evaluation in tourism, and (7) service quality’s influence on customer behavior. Furthermore, the keyword network analysis results revealed the most influential keywords.