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The file attached to this record is the author's final peer reviewed version. The h-index is a citation-based metric with extensive applications, and several variants have been developed to complement it. This study formulates the optimal growth path (OGP) models of selected h-like indexes, that is, the h-index, g-index, A-index, R-index, and e-index, and analyzes their OGP-allocated strategies of citations. It is argued that the OGP is a useful tool for analyzing the sensitivity of these h-like indexes to citations. Through simulation experiments with both real and random data, the sensitivity of the selected h-like indexes to citations is compared. Interestingly, it is found that the h-index performs the worst according to the OGP. Further, it is shown that combining the h-index with the A-index decreases the sensitivity to the citations of the h-index. In summary, this study provides new insights into how to evaluate scientific outputs based on h-like indexes.

Based on a lab-scale setup, the thermal and flow performances of a single spiral-tube ground heat exchanger under certain operation mode (6 h on and 18 h off) were examined in terms of the influence of Reynolds number (3000–8000) and backfill materials (native sand, and sand/kaolin blend with 5% adding ratio of kaolin). The convective heat transfer coefficients for the tube buried in the blend were between 370 and 678 W/m2 K, which were higher than those in the sand. Also, the effectiveness of the heat exchanger in the blend was higher than that in the sand. The average values of the temperature restoration degree in the sand backfill and surrounding soil field after 18 h off increased by about 18–25%, compared to those after 6 h on, while that in the blend backfill and surrounding soil field increased by about 36–42%. It is an available option to add the kaolin into the sand for enhancing thermal performance of the ground heat exchanger. The intermittent operation mode should be also a feasible technique for prompting the thermal performance of the ground heat exchanger.

In this paper, the complete moment convergence for arrays of rowwise negatively superadditive dependent (NSD, for short) random variables is established. As applications, the complete conve...

Thermal characteristics of water in a ground U-tube with twisted tape inserts were addressed. At inlet temperatures of 60°C to 75°C, and Reynolds numbers of 3000 to 9000, the surface heat transfer coefficients for water with twisted tapes ranged from 442 to 897 W m−2 K−1, which were higher than that in smooth tube, 384–810 W m−2 K−1. Average convective heat transfer coefficient for the smooth tube in sand/graphite blend ameliorated by 36% compared to that in sand. Average apparent thermal diffusivities of sand/graphite at hot end temperature of 70°C rose by about 17% compared to sand.

Ground heat exchanger is a significant part of the ground source heat pumps system with environment-friendly and energy-saving. The coefficient of performance for the ground source heat pump systems is closely associated with the performance of the ground heat exchanger. Some important research development about the ground heat exchanger has been addressed over the last decades. This paper aims to overview the previous research on improving the thermal and flow performance of the ground heat exchanger. Various and special ground heat exchanger parameters factors: working fluid (gas, antifreeze solution, microencapsulated phase change slurry and nanofluid), turbulence promoter, ground tube (material, structure parameters and optimization tube), backfill materials (conventional type, controlled low strength material and phase change material), soil field (convention type, frozen soil and groundwater) and other factors (operation mode and composite systems). This paper is divided into six parts. The working fluid, the thermal conductivity of the backfill material and groundwater have the greatest impact on increasing the performance compared to other parameters. The composite system is an effective method to enhance the performance of the ground source heat pump systems.

Heat transfer performance of ground heat exchanger with a vertical U-shaped internally helically groove tube for hot climatic condition was addressed in terms of the influences of inlet water temperatures (30–45 °C), Reynolds numbers (4000–10,000) and backfill materials (raw soil; soil/polyacrylamide blend). The temperature drops of the water in the tube buried in the blend increased with respect to the raw soil backfill materials. Thermal diffusivities and water retaining ability of the soil were enhanced with increasing the blending ratio of polyacrylamide from 1.5% to 3.0%. The surface heat transfer coefficients of the water in the tube buried in the blend were much higher than those in the raw soil. The dimensionless surface heat transfer correlations of the water in the internally helically groove tube heat exchanger buried in the two samples were obtained. The correlation can well predict heat transfer characteristics with high coefficient of determination (R 2 ). Meanwhile, thermal and moisture diffusions in the two samples were evaluated. Thermal diffusion of soil was enhanced by adding the polyacrylamide, and water retaining ability of the additive was also verified. Adding the polyacrylamide into soil can be an effective manner for enhancing the heat transfer of the ground heat exchanger.

Ground source heat pump (GSHP) systems have been applied widely because of their environmental-friendly, energy-saving, and sustainable nature. In this work, heat transfer performance of a single vertical small-scale U-shaped tube ground heat exchanger under hot climatic condition is addressed considering the influences of inlet water temperature, Reynolds number, and backfill materials (raw soil; soil–polyacrylamide (PAM) blend (0.27% blending ratio for PAM). The backfill materials had an important effect on the heat transfer of the ground heat exchanger. At an inlet water temperature of 45°C and Reynolds numbers of 3104 and 4656, the temperature drops of water in the tube in the soil–PAM blend increased by about 0.3 and 0.4°C compared to that in the raw soil. Within Reynolds number from 3104 to 6208, the average surface heat transfer coefficients of the water in the tube in the soil–PAM blend and raw soil at an inlet water temperature of 45°C were 411 and 231 W m−2K−1, respectively. The results ...

Sewage sludge can be converted into bio-material or bio-fuel by means of thermal–chemical technique. Torrefaction characteristics of municipal sewage sludge were investigated based on a thermogravimetric analysis technique in nitrogen atmosphere. The whole torrefaction process could be divided into two regions, which referred to coexistence and devolatilization. Moreover, the torrefaction kinetics of sewage sludge was evaluated based on the distributed activation energy models with differential and integral methods. There was a linear dependency between activation energy and pre-exponential factor at different conversion levels. The Gauss-Peak function was employed to depict the distribution curves of the activation energies for both methods. The distributed activation energy model developed by the integral method predicted accurately the conversion degree of the sewage sludge torrefaction, whereas the model developed by the differential method only had a good prediction for high conversion degrees.

The oxy-fuel co-combustion behavior of two herbaceous biomass species (Bermuda grass and cornstalk) with bituminous coal was investigated by thermal gravimetric analysis (40°C/min). The incorporation of Bermuda grass or cornstalk could improve combustion indices of the bituminous coal. Once blending the biomass with bituminous coal, ignition temperatures of blends could be advanced by about 100–170°C. With increasing the oxygen concentration or blending ratio, the comprehensive performance index of the most blends and their parent samples increased. For the 80%grass/20%coal blend, there was a strong synergistic effect in its parent samples at 60% oxygen concentration.

Thermal behavior on the municipal sewage sludge thin-layer in a bench-scale hot air forced convective dryer was investigated at a hot air temperature range of 100–160 °C and three hot air speeds (0.6, 1.4, and 2.0 m s −1 ). The drying process presented four distinctive stages: a warm up stage, a constant rate stage, the first and the second falling rate stages. The temperature of the thin-layer increased rapidly in the first falling rate stage, whereas it rose slightly in the second falling rate stage. The average surface heat transfer coefficients in the first falling rate stage were about 3 times more than that in the second falling rate stage. The average surface heat and mass transfer coefficients at 0.6 m s −1 hot air speed increased by about 39% and 91% with an increase of the hot air temperature from 100 to 160 °C. The dimensionless surface heat transfer correlation of the sewage sludge thin-layer was obtained for the first falling rate stage. The model could fit the experimental data within ±25% deviation.

One of the most crucial problems in using biomass fuel is the amount of solid wastes produced, which will cause serious deposition and corrosion. This work is mainly focused on an evaluation of ash fusion characteristics of eucalyptus bark, lignite and their blends by using thermal analysis technique. The ash deformation temperatures of eucalyptus bark and lignite were 1181 °C and 1320 °C. The differences between ash softening temperature and hemispherical temperature were 31 °C and 13 °C for biomass/lignite blends with biomass blending ratios of 20% and 80%. Also, the influences of blending ratio and heating rate on the co-fusion kinetics of eucalyptus bark and lignite were revealed based on two-stage scheme, which referred to pre-peak and post-peak around maximum reaction rate point in the main ash fusion region. The activation energy of ash fusion for eucalyptus bark/lignite blends in the pre-peak stage and the post-peak stage was in the range of 419–828 kJ/mol, and 322–702 kJ/mol, respectively. The biomass blending ratio should be controlled within 40% in order to reduce the possibility of sintering for eucalyptus bark/lignite blends. The ash fusion kinetic characteristics of mixture samples had no linear relation with blend ratios due to interaction between biomass and coal.

The LNT microwave-multiphase transport model has been applied to the microwave drying of lignite thin layer. Microwave energy, temperature and moisture distribution were obtained to gain a comprehensive understanding on the heat and mass transfer mechanism of the drying process. The required drying time of experiments decreased by 50, 63, 67, and 83%, respectively, with the power level rising from 119 to 700 W, while that decreased by 60, 72, 76 and 86%, respectively, for simulation results. The temperature values of the corner and edge of the lignite thin layer were higher than that of the center region, which corresponded to the microwave energy distribution. The moisture ratio profiles, temperature profiles and temperature distribution indicated good agreement between the experimental and simulation results, providing confidence in the modeling approach, which made it possible to obtain the moisture distribution successfully via simulation method.Keywords: microwave; lignite; thin layer.

Log Diameter Classes 3D measurement with binocular stereo vision system was adopted. According to the log-end histogram feature, a region labeling method was proposed based on the maximum entropy threshold segmentation. Adopting the region labeling based on pixel labeled method of connecting area, each log could be precisely identified and counted by the system. Extraction of log edge using a Canny operator, completed stereo matching based on the epipolar line rectification, then obtained the matching 3D coordinate points. According to the quasi-circular of the log ends, selected the appropriate initial value to fit the elliptic boundary value. The smallest Euclidean distance between the boundary points and fitting points was calculated by using least squares principle, thus the best fitting ellipse and log diameter class parameters of major axis and minor axis were gotten. Experiment shows that the proposed algorithms can accurately and rapidly detect the log diameter classes.

The condensation behavior for a gas/steam mixture with fine lignite particles and lignite ash particles is experimentally investigated as the particles flow over horizontal finned tube bundles. The effects of the gas velocity, inlet temperature of cooling water, excess air coefficient, and particle dimension are discussed. The total mass flow rate of the condensate and the condensation heat transfer coefficient for flue gas including particles are higher than those of flue gas excluding particles when Reynolds number is higher than 2,300. The area covered by ash depositions tends to grow from the leeward toward the windward side with increasing particle diameter.

This study investigates nonisothermal co-drying kinetics of two typical biomasses (cornstalk and red pine) with lignite in the presence of a nitrogen atmosphere using a thermal gravimetric analysis technique. The drying rate can be increased by either decreasing the blending ratio of biomass or increasing the heating rate. The activation energies of cornstalk/lignite blends and red pine/lignite blends in the two falling rate periods are less than that of their parent samples. In the first falling rate period, the dominant mechanisms of drying for lignite are described by the Avrami–Erofeev equation (n = 1.5), while the mechanisms for the cornstalk, red pine, and mixture samples are fitted to the Mample equation (n = 1.0). In the second falling rate period, the mechanisms are described by the Avrami–Erofeev equation (n = 1.5 or n = 2.0). The general kinetic compensation effect correlations are obtained for all samples within heating rates of 10–30°C/min. Significant synergistic interactions between the Chi...

The influences of salt concentrations (0, 0.0214, 0.178, 0.265, 0.438 and 0.731 mol kg−1) and freeze/thawing treatment on the drying characteristics of sewage sludge were examined in a series of ultrasound-assisted (150 W) hot air convective dryer experiments at 80–130 °C. The average drying rate of the conventional sludge and hypersaline sludge sample through freezing/thawing treatment increased. The drying rates of saline sewage sludge decreased as the salt concentration increased. The average drying rate of the hypersaline sludge decreased by 8.6 percent compared to the conventional one. The apparent activation energy of the conventional and hypersaline sludge in the first falling rate stage of the drying were 14.27 and 15.61 kJ mol−1, respectively. Moreover, surface cracking dynamics formed as a result of drying were investigated. Our results show that the surface crack ratio during ultrasound assisted hot-air convection drying of conventional sewage sludge increased by 6.1 percent compared to that of the hot-air convection drying alone.

Thermal gravimetric analysis (TGA) was applied to investigate the co-drying kinetics of biomass (Bermuda grass and red pine) with lignite. The drying rate of the lignite was much higher than that of the pure Bermuda grass and red pine. The drying of samples presented two distinctive falling rate periods. The activation energy of the pure Bermuda grass and red pine were higher than those of the grass/lignite and pine/lignite blends, respectively. In the first falling rate period, the dominant mechanism functions for the lignite, red pine and their blends were 1 − ( 1 − α ) 1 / 3 , and the functions were 1 −(1 − α)0.5 in the Bermuda grass and its blends, while in the second falling rate period, the functions of the blends and their parent samples were −ln(1 − α). The drying kinetics of blends had no linear relation with blend ratios. The blending of the lignite with the grass or pine could improve the drying of the individuals.

The oxy-fuel co-combustion behavior of two different herbaceous biomass species (beetroot and switchgrass) with bituminous coal was investigated by thermal gravimetric analysis (40 °C/min). The effects of sample kinds, oxygen concentrations and blend ratios on the co-combustion characteristics were obtained. The results showed that the incorporation of the beetroot or switchgrass could improve the combustion characteristics of the bituminous coal. The ignition temperatures ( T i ) of the blends were very close to the pure beetroot and switchgrass. The T i values of the pure beetroot and beetroot/coal blends were lower than those of the pure switchgrass and switchgrass/coal blends. The T i values and T b values of blends and their parent samples decreased with increasing the oxygen concentration. The comprehensive performance indices of blends and their parent samples increased with increasing the oxygen concentration. A significant interaction was detected between the bituminous coal and the beetroot or switchgrass during the oxy-fuel co-combustion.

High-moisture municipal solid waste leads to lower heat value, lower combustion efficiency, and frequent and serious erosion during incinerating. Municipal solid waste should be dried before being efficiently incinerated. The purpose of this work is to carry out experimental study and simulation on characteristics of moisture migration of municipal solid waste matrices at medium temperature (100°C–200°C) in a muffle furnace. Obvious shrinkage during moisture migration of biological waste matrices with high initial moisture content was observed. The results showed the initial moisture content and framework mobility of waste matrices and the rate of moisture migration influence on shrinkage; and linear relationships between shrinkage and moisture content ratio of waste matrices during the first falling-rate period at certain drying temperature were established. Certain experimental results of drying characteristics of moisture migration of biological waste matrices, such as potato slices and watermelon peel...

Experiments on the drying of high moisture municipal solid waste (MSW) were carried out in a muffle incinerator, and a series of lost-mass rate curves were obtained. The results show that lost mass is already over 80% for a castock, but only 30% for a potato block after 25 minutes when the drying temperature is higher than 120°C. Arrhenius equations and the activation energies of the drying process of castock and a potato block from a drying temperature of 100°C to 200°C were obtained from experimental data. The results show that lower energy is required for completely drying castock and a potato block. © 2009 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/htj.20252

The drying and combustion process in the combined grate and circulating fluidized bed (grate-CFB) municipal solid waste (MSW) incinerator was investigated experimentally and mathematically. The drying grate bed was simulated by a muffle furnace, which could be controlled at a constant temperature level. The kind of wastes, thickness of waste layer fed and temperature were chosen as the adjustable parameters to study their effect on the drying process. The experimental results indicated that the hydrophilic wastes were more difficult to be dried than the hydrophobic wastes. The higher the temperature is the easier the waste is to be dried. The thinner waste layer is favorable to drying the waste. The pyrolysis experiment in the furnace showed that the higher temperature level could reduce the conversion rate of carbon to carbon monoxide. The semi-empirical mathematical model that included the bed material distribution submodel, volatile matter release submodel, carbon particle combustion submodel and so on was proposed. A 260 t/d grate-CFB incinerator was modeled and the model predicted bulk density agreed with the measured value from industrial field test. The predicted flue gas (e.g. CO2, CO) concentration deviated slightly from the industrial test data. The parameters and variables used in the model were determined by the experiments or practical field test. This model can be used to design the grate-CFB incinerator and guide its operation.

In this paper, a series of experiments were conducted to investigate the drying of typical municipal solid wastes (MSW) in a muffle incinerator. From the experimental drying characteristic curves, the effects of temperature on drying process were observed to be more obvious in the low temperature region than in the high temperature region in muffle incinerator. At a specified drying temperature, drying time was highly dependent upon the packed waste thickness, having an exponent relation with the thickness. When the drying temperature increased or the thickness of potato bulks was diminished, the maximum drying rate reduced. Based on the first-order reaction, activation energy (Ea), and factor A of potato and cabbage were determined.

Simultaneous three-component six-sensor hot-wire probe measurements were made in a model of tangentially fired furnace (TFF) to measure the flow properties of an isothermal flow field. The quantities measured including the spatially resolved isothermal air velocity components and their two higher order moment statistical properties, i.e., the skewness and flatness factors, and the vorticity components and their skewness and flatness factors. Detailed experimental data provided an improved understanding of the behavior of the turbulent transport in the burner zone and in the upper and central regions of the TFF. The measured velocity and vorticity fields showed the swirl characteristics of the fluid flow in the TFF interior as expected and that the flow has attached to the walls in the burner zone and central region which is not desired in an operating TFF. The solid walls in these domains, including the pendants located in the upper region, act as vortex generators. Oscillation of the velocity components, and of the other quantities measured in the experiment, may be derived from the fragmentation of the vortexes and the coherent structures existing in the furnace interior. This work helps clarity the fouling and slagging mechanisms and the flow attachment in the burner zone and central region, the flow deviation and residual swirling downstream the pendants in the upper furnace, by giving insight into the vorticity and the coherent structures in the TFF.

The SIMPLEC algorithm with the power-law scheme and the pseudo-time-step method were employed to numerically solve the governing equations for 3-D turbulent flow field in a 2023 t/h rated boiler furnace using two grid systems. The numerical diffusion was eliminated by adding a delayed correction term. The numerical results from two gridding systems agreed quantitatively and were compared with the other and also with the experiments. The grid independent simulation results are presented for two counter-flow modes of the air jets in an isothermal model of a tangentially fired furnace. The calculated velocity distribution qualitatively agreed with the experimental data. The results suggest that, unlike the concentrated counter-flow mode (identified as case CCF), the separated counter-flow mode (identified as case SCF) can efficiently prevent flow attachment to the furnace walls. The separated mode reduces the angular moment flow rate during flow attachment and SCF improves control of the heat imbalance in the horizontal flue.

Emissions reduction in industrial processes, i.e. clean production, is an essential requirement for sustainable development. Fossil fuel combustion is the main emission source for gas pollutants, such as NO X , SO 2 and CO 2 , and coal is now a primary energy source used worldwide with coal combustion being the greatest atmospheric pollution source in China. This paper analyzes flue gas cleaning by ammonia scrubbing (FGCAS) for power plants to remove gaseous pollutants, such as NO X , SO 2 and CO 2 , and presents the conceptual zero emission design for power plants. The byproducts from the FGCAS process can be used in agriculture or for gas recovery. Experimental results presented for SO 2 removal from the simulated flue gas in a continuous flow experiment, which was similar to an actual flue gas system, showed that the effectiveness of the ammonia injection or scrubbing depends on the temperature. The FGCAS process can effectively remove SO 2 , but the process temperature should be below 60 °C or above 80 °C for SO 2 reduction by NH 3 scrubbing.