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The heat transfer characteristics of R134a during downward condensation are investigated experimentally and numerically. While the convective heat transfer coefficient, two-phase multiplier and frictional pressure drop are considered to be the significant variables as output for the analysis, inputs of the computational numerical techniques include the important two-phase flow parameters such as equivalent Reynolds number, Prandtl number, Bond number, Froude number, Lockhart and Martinelli number. Genetic algorithm technique (GA), unconstrained nonlinear minimization algorithm-Nelder-Mead method (NM) and non-linear least squares error method (NLS) are applied for the optimization of these significant variables in this study. Regression analysis gave convincing correlations on the prediction of condensation heat transfer characteristics using ±30% deviation band for practical applications. The most suitable coefficients of the proposed correlations are depicted to be compatible with the large number of experimental data by means of the computational numerical methods. Validation process of the proposed correlations is accomplished by means of the comparison between the various correlations reported in the literature. [ABSTRACT FROM AUTHOR]

In the present article, the effect of heat source temperature, heat sink temperature, short-tube orifice diameter and short-tube orifice length on the performance characteristics of HFC-140A and HFC-134a refrigeration system using a short-tube orifice as expansion device, i.e., mass flow rate, cooling capacity, compressor pressure ratio, power consumption, and second law efficiency are experimentally studied. The short-tube orifices diameters ranging from 0.849 to 1.085 mm with length ranging from 10 to 20 mm are used in this examination. The test run are done at heat source temperature ranging between 16.5 and 18.5°C, and heat sink temperature ranging between 30 and 35°C. The results show that the tendency of second law efficiency is increased as the short-tube orifice diameter and heat source temperature are enhanced, but it is decreased by increasing the short-tube orifice length and heat sink temperature. Under the similar conditions, the mass flow rate, cooling capacity, and compressor power consumption obtained from HFC-410A are higher than those obtained from HFC-134a. [ABSTRACT FROM AUTHOR]

This article describes experimental investigations of the heat transfer coefficient and pressure drop of R-134a flowing inside internally grooved tubes. The test tubes are one smooth tube and four grooved tubes. All test tubes are made from type 304 stainless steel, have an inner diameter of 7.1 mm, are 2,000 mm long and are installed horizontally. The test section is uniformly heated by a DC power supply to create evaporation conditions. The groove depth of all grooved tubes is fixed at 0.2 mm. The experimental conditions are conducted at saturation temperatures of 20, 25 and 30°C, heat fluxes of 5, 10 and 15 kW/m, and mass fluxes of 300, 500 and 700 kg/m s. The effects of groove pitch, mass flux, heat flux, and saturation temperature on heat transfer coefficient and frictional pressure drop are discussed. The results illustrate that the grooved tubes have a significant effect on the heat transfer coefficient and frictional pressure drop augmentations. [ABSTRACT FROM AUTHOR]

The purpose of this study is to numerically investigate heat transfer and flow field in a semi-confined axi-symmetric laminar air jet impinging on a concave surface, or dimple, with uniform heat flux. A commercial software package relying on the finite element method was used for the simulation, and mesh convergence was examined in order to minimize computational cost. Jet impingement on a flat plate was used as a baseline reference case, and flat plate results were validated against previously published experimental data with good agreement. The effects of various parameters involved in dimple impingement -such as Reynolds number (Re) between 100-1,400; jet-to-plate spacing (H/D) ranging from 2 to 6 jet diameters; dimple depths (d/D) of 0.1, 0.15, and 0.2; and the ratio of jet diameter and dimple projected diameter (D/D) from 0.25 to 1-were all studied. Comparisons show that heat transfer reduction occurs in the presence of dimples because of the larger impingement area, which results in less momentum flux. The dimple curvature lifts the post-impinging fluid and creates a backflow, instead of allowing it to maintain contact with the surface, as is the case with flat plate impingement. [ABSTRACT FROM AUTHOR]

The main objective of this work is to use the computational fluid dynamics (CFD) technique in analyzing and predicting the performance of a radial flow-type impeller of centrifugal pump. The impeller analyzed is at the following design condition: flow rate of 528 m3/hr; speed of 1450 rpm; and head of 20 m or specific speed (Ns) of 3033 1/min in US-Units. The first stage involves the mesh generation and refinement on domain of the designed impeller. The second stage deals with the identification of initial and boundary conditions of the mesh-equipped module. In the final stage, various results are calculated and analyzed for factors affecting impeller performance. The results indicate that the total head rise of the impeller at the design point is approximately 19.8 m. The loss coefficient of the impeller is 0.015 when 0.6 < Q/Qdesign < 1.2. Maximum hydraulic efficiency of impeller is 0.98 at Q/Qdesign = 0.7. Based on the comparison of the theoretical head coefficient and static pressure rise coefficient between simulation results and experimental data, from previous work reported in the literature [Guelich, Kreiselpumpen, Springer, Berlin, 2004], it is possible to use this method to simulate the performance of a radial-flow type impeller of a centrifugal pump. [ABSTRACT FROM AUTHOR]

Based on the Princeton Ocean Model (POM), the seasonal thermohaline feature and the ocean circulation in the Gulf of Thailand (GoT), situated between 6°N to 14°N latitude and 99°E to 105°E longitude, were studied numerically with 37 × 97 orthogonal curvilinear grid and 10 vertical sigma levels conforming to a realistic bottom topography. A spin-up phase of the first model run was executed using wind stress calculated from climatological monthly mean wind, restoring-type surface heat and salt, and climatological monthly mean fresh water flux data. In this paper, the temperature and salinity fields taken from Levitus94 data sets and the calculated temperature and salinity from the model run for 12-month mean and for each season are presented where the winter, summer, rainy, and end of the rainy seasons of Thailand are represented by the months January, April, July, and October, respectively. The simulated circulations are also described. The results show that the temperature in the GoT is warmer than the temperature of the other parts connected to the South China Sea (SCS). At any depth of inflow from SCS into the GoT, the salinity is high, but in the outflow from the GoT at the surface, the salinity is low. The strong circulations are clockwise during summer and the rainy seasons of Thailand, which are the East Asian monsoon periods, northeasterly and southwesterly during summer. They occur near Pattani and Narathiwat provinces during summer and in the central GoT during the rainy seasons. Sensitivity experiments were designed to investigate the effects of wind forcing and open boundary conditions. Wind forcing is shown to be the important factor for generating the circulation in the GoT. The lateral velocity at the open boundaries is of considerable importance to current circulation for the rainy and end of the rainy seasons, with insignificant effect for the winter and summer seasons of Thailand. [ABSTRACT FROM AUTHOR]

The results of the condensation heat transfer enhancement and pressure drop of HFC-134a by using the electrohydrodynamic (EHD) technique are presented. The test section is a horizontal tube-in-tube heat exchanger where the refrigerant flows in the inner tube and water flows in the annulus. The outer tube is a smooth copper tube havign outer diameter of 21.2 mm. Two types of inner tubes, smooth and micro-fin copper tubes, are tested. The outer diameter and length of both inner tubes is 9.52 mm and 2.5 m, respectively. A stainless steel cylindrical electrode of 1.47 mm in diameter is placed in the center of the tube. Experiments are conducted under conditions providing mass flux of 400 kg/m2s, saturated temperature of 40°C, heat flux of 20 kW/m2 and applied voltage of 2.5 kV. The experimental results indicate that the EHD enhancements of the smooth tube are higher than those of the micro-fin tube over the range of average quality. The maximum heat transfer enhancements for smooth and micro-fin tubes are 1.1. times and 1.08 times, respectively. For a smooth tube, the pressure drop induced by EHD is considerably small. However, the application of EHD in a micro-fin tube can lead to 10% increase in the pressure drop. [ABSTRACT FROM AUTHOR]

This paper is a continuation of the authors’ previous work on spiral coil heat exchangers. In the present study, the heat transfer characteristics and the performance of a spirally coiled finned tube heat exchanger under wet-surface conditions are theoretically and experimentally investigated. The test section is a spiral-coil heat exchanger which consists of a steel shell and a spirally coiled tube unit. The spiral-coil unit consists of six layers of concentric spirally coiled finned tubes. Each tube is fabricated by bending a 9.6 mm diameter straight copper tube into a spiral-coil of four turns. The innermost and outermost diameters of each spiral-coil are 145.0 and 350.4 mm, respectively. Aluminium crimped spiral fins with thickness of 0.6 mm and outer diameter of 28.4 mm are placed around the tube. The edge of fin at the inner diameter is corrugated. Air and water are used as working fluids in shell side and tube side, respectively. The experiments are done under dehumidifying conditions. A mathematical model based on the conservation of mass and energy is developed to simulate the flow and heat transfer characteristics of working fluids flowing through the heat exchanger. The results obtained from the present model show reasonable agreement with the experimental data. [ABSTRACT FROM AUTHOR]

By following the recently published paper in Science titled 'Coercive Citation in Academic Publishing', in this paper, we aim to discuss the demand of some journals that request authors to cite recently published papers in that journal to increase the impact factor of that journal. It will be mentioned that some of these demands are not ethical and consequently will diminish the reputation of the journal. [ABSTRACT FROM AUTHOR]

The affiliation of the sixth author [ABSTRACT FROM AUTHOR]

As novel technologies have been developed, emissions of gases of volatile organic compounds (VOCs) have increased. These affect human health and are destructive to the environment, contributing to global warming. Hence, regulations on the use of volatile organic compounds have been strengthened. Therefore, powerful adsorbents are required for volatile organic compounds gases. In this study, we used graphene powder with a mesoporous structure to adsorb aromatic compounds such as toluene and xylene at various concentrations (30, 50, 100 ppm). The configuration and chemical composition of the adsorbents were characterized using scanning electron microscopy (SEM), N2 adsorption-desorption isotherm measurements, and X-ray photoelectron spectroscopy (XPS). The adsorption test was carried out using a polypropylene filter, which contained the adsorbents (0.25 g), with analysis performed using a gas detector. Compared to graphite oxide (GO) powder, the specific surface area of thermally expanded graphene powder (TEGP800) increased significantly, to 542 m2 g−1, and its chemical properties transformed from polar to non-polar. Thermally expanded graphene powder exhibits high adsorption efficiency for toluene (92.7–98.3%) and xylene (96.7–98%) and its reusability is remarkable, being at least 91%. [ABSTRACT FROM AUTHOR]

The article reports on sympathy and emotions in professional network for scientists.

The article discusses the survey on scholars' opinion regarding the affiliation for several universities and educational institutions in scientific papers.

Recently, Scientometrics has published a paper titled 'Is there bias in editorial choice? Yes' (Moustafa ) in which some comments are given on our published paper in Nature titled 'Is there fame bias in editorial choice?' (Mahian et al. ). Unfortunately, the author of above mentioned paper and many other readers might misunderstand the main aim of our correspondence. Here, we try to give some explanations to clarify the main goal of analysis presented in the paper. [ABSTRACT FROM AUTHOR]

This study presents a case study of energy management in a sugar factory in Turkey. The main idea of the study is to analyse energy consumption, the quantity of material production, and figure out a suitable energy efficiency for the case study of a sugar factory subsequently. Firstly, a material production and energy consumption audit were performed for the sugar factory. Secondly, energy efficiency was calculated from the energy data. The SPSS (Statistical Package for the Social Sciences) statistical software was used to ensure the accuracy of the data. The factory’s energy consumption was calculated as 43,590.25 toe (tons of oil equivalent) over the last year. These results were used for CUSUM (Cumulative Sum Deviation Method) graphics. This research poses the consumption of energy, cost of energy and the relationship between energy usage and material production of sugar. The unit of energy cost was 688.22 [$/toe] for the last year. This result showed that the factory decreased the unit of energy by optimisation. The results indicated that the investigated sugar factory should pay attention to the energy management issue in order to comply with the Energy Efficiency of Turkish Law and Directives. [ABSTRACT FROM AUTHOR]

The article reports that some review journals do not allow students regarding review papers for research articles and mentions that some journals do not accept submissions of articles in which students are co-authors.

We examined the thermo-hydraulic characteristics for conjugate heat flow in the solar power plant having wavy channel with porous blocks (WCPB), while taking the thermal dispersion effect into account. The flow field inside the porous blocks is modelled using the Darcy–Brinkman–Forchheimer equations and the finite element method-based solver to solve the transport variables numerically. The temperature field, conductive heat flux, local Nusselt number, average Nusselt number and performance factor has been examined by changing the thermal dispersion coefficient, Reynolds number and Darcy number. We found that the average temperature decreases and conductive heat flux enhances by thermal dispersion near the bottom wall close to porous blocks. The rate of increase in average Nusselt number and performance factor with increase in dispersion coefficient is seen to be higher at the higher Reynolds number. It's interesting to note that the average Nusselt number underestimated with greater extent at higher dispersion coefficients as a result of ignoring the conjugate heat transfer effect. Moreover, the performance factor with the higher Reynolds number (= 500) is found to be more than unity. Also, when Reynolds number is 500, the performance factor for WCPB becomes larger than the plane channel with pours block at higher dispersion coefficient and Darcy number. The results of this analysis suggest that the proposed system is cost-effective to be used in the solar power plant. [ABSTRACT FROM AUTHOR]