A highly selective and sensitive benzothiazole‐based ‘turn‐on’ fluorescent sensor for Hg2+ ion

A simple benzothiazole‐based fluorescent probe (TDA) for the determination of Hg²⁺ ion in aqueous solutions was synthesised in one step and characterised by ¹H NMR, ¹³C NMR, APT, COSY, FTIR, and elemental analysis. TDA shows a significant fluorescence change upon the interaction of Hg²⁺ ion in DMF–water (v/v = 1/1), while only minor changes in fluorescence intensity are observed with 18 other metal ions. Fluorescence enhancement by a factor of 15 is achieved upon selective interaction with Hg²⁺ ion. The Hg²⁺ ion detection process is found to be pH dependent; therefore, TDA could be feasible within a pH range of 4.0–7.0.     

Energetic and exergetic performance analysis of Bethe-Zeldovich-Thompson (BZT) fluids in geothermal heat pumps

This study highlights theoretical energetic and exergetic performance evaluation results of Bethe-Zeldovich-Thompson (BZT) fluids in geothermal heat pumps. In this study, hexafluoroethane (R116), octafluoropropane (R218), and octafluorocyclobutane (RC318) were selected as possible alternative replacements to the traditional refrigerants in geothermal heat pumps. According to the calculations, coefficient of performance of 101 kW geothermal heat pumps (COP_HP) changes with range between 3.84, 3.08, and 2.92 for octafluorocyclobutane (RC318), hexafluoroethane (R116), and octafluoropropane (R218), respectively. Moreover, R116 shows the maximum exergy efficiency 68% among the selected BZT fluids.     

Energy and exergy analysis of Salihli geothermal district heating system in Manisa,Turkey

This study deals with an energy and exergy analysis of Salihli geothermal district heating system (SGDHS) in Manisa, Turkey. In the analysis, actual system data are used to assess the district heating system performance, energy and exergy efficiencies, specific exergy index, exergetic improvement potential and exergy losses. Energy and exergy losses throughout the SGDHS are quantified and illustrated in the flow diagram. The exergy losses in the system, particularly due to the fluid flow, take place in the pumps and the heat exchanger, as well as the exergy losses of the thermal water (e.g. geothermal fluid) and the natural direct discharge of the system. As a result, the total exergy losses account for 2.22, 17.88 and 20.44%, respectively, of the total exergy input to the entire SGDHS. The overall energy and exergy efficiencies of the SGDHS components are also studied to evaluate their individual performances and determined to be 55.5 and 59.4%, respectively. Copyright © 2005 John Wiley & Sons, Ltd.     

Crystallization phenomena in some polyester — urethanes

A density balance has been used to measure the crystallization isotherms of poly(ethylene adipate) and copolymers which were prepared by extending the polyester with four different diisocyanates. The occurrence of extensive secondary crystallization processes precluded satisfactory interpretation in terms of the Avrami theory and further analysis could only be based on the half-time for crystallization. This parameter has the advantage that it is determined directly and is independent of any theoretical analysis. The presence of very small concentrations of diisocyanate units can have a profound effect on the rate of crystallization if they are very different structurally from the parent polyester, e.g. a molar concentration of about 5% of 2,4-tolylene diisocyanate increases the half-time by a factor of 20 whereas the same concentration of hexamethylene diisocyanate has an insignificant effect. The temperature dependence of the half-times is discussed in relation to several theories of crystallization.     

The fuzzy logic-based modeling of a micro-scale sloped solar chimney power plant

Journal of Mechanical Science and Technology - The energy demand of world is increasing worldwide because of increasing population and developing technology. The use of environmentally friendly...     

Performance assessment of steam Rankine cycle and sCO2 Brayton cycle for waste heat recovery in a cement plant: A comparative study for supercritical fluids

The main objective of this study is to investigate the feasibility of a waste heat recovery (WHR) closed Brayton cycle (BC) working with supercritical carbon dioxide (sCO₂). For this aim, an actual WHR steam Rankine cycle (RC) in a cement plant was evaluated thermodynamically. After, a sCO₂-BC was theoretically adapted to the actual WHR system for the performance assessment. Both systems were analyzed comparatively in terms of energy and exergy. According to the results, the sCO₂-BC showed higher performance than the actual steam RC with a net electricity generation of 9363 kW where it was calculated as 8275 kW for the actual cycle. In addition, the energy efficiencies were found to be 27.6% and 24.18% where the exergy efficiencies were calculated as 58.22% and 51.39% for sCO₂-BC and steam RC, respectively. In the following part of the study, the closed BC was examined for different supercritical working fluids, namely, CO₂, pentafluoroethane (R125), fluoromethane (R41), and sulfur hexafluoride (SF6). Parametrical analyses were conducted to determine the effects of the system parameters such as turbine inlet temperature, compressor inlet temperature, and pressure ratio on the cycle performance. The simulation results of the comparative study showed that, among the supercritical fluids, the CO₂ demonstrated a higher performance for the closed BC with an energy efficiency of 27.9% followed by R41, SF6, and R125. As a result, the utilization of sCO₂-BC for WHR can be sustainably adapted and extended for environmentally friendly energy generation.     

Monitoring the film formation process of polystyrene/poly acrylamide (PS/PAAm) composite films annealed by IR heating

In this study, UV‐visible (UVV) technique was used to probe the evolution of optical transmission during the film formation from composites of polystyrene (PS) latex particles and poly acrylamide (PAAm) films annealed by the infrared radiative heating (IRH) and convectional heating. Activation energies corresponding to the void closure and the interdiffusion stages were calculated. It was shown that the activation energy for the void closure processes of viscous flow from the composite films decreased considerably in IRH annealing technique. It was observed that IRH heating speeds up the film formation process and the decrease the required energy. POLYM. ENG. SCI., 58:353–360, 2018. © 2017 Society of Plastics Engineers     

Effect of die inlet geometry on extrusion of clover sections through curved dies: Upper bound analysis and experimental verification

The effect of die inlet and transition geometry on the extrusion loads and material flow for extrusion of clover sections were investigated and presented both theoretically and experimentally. For this purpose, four different die geometries including straight tapered and cosine transition profile and each of them having round and clover inlet geometries were chosen. In the experimental study, commercially pure lead was used because of its hot forming characteristic at room temperature. A newly kinematical admissible velocity field to analyze different profiles of extrusion dies of clover section from round bars was proposed by upper bound analysis. It is clear that the extrusion loads obtained from the theoretical analysis for various die inlet-die transition geometry combinations are in good agreement with the experimental results. Axis deviations of the parts which define the dimensional quality of the products were also investigated.     

Exergy Analysis of Drying Process: An Experimental Study in Solar Greenhouse

This article examines the exergy variation during drying in solar greenhouses. Exergy efficiencies were derived as functions of drying time and temperature of the drying air. An illustrative example is considered to verify Dincer and Sahin's model and to show the applicability of the model to actual drying processes at different drying air temperatures. This work is intended not only to demonstrate the usefulness of exergy analysis in thermodynamic assessments of drying processes but to provide insights into their performances and efficiencies. In this study, the drying performance of the passively heated solar greenhouse has been investigated. Experimental results under the meteorological conditions of Izmir, Turkey (latitude 38.24 N, longitude 27.50 E), are presented.     

Monitoring of energy exergy efficiencies and exergoeconomic parameters of geothermal district heating systems (GDHSs)

In this work, the monitoring energy and exergy efficiency results of the last heating seasons of operation of the geothermal district heating systems (GDHSs) and their technical availability analysis and monitoring exergoeconomic parameters are presented. The case studies cover the actual system data taken from the systems in Afyon and Salihli GDHSs, Turkey. General energy, exergy, technical availability, and exergoeconomic analysis of the GDHSs are introduced. Furthermore, the average technical availability, real availability, capacity factor and energy and exergy efficiencies value of GDHSs have been analyzed.