Authors:Mohammad Rasoul MOUSAZADE; Mehdi SEDİGHİ, Mohammad Hasan KHOSHGOFTAR MANESH, Mostafa GHASEMİ Abstract: The release of waste oil into the environment will have destructive effects. Gasification is an advanced and environmentally friendly process for converting waste oils into clean combustible gas products. Thermochemical equilibrium modeling has been used in this method to predict the performance of a downdraft gasifier. This model uses the thermodynamic equilibrium of gasification reactions to predict the gases produced in the gas mixture. Having the percentage of gas components produced, different characteristics of the produced gas including H2:CO ratio, process temperature and calorific value of the produced gas, Cold gas efficiencies and carbon conversion efficiency are also obtained. The effect of equivalence ratio, oxygen enrichment and pressure on gasification properties is analyzed. The simulation results are compared with the reported experimental measurements through which the numerical model is confirmed. The results indicated that the equivalence ratio (mole of air in gasification per mole of air in combustion) between 0.4 and 0.42 had the potential to yield the highest calorific value about 10.5 Mj.m-3. The temperature of gaseous mixture in this range will be 2000 K that can be used for other processes such as steam generation. Using pure oxygen instead of air reduces the efficiency of the gasifier from 78% to 55%. Pressure changes from 10 to 65 bar cause gas mixture temperature changes from 1684 to 1690 Kelvin. The H2:CO ratio decreases from 1.6 to 0.6 with increasing equivalence ratio and increases from 1.2 to 1.6 with changes in oxygen enrichment. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Ayşegül ABUŞOĞLU; Alperen TOZLU, Amjad ANVARİ-MOGHADDAM Abstract: This paper presents the design, evaluation, and optimization of an electricity generation system based on the two-stage organic Rankine cycle (TS-ORC), which utilizes the waste heat of an existing fluidized bed sewage sludge incineration (FBSSI) facility. The facility incinerates an average of 300 tons per day of sewage sludge with a dry matter content of 22%. After the drying process, the sewage sludge is burned in a fluidized bed combustor, and exhaust gas at a temperature of about 850-900ºC is released due to the combustion. The system provides the energy required to dry the sludge from this exhaust gas. In this study, a TS-ORC is designed to be coupled to the exhaust gas flowlines discharged to the atmosphere at two different points in the FBSSI plant. The exergy efficiency of the FBSSI facility is found to be 70.5%. Three different working fluids are selected to examine the variations of thermodynamic and thermoeconomic performance parameters of the designed TS-ORC system. The highest power generation in the TS-ORC system (183.40 kW) is achieved using R1234yf as working fluid. R1234yf is also the most expensive fluid for electricity generation among the other working fluids (10.57 $/h). The least electricity generation in the TS-ORC (142.70 kW) occurs at the thermoeconomically most affordable cost with R245fa (9.35 $/h). PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Malaıne SALEK; N. ABABSSİ, M. CHARİA, A. BOULAL Abstract: The main objective of this article aims to enhance a single stage absorption refrigeration machine, using the ammonia-water pair as working fluid, and this from the improvement of its exergetic performances by means of a vapor rectification system. The rectifier makes it possible to emit a vapor enriched in pure fluid (ammonia) with a high flow rate; this one is thus transformed into condensate after condensation; as it also allows evacuating a liquid (water) in the form of reflux. Moreover, in order to show the role of the rectifier and to highlight its impact on the operation of the proposed installation, the methodology adopted in this work aims to develop a thermodynamic model of numerical simulation using the FORTRAN language according to two approaches. An energetic analysis approach which aims to assess, in a first time, the performance of the studied refrigeration installation. However, the exergetic approach tries to calculate the exergy efficiency, and thus to evaluate the losses of exergies of the refrigeration installation in a second time. Therefore, the obtained results showed a clear improvement in the exergetic efficiency, accompanied against by an optimization of the losses of exergies which are due to the irreversibility of the studied thermodynamic system. The novelty brought by the present study encourages the engineers and manufacturers to realize the future absorption refrigeration machines integrating rectifier systems. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Kishor GAİKWAD; Satish KHAVALE Abstract: Analysis of transient thermoelastic stress distribution of a thin circular sector disk with a time-fractional derivative of order α is proposed. The Neumann types of boundary conditions are used and the integral transform method and Caputo fractional derivative are used to obtain the analytical solutions of the temperature, displacement, and stresses. Numerical values of temperature, displacement, and stresses are computed for an Aluminum (pure) material and presented graphically with help of Mathcad software. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Hüsamettin TAN; Ali ERİŞEN Abstract: In this study, a cascade refrigeration system comprising gas and vapor compression cycles operating at ultra-low temperature was designed. In the thermodynamic analyses, R744, R404A, and R410A refrigerants in the high temperature cycle (HTC), and R1150, R170, and R23 in the low temperature cycle (LTC) were used. Thermodynamic analyses were carried out using the Engineering Equation Solver package program. Outputs considered were: system performance(COP), compression ratio, mass flow ratio and HTC cascade outlet temperature. Results show that, at different LTC condenser temperature values, R404A/R23 has the highest COP value, in the LTC, R23 has the highest compression ratio, while R1150 has the lowest one, in the HTC, R404A has the highest compression ratio, while R744 has the lowest one, the performance of the system increased with the decrease of the mass flow ratio. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Şaban UYSAL; Ufuk Sancar VURAL Abstract: Methionine is an amino acid that is extremely important for human health. To better understand the biochemical events occurring in the human body, the excess molar properties of methionine and aqueous ethanol and aqueous methanol mixtures were determined at 298.15 K. Interactions between components in solutions are explained. Negative deviations from the ideal state have been observed in methionine solutions due to hydrogen bonds, dipole interactions, charge-transfer interactions. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Ragıp YILDIRIM; Arzu ŞENCAN ŞAHİN, Erkan DİKMEN Abstract: In this study, hydrofluoroolefin R515B was used rather than hydrofluorocarbon R134a to perform energetic, exergetic, environmental and enviroeconomic analyses on vapor-compression refrigeration systems with internal heat exchangers. The exergy efficiency, exergy destruction, and coefficient of performance for cooling mode (COP) were studied. EES (Engineering Equation Solver) program was employed for thermodynamic analysis. The impact on the COP, exergy destruction, and exergy efficiency of the system was investigated at various evaporator and condenser temperatures. Performance analysis shows that the COP of R515B refrigerant is like that of R134a. It has been found that the exergetic efficiency of R515B was slightly lower (about 1.40%) than that of R134a. It has also been found that at higher evaporation temperatures, the total exergy destruction increases. The most important exergy destruction occurs in the compressor. The environmental and enviroeconomic indexes of R515B refrigerant were like those of R134a. The results demonstrated that R515B may be a good alternative to R134a in the vapour-compression refrigeration systems with internal heat exchangers. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Robert ČERNÝ Abstract: The book covers foundational principles and recent updates in the field of thermal science, presenting an authoritative overview of theoretical knowledge and practical applications across several fields. Since the first edition of this book was published in 2005, great progress has been made in the theoretical understanding - and subsequent ability to assess and apply - of the principles of thermal analysis, especially in thermodynamic intention with emphasis on temperature conditions. Features twenty-chapter contributions on 660 color pages provides an up-to-date cutting-edge themes involving the thermal analysis, thermotics, thermodynamics, thermal and applied solid-state physics, macro- and micro- dimensional approach to selected materials and their thermal properties. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Muhamed BİJEDİC; Enver ĐİDİĆ Abstract: The equations connecting speed of sound with other thermodynamic properties of gases and liquids, suitable for numerical integration with respect to temperature, density, and pressure, along isentropes, are derived. Algorithms of their solution are given too. They are tested with several substances (e.g., Ar, N2, O2, CH4, CO2, and H2O) in wide ranges of pressure and temperature. Average absolute deviation of thermal properties is 0.0129% in supercritical gaseous phase, 0.0308% in transcritical gaseous phase, and 0.0009% in liquid phase. Corresponding deviations of caloric properties are 0.1706%, 0.1863%, and 0.0702%, respectively. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Rafael PİNHO FURTADO; Reynaldo PALACİOS BERECHE, André DAMIANI ROCHA, Antonio GALLEGO Abstract: Semi-closed oxy-fuel combustion combined cycle (SCOC-CC) is a strong concept of carbon capture and storage (CCS) in gas-fired power plants. This technology is similar to a conventional combined cycle, however oxygen instead of air is used in fuel combustion. In the oxy-fuel combined cycle, the gas turbine flue gases consist mainly of CO2 and H2O. One of the problems to implement this technology is the necessity of an air separation unit (ASU) to separate the oxygen from the air, which increases the energy consumption of the power plant. Thus, a comparative thermodynamic analysis was performed between a conventional combined cycle (base case) and an oxy-fuel combined cycle. The objective is to identify each technology's pros and cons, the influence of oxygen purity in the oxy-fuel combine cycle, and the main irreversibilities of each case. The SCOC-CC optimal operating point (maximum energy efficiency) was found utilizing particle swarm optimization (PSO), which lead to the optimal ASU oxygen purity of 95.99%. It was noticed that the oxy-fuel combined cycle first law efficiency is 6.9% lower than the base case, and the second law efficiency is 6.5% lower. Despite the efficiency loss the SCOC-CC is more environmentally friendly than the conventional combined cycle since it can theoretically capture all CO2 produced in the combustion chamber. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Siham J. AL-FARİS; Raed H. AL-SAQA, Huda M. MOHHAMED, Sırwan KAREEM Abstract: The present study is a theoretical calculation for the effects of high pressure on thermodynamic properties on GaN up to 40Gpa at room temperature. Volume compression ratio (V0/Vp), lattice constant (a) and elastic bulk modulus(B) have been established. Furthermore, lattice frequencies and disruptions function by analyzing phonon frequency spectrum (PFS) at (0 K). The entire calculations rely on using of two equation of state (EOS) "Birch-Murnaghan and modified Lennard-Jones" equation of state and with the integration of Grüneisen approximation theory. From the considered equations of state, formulation of bulk modulus was derived, that predicts a rising trend of bulk modulus. The large bulk modulus value of GaN has made a small fraction of change in volume (less than 15%) of the material even under an extreme pressure up to 45Gpa. It was also found that the results of phonon frequency spectrum obtained from Birch-Murnaghan equation of state in a better agreement with the experimental data than that of modified Lennard-Jones equation of state. Given that the Birch-Murnaghan equation of state developed according to Eulerian strain theory accounted as a universal equation of state. Moreover, good agreement between theoretically present calculations and experiment data of phonon frequency spectrum, reveals the validity of the equations of state used in the present study. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Latika BAWANKAR; G. D. KEDAR Abstract: This paper studies the generalized magneto-thermoelastic problem with microtemperatures, voids taking into account initial stress and modified Ohm’s law under three theories. The analytical solution is obtained by normal modes and expressions for micro temperature, temperature distribution, displacement, components of heat flux, change in the volume fraction field as well as stress components are calculated. The effect of initial stress and thermal shock is observed on desired field variables. The results are established graphically for all physical quantities and variation is done for three theories due to the effect of modified Ohm’s law coefficient. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Bashayar AL MAQBALİ; Zohreh RAHİMİ-AHAR, Hasan MOUSA, G. Reza VAKİLİ-NEZHAAD Abstract: In this study, three desalination exergy analysis models including the Cerci et al. model (Model A), Drioli et al. model (Model B) and electrolyte solution model (Model C), were developed on an existing reverse osmosis (RO) desalination plant in Oman (Plant ALG). A modified ultrapure water (UPW) unit fed by Plant ALG has also been proposed (Plant A) based on the technology used in a UPW unit operated under the climate of Europe and fed by European river water (Plant B). The most suitable exergy model for characterizing the proposed UPW production plant was used. Model C was found to be the most proper model among its counterparts. It reflected the electrolytic behavior of the relevant streams and considered as the appropriate model. The major exergy destruction sites were also identified, and the exergy efficiency was calculated. The electro-de-ionization (EDI) and the RO unit were the highest exergy destructive components in Plant A. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Yashasvı SHARMA; Mona SHARMA Abstract: A significant credit towards today’s scientific and medical advancements goes to the technique of cryopreservation. Cryopreservation refers to the maintenance of cellular life at subzero temperatures for a definite period of time in a state of suspended cellular metabolism. The technique has become an indispensable step in most scientific research and medical applications like assisted reproduction, transplantations, and cell-based therapies where-in it allows the long-term preservation of biological specimens like gametes, embryos, viruses, cells and tissues. Although already an extensively used technique, a significant proportion of the cryopreserved samples still incur notable damage. Ultimately this leads to a decreased post-thaw viability and proliferation. Moreover, it is also possible that events during the freezing process, provoke more serious disturbances in the preserved material with regard to its identity and functionality. Hence, with the need to use the technique more judiciously, additional studies are needed for optimizing the current cryopreservation methods in use. For this, a thorough understanding of the normal physiological changes that the cryopreserved sample undergoes and the physics of cryopreservation seems plausible. The review thus aims to unravel the current knowledge on the complex physico-chemical processes and reactions that occur during the standard cryopreservation techniques. PubDate: Tue, 01 Mar 2022 00:00:00 +030
Authors:Adnan ALSHEKH; Sırwan KAREEM, Salar MAWLLOD Abstract: A nanomaterial equation of state has been combined with Grüneisen approximation in present work to investigate the influence of high pressure on phonon density of state function of C60 through evaluating variations of lattice vibration frequencies and variation of mode density. Furthermore, the effect of high pressure on Debye temperature has been determined by using a formula of volume dependence of Debye temperature. Volume compression ratio in C60 has been computed, using a nanomaterial equation of state. Expressions of pressure dependence of phonon density of state and Debye temperature have been combined with volume compression ratio value. The evaluated result of volume compression ratio and phonon density of state have been compared with the experimental observations and good agreement can be seen. PubDate: Tue, 01 Mar 2022 00:00:00 +030
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