A new pre-concentration scheme for brine treatment of MED-MVC desalination plants towards low-liquid discharge (LLD) with multiple self-superheating

Understanding the role of nanoparticle size on energy, exergy, thermoeconomic, exergoeconomic, and sustainability analyses of an IC engine: A thermodynamic approach

Exergy and thermoeconomic analyses of the diffusion absorption refrigeration system with various nanoparticles and their different ratios as work fluid

Life cycle assessment (LCA) of a novel geothermal-based multigeneration system using LNG cold energy- integration of Kalina cycle, stirling engine, desalination unit and magnetic refrigeration system

Boosting the job performance of academic staff in Nigerian tertiary institutions has remained a challenging managerial problem in the country. This study is an attempt to empirically examine the effects of work environment (with specific emphasis on electric power supply) on job performance of academic staff in public and private universities in Nigeria. Nigerian university system allows for government (public) and private ownership of universities under the regulatory guide of the National University Commission (NUC). One of the challenges facing Nigerian universities is infrastructure inadequacies (particularly electric power supply) fundamental to drive forward the system. This therefore, calls for a study of this nature to establish the effect(s) of this on the job performance of lecturers in the university system. In conducting the study, five research questions were designed to assess the regularity of electric power supply to offices of academic staff; establish whether the supply of electric power to the offices of academic staff is adequate and regular to create a conducive work environment; unravel the duties of academic staff which are dependent on the supply of electric power and establish the effects of electric power supply on the discharge of the duties of academic staff. Two hypotheses were also formulated to guide the study. The study adopted a survey design supplemented by other methods. A sample size of 300 respondents purposively selected from public and private universities was used as s basis for making inferences and generalisations. Data were generated through primary (questionnaire and observation) and secondary sources like textbooks, internet materials, journals articles, government publications, conference papers, newspapers and magazines. A questionnaire consisting of important questions was designed and administered. The responses from the questionnaires were coded and analyzed using descriptive method and the two hypotheses of the study were tested via Independent T-test statistical technique computed with the aid of the Statistical Package for Social Science (SPSS). Results revealed the existence of a significant positive relationship between regular and adequate electric power supply to offices and the job performance of lecturers in terms of teaching, research and administration. The study also revealed that work related factors like internet facilities, good library, conducive work environment, regular and good remuneration, training opportunities, regular promotion, access to affordable medical care, recognition/awards are significant determinants of the job performance of academic staff in Nigerian Public and Private Universities. It is therefore recommended among others that concerted efforts should be made by government and managers of Nigerian universities to ensure regular and adequate electric power supply in the system; and provide functional internet facilities, good library, regular and good remuneration, conducive work environment, training opportunities, access to well equipped and affordable medical care, regular promotion, recognition/awards since they are known to have positive effects on the effective performance of the duties of academic staff.

Predetermined by the need to increase effectiveness of electric power supply and electric power consumption, the interconnected problems of effectiveness of these processes were explored. The object of present study is effectiveness of operation of electric power systems and the subject of the study is the processes to increase their effectiveness. The problems are caused by energy-consuming technologies, unstable consumption of electricity and out-dated organization. On the one hand, it is the variable system of electric power consumption, on the other hand, the unstable system of electric power supply. It was established in the work that these systems could be balanced by their constant optimization. All operative factors of influence are established for this. Based on this, the processes of electric power consumption and supply are optimized with the help of the diagram of cause-effect interrelations. All factors, which influence effectiveness of electric power consumption and electric power supply, are represented by the Ishikawa Kaoru diagram and are divided into four groups: organizational, technical, technological and economic with their specific definition. It was followed by an analysis of their influence with separating 7–9 basic factors in each group. The establishment of the optimum variant of EPS and EPC is classically reduced to determining characteristic of distributive function, strategy and modes at minimization of effectiveness indicators. It is simpler to establish the optimum structure of electric power supply and electric power consumption, using, to describe them, directed graphs, the vertices of which correspond to the elements of the structure, and arcs correspond to relationships between them. For further mathematical processing, this directed graph is described by the system of matrix equations and the task is reduced to the search for minimum or maximum paths in the directed graph.

Unlike the first law analysis which quantifies energy in systems, the second law of thermodynamics specifies the quality of energy and the direction of the processes. In this research, a novel heat sink based on micro-jet impingement for cooling inverters in electric vehicles is thermodynamically analyzed to establish the entropy generation and exergy destruction rates. The numerical simulations are performed using the finite volume method implemented in ANSYS Fluent. Numerical analyses are performed for typical motor inverter heat fluxes ranging from 100 to 300 W/cm2, Reynolds number between 5,000 and 20,000. Alumina-water nanofluid was considered with nanoparticles at concentrations of 0, 0.008, and 0.017 by volume. Results indicate that the maximum reduction in the thermal entropy generation rate is 6.65% when the nanoparticle concentration rises to 0.017. Whereas the frictional entropy generation rate increases by 73% for the same increase in nanoparticle volume fraction. Despite this, the total irreversibility drops as the concentration rises such that the highest reduction in the total irreversibility is 6.1% since the thermal entropy generation rate is the dominant source of irreversibility. With this, utilizing nanofluids decreases the exergy destruction rate leading to a lower amount of wasted energy. When the concentration is increased from 0 to 0.008 and 0 to 0.017 at a heat flux of 100 W/cm2, the optimal Reynolds numbers for maximum reduction in exergy destruction are 10,000 and 5,000, respectively.

Desalination is the sole proven technique that can provide the necessary fresh water in arid and semi-arid countries in sufficient quantities and meet the modern needs of a growing world population. Multi effect desalination with thermal vapour compression (MED-TVC) is one of most common applications of thermal desalination technologies. The present paper presents a comprehensive thermodynamic model of a 24 million litres per day thermal desalination plant, using specialised software packages. The proposed model was validated against a real data set for a large-scale desalination plant, and showed good agreement. The performance of the MED-TVC unit was investigated using different loads, entrained vapour, seawater temperature, salinity and number of effects in two configurations. The first configuration was the MED-TVC unit without preheating system, and the second integrated the MED-TVC unit with a preheating system. The study confirmed that the thermo-compressor and its effects are the main sources of exergy destruction in these desalination plants, at about 40% and 35% respectively. The desalination plant performance with preheating mode performs well due to high feed water temperature leading to the production of more distillate water. The seawater salinity was proportional to the fuel exergy and minimum separation work. High seawater salinity results in high exergy efficiency, which is not the case with membrane technology. The plant performance of the proposed system was enhanced by using a large number of effects due to greater utilisation of energy input and higher generation level. From an economic perspective, both indicators show that using a preheating system is more economically attractive.

Performance enhancement of a conventional multi-effect desalination (MED) system by heat pump cycles

The risk of electric power supply and demand is becoming more and more outstanding. So in order to avoid electric power supply and demand risks, we should set up the electric power supply and demand early warning management system. In this paper, the influencing factors of electric power supply and demand are analyzed, and then the principal component analysis method is used to reduce factors, then the support vector machine method is used to realize the early warning of the electric power supply and demand. At last, it is validated that the results by this method is feasible for early warning.

Biomass energy recently has received much attention due to its renewability and relatively low environment impact, both of which suggest it has good prospects as are placement for fossil fuels in the future. Furthermore, biomass gasification reduces problems associated with direct burning of biomass, and the producer gas from the gasification process can be utilised in various power generation systems. In this article, a biomass post-firing combined cycle is proposed and energy and exergy analyses are reported for the cycle. The cycle energy and exergy efficiencies are both determined peak at specific compressor pressure ratio, and increasing the compressor pressure ratio reduces the mass of air per mass of steam in the cycle and, correspondingly, the gas turbine size. With increasing compressor pressure ratio and decreasing gas turbine inlet temperature, the quantity of natural gas required relative to biomass is observed to decrease, while the exergy loss and exergy destruction rates are seen to increase. Furthermore, as the gas inlet temperature to the heat recovery steam generator rises, the exergy destruction rate increases and the exergy loss rate decreases. The highest exergy efficiency is exhibited by the gas turbine and the lowest by the combustor and the condenser.

Hydrogen production from biomass gasification; a theoretical comparison of using different gasification agents

Exergy analysis of a combined RO, NF, andEDR desalination plant

After the recent renewed interest in CO2 as the refrigerant (R744) for the food retail industry, many researchers have focused on the performance enhancement of the basic transcritical R744 supermarket refrigeration unit in warm climates. This task is generally fulfilled with the aid of energy-based methods. However, the implementation of an advanced exergy analysis is mandatory to properly evaluate the best strategies needing to be implemented to achieve the greatest thermodynamic performance improvements. Such an assessment, in fact, is widely recognized as the most powerful thermodynamic tool for this purpose. In this work, the advanced exergy analysis was applied to a conventional R744 booster supermarket refrigerating system at the outdoor temperature of 40 °C. The results obtained suggested the adoption of a more sophisticated layout, i.e., the one outfitted with the multi-ejector block. It was found that the multi-ejector supported CO2 system can reduce the total exergy destruction rate by about 39% in comparison with the conventional booster unit. Additionally, the total avoidable exergy destruction rate was decreased from 67.60 to 45.57 kW as well as the total unavoidable exergy destruction rate was brought from 42.67 down to 21.91 kW.

Short circuit analysis of electrical power supply building # 71 BATAN has been carried out. The electric power supply system in building # 71 consists of the main electrical power supply from PLN of 2500 kVa and an emergency power supply supplied from a diesel generator that supplies office lighting and a nuclear standard laboratory of 200 kVa. The purpose of this study is to study the emergency power supply protection system components as well as the normal short circuit current, because the power supply system in nuclear power plants has a high safety margin. The load that is loaded consists of a mixture load of either 3 phases or 1 phase in the amount of 50 kVA, and the lighting load is 36 kVA. From the analysis using ETAP software which consists of short phase to ground, between phases, showing the value of short circuit current flowing in each system and component, the current of short circuit is 64.6 kA the existing CB panel bus of the system is 80 kA, it means the safety margin is still far above that installed. This value is used to evaluate the rating of low power nuclear power supply protection systems between 3 MW to 10 MW, with 200 kVA emergency power supply.Short circuit analysis of electrical power supply building # 71 BATAN has been carried out. The electric power supply system in building # 71 consists of the main electrical power supply from PLN of 2500 kVa and an emergency power supply supplied from a diesel generator that supplies office lighting and a nuclear standard laboratory of 200 kVa. The purpose of this study is to study the emergency power supply protection system components as well as the normal short circuit current, because the power supply system in nuclear power plants has a high safety margin. The load that is loaded consists of a mixture load of either 3 phases or 1 phase in the amount of 50 kVA, and the lighting load is 36 kVA. From the analysis using ETAP software which consists of short phase to ground, between phases, showing the value of short circuit current flowing in each system and component, the current of short circuit is 64.6 kA the existing CB panel bus of the system is 80 kA, it means the safety margin is still far above t...

Comment on "efficient photochemical water splitting by a chemically modified n-TiO2" (III).