In this paper, exergy analysis is used to evaluate the performance of a combined cycle: organic Rankine cycle (ORC) and absorption cooling system (ACS) using LiBr–H2O, powered by a solar field with linear concentrators.The goal of this work is to design the cogeneration system able to supply electricity and ambient cooling of an academic building and to find solutions to improve the performance of the global system. Solar ACS is combined with the ORC system-its coefficient of performance depends on the inlet temperature of the generator which is imposed by the outlet of the ORC. Exergetic efficiency and exergy destruction ratio are calculated for the whole system according to the second law of thermodynamics. Exergy analysis of each sub-system leads to the choice of the optimum physical parameters for minimum local exergy destruction ratios. In this way, a different connection of the heat exchangers is proposed in order to assure a maximum heat recovery.

Today, renewable energies are of more interest due to the depletion of the ozone layer, an increase in the cost of fossil fuels, and their friendliness with the environment. The sun is a great source of energy which is readily accessible. It has many applications in lighting, heating, and cooling. In this study the thermal performance of a solar ejector cooling cycle is evaluated using several different working fluids. The effect of operating conditions--namely the generator, condenser, and evaporator temperatures--on the system performance is also investigated. Based on weather conditions in different regions, the performance of ejector cooling cycle in several months of the year is also determined. The results show that the operating conditions have a determinant effect on cycle performance. It is observed that an increase in the generator exit temperature results in an increase in cycle coefficient of performance. It is also deduced that the rates of COP increase for the evaporator temperature ranges of 13-15°, C and 7-9°, C are about 8 and 6% respectively. It is also concluded that a larger collector area is required in warmer weather conditions.

A detailed modular modeling of an absorbent cooling system is presented in this paper. The model including the key components is described in terms of design parameters, inputs, control variables, and outputs. The model is used to simulate the operating conditions for estimating the behavior of individual components and system performance, and to conduct a sensitivity analysis based on the given control variables. The proposed model has been validated by means of comparing the predicted results with the experimental data in a full-scale absorbent cooling system installed at MERC. Careful attention was given to estimate the behavior of the system at transient mode. Based on operating conditions, a range of time-constant start-up time had been estimated for generator and evaporator. The results indicated that the model predictions were in good agreement with experimental data. Sensitivity analysis also showed that the performance characteristics of the system could be approximated by generalized polynomial functions of order 2 in terms of control variables. Finally typical performance results are discussed.

Turbine inlet temperature strongly affects gas turbine performance. Today blade cooling technologies facilitate the use of higher inlet temperatures. Of course blade cooling causes some thermodynamic penalties that destroys to some extent the positive effect of higher inlet temperatures. This research aims to model and evaluate the performance of gas turbine cycle with air cooled turbine. In this study internal and transpiration cooling methods has been investigated and the penalties as the result of gas flow friction, cooling air throttling, mixing of cooling air flow with hot gas flow, and irreversible heat transfer have been considered. In addition, it is attempted to consider any factor influencing actual conditions of system in the analysis. It is concluded that penalties due to blade cooling decrease as permissible temperature of the blade surface increases. Also it is observed that transpiration method leads to better performance of gas turbine comparing to internal cooling method.

In this paper, the first level of a solid oxide fuel cell combined cycle and gas turbines, heat recovery, are considered as the basic cycle. Since heat recovery from exhaust gas turbine to produce injecting steam into the combustion chamber and also increase the cooling system evaporative inlet air to the inlet air compressor and water injection technology is a known to be efficient, to improve the basic cycle to work have been taken. The electrochemical fuel cell modeling and to identify loss voltages within the fuel cell voltage at different working conditions are achieved. The electrochemical analysis, the thermodynamic modeling however elements of the cycle are discussed. The results of modeling show that the benefits of improved cycle by injection of steam and water cycle of the base shows that has increased 18.95 percent compared to the basic cycle. Finally, cycle performance parameters compared to the three major factors: density, fuel cell, pressure, density and mass flow of fuel carried.

A multi-stage open cooling cycle of scramjet for electricity and hydrogen co-production is proposed in which the fuel of scramjet is used as a coolant of the cooling cycle. Thermodynamic and exergetic examinations of the advanced system have been conducted to appraise the performance of the cycle, electricity and hydrogen production. In this integral system, the waste heat of scramjet drives the power sub-cycle whilst the PEM electrolyzer input electricity is supplied by a portion of the net electricity output of the cycle. It is fi gured out that the multi-expansion process reveals more advantages in comparison to the single-expansion process in terms of more cooling capacity, electricity, and production. For the fuel mass fl ow rate of 0. 4 kg/s, the cooling capacity of the new proposed cycle is computed 9. 16 MW, the net electricity output is calculated about 3. 38 MW and the hydrogen production rate is attained 42. 16 kg/h. On the other hand, the exergetic analysis results have proved the fact that the PEM electrolyzer has the highest exergy destruction ratio by 48% among all components of the cycle. In this case, the energy and exergy effi ciencies of the overall set-up are acquired by 12. 95% and 22. 16%, correspondingly. The outcomes of parametric evaluation demonstrated that electricity and hydrogen productions are directly proportional to the backpressure of the pump accordingly, more electricity and hydrogen are generated by higher backpressure. But, increasing the mass fl ow rate of fuel does not have any tangible impact on energy and exergy effi ciency of the whole set-up thus both remain approximately constant.

Combined cycle performance can be improved by improving the performance of gas turbine based topping cycle. Amongst various options the effective cooling of gas turbine blade for realizing the higher turbine inlet temperatures is one of the attractive options. The present paper deals with the thermodynamic analysis of advanced technology gas/steam combined cycle based power plant having closed loop cooling in gas turbine stages employing water/steam as coolants. Results have been obtained for the cycle pressure ratios varying between 12 to 20 and turbine inlet temperatures (TITs) varying in 1400 K to 1700 K for studying the influence of water and steam coolants upon the overall cycle performance.

There are small cracks in rocks; therefore, when rocks undergo loading, stresses are concentrated at the tip of cracks causing rock fracture before reaching its ultimate strength. The critical value of the stress intensity factor at the crack tip is called fracture toughness. The tensile strength of rocks is weak; therefore, Mode I (tensile mode) is the most critical loading mode. In some cases, rocks continuously experience heating-cooling. Therefore, it is necessary to determine the effect of heating-cooling cycle number on mode I fracture toughness, which is the objective of this research. To achieve this objective, we conducted three-point bending test on semi-circular specimens of three types of natural rock including sandstone, limestone and andesite to determine the mode I fracture toughness. A series of concrete specimen was also tested for further investigation. The specimens were heated up to 700° C in 1, 5 and 10 cycles and then cooled. A series of experiments were also conducted on the specimens at room temperature (25 ° C). According to the rising of temperature in firing process, the rate of temperature rise for specimens in the electric furnace is determined to be 15 ° C per minute. Fracture toughness of andesite rock, sandstone and limestone specimens decreases under cyclic conditions. Results indicate the generation and expansion of micro fractures in some rocks after undergoing cycles of heating-cooling, which causing an increase in the effective porosity and decrease in the P-wave velocity in rocks.

In Islamic traditional textbooks modal operators sometimes come before propositions, sometimes before the predicates and sometimes at the end of propositions. This makes the interpretation of modality in each case as de re or de dicto difficult. Given Ibn SVnÏ's discussion of and sensitivity to this distinction, in this paper by examining the position of modality in the contradictories and converses of modal categorical propositions as well as their positions in modal syllogisms I will try to find a reasonable answer to this important issue.

In this paper the effect of site conditions, which are Altitude, Temperature and Relative Humidity and also Heat Dissipation Capacity are investigated on the optimized design of natural draft dry cooling towers with specific kind of heat exchangers, known as Forgo T60 type. A genetic algorithm program has been developed for optimized design of these cooling towers. Objective function includes both cost and performance of the tower. The optimized dimensions of the tower, the number of heat exchangers and mass flow rate of water and air are the results of this optimization program. The results show it is possible to find the variation of the optimized value of each design variable versus the variations of the site conditions and heat dissipation capacity. Also finding an optimum for all design parameters for any site condition is possible, however it is very dependent on how exact the cost analysis is.