alireza binesh

In this paper, it is determined exactly how much of the loss of exergy in a specify component is concerning the own component and how much of the exergy loss is due to the effects of the rest of the components on that component. In this new method of exergy analysis, at first, the exergy loss in a component is classified as avoid. /unavoid categories. With this classification, it is possible to understand what quantity of the exergy loss of a component is eliminated by optimizing that component and how much of the exergy dissipation can never be eliminated and is related to the nature of the component. In the next classification, by categorizing the exergy loss into endo./exo., we can find out how much of the exergy destruction is due to the non-optimality of other components and has nothing to do with the component itself. Finally, the categories are divided into avoid-endo, unavoid-endo, avoid-exo and avoid-enxo. By performing this new method, the results demonstrate that the highest exergy destruction (1.976 MW) happens in the evaporator, 68% of which is unavoid-endo. exergy loss. The highest avoid. exergy loss relates to low pressure turbine (0.5791 MW). It is shown that optimizing of surrounding components of deaerator, economizers, and evaporators has a greater effect on decreasing the exergy dissipation of these own components, and the most Avoid. exergy destruction is in heat exchangers, pumps, condensers, turbines, expansion valves, reheaters, and superheaters.

In this study, the total resistance and effects of different parameters on the hydrodynamic behavior of a twin-hull unmanned surface vessel have been investigated using the numerical method (CFD) using STAR-CCM+ and the experimental method (towing tank test) in Kowsar towing tank (KTT). Hull has been tested in two tonnages and at four different speeds. The comparison of the results of both methods shows an eligible match between the results of experimental and numerical analysis. Finally, it was found that vessel weight increasing to its maximum value at the operating speed will only increase the total resistance by 17%. Also, during the experiments, it was found that despite the vessel's design for low operating speeds, it is possible to achieve planning speeds or higher. Still, due to a lack of hydrodynamic lift generation at high speeds, hydrodynamic resistance will increase significantly. An increase of 4 kg in hull mass will increase the pitch angle up to 9%, the maximum pressure on the body up to 12%, and the wave height near the body up to 9%.

Proper design of ducting in the air conditioning system in ships is one of the most important parameters affecting the comfort of personnel. Currently, ducting on ships is designed based on the maximum transferable discharge in living spaces, while in practice the discharge required by living spaces varies at different time intervals. Therefore, duct design should be designed based on variable air volume. Among the three methods introduced for the design of ductwork for air conditioning systems in the 1997 ASHRAE Standard for ships, the only method based on optimization is the T method. In this method, the goal is to determine the size of the channels to reduce the cost of the life cycle. For variable volume air systems, a method based on the equations of the T-method and using the evolutionary algorithm of colonial competition has been performed in this paper. The conditions of the sample for design based on the proposed optimization method include changes in the inlet air flow rate to the ducts and changes in the rate of energy consumption calculation parameters. The colonial competition algorithm showed that it has the ability to show a more appropriate performance in achieving the optimal answer than the previous algorithms.

Using transverse steps is a way to reduce friction resistance and also increase the velocity of stepped planing hull vessels. In stepped planing hull vessels, by increasing the velocity and entry to the planing regime and finally separation fluid flow from the step, the wetted area decreases and as a result, the drag force will decrease. In this research, an appropriate analytical method is presented to study the hydrodynamic characteristics of the stepped planing hull vessels and the results of this procedure are validated with experimental data of a specified stepped planing hull vessel for three step heights of 2, 4 and 6% of width. In the mentioned approach, using available semi-empirical relations for the geometric dimensions of the produced waves at heel of the stepped planing hull vessels, the Savitsky method is developed. The results reveal that the developed method has a much better performance compared to the Savitsky method and has an acceptable agreement with the experimental data. After validating the proposed analytical method, the effect of geometric parameters including step height, center of mass location and transvers step position on the hydrodynamic behavior of the stepped planing hull vessel is examined and the optimal value of the mentioned parameters are achieved.

Nature and living organisms provide an abundance of creative designs that can be used to solve many technical and engineering problems. Fast swimming shark skin is covered with low drag microstructures which is a good source of inspiration from nature for numerous engineering applications. The main objective of this research is to explore the abilities of additive manufacturing methods and to use 3D printing technology to fabricate drag-reducing riblet surfaces. Thus, the shark skin imitated riblet surfaces have been designed and fabricated in micron scale by using a yellow resin specially-formulated for 3D printers and the DLP technique. Then, a closed channel made of Plexiglas with its bottom surface covered with a riblet surface has been designed and constructed to evaluate the ability of these surfaces in reducing the pressure drop. An engineering system including a pump, rotameter, water tank, connecting tubes, differential pressure transmitter, power supply and monitor has been installed to measure the amount of pressure drop across the channel for various riblet surfaces. The tests have been performed for different Reynolds numbers and various riblet surfaces, and the pressure drop results have been compared with empirical data for a channel with simple sample. The findings indicate the ability of riblet surfaces in reducing the pressure drop across the channel.

Axial vane rotary engine (AVRE), as a novel type of rotary engines with special and exclusive features, is still under research in some of the reliable engine research centers around the world. The engine is a positive displacement mechanism that permits the four "stroke" action to occur in one revolution of the shaft with a minimum number of moving components in comparison with reciprocating engines. In this paper, a two-zone combustion model is developed for a spark ignition axial vane rotary engine. Spark ignition engine cycle simulation has been performed on the equivalent four stroke reciprocating engine of the AVRE engine. In this paper, the effect of compression ratio, blowby coefficient, and engine speed on the maximum pressure and temperature of the AVRE are investigated. The modelling is based on equations for energy and mass conservation, equation of state, and mass fraction burned. Combustion chamber is divided into burned and unburned zones, and differential equations are developed for the changes in pressure and changes in temperature in each zone. The developed code for engine simulation in MATLAB is applied to another engine and there has been a good agreement between results of this code and the results related to the engine chosen for validation.

The main goal of this research is to study of interaction between the propulsion system and the WIG Craft main parts. Therefore, the effects of some parameters such as the propeller rotation direction and the propulsion system location on the aerodynamic quality of the WIG craft have been studied deeply. Using ANSYS-CFX Software, The SIMPLE algorithm has been utilized to consider the pressure-velocity coupling, additionally the k-ω SST model has been applied as a turbulence model to take the account of the flow separation. The numerical approach is verified by comparing its results with experimental data of a three-blade aerial propeller. These comparisons indicated that there was a good agreement between present numerical results and experimental ones. The results revealed that the propeller rotation direction has no significant effect on the aerodynamic quality of the WIG craft and at α=3o, the highest aerodynamic quality is achieved. Moreover, as the propulsion system approached closer to the WIG craft center line, the drag and lift forces on the horizontal tail are respectively enhanced and decreased, subsequently in this situation the longitudinal stability of the vehicle is decreased; whereas by changing the vertical position of the propulsion system, the drag and lift forces on the horizontal tail are correspondingly reduced and increased, Thus the longitudinal stability of the WIG craft is increased.

Increase in speed and range of hydrodynamic systems, which ultimately lead to enhance in its performance, is one of the most important goals in design of marine systems. Achieving this goal, is required to reduce hydrodynamic drag. Micro-bubble injection technique is one of the active methods to reduce hydrodynamic drag. This approach has high efficiency for drag reduction and in comparison to the other active methods, it has less environmental pollution and it is easy to install on the hydrodynamic vehicles. The main aim of this research is experimental investigation of the hydrodynamic drag reduction of a catamaran vessel using micro-bubbles injection method and determining the effective parameters on the performance of this technique. For this purpose, at first, a catamaran vessel model is made with length of 70cm. In the following, the micro-bubble injectors are designed and installed with necessary equipment, for measurement of air flow rate, on three locations at fore, middle and aft sections of model. Experimental tests are carried out in towing tank laboratory for catamaran vessel with and without injection system for Froude numbers in the range of 0.44 to 1.48 and finally, the ability of micro-bubbles injection method to reduce hydrodynamic drag of catamaran vessel model is evaluated at different velocities. The experimental results revealed that, the average hydrodynamic drag reduction is attained about 17%. additionally, by increasing Froude number, the capability of miro-bubble injection method to reduce drag has been decreased from 21.15% to 11.8% for Fr=0.54 and Fr=1.25, respectively.

Radon and Thoron are the radioisotopes which radiate high alpha energy particles. These two gases can enter in the body by different ways such as inhalation, eating and drinking and then destroy body`s internal tissues and cause the lung cancer. The condensation of these gases differs in various areas and is more in zones near active faults. In this research, first the relation of Radon and Thoron concentration with the effect of distance of North east active faults in about 100 residential places of Iran is studied. Results show that residential places near active faults have more concentration of Radon and Thoron than other places. Also in these places the concentration of Thoron is two or three times more than Radon. The maximum amounts of Radon and Thoron concentration are 188Bq/m3 and 803Bq/m3 with the average amounts of 71.52Bq/m3 and 326/44Bq/m3 respectively.

Effective communicating is not only one of the patient’s most important needs, but also is the base of nursing work. This study aimed to evaluate the effect of solution-focused communication techniques on nurse communication skills. In this quasi-experimental [before-after] study, one group of 71 male and female nurses from medical-surgical departments of a hospital in Tehran participated. Solution-focused Communication techniques in a one-day workshop [8 hours] were trained. Nurse’s communication skills were assessed by questionnaire at pre-test and post-test [two months after the intervention]. Reliability was confirmed with correlation coefficient [α=0.86] through inter-rater reliability. For any participant, three questionnaires were completed [by themselves, their head nurse & their colleagues]. Data were analyzed using descriptive and analytical statistics. The mean score of nurse's communication skills before and after the intervention found statistically significant differences [P= 0/001]. Statistically significant differences were also observed between mean scores of the four subscales of nurse's communication skills before and after the intervention [P=0/001]. Solution-focused communication training [SFCT] for nurses could have a positive effect on different aspects of their communication skills, containing; general and therapeutic communication, spiritual supporting and their attitudes toward communicating with patients.