مجله مهندسی مکانیک
سال پنجاهم شماره 2 (پیاپی 91، تابستان 1399)

Absorption systems have been in the spotlight of scientists due to their capability to utilize excess energy and heat produced by other working systems. One of the inhibitory factors in using these systems is their low efficiency. This inhibitory factor has been a reason for scientists to propose different configurations for these systems. Investigation of these systems using the second law of thermodynamics could lead to understanding of the reasons behind their low efficiency. In this paper, variations of coefficient of performance and exergetic efficiency of single, double and triple effect parallel and series water-lithium bromide absorption systems with generator temperature in different evaporator temperatures are analyzed using a code written in Engineering Equation Solver (EES). The obtained results demonstrate the excellence of triple effect absorption systems in comparison to double and single effects. Exergetic efficiency increases 10 to 18 percent for each increase of complexity of system. These results also depicts the excellence of parallel systems to series ones. Also, the rate of refrigerant fluid working in the cycle to heat delivered to the high temperature generator is higher for parallel systems compared to series ones and is higher for triple effect systems.

One of the conventional ways to increase velocity of a fluid flow is using a nozzle in stream wise. In this paper, in order to increase the flow velocity in a low speed wind tunnel, and to carry out experiments at higher velocities. An optimal nozzle profile, by considering constraints such as the nozzle inlet cross section, inlet velocity, and nozzle length has been designed using computational fluid dynamics. Design variables were the nozzle inlet cross section, outlet velocity, the turning point of the nozzle profile, the uniformity of the outlet flow and the effective length of the test section. The performance of the designed nozzle was experimentally investigated. According to the results, the velocity increased by 13 m/s and the uniformity of the flow decreased by ±1%.

In this paper, finite element method is employed to study the buckling behavior and mechanical properties of double-walled carbon nanocones. In this regard, double-walled nanocones with different geometries, including lengths and angles, and boundary conditions are investigated. Based on the similarity between the nanostructures and space frames, structural mechanics approach is employed to study the mechanical behavior of the nanocones. In this approach, the carbon nanocones are considered as space frame and beam and mass elements are utilized to model the atoms and bonds. The results show that the elastic modulus of the carbon nanocones decreases by increasing the apex angle and length. Besides, it is shown that the influence of the apex angle on the critical buckling force of the carbon nanocones is more significant than the length effect. Increasing apex angle and length of the carbon nanocones lead to increasing and decreasing of the critical buckling force, respectively.

Using inducers in order avoiding pressure reduction at the centrifugal pump impeller inlet and consequently increasing pump performance at high suction speeds are important in many applications. The inducer which is an axial pump with lower number blades than impeller’s (usually 3 or 4), located on the upstream impeller and rotates with the same rotational speed and direction as the pump. In this research, changing inducer design parameters such as the blade pitch and the length to the diameter ratio on its and pump hydraulic performance is investigated, numerically. The results show that using inducer and changing its blade pitch ratio from 0.24 to 0.48, causes average pressure ratio increasing from %10 up to %34 at the pump impeller inlet. Unlike the pitch ratio changing effects, increasing the length to blade diameter ratio from 7/12 to 16/12 show a fairly constant average pressure ratio increasing up to %23. For the large pitch ratio, pump impeller induced head; decreases for low flow rate. Meanwhile, decreasing pitch ratio in high flow rate causes flow counter rotation at the pump impeller inlet that increases the pump impeller head.

This study explores the free vibration analysis of a functionally-graded rectangular plate which has been reinforced by carbon nanotubes (CNT) using the novel theory of trigonometric higher-order shear deformation. Carbon nano-tubes have been distributed through the thickness direction in a linear, symmetric and non-symmetric fashion. The foundation pertaining to Pasternak , or rather duo-parameter, has been utilized in the modeling; moreover, the new mixtures rule has been used for estimating the plate properties. The governing equations have been derived using the Hamilton’s principle, and the Navier’s solution has been used for dealing with a rectangular plate boundary conditions. Lastly, the effects of diverse parameters have been examined upon the vibrational behavior of the plate, such as the different distributions of CNT and the geometric properties of the plate. The results show that the amount of natural frequencies rise in proportion with an increase in the ratio of thickness to the width of the plate (h/b); a decrease in the ratio of length to the width of the plate (a/b); as well as an increase in the coefficients of the elastic foundation, such that the changes in the amounts of natural frequencies will be tremendously decreased in proportion with K> 10000 and K> 1000, and such changes will not be tangible.Furthermore, the highest amounts of frequencies will be pertinent to the X distribution, and the lowest amounts of frequencies will be pertinent to the O distribution

In this paper, based on the theory of two-dimensional thermo-elasticity steady state, the influence of parameters affecting stress field created around a non-circular hole in an infinite isotropic plate under a heat source is investigated. The isotropic plate has a point heat source near the hole and the boundary of the hole is insulated. By using the complex potential functions and applying conformal mapping and solving the integral equations, stress distribution around the hole is represented. The used method is the expansion of the complex variable method for an infinite isotropic plate with circular and elliptical holes. Bluntness and rotation angle of the hole are important parameters that are considered in this research. The results of this study show that the bluntness parameter has a significant effect on the stress distribution around the holes and near the heat source.

In this research, a tri-generation system based on ammonia fed solid oxide fuel cell is proposed and investigated. This study involves thermodynamic modeling of the fuel cell to conduct energy and exergy analysis of the system components in order to evaluate the energy and exergy efficiencies of the tri-generation system. In the proposed system, a solid oxide fuel cell with hydrogen-proton conducting electrolyte is used as the prime mover, which has the best performance for ammonia-fed fuel cells based on the reported results in the literature. The effects of important parameters such as current density, operating temperature and pressure are investigated on the performance of the proposed tri-generation system. Based on the results, assuming 1073 K and 505 kPa for the fuel cell working conditions, the energy utilization factor and exergetic efficiency of the proposed system are calculated to be 108.9% and 75%, respectively and overall output power is increased 633 kW by using tri-generation system instead of fuel sell stack only, regardless of the cooling and heating load produced.

A Rod Baffle shell-tube heat exchanger was simulated using HTRI software and Computational Fluid Dynamics (CFD). The results from both models were compared with available experimental data. In addition, the effects of distance of baffles and cold fluid’s velocity on the heat exchanger’s performance were analyzed. The obtained results showed that decreasing the distance between baffles can improve the heat transfer. However, diminution of this distance more than a threshold can lead to a significant reduction in the heat transfer. By comparing the two employed methods for simulation of shell-tube heat exchangers with bar baffles, one can say that the use of HTRI software is easier and faster than the CFD method and achieves acceptable responses, on the other hand, the CFD results are more accurate. Furthermore, the details of the temperature and velocity profiles of the fluid inside the heat exchanger can be calculated and analyzed. The results of this research can be an effective step in developing the application of this type of heat exchanger and redesigning of it.

The friction factor between workpiece and die is one of the important factors that affects the design steps of a forging process. By now, various methods, that each one has its own advantages and disadvantages, have been used by other researchers in order to estimate the friction factor. In this paper, a new method ,which has been named open die compression of a cylindrical rod, has been presented to estimate the friction factor and investigated numerically and experimentally. As Titanium alloys are classified as a kind of hard to work metal alloys and it is important to investigate friction in forming processes of titanium, a sample of Ti-6Al-4V bar has been investigated in experimental test. The results show that this method has an agreeably high sensitivity to friction factor value; So that calibration graphs are separate enough. Also, the geometrical shape of the workpiece causes a great surface expansion during the test.

In the present study, the effects of turbulent flow are experimentally investigated on the drag coefficient of tandem cylinders with non-equal diameters in different Reynolds numbers. Drag coefficient test for downstream cylinder in diameters A=15.5 mm and B=21.3 mm, was experimentally carried out at two longitudinal distance at five Reynolds numbers based on the upstream cylinder diameter for two turbulence intensity of 4.5 and 7% respectively. The position of the upstream cylinder to the downstream cylinder changes at five angels 0, 22.5, 45, 67.5 and 90 degrees. Results for downstream cylinder in the 4.5% turbulence intensity indicate that with increasing the diameter ratio of the cylinders and increasing the longitudinal distance between the two cylinders, the drag coefficient increases. However, with increasing aligning angels of the upstream cylinder with respect to the downstream cylinder, the drag coefficient varies depending on the nature of flow. Finally, by increasing the flow turbulence intensity, the drag coefficient decreases significantly at all stages of the experiment.

Today, Production in the shortest possible time, with the lowest cost and highest quality is the one of the most important criterions in the industry. Tube hydroforming (THF), because of its unique feature, increasingly used in military, industries, automobile manufacturing, aerospace, and bicycle industries. Most tube hydroformed parts are produced by a multistage loading process which the suitable loading condition in THF with regard to internal pressure and axial feeding should be designed to improve formability and to avoid failure modes on the final hydroformed product. This study deals with the procedure for the determination of the proper loading path in THF using a fuzzy logic control algorithm, which avoids the failure of the tube due to excessive induced strain during the forming process. For this purpose, Mamdani fuzzy control algorithm was used in conjunction with Abaqus FEA code for simulation of the THF process. The wrinkling measurements and the thickness variation obtained from simulation are used as input in fuzzy control and fuzzy control outputs are used to set the loading path. A controlled algorithm is designed to maximize the expansion of the tube and minimize the thickness variation of the wall and wrinkling at the same time. The numerical results were verified and validated by conducting experiments where a good agreement was obtained between the experimental results and simulations

The delamination and debonding phenomena of the layer are two of the defects that occurs in composite-reinforced sandwich structures. In this paper, the debonding and debonding growth of buckling load has been investigated. Debonding growth is modeled by cohesive elements with defect code in Abaqus finite element software. In this study, debonding and growth of debonding between composite and core layers has been investigated. In this model, three simulations were performed and the results were compared with the results of previous research. The first model is a structure with no defect, the second considers the initial defect of debonding, and the third model is the structure considering the initial defect of debonding and its growth. In the second and third models, the initial debonding is considered to be 25 and 50 mm in length. The results in the second and third models indicate two stages in the load-displacement diagram that justify the occurrence of local buckling at the site of debonding. As expected, an increase in the length of the initial debonding would reduce the local and global buckling load. In contrary to previous research, considering the growth of debonding and the use of defect code, the results of load-displacement are closer to the empirical results.

In this study, aging temperature effect on the fracture mode and wear mechanism of the Hadfield steel was investigated. For this purpose, 5 blocks were casted from Hadfield steel. After the casting, all blocks austenitized in 1100°C for 2 hours and immediately quenched in the pure water. Then, one block at austenitising conditions remained and four other blocks the aging heat treatment in 450, 500, 550 and 600°C for 1 hours. In the next step, uniaxial tensile, hardness measuring by Vickers method and wear by pin-ondisk method tests were applied on them. To evaluation of the microstructures was conducted by optical microscopy and the fractured surfaces and wear mechanism were observed by scanning electron microscopy. Optical microscopy observations showed that the aging heat treatment temperature increase, leads to increases carbide precipitates and decreasing austenite grains size in the Hadfield steel microstructure. The results of mechanical tests showed that aging temperature increase lead to increase in hardness, strength and wear resistance of Hadfield steel, but in return reduces fracture strain. Also, scanning electron microscopy images from wear and fractured surfaces showed that aging temperature increase lead to the creation of brittle fracture and in all aged samples sticky wear took place.

Sandwich panels with corrugated cores have wide applications and play an important role in industries like vehicle, aerospace and marine industry. Corrugated-cores in the middle of the sandwich structures make them stronger under bending loads. Due to their high efficiency with low weight, considerable researchers studied the behavior of sandwich panels and most of them used numerical methods. In the other word, there is a few studies presents an analytical solution for corrugated sandwich panels. As first time in this paper, sandwich panels with corrugated core is investigated by using an analytical solution based on power-series method. By using this method, one can overcome restrictions of other methods which limit the analytical solution to special boundary conditions. First, by using double Maclaurin series, partial differential equations is extended based on first order shear deformation theory. Then, the obtained equations are solved by considering various types of boundary conditions. It is assumed that panel rested on elastic foundation and Winkler elastic foundation is used to model it. The obtained results are validated by available researches. Moreover, detailed parametric study is conducted involving geometrical parameters like core and face thickness, angle and pitch of corrugated core, type of boundary condition and stiffness of elastic foundation.

In this study, the viscous fingering instability in miscible displacement of Newtonian fluid by viscoelastic fluid in an anisotropic porous media is investigated for the first time. The Oldroyd-B model has been used as the constitutive equation. The roll of velocitydependent transverse and longitudinal dispersions on the fingering instability is investigated through linear stability analysis and nonlinear simulations. The results of linear stability analysis show that the growth rate of instability is decreased by increasing the rate of transverse to longitudinal dispersions and the flow becomes more stable. The nonlinear simulations are performed by use of spectral method and Hartly transformation and the results are included concentration contours, transversely averaged concentration profiles, mixing length and sweep efficiency. The results show that the flow becomes more unstable by increasing the rate of longitudinal to transverse dispersions.

Aerodynamic characteristics of an aircraft with delta wing are considerably affected under the ground effect in take-off and landing phases. In this research, static ground effect of a 60 degrees delta wing with axisymmetric sharp edges in combination of body and vertical tail at low speed wind tunnel are investigated. The wind tunnel is closed type has an opened test section that its dimensions is 2.8 m × 2.2 m and maximum velocity is 90 m/s. In these tests ground effect is simulated using a fixed plane that its height is variable. With decreasing the height from the ground plane, the lift force is increased, induced drag force is decreased, total drag force is increased and nose-down pitching moment is increased nonlinearly. The rate of increasing of lift coefficient in linear regions increased with decreasing of height from ground plane. At the positive angle of attack the most percentage increasing of lift coefficient is due to 5 degrees angle of attack as the result of existence of perfect vortex flow over the whole wing surface. The minimum case is due to 30 degrees of angle of attack.

In this paper, a new active robust fault detection method based on combination of bond graph and Unknown Input Observer (UIO) is proposed. The proposed two-stage method will satisfy some desirable criteria of a fault detection system. In the first stage, an UIO based on derived state space representation form from the bond graph model is used to estimate the states and outputs of the system, which are insensitive to disturbances in the system. Then, the obtained Analytical Redundancy Relations (ARRs) are considered based on the output estimation error of the observer, which are sensitive to faults while are robust against the disturbances. This form of residuals is called Error-based Analytical Redundancy Relations (EARRs), which further becomes robust against parametric uncertainties by defining adaptive thresholds on the parameters’ values of bond graph model. Simulation results for an active suspension system are provided to show the great performance of the proposed method.

In this paper, a heat exchanger in the Toos power plant in Mashhad has been studied, which is used in a two-stage air compressor as a middle cooler. The purpose of paper is increase the efficiency of this heat exchanger with Keep the shell and tube sizes and arrangement of tubes to increase efficiency of two-stage air compressor. According to the results obtained by increasing the tubes number of 66 to 74, the heat transfer area increasing 13 percent; as well as, the efficiency of heat exchanger increase of 81.16 to 82.7 percent. In general, two-stage air compressor efficiencies increase of 41 to 42 percent. Increasing the efficiency of the compressor will save 1.12 KW power in the compressor engine.

In this paper, thermal effects of Gaussian and super Gaussian pumping on the rod laser are analytically investigated. The crystal is considered as a rod, with isotropic thermomechanical characterizations, which is end-pumped. The intensity distribution of pumping spot is considered in three-types including Gaussian, second order and third order of super-Gaussian, and effects of any type on the thermal distribution and thermal lensing are compared with each other. First, the heat generations due to emission in the crystal are calculated for Gaussian and super Gaussian pumping and then the equation of temperature distribution is analytically solved and a closed form solution for temperature distribution of the rod laser is obtained. The analytical results are compared with the results of finite element method. Thereupon, the temperature distributions and the values of thermal lens for various pumping powers are calculated. The results show that calculated maximum temperature for Gaussian case is lower than for supper-Gaussian cases. In addition, the distances between focal point and the input pumping plane obtained for super-Gaussian pumping are larger than those calculated for Gaussian pumping.

In this research a nocturnal radiative cooling system is studied. Firstly the nocturnal radiative cooling potential in Zahedan climate is considered. Then the effect of water volume flow rate and storage tank volume on cooling load is investigated. Thermal stratification model is used for the storage tank modeling. In this article, the effect of the thermal layer numbers on the result accuracy is studied. The article results show that Zahedan has high potential for using nocturnal radiative cooling. On the other hand, the considerations show that the water volume flow rate increasing causes the stored water temperature decrease. Also when storage tank capacity increases, the stored water temperature increases, but when the amount of water increases, it can help to save more cooling at night. Finally assuming the thermal layer number between 3 and 10, can decrease the computation’s error.

In this article the prediction accuracy of Johnson-Cook and Zerilli Armstrong constitutive equations in describing materials behavior in drawing process of copper wires in moderate strain rate condition were investigated. Wire drawing force was measured in different combinations of drawing speed and areal reductions using a load cell connected to the drawing die. Simulation of wire drawing process according to experimental test was done using Johnson Cook and Zerilli Armstrong constitutive equations. A VUHARD subroutine was developed to introduce the constitutive equations to finite element code and was called during the simulation. The drawing force was considered as a parameter to compare the simulation results with the experimental ones. Results showed that the simulation with Zerilli Armstrong equation has better correlation with experimental results comparing to the Johnson Cook equation, and in some circumstances, it completely fits on the experimental results. This shows the high accuracy of simulation and constitutive models.

The present study, obtain an axial compressor performance map by using of the software calculations and adaptation of the Moore-Gritter curve in combination This method has high computing speed beside very low-cost and availability. Numerical solution of the rotor is performed by the rotor design process and then the results are plotted as curve fitting Third Grade Maps compressor at three rpm speeds of 70, 90 and 100%. According to the obtained results with the results of the calculation error maximum pressure and mass flow is minimal. Predict point in three rpm work instability, error is encountered. Working around 100, the percentage of error in predicting maximum pressure of 0.4490% and 1.8993% of the Predict mass flow is equal at this point. Working around 90 percent, the error in predicting maximum pressure of 0.6685% and 4.3578% of the Predict mass flow rate was calculated at this point and around 70 percent, the error in predicting maximum pressure of 0.9363 percent and 8.9840 percent predicted mass flow rate at this point is equal.

In this paper, an ammonia-water absorption refrigeration system has been modeled with mass and energy balances by EES software, the effect of RHE efficiency on system's operating parameters by coupling the EES and MATLAB software is studied thermodynamically, and the system's performance is analyzed under different conditions, in first case, similar to the published researches, at an optimal obtained value for low pressure and generator temperature proportional to the investigation range of RHE efficiency, and in second case, due to a high dependence of this system's parameters together, as the main novelty of this research, at optimal obtained values for these parameters according to the RHE efficiency variations. The results show that, low pressure, generator temperature and COP increasing, decreasing and increasing in the range of 0.6217-2.8770 bar, 152.6-114.6℃ and 0.2909- 0.5923, respectively, by increasing the RHE efficiency from 0-1 which demonstrates the considerable effect of RHE efficiency on system's operating parameters. Also it was shown that in this case study, the RHE should be considered as an essential component, and choosing efficiency values higher than 73.95% must necessarily have economic justification.

Effect of different nanoparticle on thermo-economic optimization of a shell and tube heat exchanger (STHE) is investigated in this paper. Aluminum oxide (Al2O3) and silicon dioxide (SiO2) are used as nanoparticles. Thermal modeling by "ε-NTU" method and multi-objective optimization using genetic algorithm is used to increase effectiveness and reduce total annual cost. Tube arrangement, tube diameter, tube pitch ratio, tube length in each pass, tube number, baffle spacing ratio, baffle cut ratio, cold stream flow allocation, tube pass number and particles volumetric concentration are considered as ten design parameters. The results as a set of solutions (Pareto optimal front) is displayed. The results showed that efficiency and total annual cost improved in the case with nanoparticles. For example, 4.174% and 2.028%, improvement in the effectiveness are find respectively for aluminum oxide and silicon oxide compared with base fluid and for a fixed value of annual cost=5000 $/year. Furthermore, the effect of nanoparticle on some of heat exchanger specifications is studied and results are reported.

In this paper, the simulation of the natural gas dehydration process by adsorption method has been studied. This process has been designed to remove water and reaching it to the allowed amount in the natural gas. The process consists of four beds, and each bed has two layers. Three beds are adsorbing and the fourth bed is regenerating. Molecular absorbents and active alumina have been used to absorb water in gases. The feed gas in this process is saturated from the water and includes methane, nitrogen, water, and carbon dioxide, and is entered to the bed at the temperature of 42 ° C and the pressure of 90 bar. Aspen and Matlab have been used to design and model this process. In this simulation, the amount of water in the gas reaches to less than 0.09 ppm, with an allowable value of 0.1 ppm. The results show the developed model can predict the process outputs with acceptable accuracy.

In this paper, the effect of composite patch on reinforcement of cylindrical tube containing a surface crack under internal pressure is investigated using a three dimensional finite element method. The cylindrical tube contains an external circumferential semielliptical crack and the aspect ratio of the cracks is between 0.2 and 1 and its relative depths are 0.2 and 0.8. In order to ensure the accuracy of modelling, first, a cylinder containing a surface crack is simulated under uniform tension loading and the results are compared with the available data. The stress intensity factor at the crack tip is determined using the J-integral. Then, the cracked cylinder under internal pressure is repaired using topical composite patch. In this regard, in order to select the appropriate patch, the effect of different parameters such as length, width, thickness, material and angle of composite multi-layer fibers on the stress intensity factors are examined. The results indicate that the stress intensity factors can decrease about 23% by using the appropriate patches which caused the increase of fatigue life due to the decrease of fatigue crack growth rate.

Offering deposition of dense coating at solid state, cold spray consolidating method can be used for deposition of a wide variety of composite coatings including metal-matrix composite coatings. In this research, deposition of Ni-Ti composite coating using cold spraying and formation of intermetallics after post spray heat-treatment were investigated. Ni and Ti powders were physically blended with equivalent volume ratio (68.3% at. Ni-31.7%at. Ti), sprayed as the feedstock powder and composite coating with 35.2 at. % Ni- 64.8 at. % Ti composition was obtained. Post heat-treatments were conducted at 740 ̊C, 900 ̊C, and two-step heat-treatment 740 ̊C and 960 ̊C for different times. Microstructural investigation showed that all three equilibrium intermetallics of binary Ni-Ti phase diagram including Ni3Ti, Ti2Ni and NiTi phases were formed at all heat-treatment experiments and fraction of Ni3Ti phase decreased with consumption of the Ni precursor. Additionally, it was found that cold sprayed composite coatings had fast intermetallics formation and growth kinetics compared with those of common press and sinter samples which was addressed through deformation enhanced interdiffusion and particle/particle bonding of cold sprayed coatings.

Chemical Mechanical Polishing (CMP) is one of the nano-metric polishing processes of non-metal balls and wafers such as silicon nitride balls and various ceramics. In this process, abrasive particles (Fe2O3, CeO2 and ZrO2) which have lower hardness than workpiece are floated in some fluid. In this state, the workpiece reacts chemically with base fluid (water, air, hydrogen peroxide and or oil), forming a thin layer of silica (SiO2) on the surface of the workpiece. Removal of the thin oxidized surface layer of the workpiece by abrasive particles, as a result of the chemical reaction, is easily done. Effective parameters of Chemical- Mechanical Polishing include 1- density of abrasive particles, 2- spindle speed of milling machine, 3- polishing time and 4- kind of abrasive particles which by altering of each, factors such as 1- surface roughness, 2- sphericity and 3- material removal rate change. In the present research, a laboratory device is designed and manufactured for chemically- mechanically polishing of silicon nitride balls and 24 experiments are designed by Minitab software and done to investigate effects of the mentioned factors on surface roughness and material removal rate. For each of the factors two levels is set, after variance analysis of the experimental results, regression equations of the surface roughness and material removal rate were achieved. By increase of polishing time, spindle speed of milling machine and density of all three kinds of abrasives during experiments, material removal rate increased and surface roughness enhanced. Morphology of surface roughness by X-Ray photo-electron spectroscopy (XPS) was studied. Probability of chemical reactions by Gibbs free energy equations was also investigated. Eventually, approaches for optimized polishing of ceramic balls were proposed due to the experimental conditions and analysis of variance. Comparison of the experimental results showed that the surface roughness of balls polished by the Fe2O3 abrasive particles (Ra= 69 nm) was far better than the other two abrasives, and equals.

This project is conducted to provide mathematical modeling as well as experimental investigation on a hybrid photovoltaic/thermal collector with solar still system. The performance comparison of the system with conventional solar desalination systems is the other result of the project. In this regard, two different experimental setup have been investigated: active mode (including solar still, heatpipe, and photovoltaic cells), passive mode (solar still, exclusively). At first, the convenient depth of brine water in the basin was determined. Then, the amount of distilled water on the solar still glass cover as well as its walls was measured. The maximum water recorded for passive mode is at 14:00 up to 0.292 Kg/m2 .h, and for active mode is 0.406 Kg/m2 .h at 14:00. The mathematical modeling was done based on thermodynamic and heat transfer relations convenient for the setup arrangement. The reliability of the model results is checked by the experimental results and a discussion is proposed

The performance of dry cooling tower (Heller Type) is highly affected by environmental conditions, especially wind condition. Under wind conditions, due to the loss of symmetry of the distribution of pressure around the tower, as well as the wind covering phenomenon on the top of the tower, the inlet airflow to the tower and so the efficiency of the cooling tower decreases. One of the methods recently proposed to improve cooling tower performance under wind conditions is the flue gas injection from a recovery boiler, which is about 130oC, into the cooling tower at combined cycle power plants. In the present study, a Heller dry tower, with a solution domain around it, is modeled using computational fluid dynamics. The amount of numerically calculated heat released from the cooling tower, with and without injection at the design conditions of the tower under crosswind effect, has been used to perform an exergy analysis on the components of the combined cycle power plant. Finally, the positive and negative effects of flue gas injection into the Heller Tower have been studied on the overall performance of the combined cycle power plant, indicating an increase about 0.94% and 0.88% in the overall first and second law efficiencies of combined cycle power plant respectively.