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In this study, an optimization of the maximum cooling of three radiant heat sources inside a closed square porous environment is performed. Three radiant-heat sources are cooled by airflow in a porous medium with an inclination angle. It is applied in the cooling of electronic equipment inside laptop computers. The cooling phenomenon is a function of five independent variables, such as the length of heat source, radiation parameter, Darcy number, the angle of inclination of a porous medium, and Rayleigh number. Differential equations are solved using the finite-difference approach. And those are solved by the Gauss-Seidel approach. Simulation is a numerical solution of the vorticity–stream equations. Coding is done in MATLAB software. And it is obtained the maximum objective function using the algorithm of particle swarm optimization. Cooling simulations are performed by drawing flow lines, constant temperature lines, dimensionless velocity component profiles, local Nusselt numbers, and mean Nusselt numbers. The main goal is to find the highest cooling rate in different amounts of five independent variables. The flow is in the laminar flow regime, and inclination angles are between 0 to 360°. The present study is the first study on the numerical solution of the cooling of three radiant-heat sources with an inclination angle by the porous media-filled square environment. And it is developed from the cooling of hot radiation walls problems in an inclined enclosure with constant temperature local radiant heat sources. This investigation showed the flow lines and their direction are influenced by the inclination angle of the porous medium strongly, and the maximum heat transfer is achieved at an angle of inclination of zero degrees. This investigation showed at the Darcy number, 0.001, and the radiation parameter, 1. The maximum and minimum Nusselt number is obtained for the inclination angle 60 and 180°, respectively.

In this study, a numerical study is performed on the cooling phenomenon of three heat source electronic devices. The electronic devices are cooled in the form of natural heat transfer by the airflow in a porous medium. Electronic devices are installed on the boundary walls of a square environment. Cooling simulations are performed by drawing flow lines and constant temperature lines. Our main goal is to find the highest cooling rate in different Darcy numbers and different Rayleigh numbers in our investigation. The range of Darcy numbers and Rayleigh numbers is between 0.0001 to 0.01 and 1000 to 100,000, respectively. Our investigation showed the maximum cooling is obtained at the Darcy number of about 0.01. And also, by decreasing the value of Darcy number, a higher cooling rate for the hot boundary walls is achieved.

A structure has been proposed in this paper for generating electricity from a waste heat recovery system using various experiences of research on the exploitation of thermoelectric effect, which allows the direct conversion of thermal energy into electrical energy. For this purpose, this paper has presented a new method for waste heat recovery in industry and converting it to electricity using a thermoelectric generator (TEG). The proposed system is a combination of a heat pipe and a thermoelectric generator. Indeed, the system consists of a thermoelectric generator (TEG) based on bismuth telluride (Bi2Te3), placed between two heat pipes. The proposed system is presented in two separate designs including a heat exchanger based on simple TEM1 and volumetric TEMs and has been implemented in MATLAB software. The simulation results show that the heat exchanger based on volumetric TEMs is 18% superior to the heat exchanger with simple TEM in producing electricity.

Providing a suitable method for predicting the effect of particle aggregation on photovoltaic (PV) performance can be one of the best ways to make better use of solar energy. In this study, a mathematical method was used and modified to provide a better prediction of angular losses coefficient ( α r ). The modified coefficient as well as a computational method were used to find the performance of dusty modules equipped with one-axis (East-West (EW), North-South (NS)), and dual-axis (DAT) solar tracking systems. The modified α r , which here is called the degree of surface dirtiness, can be used to estimate the area covered by particles per cm 2 , i.e. A ∗ C ( θ ) . A better prediction of α r causes a better prediction of power loss due to dust settlement. Results showed that A ∗ C ( θ ) is the factor that shows the role of incidence angle in visualizing the type of dust cover, while α r shows the effect of slope angle on dust deposition density. Furthermore, combination of α r with the computational model revealed that the dirty DAT module has the least daily power loss which is 9% of the clean counterpart power. The power losses for the NS and EW dusty modules are 13% and 20.5% lower than the clean counterparts, respectively. It should be noted that the obtained results in this study are in a good compromise with the experimental and computational data available in the literature.

An experimental setup for pool boiling of dilute dispersions of titanium dioxide (TiO2) nanoparticle in water-ethylene glycol 50 (WEG50) as the base fluid was developed. The nanofluid was stabilized by using sodium lauryl sulfate as a surfactant. The heater surface roughness was affected by the deposition of nanoparticles during boiling which consequently changes the heat transfer characteristics. Three copper heater surface roughnesses: smooth, semi-rough and rough, were used. The effect of surface roughness and nanofluid on boiling heat transfer coefficient (BHTC), surface wettability and nucleation site density were examined. The results showed that BHTC and nucleation site density were increased by increasing the heater surface roughness in the base fluid of WEG50. The findings of this study revealed that the effect of volume concentration of nanofluid on the BHTC significantly depends on the heater surface roughness. At heater surface roughness of 0.062 μm, BHTC increases compared to WEG50 base fluid for all volume concentrations of TiO2-WEG50 nanofluid. With increasing the volume concentration of nanofluid up to 0.005%, an increasing tendency in BHTC was observed but beyond that a decreasing trend was observed for heater surface roughness of 1.213 μm. However, as heater surface roughness reaches 3.146 μm, BHTC decreased by increasing nanofluid volume concentration, compared to WEG50 base fluid. Also, increment of heater surface roughness causes the nucleation site density to increase when either base fluid or nanofluid is used. By measuring static contact angle of sessile water droplet on heater surface before and after experiment, it was found that using TiO2-WEG50 nanofluid causes to surface wettability increased.

This study has been conducted to illustrate combined heat transfer in a PolyMethylMethAcrylate (PMMA) sample. PMMA is a promising polymer utilized to optical, pneumatic actuation, sensor, analytica...

Erosion has been recognized as one of the major threats for industries involving multiphase transportation pipelines. Within the last decades, effective parameters on wear pattern have been identified. As a result, the (famous) V-shaped erosion profile has been detected for the pipes' elbow section. In this study, CFD is employed to investigate the erosion mechanism on the square duct elbows. A novel erosion pattern has been observed for square ducts in comparison with the pipes. The impact of several parameters (particle and flow velocity, secondary flow, turbulent intensity, particle streamline) has been inspected as well. It has been led to the conclusion that the erosion rate of square ducts is lower than common pipes, especially when either higher flow velocities or bigger particles size are employed.

In recent years, the limited energy sources and their huge costs in many countries to save money have attracted the attention of many scholars. The purpose of the energy consumption assessment of a building is to reduce the waste of the energy, and this reduction in the energy has a direct relationship to the lower costs. In this paper, the researcher tends to investigate the sensitivity and the energy analysis of a warm and dry residential complex in Iran (Yazd). Initially, the simulation of the energy consumption of a building was calculated by using the eQUEST software, to determine the thermal load of the building for a range of important parameters (such as wall insulation, roof and floor insulation, air penetration, glass type and window size). Then by using the SPSS software, the relationships have been extracted to connect the energy of the building with these factors. Then, by using the SPSS software, it attempted to connect a meaningful relationship between the energy consumption of the building and the mentioned factors. Also, the energy efficiency of the building was optimized by converting the data to the neural network, by using the genetic algorithm. Finally, this study was also carried out in warm and dry areas, to describe the accuracy of the results, and in each step, appropriate validations have been done.

In this study, energy consumption is simulated for a residential complex in the cold weather condition of Iran. For this purpose, Tabriz is selected as the representative city. The mathematical equ...

In this research, it is investigated to numerically evaluate the performance of a polymer electrolyte membrane fuel cell (PEMFC). The performance is investigated through the nonuniformity gradient loading at the catalyst layer (CL) of the considered PEMFC. Computational fluid dynamics is used to simulate a 2D domain in which a steady‐state laminar compressible flow in two‐phase for the PEMFC has been considered. In this case, a particular nonuniform variation inside the CL along the channel is assumed. The nonuniform gradient is created using a nonisothermal domain to predict the flooding effects on the performance of the PEMFC. The computational domain is considered as the cathode of PEMFC, which is divided into three regions: a gas channel, a gas diffusion layer, and a CL. The loading variation inside the catalyst is defined as a constant slope along the channel. In order to find the optimum slope, different slope angles are analyzed. The results point out that the nonuniform loading distribution of the catalyst (platinum) along the channel could improve the fuel cell performance up to 1.6% and 5% for power density and voltage generation, respectively. It is inferred that it is better to use more catalyst in the final section of the channel if the performance is the main concern.

This paper investigated an optimization model for heat exchanger network by detailed design method for each heat exchanger unit. Particle swarm optimization technique is used to determine to optimum results in the mixed material heat exchanger network which included the capital and energy costs of heat exchangers. Mixed materials used in corrosive flows and included three types of exchangers such as cheap, expensive and mixed. Two methods used for achieving the optimum the total annual cost in mixed materials heat exchanger networks such as total and partial decompositions methods. The case study was used to show the application of the proposed method. The total annual cost has been reduced by detailed design in each heat exchanger by optimization technique. It has been reduced 20.7% compared with initial case in full integration method. The reduction of the total annual cost by detailed design in the partial decomposition method is 12.4% compared with the full integration method and 5.78% compared with the total decomposition method.

In this paper, multi-objective particle swarm optimization method is developed for optimizing thermo-hydrodynamic journal bearings. This paper focuses on the use of multi-objective particle swarm optimization algorithm with a combination of the thermal hydrodynamic governing equations of the fluid film (i.e. momentum and energy equations) to optimize hydrodynamic partial pad journal bearings and compare with other articles. The governing equations are solved by the central difference method with a successive over-relaxation scheme and the backward difference with an iterative technique. In the paper, the lubricant viscosity changes with the temperature variation in whole fluid film. In this optimization, the bearing power loss, the minimum oil film thickness, and the maximum oil temperature are considered as objective functions and the radial clearance and length to diameter ratio are selected as design variables. The results of the objective functions are compared to other articles. Also, this study discusses the entropy and availability of two concentric cylinders with low curvature and constant wall temperature. Calculations showed that by increasing the Eckert number, the availability increases.

In this study, the synthetic jet position was optimized to obtain the maximum rate of heat transfer and the best state of temperature uniformity on a heated surface in micro-channels. Based on micro-channel length, several cases were simulated to investigate the effects of synthetic jet position on the heat transfer rate and temperature uniformity. After that, the synthetic jet position was optimized using the CFD results and the GMDH-MOGA optimization code. The obtained results show that the synthetic jet placement in all longitudinal positions of micro-channel increases the heat transfer rate, although the improvement of temperature uniformity of heated surface decreases at some positions as compared to the micro-channel without synthetic jet. The optimization results show that for obtaining the maximum value of heat transfer and the best state of temperature uniformity on the heated surface, the dimensionless longitudinal position of synthetic should be between 0.45 and 0.65. The maximum rate of heat transfer and the best state of temperature uniformity have been observed in the vicinity of lower and upper bounds of this range, respectively.

Purpose This paper aims to examine total annual cost from economic view mixed materials heat exchangers based on three optimization algorithms. This study compares the use of three optimization algorithms in the design of economic optimization shell and tube mixed material heat exchangers. Design/methodology/approach A shell and tube mixed materials heat exchanger optimization design approach is expanded based on the total annual cost measured by dividing the costs of the heat exchanger to area of surface and power consumption. In this study, optimization and minimization of the total annual cost is considered as the objective function. There are three types of exchangers: cheap, expensive and mixed. Mixed materials are used in corrosive flows in the heat exchanger network. The present study explores the use of three optimization techniques, namely, hybrid genetic-particle swarm optimization, shuffled frog leaping algorithm techniques and ant colony optimization. Findings There are three parameters as decision variables such as tube outer diameter, shell diameter and central baffle spacing considered for optimization. Results have been compared with the findings of previous studies to demonstrate the accuracy of algorithms. Originality/value The present study explores the use of three optimization techniques, namely, hybrid genetic-particle swarm optimization, shuffled frog leaping algorithm techniques and ant colony optimization. This study has demonstrated successful application of each technique for the optimal design of a mixed material shell and tube heat exchanger from the economic view point.

Mathematical models and numerical methods are used in predicting the various approaches of the cancer treatment process. In the present study, the drug delivery is investigated in three different biological tissues, i.e., tumor, normal, and normalized ones with different transport properties to study the effect of the intensity of vascular normalization on the behavior of interstitial fluid flow and drug distribution. The continuity, momentum (Darcy’s law), and convection–diffusion equations in the porous media are solved numerically. Results show that vascular normalization reduces the interstitial fluid pressure and sets up the pressure gradient, which can cause fluid flow throughout the tumor. The drug delivery improvement is shown by solute transport analysis, also. It is concluded that the amount of the maximum rate of drug concentration increases in time by vascular normalization. Moreover, normalization can establish the concentration gradient, which consequently improves the penetration of the drug into the inner parts of the tumor.

In this study the first and the second laws of thermodynamics are evaluated for a single effect absorption chiller. Entropy generation and COP are selected as the objective functions and their variations are studied by varying the generator temperature for various condensing temperatures. For this purpose, the enthalpy and the entropy data of the super-heated steam, saturated steam and the saturated water are formulated in the mathematical equations. Also to provide the required steam of generator, prime mover in the form of internal combustion engine is applied and its partial load conditions are analyzed. A residential tower is considered as the case study for selecting the proper prime mover capacity. The number of prime movers is estimated based on the required heating power of the generator steam for each partial load. It is seen, the entropy generation would be decreased rapidly by increasing the generator temperature and after a while, the entropy generation would be approximately constant. The optimum entropy generation for each condensing temperature and the generator temperature may be decreased by increasing the evaporator temperature. It is deduced that COP is increased rapidly by increasing the generator temperature but in the following, the COP will be constant. The maximum amount of COP is decreased by increasing the condensing temperature. Also the COP is increased by increasing evaporator temperature for a certain generator and condensing temperatures.

In this research heating, cooling and electrical demands of a residential tower are evaluated for Iran various weather conditions. For this purpose, several cities are selected as the representativ...

The main purpose of this research is to study the techno-economic analysis of a photovoltaic thermal collector (PVT) combined with phase change materials (PCM) and ground source heat pump (GSHP). In the first step of this study, a numerical transient simulation of a water-to-water GSHP was developed by using a vertical U-type ground source heat exchanger (GSHX) and variable speed drive (VSD) compressor in the multi-usage operation modes (heating and cooling). To achieve the most supreme system performance, the multi-objective optimization of the Levelized cost of energy (LCOE) and exergy efficiency was done by using the multi-objective non-dominated sorting genetic algorithm version || (NSGA-||). This algorithm considers substantial elements such as the number of boreholes, depth of drilling for the location of pipes in GSHX, setpoint temperature of fan coil, length of converters, the number of PVT panels, slope and direction of PVT panels, the number of batteries, volume of the storage tank of phase change materials and percentage of phase change materials in the tank. The simulation of the heat pump is accomplished through a numeral coding in the Engineering Equation Solver (EES) and also for the optimization part, a programming method used in the MATLAB program. Moreover, due to the evaluation of the transient response of the model, TRNSYS software was implemented. Based on the research achievements, the Single objective optimization of exergy efficiency for the combined PVT-PCM and GSHP systems can be conducted to the highest solar factor (SF) and the lowest amount of urban electricity consumption. Furthermore, the calculation of the annual required load of the building for different scenarios has shown that the use of collectors in this combined system has reduced the total load of the building by 6.5%. The maximum percentage of PVT energy efficiency belongs to the first scenario with a value of 53% and the lowest one with a difference of 43% is for the fourth scenario.

Motivation The inconvenient treatment of the current velocity-pressure coupling strategies is still a debating issue. Whether the procedures are formed on coupled or segregated solution strategy, the substituted equation for pressure, which is applied instead of the original continuity equation, is known to cause convergence problems for complex fluid flow situations. Challenge and approach The present study aims to evaluate two fully implicit, non-pressure-based coupled algorithms known as FICS and SICS (Fully/Simplest Implicit Coupled Procedures) that are able to solve the flow equations without utilizing any additional formulations (Poisson-type or else) for pressure. To do so, a numerical code using C++ was developed, and the noted coupled procedures were implemented alongside the well-known SIMPLEC (Semi-Implicit-Pressure-Linked-Equation-Consistent) algorithm, which was utilized as a benchmark procedure. The evaluations of the noted algorithms seek to compare the stability, solution speed, and compatibility to various physical phenomena such as turbulence and heat transfer that are the main subjects used to compare the fluid mechanic procedures. Significant results Obtained results indicate that coupled procedures are irrefutably stable whether only the laminar equations are solved or other highly influential scalar equations have participated. As an instance, it was observed that FICS-2 achieved convergence at least two times faster than SIMPLEC while applying the least amount of relaxation to amend for both non-linearity and the pressure-velocity coupling. Impact of the study and conclusion As a result, it is concluded that the primitive form of continuity equation is a more efficient alternative than the standard Poisson-based formulation and could be considered for future developments in commercial CFD purposes.

Supplying an energy source for impressed current cathodic protection is considered as the main challenge for pipelines corrosion protection in remote areas. The purpose of this study is to construct and evaluate the performance of an impressed current cathodic protection system using waste heat to replace the external electrical power supply. The system consists of four thermoelectric modules producing the electrical power from the hot combusted gas stream. Mathematical modeling and Buckingham Pi theorem were applied to obtain five dimensionless parameters and several models to estimate the system performance. According to the experimental results, the generated voltage, electrical current, and temperature difference have been increased rapidly during the experiment up to 201 mV, 44 mA, and 20 K, respectively. Moreover, mathematical modeling and Buckingham Pi theorem were also utilized to obtain three equations, two nonlinear and one dimensionless equation, to calculate the generated electrical voltage with the maximum error of 1.22%, 9.11%, and 10%, respectively. The results indicate that the temperature difference (between inlet gas and environment) and the figure of merit have a direct effect, and heat sink thermal resistance has an inverse effect on the generated electrical voltage.

In underground U-tube heat exchangers (boreholes) it is important to predict its heating performance to design and select the proper parameters such as length, diameter, material etc. to have an optimized borehole from the point of view of heat capacity and economical aspects. For this reason, having trusty equations is vital to foresee borehole heating performance and applying it in design issues. In this study a single vertical U-tube borehole with constant wall temperature is considered and analytical equations for temperature distribution in the surrounding ground around the borehole is evaluated based on one and two dimensional heat conduction respectively. The analytical equation is compared to experimental data for a borehole with 50 m depth in which warm water of 40 C is pumped into it a time period of 120 hours and the heat transfer rate per unit length is recorded. The comparison between analytical expression and experimental data shows a good agreement between them. Also the borehole entropy generation number is studied and the optimized parameters are evaluated to minimize it. It is concluded that for the considered borehole, entropy generation number is decreased by increasing its length and by decreasing the borehole radius and pipe outer radius.

In the present study, a novel inverse heat transfer methodology is presented for thermal energy analysis of residential buildings equipped with radiator Heating, Ventilation, Air Conditioning systems using a combination of numerical simulation and sensitivity analysis. With the use of numerical simulation, thermal analysis of building components is simulated in order to calculate temperature field in the computational domain. With inverse analysis technique, we perform the estimation of some thermal parameters with the use of Levenberg–Marquardt and conjugate gradient methods and reported the results with the use of sensitivity analysis inside the building. To confirm the accuracy of numerical simulation, the problem is also simulated with commercial software such as Carrier and Energy-Plus. Then, thermal parameter estimation results of inverse simulation are presented. The present study illustrates the sufficiency of inverse analysis in order to calculate building thermal design parameters with excellent...

This research presents different scenarios of hybrid photovoltaic-geothermal heat pump system that can provide the requirements of the heating and cooling load consumption in a residential building during the year. One of the major purposes of the present study is to explore the optimum contribution of the solar and ground source energies in which the generation energy costs are reasonable with respect to the total costs, lifetime, and energy losses. For this purpose, a numerical dynamic model consisting of different solar photovoltaic (PV) panels of polycrystalline, monocrystalline, and thin-film cells, batteries, inverter, and ground source heat pump (GSHP) was developed using the engineering equation solver and TRNSYS software. In order to reach the best performance of the system, multi- and single-objective optimizations of the life cycle cost and irreversibility were carried out using the particle swarm optimization algorithm considering all effective parameters of the system including surface area, slope, direction of PV panels and battery capacity. Moreover, the optimization tool which was developed in MATLAB software, was adopted for data interaction between TRNSYS and MATLAB. The results indicate that among various scenarios, the optimized hybrid polycrystalline PV system with an area of 35 m2 and a solar fraction of 31% can be cost-effective up to a 24% inflation rate. Also, the payback period of the optimized hybrid system compared to the regular GSHP is 3 years with the average global costs, while this value is 10 years for Iran’s economic situation.

The present study investigates the use of HVAC and solar heating systems inside residential zones using a combination of direct numerical modeling and genetic optimization method in different climates of Iran. The direct numerical modeling is capable of calculating temperature field inside buildings. Then, direct modelling algorithm is used to determine energy consumption rate of the building in the different climates of Iran. The results of direct numerical modelling are checked against those of carrier and energy-plus software. The results show good accordance with those of numerical simulations presented in the open literature.

The purpose of this research is to present a novel approach to estimate thermal design parameters with unknown values in a building equipped with radiative panels with the use of inverse methodology. A direct model is selected to analyze thermal behavior of building components in order to determine indoor temperature field using direct numerical modeling. Using inverse analysis, three thermal design parameters with unknown values, such as conductivity, internal and external convection and total heat transfer coefficients, are estimated using Levenberg–Marquardt and conjugate gradient methods with the knowledge of temperature field resulted from direct modeling. To illustrate the sufficiency of inverse technique, the results of both noisy and non-noisy estimations are presented using sensitivity analysis. To verify the accuracy of the present study, the results of inverse analysis are compared with those of numerical simulation presented in the literature, which indicates a good agreement between numerical and inverse solutions. It is shown that inverse analysis can be used as an applicable approach to increase computational precision in building thermal design phase.

In the present study, a new thermal design approach is presented to simulate HVAC cooling systems inside buildings using a combination of direct cooling load modeling and inverse analysis technique. With the use of direct cooling load modeling, a sample building equipped with an HVAC cooling system is modeled using finite-volume scheme in order to calculate cooling load and temperature field inside the domain. Energy consumption of the building is computed using the building energy simulation algorithm. Then, the results of the indoor temperature field are used as input data for the inverse algorithm to estimate thermal design parameters in the building. To verify the accuracy of the present study, we compare the results of numerical developed code with Carrier and Energy-Plus software for direct energy modeling and then the results of inverse simulation are presented for the sample building.

Thermal analysis of fluid flow is always regarded as an important research issue within cavities in order to become familiar with the characteristics of fluid flow phenomenon in enclosures. This research paper investigates the fluid and heat transfer analysis of fluid flow inside a triangular cavity using natural element methodology (NEM). This Galerkin-based methodology has been introduced for a decade and almost demonstrated its efficiency in the numerical heat transfer analysis of problems in most engineering sciences. The fluid flow contains natural convection along with conduction and radiation heat transfer with medium's walls, which have absorbing, emitting, semitransparent, and nonscattering characteristics. The final results investigate the effects of radiative and natural convection heat transfer on the fluid flow pattern as expressed in Rayleigh number, stream function, strength of natural convection regime, etc., which are checked with other similar studies presented in the literature and shows how promising NEM can be as an efficient numerical approach to improve computational precision when dealing with fluid mechanic problems.

U radu se istražuju karakteristike protoka i prijenosa topline mikropolarnog toka fluida preko elastičnog lima. Istražuju se utjecaji magnetskog polja, toka topline radijacije i poroznog lima, uz pretpostavku da su viskoznost i toplinska vodljivost ovisne o temperature. Primijenjene su jednadžbe formulirane aproksimacijom graničnog sloja i teorijom mikropolarnih fluida. Za rješenje problema, parcijalne diferencijalne jednadžbe transformirane su u obične diferencijalne jednadžbe primjenom rješenja sličnosti, a dobivene jednadžbe rješavane su metodom izbacivanja i metodom Runge-Kutta četvrtog reda (fourth-order Runge-Kutta). Rezultati pokazuju da djelovanje magnetskog polja i poroznosti rezultira smanjenjem vrijednosti brzine u graničnim slojevima, strujanje topline radijacije rezultira povećanjem debljine graničnog sloja. Nadalje, debljina toplinskog graničnog sloja smanjuje se porastom usisnog parametra i redukcijom učinaka radijacijskog i magnetskog polja., In this paper, the flow and heat transfer characteristics of a micropolar fluid flow over a stretching sheet are studied. The effects of magnetic field, radiation heat flux and porous sheet are investigated, and the viscosity and thermal conductivity are supposed temperature-dependent. The governing equations are formulated by boundary layer approximation and the theory of micropolar fluids. To solve the problem, the partial differential equations are transformed into the ordinary differential equations by using similarity solutions, and the achieved equations are solved by shooting method and fourth-order Runge-Kutta. The results show that the effects of magnetic field and porousness result in decrease of the velocity values in the boundary layers, but the presence of radiation heat flux results in the growth of the boundary layer thickness. Furthermore, the thickness of thermal boundary layer declines by increase of suction parameter and reduction of radiation and magnetic field effects.

In this paper the effects of radiation and dissipation in the entropy generation in microtube is evaluated. Governing equations are solved with analytically solution. Fluid flow in the entrance area is laminar and independent of time, and radiation is also a fluid property. Results in this paper extracted with dimensionless numbers Knudsen (k n ), Brinkman (Br) and Prandtl (Pr) that compared with the case without radiation. It is shown that entropy generation decreases with increasing Knudsen number. It can be observed that increasing Br augments the entropy generation.

The main purpose of this research is to optimize the life cycle cost (LCC) while minimizing the annual irreversibility of the system in three different modes of a vertical ground heat pump (water-to-water) including heating, cooling, and multi-usage. The multi-objective optimization of the LCC and exergy destruction was done by using the multi-objective particle swarm optimization (MOPSO) algorithms and also by considering all involving effective parameters such as the number of boreholes, depth of buried pipes in ground source heat exchanger (GSHX), fan coil setpoint temperature and surface area of condenser and evaporator. In order to reduce energy consumption and meet the building's heat requirement at any time, the compressor was simulated with variable speed drive (VSD) in transient operations. In this study, the investigated refrigerant was R134a, and the shell-and-tube type of heat exchanger was considered for the condenser and evaporator. The obtained results show that the use of the heat pump in single heating mode leads to lower exergy destruction and better performance of the system in terms of exergy efficiency. Also, the economic results indicate that the total initial costs for the multi-usage mode is 27% higher than the single heating mode while it is 8.5% higher than the single cooling mode. The average electricity cost per operation time in multi-usage is 15% higher than single heating and 3% lower than single cooling and equal to 0.139 $/hour.