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Abstract- Considering the diverse climates of Iran, the need for architectural design according to climate zones is obvious. Especially in critical thermal conditions this need will be more important and becomes the architect’s most important challenge. Cold climate is one of the important climates which deserve special design. In cold climate, summer is very short and environmental temperature is often below the comfort range, so the most important issue is heating. Since in most of the time we require to increase the temperature up to the comfort range. This article aims to provide solutions for critical climate conditions. So Tabriz with a dry and cold climate was selected and its thermal analysis was done. Through this analysis we find out when there is heating problems and we can design solutions based on these findings. This information will help us to design the selected site conditions.

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Aims:In the architecture of traditional houses, the environment used to be formed by the mutual interaction of human beings and nature. With the emergence of environmental crises in the contemporary world, the integration of natural and human processes became the most important ecological issue in the domain of sustainability. The aim of the current study is to recognize those ecological criteria of traditional houses which can be productive in the contemporary world so as to arrive at ecological solutions based on the thermal behavior of these houses in cold regions.
Methods:These factors are investigated in two traditional houses in Ardabil using descriptive methods, field observations, and quantitative analyses.
Findings:The investigation of the most critical climatic condition of the region is indicative of the thermal resistance of the rooms against temperature fluctuations. Furthermore, the analysis of the architectural features taken from physical environment (topography, climate) and structural environment (building form, spatial organization, material, landscape, infrastructure) shows that there is an optimal interaction between these components. The recognition of these architectural features can also provide ecological solutions.
Conclusion: The results of the assessment of the ecological criteria in the houses are also indicative of their conformity with the environment.In fact,these structures have overcome climatic effects via the use of natural resources in a way that rooms like shahneshin and basement which have seasonal function, have optimal performance against temperature fluctuations. For example, in a sample shahneshin room in smaller dimensions, the minimum difference between the inside and outside temperature is 13 °C

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Nowadays, computer simulations are becoming more and more important in performance investigation of thermal systems. In this article, radiator of cooling system of diesel engine of ER24PC locomotive is simulated. The radiator is composed of parallel and series arrangement of compact heat exchangers with offset strip fins. It also has two high and low temperature sections. Due to the complexity and compactness of heat transfer plates implemented in the radiator, the simulation is carried out in two steps. First, a relation for coolant-side and air-side heat transfer coefficient is correlated using computational fluid dynamics. Due to vortex shedding phenomenon in the staggered fin arrays, governing equations are solved transiently in two-dimensional space. Appropriate timestep for the transient solution is chosen according to time period of vortex shedding from the surface. In the second step, using the developed computational code, the overall thermal performance of the radiator is simulated as a heat exchanger. Consequently, temperature distribution inside the radiator and its thermal performance are studied. Amount of heat released from the radiator in different flow rates and temperatures of fluid flowing out of radiator are among the outputs of the developed code. Finally, thermal performance curve of radiator is obtained.

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The use of metal foam as a distributor flow field in a polymeric electrolyte membrane fuel cells reduces the weight and volume of the fuel cell, causes more uniform distribution of the reactant gases, and in some cases eliminates the machining process required to create the flow channels. In this paper five models of polymer electrolyte membrane fuel cells are simulated including: the model that the bipolar plate consists of two parallel channels (model 1); The model that is similar to model 1 except that in this case channels are filled with metal foam (model 2); The model that the rib between the channels in anode and cathode side are eliminated and in the anode, metal foam is placed (model 3); the model that is similar to model 3 except that the metal foam is placed on the cathode side (model 4); in model 5, both the anode side and the cathode side are filled with metal foam. The results show that the use of metal foam in the anode or the cathode side in addition to decreasing maximum temperature in the models also helps a more uniform temperature distribution. The uniformity index shows that the distribution of current density is much better and more uniform, when the ribs in models 3, 4 and 5 are eliminated. Comparison conducted between different models shows that the pressure drop caused by the presence of the metal foam, due to the high coefficient of permeability and porosity ‍ of the foam, is small.

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Considering the determinant role of glazing systems in energy consumption, it is imperative to survey the thermal performance of double coated glazing systems in accordance with the harsh climatic conditions and available local and foreign products' situation. In this paper, the radiative properties of local coated and non-coated glazing units are measured by the spectrophotometer and emissometer apparatus. These thermal and solar properties were not available in any datasheet. In the second step, through the accurate calculation method of EnergyPlus software, the amount of energy loss due to the radiative properties of glazing units was simulated in two extreme climates (very hot and humid climate and cold climate). By choosing the simulation method instead of real measurements in this step, it became possible to evaluate the effect of different parameters (such as climate, orientation and glazing specification) on the annual energy loss through the glazing units by eliminating other factors like energy transfer through opaque surfaces and ventilation. The simulation results indicate that using double glazing unit with low-E coating on the third surface (from the exterior) of the double glazing, significantly reduces energy consumption of the glass unit (up to 97 percent) for all orientations in the cold climate. In hot climates like Bandarabbas, using reflective coatings (with dark blue color) in double glazing units is the best possible alternative since it lessens the energy transfer through the glass unit (up to 70 percent) compared to the clear double glazed ones.

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Direct-expansion solar-assisted heat pumps (DX-SAHP) have been used widely to heat the consuming water of buildings and industrial facilities, domestic and industrial space heating and also, air conditioning. These systems transfer energy from lower temperature source to a higher temperature source. In DX-SAHP systems, In order to optimize the heat transfer of solar radiation to the refrigerant, the flat plate solar collector is used as the evaporator. In this paper, the thermal performance of a DX-SAHP has been studied using numerical simulation for heating the water of a house in Kermanshah. The system mainly employs a bare flat-plate solar collector with a surface area of 4 m2, a hot water tank with the volume of 150 L, a rotary-type hermetic compressor, a thermostatic expansion valve and R-134a is also used as working fluid in the system. The results show that the hours of system operation, during different months in the climate of Kermanshah, vary between 37 to 130 hours and the monthly average COP and the solar collector efficiency vary between 3.96 to 6.71 and 68 to 99 percent respectively. The effect of various parameters, including solar radiation, ambient temperature, collector area, compressor speed, number of collector cover and wind speed have been analyzed on the thermal performance of the system.

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Vacuum tube solar water heaters are one of the most common types of solar water heaters, and they have been used widely in recent years. Evacuated tube solar collectors compared to flat plate collectors have higher absorption coefficient and lower heat loss. Many factors are effective on thermal efficiency of evacuated solar water heaters and many studies have been done to increase their efficiency. In this study, thermal performance of a modified model has been investigated experimentally. Two laboratory samples, one of them with the modified structure and the other like commercial samples have been made and their performance has been studied under equal solar radiation and ambient temperature. The results have shown that this structure modification has a positive effect on collector performance. This change has made the temperature distribution in the pipe and tank more uniform, and has increased the efficiency to 11 percent. Absorbing thermal energy in the modified model was more than typical model about 25 percent in duration one hour. Also, effects of solar radiation on the average temperature of water in the storage tank have been investigated in both cases. In this study, an experimental method is used to calculate the radiation received to vacuum tubes.

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Courtyard has been recognized as one of main elements in the Iranian culture, architecture and building design. According to its micro-climate effect in improving thermal performance of building, courtyard has been considered as a considerable subject for many researches. This paper investigates the courtyard’s design parameters and geometric configurations in pre-design states for improving thermal performance and comfort. For achieving this point, in this research the influence of courtyard orientation, horizontal dimensions and other parameters related to geometry have been evaluated. Due to micro-climate effect of courtyard on parameters related to thermal comfort, three main geometric layouts such as closed, semi-closed and open geometry have been investigated and compared by CFD simulations in ENVI-met software. The thermal comfort parameters are also investigated through comparing mean PMV in all simulations cases, using Fanger’s extended model. The results showed that thermal performance of closed shaped courtyard is better than other layouts. Also the comparison of results related to different aspect ratios (length to width ratios), put into evidence that thermal performance improves as the aspect ratio gets close to 1. That means as the courtyard shape encloses to square, the thermal performance improves and the mean air temperature in the investigated microclimates declines. To determine best configuration for Tehran’s climate, the results showed north-south orientation of building and increase of the height of the courtyard, are the two most appropriate considerations that will directly improve the thermal performance and comfort, specifically in closed and semi-closed layout.

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In the present study, thermal performance of a microchannel heat sink with superhydrophobic walls is studied for different ratios of the wall convergence. To this end, three-dimensional Navier-Stokes equations and energy equation subject to the slip boundary conditions, viz. velocity slip and temperature jump, are numerically solved using the finite volume method. Then, the variations of thermal resistance of the heat sink with the number of channels, width- and height-tapered ratios, are studied for a fixed pumping power. The results show that by utilizing the superhydrophobic walls, the optimum width-tapered ratio of the channel is higher than that of the hydrophilic walls. The accentuated effect of the number of channels on thermal performance in the presence of liquid-solid interfacial slip weakens the effect of converging the width of the channel. It is also revealed that the optimum number of channels also increases to give prominence to the effect of interfacial slip by diminishing the smallest dimension of the channel. Finally, it is shown that for a pumping power of 0.05 W, using a heat sink with converging microchannels and superhydrophobic walls, reduces the overall thermal resistance by 28 percent, compared to that with conventional microchannels. In fact, the increase in fluid flow rate resulting from the use of converging microchannels with superhydrophobic walls outweighs the undesirable effect of temperature jump on heat transfer, in a sense that the heat sink performance augments considerably.

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Rotary Regenerative Air Preheater (RRAPH) is one of the main equipments for energy recovery in the steam power plants. In this study, air preheater of the Bisotoun Power Plant of Kerrmanshah has been investigated with the aim of optimizing its thermal performance. So, with Computational Fluid Dynamics (CFD), three-dimensional simulation of the rotary air preheater has performed to solve the continuity, momentum and energy equations in porous medium by using moving refrence frame (MRF) method. The results showed acceptable accuracy in comparison with the experimental results which is achieved from the power plant data. In this research, the effect of rotational speed on the efficiency of air preheater in different loads and mass flow rates for both without and with leakage conditions has investigated. The results showed that the impact of the rotational speed on the performance of RRAPH is noticeable in the range of 0.5 to 4 rpm, and after this increase in speed does not have a significant effect on efficiency. The present study also showed that leakage has a significant effect on reduction of the efficiency of the RRAPH in all loads and rotational speeds. In the following, the effect of matrix material change on the efficiency of RRAPH has investigated. According to the results, for both without and with leakage, the best thermal performance is related to the stainless steel, which has the least thermal diffusivity, also the least thermal performance is related to the copper, which has the highest thermal diffusivity.

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This study has experimentally investigated the effect of Fe₃O₄ and secondary flow injection on convection heat transfer and friction coefficient on a horizontal pipe. Secondary flow injected to main flow to make more turbulence to five different models. Water and Fe₃O₄ have been considered in5865 to 18800 Reynolds range and three0.01%,0.03% and0.06% volume concentrations. Length and diameter of test tube considered 65 cm and 1.7 cm, respectively, the diameter of secondary flow injection holes considered 3 mm and 4.5 mm, the ratio of volumetric flow rate to total flow considered 10% and 20% and distance between secondary flow injection holes considered 4 and 2. The results show that the increase of diameter of secondary flow injections holes, the ratio of secondary flow volumetric flow rate to total flow and the decrease of distance between secondary flow injection holes are effective on coefficient of utilization increase. The highest coefficient of utilization achieved   =20%,  =2 in each model using water fluid in d=4.5 state. In this state, the mean of coefficient of utilization achieved 1.256, 1.266, 1.31, 1.45 and 1.52 for first, second, third, fourth and fifth models in all Reynolds, respectably. The above state has the highest thermal performance in the fourth and fifth models. The mean of coefficient of utilization in all Reynolds increased 0.91%, 3.97% and 4.98% for the above state in the fourth model using Fe₃O₄ with three0.01%,0.03% and0.06% volume concentrations to water fluid, respectively. Similarly, this increase achieved 1.58%, 4.56% and 5.66% in the fifth model, respectively.