Search results for: static heat load

Authors: S. Dias, A. Tadeu, J. Antonio, F. Pedro, C. Serra

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The goal of the present work is to experimentally evaluate the feasibility of using vibration isolators made of expanded cork agglomerate. Even though this material, also known as insulation cork board (ICB), has mainly been studied for thermal and acoustic insulation purposes, it has strong potential for use in vibration isolation. However, the adequate design of expanded cork blocks vibration isolators will depend on several factors, such as excitation frequency, static load conditions and intrinsic dynamic behavior of the material. In this study, transmissibility tests for different static and dynamic loading conditions were performed in order to characterize the material. Since the material’s physical properties can influence the vibro-isolation performance of the blocks (in terms of density and thickness), this study covered four mass density ranges and four block thicknesses. A total of 72 expanded cork agglomerate specimens were tested. The test apparatus comprises a vibration exciter connected to an excitation mass that holds the test specimen. The test specimens under characterization were loaded successively with steel plates in order to obtain results for different masses. An accelerometer was placed at the top of these masses and at the base of the excitation mass. The test was performed for a defined frequency range, and the amplitude registered by the accelerometers was recorded in time domain. For each of the signals (signal 1- vibration of the excitation mass, signal 2- vibration of the loading mass) a fast Fourier transform (FFT) was applied in order to obtain the frequency domain response. For each of the frequency domain signals, the maximum amplitude reached was registered. The ratio between the amplitude (acceleration) of signal 2 and the amplitude of signal 1, allows the calculation of the transmissibility for each frequency. Repeating this procedure allowed us to plot a transmissibility curve for a certain frequency range. A number of transmissibility experiments were performed to assess the influence of changing the mass density and thickness of the expanded cork blocks and the experimental conditions (static load and frequency of excitation). The experimental transmissibility tests performed in this study showed that expanded cork agglomerate blocks are a good option for mitigating vibrations. It was concluded that specimens with lower mass density and larger thickness lead to better performance, with higher vibration isolation and a larger range of isolated frequencies. In conclusion, the study of the performance of expanded cork agglomerate blocks presented herein will allow for a more efficient application of expanded cork vibration isolators. This is particularly relevant since this material is a more sustainable alternative to other commonly used non-environmentally friendly products, such as rubber.

Keywords: expanded cork agglomerate, insulation cork board, transmissibility tests, sustainable materials, vibration isolators

Procedia PDF Downloads 315

Authors: Shagufta Tabassum, V. P. Pawar

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The study of static dielectric properties in a binary mixture of 1,2 dichloroethane (DE) and n,n dimethylformamide (DMF) polar liquids has been carried out in the frequency range of 10 MHz to 30 GHz for 11 different concentration using time domain reflectometry technique at 10ºC temperature. The dielectric relaxation study of solute-solvent mixture at microwave frequencies gives information regarding the creation of monomers and multimers as well as interaction between the molecules of the binary mixture. The least squares fit method is used to determine the values of dielectric parameters such as static dielectric constant (ε₀), dielectric constant at high frequency (ε_∞) and relaxation time (τ).

Keywords: shagufta shaikhexcess parameters, relaxation time, static dielectric constant, time domain reflectometry

Procedia PDF Downloads 219

Authors: Mehrdad Mahmudizad, Roya Ahmadi Ahangar

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This paper presents the method of designing the type 2 fuzzy PID controllers in order to solve the problem of Load Frequency Control (LFC). The Harmony Search (HS) algorithm is used to regulate the measurement factors and the effect of uncertainty of membership functions of Interval Type 2 Fuzzy Proportional Integral Differential (IT2FPID) controllers in order to reduce the frequency deviation resulted from the load oscillations. The simulation results implicitly show that the performance of the proposed IT2FPID LFC in terms of error, settling time and resistance against different load oscillations is more appropriate and preferred than PID and Type 1 Fuzzy Proportional Integral Differential (T1FPID) controllers.

Keywords: load frequency control, fuzzy-pid controller, type 2 fuzzy system, harmony search algorithm

Procedia PDF Downloads 243

Authors: M. V. Bartashevich

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The problem of heat transfer at thin laminar liquid film is solved numerically. A thin film of liquid flows down an inclined surface under conditions of variable heat flux on the wall. The use of thin films of liquid allows to create the effective technologies for cooling surfaces. However, it is important to investigate the most suitable cooling regimes from a safety point of view, in order, for example, to avoid overheating caused by the ruptures of the liquid film, and also to study the most effective cooling regimes depending on the character of the distribution of the heat flux on the wall, as well as the character of the blowing of the film surface, i.e., the external shear stress on its surface. In the statement of the problem on the film surface, the heat transfer coefficient between the liquid and gas is set, as well as a variable external shear stress - the intensity of blowing. It is shown that the combination of these factors - the degree of uniformity of the distribution of heat flux on the wall and the intensity of blowing, affects the efficiency of heat transfer. In this case, with an increase in the intensity of blowing, the cooling efficiency increases, reaching a maximum, and then decreases. It is also shown that the more uniform the heating of the wall, the more efficient the heat sink. A separate study was made for the flow regime along the horizontal surface when the liquid film moves solely due to external stress influence. For this mode, the analytical solution is used for the temperature at the entrance region for further numerical calculations downstream. Also the influence of the degree of uniformity of the heat flux distribution on the wall and the intensity of blowing of the film surface on the heat transfer efficiency was also studied. This work was carried out at the Kutateladze Institute of Thermophysics SB RAS (Russia) and supported by FASO Russia.

Keywords: Heat Flux, Heat Transfer Enhancement, External Blowing, Thin Liquid Film

Procedia PDF Downloads 122

Authors: Priya Pawar, Rithika Susan Thomas, Emmanuel Blonkowski

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Due to the solar geometry of Singapore, which lay within the geographical classification of equatorial tropics, there is a great deal of thermal energy transfer to the inside of the buildings. With changing face of economic development of cities like Singapore, more and more buildings are designed to be lightweight using transparent construction materials such as glass. Increased demand for energy efficiency and reduced cooling load demands make it important for building designer and operators to adopt new and non-invasive technologies to achieve building energy efficiency targets. A real time performance evaluation study was undertaken at School of Art Design and Media (SADM), Singapore, to determine the efficiency potential of a new generation solar insulation film. The building has a window to wall ratio (WWR) of 100% and is fitted with high performance (low emissivity) double glazed units. The empirical data collected was then used to calibrate a computerized simulation model to understand the annual energy consumption based on existing conditions (baseline performance). It was found that the correlations of various parameters such as solar irradiance, solar heat flux, and outdoor air-temperatures quantification are significantly important to determine the cooling load during a particular period of testing.

Keywords: solar insulation film, building energy efficiency, tropics, cooling load

Procedia PDF Downloads 169

Authors: Chih-Hao Chen, Yu-Heng Fang, Jyi-Ching Perng, Wei-Chih Lee, Yi-Hsiang Chen, Jiun-Jen Chen

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Emerging markets are almost in the high temperature and high humidity area. Regardless of industry or domestic fields, the energy consumption of air conditioning systems in buildings is always significant. Moreover, the proportion of latent heat load is high. A liquid desiccant dehumidification system is one kind of energy-saving air conditioning system. However, traditional absorbents such as lithium chloride are hindered in market promotion because they will crystallized and cause metal corrosion. This study used the commercial ionic liquid to build a liquid desiccant dehumidification system with an air volume of 300 CMH. When the absolute humidity of the inlet air was 15g/kg, the absolute humidity of the outlet air was 10g/kg. The operating condition of a hot water temperature is 45 °C, and the cooling water temperature is 15 °C. The test result proves that the ionic liquid desiccant can completely replace the traditional liquid desiccant.

Keywords: ionic liquid desiccant, dehumidification, heat pump, air conditioning systems

Procedia PDF Downloads 137

Authors: Vipul M. Patel, H. B. Mehta

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Closed Loop Pulsating Heat Pipe (CLPHP) is a passive two-phase heat transfer device having potential to achieve high heat transfer rates over conventional cooling techniques. It is found in electronics cooling due to its outstanding characteristics such as excellent heat transfer performance, simple, reliable, cost effective, compact structure and no external mechanical power requirement etc. Comprehensive understanding of the thermo-hydrodynamic mechanism of CLPHP is still lacking due to its contradictory results available in the literature. The present paper discusses the experimental study on 9 turn CLPHP. Inner and outer diameters of the copper tube are 2 mm and 4 mm respectively. The lengths of the evaporator, adiabatic and condenser sections are 40 mm, 100 mm and 50 mm respectively. Water is used as working fluid. The Filling Ratio (FR) is kept as 50% throughout the investigations. The gravitational effect is studied by placing the evaporator heater at different orientations such as horizontal (90 degree), vertical top (180 degree) and bottom (0 degree) as well as inclined top (135 degree) and bottom (45 degree). Heat input is supplied in the range of 10-50 Watt. Heat transfer mechanism is natural convection in the condenser section. Vacuum pump is used to evacuate the system up to 10^-5 bar. The results demonstrate the influence of input heat flux and gravity on the thermal performance of the CLPHP.

Keywords: CLPHP, gravity effect, start up, two-phase flow

Procedia PDF Downloads 246

Authors: R. Chouatah, E. G. Filali, B. Zouzou

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It has been well established that there are no differences between microscale and macroscale flows of incompressible liquids. However, surface roughness has been known to impact the transport phenomena. The effect of structured roughness on the dynamics and heat transfer of water flowing through minichannel was numerically investigated in this study. Our study consists in characterizing the dynamic field and heat transfer aspect of a flow in circular minichannel equipped with structured roughness using CFD software, CFX. The study is performed to understand the effect of various roughness elements (rectangular, triangular), roughness height and roughness pitch on the friction factor and heat transfer coefficient. Our work focuses on a water flow inside a circular mini-channel of 1 mm in diameter and 10 cm in length. The speed entry into the mini-channel varies from 0.1 m/s to 25 m/s. The wall of the mini-channel is submitted to a constant heat flux; q=100,000 W/m². The simulations results are compared to those obtained with smooth minichannel and the existing experimental and numerical results in the literature.

Keywords: heat transfer, laminar and turbulent flow, minichannel, structured roughness

Procedia PDF Downloads 319

Authors: Ali Rabiee, Hessam Ghasemnejad

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Extensive experimental investigation on the effect of stitching pattern on tubular composite structures was conducted. The effect of stitching reinforcement through thickness on using glass flux yarn on energy absorption of fiber-reinforced polymer (FRP) was investigated under high speed loading conditions at axial loading. Keeping the mass of the structure at 125 grams and applying different pattern of stitching at various locations in theory enables better energy absorption, and also enables the control over the behaviour of force-crush distance curve. The study consists of simple non-stitch absorber comparison with single and multi-location stitching behaviour and its effect on energy absorption capabilities. The locations of reinforcements are 10 mm, 20 mm, 30 mm, 10-20 mm, 10-30 mm, 20-30 mm, 10-20-30 mm and 10-15-20-25-30-35 mm from the top of the specimen. The effect of through the thickness reinforcements has shown increase in energy absorption capabilities and crushing load. The significance of this is that as the stitching locations are closer, the crushing load increases and consequently energy absorption capabilities are also increased. The implementation of this idea would improve the mean force by applying stitching and controlling the behaviour of force-crush distance curve.

Keywords: through-thickness stitching, 3D enforcement​, energy absorption, tubular composite structures

Procedia PDF Downloads 236

Authors: Amir Dehshiri, Mohammad Reza Salimpour

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In the present article, we investigate experimental laminar forced convective heat transfer specifications of TiO2/water nanofluids through conduits with different cross sections. We check the effects of different parameters such as cross-sectional shape, Reynolds number and concentration of nanoparticles in stable suspension on increasing convective heat transfer by designing and assembling of an experimental apparatus. The results demonstrate adding a little amount of nanoparticles to the base fluid, improves heat transfer behavior in conduits. Moreover, conduit with circular cross-section has better performance compared to the square and triangular cross sections. However, conduits with square and triangular cross sections have more relative heat transfer enhancement than conduit with circular cross section.

Keywords: nanofluid, cross-sectional shape, TiO2, convection

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Authors: F. A. Gdhaidh, K. Hussain, H. S. Qi

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A numerical study of natural convection heat transfer in water filled cavity has been examined in 3D for single phase liquid cooling system by using an array of parallel plate fins mounted to one wall of a cavity. The heat generated by a heat source represents a computer CPU with dimensions of 37.5×37.5 mm mounted on substrate. A cold plate is used as a heat sink installed on the opposite vertical end of the enclosure. The air flow inside the computer case is created by an exhaust fan. A turbulent air flow is assumed and k-ε model is applied. The fins are installed on the substrate to enhance the heat transfer. The applied power energy range used is between 15- 40W. In order to determine the thermal behaviour of the cooling system, the effect of the heat input and the number of the parallel plate fins are investigated. The results illustrate that as the fin number increases the maximum heat source temperature decreases. However, when the fin number increases to critical value the temperature start to increase due to the fins are too closely spaced and that cause the obstruction of water flow. The introduction of parallel plate fins reduces the maximum heat source temperature by 10% compared to the case without fins. The cooling system maintains the maximum chip temperature at 64.68℃ when the heat input was at 40 W which is much lower than the recommended computer chips limit temperature of no more than 85℃ and hence the performance of the CPU is enhanced.

Keywords: chips limit temperature, closed enclosure, natural convection, parallel plate, single phase liquid

Procedia PDF Downloads 244

Authors: Tasneem Firdous Islam, G. D. Kedar

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The aim of this paper is to study the effect of internal heat generation in a transient infinitely long annular cylinder subjected to hygrothermal loadings. The linear dependence theory of moisture and temperature is derived based on Dufour and Soret effect. The meticulous solutions of temperature, moisture, and thermal stresses are procured by using the Hankel transform technique. The influence of the internal heat source on the radial aspect is examined for coupled and uncoupled cases. In the present study, the composite material T300/5208 is considered, and the coupled and uncoupled cases are analyzed. The results obtained are computed numerically and illustrated graphically.

Keywords: temperature, moisture, hygrothermoelasticity, internal heat generation, annular cylinder

Procedia PDF Downloads 89

Authors: Alireza Mirzaee, Soosan Abdollahi, Mohammad Abdollahi

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Unreinforced Masonry (URM) wall is vulnerable in resisting horizontal load such as wind and seismic loading. It is due to the low tensile strength of masonry, the mortar connection between the brick units. URM structures are still widely used in the world as an infill wall and commonly constructed with door and window openings. This research aimed to investigate the behavior of URM wall with openings when horizontal load acting on it and developed load-drift relationship of the wall. The finite element (FE) method was chosen to numerically simulate the behavior of URM with openings. In this research, ABAQUS, commercially available FE software with explicit solver was employed. In order to ensure the numerical model can accurately represent the behavior of an URM wall, the model was validated for URM wall without openings using available experimental results. Load-displacement relationship of numerical model is well agreed with experimental results. Evidence shows the same load displacement curve shape obtained from the FE model. After validating the model, parametric study conducted on URM wall with openings to investigate the influence of area of openings and pre-compressive load on the horizontal load capacity of the wall. The result showed that the increasing of area of openings decreases the capacity of the wall in resisting horizontal loading. It is also well observed from the result that capacity of the wall increased with the increasing of pre-compressive load applied on the top of the walls.

Keywords: masonry constructions, performance at earthquake, MSJC-08 (ASD), bearing wall, tie-column

Procedia PDF Downloads 227

Authors: Slim Chokri

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Load forecasting is one of the central functions in power systems operations. Electricity cannot be stored, which means that for electric utility, the estimate of the future demand is necessary in managing the production and purchasing in an economically reasonable way. A majority of the recently reported approaches are based on neural network. The attraction of the methods lies in the assumption that neural networks are able to learn properties of the load. However, the development of the methods is not finished, and the lack of comparative results on different model variations is a problem. This paper presents a new approach in order to predict the Tunisia daily peak load. The proposed method employs a computational intelligence scheme based on the Fuzzy neural network (FNN) and support vector regression (SVR). Experimental results obtained indicate that our proposed FNN-SVR technique gives significantly good prediction accuracy compared to some classical techniques.

Keywords: neural network, load forecasting, fuzzy inference, machine learning, fuzzy modeling and rule extraction, support vector regression

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Authors: Alireza Taghdiri, Sara Ghanbarzade Ghomi

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With the gravity load reduction in the structural and non-structural components, the lightweight construction will be achieved as well as the improvement of efficiency and functional specifications. The advantages of lightweight construction can be examined in two levels. The first is the mass reduction of load bearing structure which results in increasing internal useful space and the other one is the mass reduction of building which decreases the effects of seismic load as a result. In order to achieve this goal, the essential building materials specifications and also optimum load bearing geometry of structural systems and elements have to be considered, so lightweight materials selection particularly with lightweight aggregate for building components will be the first step of lightweight construction. In the next step, in addition to selecting the prominent samples of Iran's traditional architecture, the process of these works improvement is analyzed through the viewpoints of structural efficiency and lightweighting and also the practical methods of lightweight construction have been extracted. The optimum design of load bearing geometry of structural system has to be considered not only in the structural system elements, but also in their composition and the selection of dimensions, proportions, forms and optimum orientations, can lead to get a maximum materials efficiency for loads and stresses bearing.

Keywords: gravity load, light-weighting structural system, load bearing geometry, seismic behavior

Procedia PDF Downloads 511

Authors: C. J. W. Habets, D. J. Peters, J. G. de Gijt, A. V. Metrikine, S. N. Jonkman

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Conventional seismic designs of quay walls in ports are mostly based on pseudo-static analysis. A more advanced alternative is the Performance-Based Design (PBD) method, which evaluates permanent deformations and amounts of (repairable) damage under seismic loading. The aim of this study is to investigate the suitability of this method for anchored sheet pile quay walls that were not purposely designed for seismic loads. A research methodology is developed in which pseudo-static, permanent-displacement and finite element analysis are employed, calibrated with an experimental reference case that considers a typical anchored sheet pile wall. A reduction factor that accounts for deformation behaviour is determined for pseudo-static analysis. A model to apply traditional permanent displacement analysis on anchored sheet pile walls is proposed. Dynamic analysis is successfully carried out. From the research it is concluded that PBD evaluation can effectively be used for seismic analysis and design of this type of structure.

Keywords: anchored sheet pile quay wall, simplified dynamic analysis, performance-based design, pseudo-static analysis

Procedia PDF Downloads 359

Authors: Phan Minh Trang, Joacim Rocklöv, Kim Bao Giang, Gunnar Kullgren, Maria Nilsson

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There are recent studies from high income countries reporting an association between heat waves and hospital admissions for mental health disorders. It is not previously studied if such relations exist in sub-tropical and tropical low- and middle-income countries. In this study from Vietnam, the assumption was that hospital admissions for mental disorders may be triggered, or exacerbated, by heat exposure and heat waves. A database from Hanoi Mental Hospital with mental disorders diagnosed by the International Classification of Diseases 10, spanning over five years, was used to estimate the heatwave-related impacts on admissions for mental disorders. The relationship was analysed by a Negative Binomial regression model accounting for year, month, and days of week. The focus of the study was heat-wave events with periods of three or seven consecutive days above the threshold of 35oC daily maximum temperature. The preliminary study results indicated that heat-waves increased the risks for hospital admission for mental disorders (F00-79) from heat-waves of three and seven days with relative risks (RRs) of 1.16 (1.01–1.33) and 1.42 (1.02–1.99) respectively, when compared with non-heat-wave periods. Heatwave-related admissions for mental disorders increased statistically significantly among men, among residents in rural communities and in elderly. Moreover, cases for organic mental disorders including symptomatic illnesses (F0-9) and mental retardation (F70-79) raised in high risks during heat waves. The findings are novel studying a sub-tropical middle-income city, facing rapid urbanisation and epidemiological and demographic transitions.

Keywords: mental disorders, admissions for F0-9 or F70-79, maximum temperature, heat waves

Procedia PDF Downloads 218

Authors: Chunye Gong, Ming Tie, Jie Liu, Weimin Bao, Xinbiao Gan, Shengguo Li, Bo Yang, Xuguang Chen, Tiaojie Xiao, Yang Sun

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Large-scale CFD simulation relies on high-performance parallel computing, and the load balance is the key role which affects the parallel efficiency. This paper focuses on the load-balancing problem of parallel CFD simulation with structured mesh. A mathematical model for this load-balancing problem is presented. The genetic algorithm, fitness computing, two-level code are designed. Optimal selector, robust operator, and local optimization operator are designed. The properties of the presented genetic algorithm are discussed in-depth. The effects of optimal selector, robust operator, and local optimization operator are proved by experiments. The experimental results of different test sets, DLR-F4, and aircraft design applications show the presented load-balancing algorithm is robust, quickly converged, and is useful in real engineering problems.

Keywords: genetic algorithm, load-balancing algorithm, optimal variation, local optimization

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Authors: K. Digheche, K. Saadi, Z. Boumerzoug

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Welding is one of the most important technological processes used in many branches of industry such as industrial engineering, shipbuilding, pipeline fabrication among others. Generally, welding is the preferred joining method and most common steels are weldable. This investigation is a contribution to scientific work of welding of low carbon steel. This work presents the results of the isothermal heat treatment effect at 200, 400 and 600 °C on microstructural evolution in weld region of X70 pipeline steel. The welding process has been realized in three passes by industrial arc welding. We have found that the heat treatments cause grain growth reaction.

Keywords: heat treatments, low carbon steel, microstructures, welding

Procedia PDF Downloads 425

Authors: A. D. Parekh

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The present work describes relative contributions of operating parameters on required heat transfer area of three heat exchangers viz. evaporator, condenser and cascade condenser of two stage R404A-R508B cascade refrigeration system using Taguchi method. The operating parameters considered in present study includes (1) condensing temperature of high temperature cycle and low temperature cycle (2) evaporating temperature of low temperature cycle (3) degree of superheating in low temperature cycle (4) refrigerating effect. Heat transfer areas of three heat exchangers are studied with variation of above operating parameters and also optimum working levels of each operating parameter has been obtained for minimum heat transfer area of each heat exchanger using Taguchi method. The analysis using Taguchi method reveals that evaporating temperature of low temperature cycle and refrigerating effect contribute relatively largely on the area of evaporator. Condenser area is mainly influenced by both condensing temperature of high temperature cycle and refrigerating effect. Area of cascade condenser is mainly affected by refrigerating effect and the effects of other operating parameters are minimal.

Keywords: cascade refrigeration system, Taguchi method, heat transfer area, ANOVA, optimal solution

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Authors: Javier Delgado-Gonzaga, Wilfrido Rivera, David Juárez-Romero

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Cooling and water purification are processes that have contributed to the economic and social development of the modern world. However, these processes require a significant amount of energy globally. Nowadays, absorption heat pumps have been studied with great interest since they are capable of producing cooling and/or purifying water from low-temperature energy sources such as industrial waste heat or renewable energy. In addition, absorption heat pumps require negligible amounts of electricity for their operation and generally use working fluids that do not represent a risk to the environment. The objective of this work is to evaluate a system that integrates an absorption heat transformer and an absorption cooling system to produce fresh water and cooling from a low-temperature heat source. Both cycles operate with the working pair LiBr-H2O. The integration is possible through the interaction of the LiBr-H2O solution streams between both cycles and also by recycling heat from the absorption heat transformer to the absorption cooling system. Mathematical models were developed to compare the performance of four different configurations. The results showed that the configuration in which the hottest streams of LiBr-H2O solution preheated the coldest streams in the economizers of both cycles was one that achieved the best performance. The interaction of the solution currents and the heat recycling analyzed in this work serves as a record of the possibilities of integration between absorption cycles for cogeneration.

Keywords: absorption heat transformer, absorption cooling system, water desalination, integrated system

Procedia PDF Downloads 56

Authors: Dilek Ozlem Esen, Mesut Kaya

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The focus of this study is to analyse the results of heat recovery from exhaust gas which is produced by an internal combustion engine (ICE). To obtain a small amount of energy, an exhaust system which is suitable for recovery waste heat has been constructed. Totally 27 TEGs have been used to convert from the heat to electric energy. By producing a small amount of this energy by the help of thermoelectric generators can reduce engine loads thus decreasing pollutant emissions, fuel consumption, and CO2. This case study is conducted in an effort to better understand and improve the performance of thermoelectric heat recovery systems for automotive use. As a result of this study, 0,45 A averaged current rate, 13,02 V averaged voltage rate and 5,8 W averaged electrical energy have been produced in a five hours operation time.

Keywords: thermoelectric, peltier, thermoelectric generator (TEG), exhaust, cogeneration

Procedia PDF Downloads 624

Authors: L. Haddad, Z. Aouachria

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The development of transport systems has negative impacts on the environment although it has beneficial effects on society.. The car policy caused many problems such as: - the spectacular growth of fuel consumption hence the very vast increase in urban pollution, traffic congestion in certain places and at certain times, the increase in the number of accidents. The exhaust emissions from cars and weather conditions are the main factors that determine the level of pollution in urban atmosphere. These conditions lead to the phenomenon of heat transfer and radiation occurring between the air and the soil surface of any town. These exchanges give rise, in urban areas, to the effects of heat islands that correspond to the appearance of excess air temperature between the city and its surrounding space. In this object, we perform a numerical simulation of the plume generated by the cars exhaust gases and show that these gases form a screening effect above the urban city which cause the heat island in the presence of wind flow. This study allows us: i. To understand the different mechanisms of interactions between these phenomena. ii. To consider appropriate technical solutions to mitigate the effects of the heat island.

Keywords: atmospheric pollution, impact on the health, urban transport, heat island

Procedia PDF Downloads 365

Authors: A. D. Parekh

Abstract:

The present work describes relative contributions of operating parameters on required heat transfer area of three heat exchangers viz. evaporator, condenser and cascade condenser of two stage R404A-R508B cascade refrigeration system using Taguchi method. The operating parameters considered in present study includes (1) condensing temperature of high temperature cycle and low temperature cycle (2) evaporating temperature of low temperature cycle (3) degree of superheating in low temperature cycle (4) refrigerating effect. Heat transfer areas of three heat exchangers are studied with variation of above operating parameters and also optimum working levels of each operating parameter has been obtained for minimum heat transfer area of each heat exchanger using Taguchi method. The analysis using Taguchi method reveals that evaporating temperature of low temperature cycle and refrigerating effect contribute relatively largely on the area of evaporator. Condenser area is mainly influenced by both condensing temperature of high temperature cycle and refrigerating effect. Area of cascade condenser is mainly affected by refrigerating effect and the effects of other operating parameters are minimal.

Keywords: cascade refrigeration system, Taguchi method, heat transfer area, ANOVA, optimal solution

Procedia PDF Downloads 361

Authors: Hai Hoang, Thanh Xuan Nguyen Thi, Guillaume Galliero

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Coarse-Grained (CG) molecular simulations have shown to be an efficient way to estimate thermophysical (static and dynamic) properties of fluids. Several strategies have been developed and reported in the literature for defining CG molecular models. Among them, those based on a top-down strategy (i.e. CG molecular models related to macroscopic observables), despite being heuristic, have increasingly gained attention. This is probably due to its simplicity in implementation and its ability to provide reasonable results for not only simple but also complex systems. Regarding simple Force-Fields associated with these CG molecular models, it has been found that the four parameters Mie chain model is one of the best compromises to describe thermophysical static properties (e.g. phase diagram, saturation pressure). However, parameterization procedures of these Mie-chain GC molecular models given in literature are generally insufficient to simultaneously provide static and dynamic (e.g. viscosity) properties. To deal with such situations, we have extended the corresponding states by using a quantity associated with the liquid viscosity. Results obtained from molecular simulations have shown that our approach is able to yield good estimates for both static and dynamic thermophysical properties for various real non-associating fluids. In addition, we will show that on simple (e.g. phase diagram, saturation pressure) and complex (e.g. thermodynamic response functions, thermodynamic energy potentials) static properties, results of our scheme generally provides improved results compared to existing approaches.

Keywords: coarse-grained model, mie potential, molecular simulations, thermophysical properties, phase equilibria

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Authors: Anjanna Matta, P. A. L. Narayana

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An investigation has been presented to analyze the effect of internal heat source on the onset of Hadley-Prats flow in a horizontal fluid saturated porous medium. We examine a better understanding of the combined influence of the heat source and mass flow effect by using linear stability analysis. The resultant eigenvalue problem is solved by using shooting and Runga-Kutta methods for evaluate critical thermal Rayleight number with respect to various flow governing parameters. It is identified that the flow is switch from stabilizing to destabilizing as the horizontal thermal Rayleigh number is enhanced. The heat source and mass flow increases resulting a stronger destabilizing effect.

Keywords: linear stability analysis, heat source, porous medium, mass flow

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Authors: Ashok K. Satapathy, Prerana Nashine

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Radiative heat transfer in participating medium was anticipated using the finite volume method. The radiative transfer equations are formulated for absorbing and anisotropically scattering and emitting medium. The solution strategy is discussed and the conditions for computational stability are conferred. The equations have been solved for transient radiative medium and transient radiation incorporated with transient conduction. Results have been obtained for irradiation and corresponding heat fluxes for both the cases. The solutions can be used to conclude incident energy and surface heat flux. Transient solutions were obtained for a slab of heat conducting in slab by thermal radiation. The effect of heat conduction during the transient phase is to partially equalize the internal temperature distribution. The solution procedure provides accurate temperature distributions in these regions. A finite volume procedure with variable space and time increments is used to solve the transient energy equation. The medium in the enclosure absorbs, emits, and anisotropically scatters radiative energy. The incident radiations and the radiative heat fluxes are presented in graphical forms. The phase function anisotropy plays a significant role in the radiation heat transfer when the boundary condition is non-symmetric.

Keywords: participating media, finite volume method, radiation coupled with conduction, heat transfer

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Authors: Rafał Urbaniak, Robert Kłosowiak, Michał Ciałkowski, Jarosław Bartoszewicz

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The Chair of Thermal Engineering at Poznan University of Technology has been conducted research works on the possibilities of using carbon nanostructures in energy and mechanics applications for a couple of years. Those studies have provided results in a form of co-operation with foreign research centres, numerous publications and patent applications. Authors of this paper have studied the influence of multi-walled carbon nanostructures on changes in static friction arising when steel surfaces were moved. Tests were made using the original test stand consisting of automatically controlled inclined plane driven by precise stepper motors. Computer program created in the LabView environment was responsible for monitoring of the stand operation, accuracy of measurements and archiving the obtained results. Such a solution enabled to obtain high accuracy and repeatability of all conducted experiments. Tests and analysis of the obtained results allowed us to determine how additional layers of carbon nanostructures influenced on changes of static friction coefficients. At the same time, we analyzed the potential possibilities of applying nanostructures under consideration in mechanics.

Keywords: carbon nanotubes, static friction, dynamic friction

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Authors: Carlos H. Cuadra, Nobuhiro Shimoi

Abstract:

Application of piezoelectric sensors to detect structural damage due to seismic action on building structures is investigated. Plate-type piezoelectric sensor was developed and proposed for this task. A film-type piezoelectric sheet was attached on a steel plate and covered by a layer of glass. A special glue is used to fix the glass. This glue is a silicone that requires the application of ultraviolet rays for its hardening. Then, the steel plate was set up at a steel column-beam joint of a test specimen that was subjected to bending moment when test specimen is subjected to monotonic load and cyclic load. The structural behavior of test specimen during cyclic loading was verified using a finite element model, and it was found good agreement between both results on load-displacement characteristics. The cross section of steel elements (beam and column) is a box section of 100 mm×100 mm with a thin of 6 mm. This steel section is specified by the Japanese Industrial Standards as carbon steel square tube for general structure (STKR400). The column and beam elements are jointed perpendicularly using a fillet welding. The resulting test specimen has a T shape. When large deformation occurs the glass plate of the sensor device cracks and at that instant, the piezoelectric material emits a voltage signal which would be the indicator of a certain level of deformation or damage. Applicability of this piezoelectric sensor to detect structural damages was verified; however, additional analysis and experimental tests are required to establish standard parameters of the sensor system.

Keywords: piezoelectric sensor, static cyclic test, steel structure, seismic damages

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Authors: Helena Pera, Arcadi Sanmartin, Albert Falques, Rafael Rebolo, Xavier Ametller, Heiko Zillgen, Cecile Prum, Boris Even, Eric Kapornyai

Abstract:

Sheet piles system can be an interesting solution when dealing with harbors or quays designs. However, current design methods lead to conservative approaches due to the lack of specific basis of design. For instance, some design features still deal with pseudo-static approaches, although being a dynamic problem. Under this concern, the study particularly focuses on hydrodynamic water pressure definition and stability analysis of sheet pile system under seismic loads. During a seismic event, seawater produces hydrodynamic pressures on structures. Currently, design methods introduce hydrodynamic forces by means of Westergaard formulation and Eurocodes recommendations. They apply constant hydrodynamic pressure on the front sheet pile during the entire earthquake. As a result, the hydrodynamic load may represent 20% of the total forces produced on the sheet pile. Nonetheless, some studies question that approach. Hence, this study assesses the soil-structure-fluid interaction of sheet piles under seismic action in order to evaluate if current design strategies overestimate hydrodynamic pressures. For that purpose, this study performs various simulations by Plaxis 2D, a well-known geotechnical software, and CFD models, which treat fluid dynamic behaviours. Knowing that neither Plaxis nor CFD can resolve a soil-fluid coupled problem, the investigation imposes sheet pile displacements from Plaxis as input data for the CFD model. Then, it provides hydrodynamic pressures under seismic action, which fit theoretical Westergaard pressures if calculated using the acceleration at each moment of the earthquake. Thus, hydrodynamic pressures fluctuate during seismic action instead of remaining constant, as design recommendations propose. Additionally, these findings detect that hydrodynamic pressure contributes a 5% to the total load applied on sheet pile due to its instantaneous nature. These results are in line with other studies that use added masses methods for hydrodynamic pressures. Another important feature in sheet pile design is the assessment of the geotechnical overall stability. It uses pseudo-static analysis since the dynamic analysis cannot provide a safety calculation. Consequently, it estimates the seismic action. One of its relevant factors is the selection of the seismic reduction factor. A huge amount of studies discusses the importance of it but also about all its uncertainties. Moreover, current European standards do not propose a clear statement on that, and they recommend using a reduction factor equal to 1. This leads to conservative requirements when compared with more advanced methods. Under this situation, the study calibrates seismic reduction factor by fitting results from pseudo-static to dynamic analysis. The investigation concludes that pseudo-static analyses could reduce seismic action by 40-50%. These results are in line with some studies from Japanese and European working groups. In addition, it seems suitable to account for the flexibility of the sheet pile-soil system. Nevertheless, the calibrated reduction factor is subjected to particular conditions of each design case. Further research would contribute to specifying recommendations for selecting reduction factor values in the early stages of the design. In conclusion, sheet pile design still has chances for improving its design methodologies and approaches. Consequently, design could propose better seismic solutions thanks to advanced methods such as findings of this study.

Keywords: computational fluid dynamics, hydrodynamic pressures, pseudo-static analysis, quays, seismic design, steel sheet pile

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