Thermal Engineering

A heat exchanger is a system used to transfer heat between two or more fluids or is a device which transfers heat from one medium to another. Heat Exchangers are used in both cooling and heating processes. The fluid may be separated by a solid wall to prevent mixing in both counter flow and parallel flow heat exchangers. The objective of this simulation is, To model a sheel and tube Counter Flow Heat Exchanger by using Solid work Premium 2016, To model Parallel Flow Heat Exchangers by using Solid work Premium 2016, To perform CFD analysis of both type heat exchangers by using Solid work 2016 Flow simulation, To find the temperature of Outlet hot water and outlet cold water in both Heat Exchangers and Finally to find the LMTD of both Heat Exchangers from the simulation.

Industrial control systems are nowadays exposed in environments with rapid and unstable parameter changes and uses measuring equipments with critical output sensitivity. In the case of thermal gas analyzer, measurement errors are contributed by temperature, gas flow, and pressure. Error compensation is a key problem for these control systems. In recent years, it has been proven in the literature that artificial neural network (ANN) is a reliable and low cost solution to manage errors. Among all the algorithms of ANN, the back propagation is commonly used because of its simplicity and learning methodology is easy to realize. However, it has two notable drawbacks: (a) it is likely to run into local minimum, and (b) convergence is slow. Thermal conductivity gas analyzer often works in adverse surroundings, which requires fast and accurate measurements. Therefore, a strong learning network is needed. This paper proposes a novel thermal gas analyzer using adaptive neuro-fuzzy inference system. The effectiveness and validity of the proposed method is verified by simulation studies using MATLAB. Fuzzy membership rules are created to allow regulation of learning parameters. Further, the fuzzy adaptive network model is constructed to train large data samples while the high precision compensation of sensor error is realized by the improved flow. Simulation results reveal that the convergence speed and output accuracy is improved and the learning parameters in thermal gas analyzer are automatically corrected by the proposed method in comparison with the back propagation algorithm of artificial neural network.

In the past decade, rapid advancements of nanofluids science in many areas have been observed. In recent years, refrigerant-based nanofluids have been introduced as nanorefrigerants due to their better heat transfer performance. The objectives of this research include preparation, characterization and investigation of the thermophysical and migration properties of nanorefrigerants. Al2O3/R141b and TiO2/R141b
nanorefrigerants with various proportions of concentrations have been prepared to investigate their fundamental properties. Nanoparticles size, shape, and elemental
proportion have been characterized with Field Emission Scanning Electron Microscope (FESEM) and Transmission Electron Microscope (TEM). Moreover, this study investigated thermal conductivity, viscosity, and density of Al2O3/R141b
nanorefrigerants for different concentrations and temperatures. In addition, migration properties of Al2O3 and TiO2 nanoparticles with R141b refrigerant along with
lubricating oil have been investigated for different heat fluxes, initial liquid level heights, vessel sizes, insulation, nanoparticle sizes, and oil mixture. In this study, the thermal conductivity of Al2O3/R141b nanorefrigerant increased with the
augmentation of particle concentration and temperature. Besides, viscosity and density of the nanorefrigerant increased with the increase of volume fractions. However, these parameters decreased accordingly with the increment of temperature. Migration of nanoparticles during pool boiling increased with the increase of initial nanoparticle mass fraction, nanoparticle size, heat flux, and insulation. However,
migration of nanoparticles decreased with the increase of particle's self-density, boiling vessel size, and initial liquid level height. Therefore, nanoparticle has strong relationship with thermophysical and migration properties of refrigerants.

This paper introduces various electrical and thermal energy generation, consumption, and storage components in solar powered low-energy buildings. Dynamic management of such energy components is essential given the stochastic solar resources. Emphasis is put on power electronic HVAC (heating, ventilation, and airconditioning) drives, which can act as an effective electric swing bus to mitigate solar power variability. In doing so, grid power flows become substantially more constant, reducing the need for fast grid resources or dedicated energy storage such as batteries. The concept is equivalent to using building thermal energy as virtual dynamic storage in support of power grid operation. The paper defines a bandwidth over which such HVAC drives can operate. A practical band-pass filter is realized that provides 1) lower frequency bounds such that the building maintains consistent room temperature via the HVAC system as demonstrated by a thermal modeling study, and 2) upper frequency bounds that ensure commanded HVAC fan speeds do not update arbitrarily fast. The latter primarily avoids acoustic discomfort to users. The combination is illustrated by experimental results based on various update rates of a variable frequency fan drive over a sample of actual stochastic solar data. Building electrical and thermal energy systems modeling by MATLAB is addressed throughout the paper, including solar and HVAC systems as well as batteries and water tanks. Index Terms—Low-energy buildings, frequency domain analysis, grid-level energy storage, HVAC systems, solar energy, thermal storage, power electronic drives, complex system energy management

ABSTRACT Thermal effects are critical factors on the performance and life of a Polymer Electrolyte Membrane (PEM) fuel cell system. Heat generation in a fuel cell stack is largely influenced by the exothermic electrochemical reactions at the cathode. Due to non-uniformity of reactions over the MEA area, heat generation and temperature distribution over the stack is also theoretically non-uniform. This work attempts to profile the thermal performance of an industrial PEM fuel cell stack. The stack power generation and cooling rates at the heat exchanger were monitored under specific working conditions. The discussion focused on causes of the temperature gradient, heat generation, cooling effectiveness, and the quality of the heat exchanger. The analysis demonstrates a significant relationship between stack temperature and generated power to the heat exchanger performance and coolant conditions.

— In digital communication system, digital information can be sent on a carrier through changes in its fundamental characteristics such as phase, frequency and amplitude. The use of a filter plays an important part in a communication channel because it is effective at eliminating spectral leakage, reducing channel width, and eliminating interference from adjacent symbols (Inter Symbol Interference) ISI. It describe the developed and dynamic method of designing finite impulse response filter with automatic rapid and less error by an efficient genetic and neural approach. GA and Neural are powerful global optimization algorithm introduced in combinational optimization problems. Here, FIR filter is designed using Genetic, Neural approach by efficient coding schemes. We need to design these filters with some constraints imposed by requirements of the communication system in which we are going to use them. The use of optimization techniques have been proved to be quite useful towards the design of those digital filters with certain specifications. This paper reviews about the uses of optimization systems in digital filter design.

— Designing an efficient Distributed Database System (DDBS) is considered as one of the most challenging problems because of multiple interdependent factors which are affecting its performance. Allocation and fragmentation are two processes which their efficiency and correctness influence the performance of DDBS. Therefore, efficient data fragmentation and allocation of fragments across the network sites are considered as an important research area in distributed database design. In this paper presents an approach which simultaneously fragments data vertically and allocates the fragments to appropriate sites across the network. Bond Energy Algorithm (BEA) is applied with a better affinity measure that improves the generated clusters of attributes.

The paper presents results of an experimental investigation of convective drying of Idared apple in full recirculation laboratory scale dryer. The experiments were conducted with cube-shaped apple samples (side length 10 and 13 mm), without pre-treatment. The parameters of air stream over the tray with samples were fully controlled and adjusted in several sets of experiments, while always remaining in the following ranges: temperature 35–55 °C, relative humidity 10–30%, velocity 1–2 m/s. The drying kinetics of the apple samples was recorded, the results were analyzed and compared to the existing drying models. The analysis of the experimental results enabled derivation of correlations between drying parameters in a form k = f(T,RH), within Henderson & Pabis drying model MR = aexp(−kτ), as well as the calculation of effective moisture diffusivity during the process.► An experiment for low-temperature convective drying of apple cubes is conducted. ► A convective laboratory scale dryer with full air recirculation is built. ► The experiments are in ranges: 35–55 °C, 10–30% RH, 1–2 m/s, cube size 10 and 13 mm. ► The analysis of the results enabled derivation of drying parameters correlations. ► Different combinations of drying parameters can produce similar drying effects.

 Abstract— Distribution design involves making decisions on the fragmentation and allocation of data across the sites of a computer network. Multiple vertical splitting is the process of subdividing the attributes of a relation to generate fragments. In this paper, we propose an analysis for multiple vertical splitting algorithm using Slop Based Partitioning Algorithm (SBPA). This approach starts from the attribute affinity matrix and generates initial clusters based on the affinity values between attributes. Then, it uses the database according to optimal splitting solution to produce final groups that will represent the fragments. Then we analyzed these fragments according to their contribution level. The result is generated that shows how to find optimal solutions.

In recent year's commercialization of Renewable energy plays a vital role in extending the existence of fossil fuels. Solar energy is one of the easily available and most utilized energy sources all over the world. Solar energy is used in various forms like power generation, desalination, cooking, drying and water heating. This work concentrates on Domestic Solar Water Heater (SWH). Even though SWH is fitted in 75% of houses, inconvenience in SWH is unobtainable of hot water round the clock. Research for increasing the performance of SWH is by either modifying the design or using storage materials. In this work conventional sensible heat storage materials like pebbles, sand and inorganic salts used for latent heat storage materials like Sodium Chloride (NaCl), Potassium Chloride (Kcl), zinc Chloride (Zncl2), Carbamide and mixture of Zncl2, Kcl, Carbamide are employed. Inorganic salts and eutectic mixtures are used only as latent heat storage materials and not as sensible storage materials. In this work an attempt is made to study the performance of SWH using the latent heat storage materials as sensible heat storage.

In this study pongamia methyl ester was prepared by transesterification using potassium hydroxide (KOH) as catalyst and was used as fuel in a four stroke, water cooled, single cylinder, direct injection diesel engine. Pongamia methyl ester fuel blends (75% and 100%) were used for conducting the engine performance tests at varying loads (20%, 40%, 60%, 80%, and 100%). Tests were carried out over entire range of engine operation at varying conditions of load. The performance, combustion and emission characteristics were determined. Based on these, the parameters such as brake thermal efficiency, specific fuel consumption, exhaust gas temperature, emissions in exhaust such as CO, CO 2 , O 2 , HC and NOx were recorded. The results show that the blend of pongamia oil with diesel fuel can be used as an alternative fuel successfully in a diesel engine without any modification.

Since decades, the only source of the material is reinforced alloys of such as iron, steel or aluminium are used in the automobile industry but due to high demand for performance. Researchers found introducing ceramic components can withstand elevated temperatures which are produced during working. Nowadays ceramics are used in Pistons, piston-skirts, cylinder heads, intake manifolds, etc. The work here is been carried out by scrutinizing different compositions of ceramics on a 3D model brake disc in replace of a traditional cast-iron disc. Apart from withstanding high temperature, foremost is heat dissipation to the airstream. Performing transient thermal analysis shows the characteristics of thermal stability, heat dissipation and other mechanical behaviour w.r.t various conditions. Giving the results of better thermo-mechanical stability over present materials such as thermal behaviour, strength to weight ratio, wear and tear resistance, withstanding chemical erosion subjected to acidic and caustic environments that occurs in other materials. I. INTRODUCTION Present day industries of aerospace and automobile are been upgrading to advance manufacturing techniques about brake discs using ceramic composites replacing present alloys to compete over different mechanical properties of elasticity, hardness, tensile strength at soaring temperatures keeping their wear and tear resistance to minimum using different materials to have the optimum strength to weight ratio. As ceramics deliver high performance in both dry and wet conditions of comfort, durability, resistance, corrosion and high-tech appeal. A ceramic is an inorganic non-metallic solid made up of either metal or non-metal compounds that have been shaped and then hardened by heating to high temperatures. In general, they are hard, corrosion-resistant and brittle. Traditional ceramics are clay-based, but high-performance or advanced ceramics are being developed from a far wider range of inorganic non-metal materials. Advanced ceramics have the properties of high strength, high hardness, high durability and high toughness. These advanced ceramics are generally oxides of elements or non-oxides (like borides, nitrides and silicide's) Production processes firstly involve thoroughly blending the very fine constituent material powders. After shaping them into a green body, this is high-temperature fired (1,600-1,800°c). This step is often carried out in an oxygen-free atmosphere. The high temperature allows the tiny grains of the individual ceramic components to fuse together, forming a hard, tough, durable and corrosion-resistant product. This process is called Sintering.

https://www.ijert.org/cfd-investigation-on-optimized-basket-profile-elements-in-ljungstrom-air-preheater

https://www.ijert.org/research/cfd-investigation-on-optimized-basket-profile-elements-in-ljungstrom-air-preheater-IJERTV8IS080003.pdf

Rotary regenerative ljungstrom air preheater is a type of heat exchanger. This heat exchanger is utilized to heat the cold air at coal based thermal power stations. The heat is exchanged between the hot flue gases and cold air which is flowing in opposite direction i.e, in different sectors. As APH rotates at 2-4 rpm, the hot flue gases flow in one section that hot section moves in to the cold section. Such that, the cold air extracts heat from this heating element profiles. In this CFD analysis study, experiment details were collected from the 210MW of RTPS shaktinagar. To study about CFD analysis different element profiles were developed in solid works and imported to ANSYS 18.1. After precise CFD simulations the outlet temperature of element profiles were obtained. This analysis gives relatively good results.

The narrow gauge steam locomotives of the Darjeeling Himalayan Railways are the existing examples of the external combustion engines, which played a key role for transportation in the region before the advent of the automobiles. However, their condition today is grim. In this paper we present the various technical shortcomings and suggestions for improvement of the Class B narrow gauge steam locomotives.

— Thermo-physical properties of butter, hydrogenated fat, palm oil, coconut oil, sunflower oil, and groundnut oil were examined. Experimental results revealed the highest slip melting point (38oC) and specific gravity for hydrogenated fat whereas the lowest slip melting point (-18oC) and hardness values for sunflower oil. However, sunflower oil showed the highest refractive index. The consistency of butter and hydrogenated fat was reported acceptable plastic and spreadable. Palm oil was found soft and spreadable. The melting curve of palm oil, butter, and hydrogenated fat showed two endothermic peaks. However, coconut oil, sunflower oil, and groundnut oil showed only one peak. The solid fat content (SFC) of butter, hydrogenated fat, palm oil, and coconut oil were found within the recommended range for baking performance. Melting enthalpy was strongly correlated to hardness (r = 0.8604, P < 0.001) of fat and oil samples. Correlation coefficient (r) of 0.8977 (P < 0.001) was found between SFC and hardness. The results strengthen the premise that hardness of the fat is not dependent solely on the SFC and as the results demonstrated that the melting enthalpy also plays a key role in influencing the hardness of fats and oils.

Identify of potential risks is the first step in the management risk of software projects. It is a key step that other steps are based on it. In this paper a model is presented to improve the process of identifying potential risks. This model can vouch (assure) development of software projects. A matrix solution is given (is presented) to identify the levels of potential risks. Solutions and the causes of risks are classified based on the known and unknown, and also the levels were determind. The design of this model, in addition to strategy (admission, transfer) to avoid risks and probabilities are modified with new informations. A search algorithm (condition-action) is used to identify and prioritize potential risks based on sequence data structure. This algorithm has been implemented based on the C# codes and it also works on boolean variables. To implement the algorithm operating functions such as searching, planning, control, events, and management were used. To complete it these functions provided by the law-condition apply the potential risks are identified and then prioritized. Zero, and one decision variables to store intermediate results in their practice of inference, as intelligently manage event risks. The implementation of this model in various stages leading to optimized selection of the new solution, and output of model reduces the cost, schedule, and quality of software development. Also the risks and complexities and uncertainties are controlled. The validity of this method is assessed qualitatively using a practical example. This example relates to the users of ICT in training and education center in mazandaran were evaluated.

Desalination plays critical role in filling the gap between fresh water demand and availability in water scarce Sultanate of Oman since 1976. Installed desalination capacity in the country has almost increased by 60 times that in 1976 with increasing fresh water demand. Even though desalination share in meeting the fresh water demand is increasing, 80-85% of fresh water demand today is still satisfied with ground water. This is leading to increased soil salinity in recent years affecting the crop production. All the planned and installed desalination plants in the country use conventional fuels for their operation. None of the plant is based on any form of renewable energy source. Consumption of fossil fuels for the operation of plants is increasing at an average rate of 3-5% affecting the net export for the country. Sultanate of Oman is considered to be one of the most suitable destinations for solar energy applications and can play a vital and sustainable role in meeting the gap b...

— Preliminary investigation on laterite soil sample collected from old Julius Berger borrow pit in Ejio area of Arigbajo in Ifo Local Government Area, Ogun State (6.849˚N, 3.211˚E), classified the soil as A-2-7(4) [AASHTO classification]. The soil was mixed with Banana Leaf Ash (BLA) in varying percentages of 0%, 2%, 4%, 6%, 8%, 10%, and 12% and the effect of BLA on the soil sample was determined for Liquid Limit, Plastic Limit, Compaction (MDD % OMC), CBR and Unconfined Compression Test. These tests were repeated for the soil sample + BLA + cement. The results of the treated soil showed increase in the plastic limit, liquid limit, plasticity index and optimum moisture content (OMC) as the BLA content increased. The values of maximum dry density (MDD), California Bearing Ratio (CBR) and Unconfined Compressive Strength (UCS) increased up to 2% BLA before starting to decrease steadily. This implies that the Banana Leaf Ash (BLA) is a weak pozzolan. Index Terms— Laterite; Banana Leaf Ash (BLA); Stabilization; California Bearing Ratio (CBR); Unconfined Compressive Strength (UCS)

— Stealth refers to the act of trying to hide or evade detection. Stealth technology is ever increasingly becoming a paramount tool in battle especially " high technology wars " if one may occur in the future where invincibility means invincibility. Able to strike with impunity, stealth aircraft, missiles and warships are virtually invisible to most types of military sensors. The experience gained at the warfront emphasizes the need to incorporate stealth features at the design stage itself. The other purpose is to share the recent achievements related to the advanced composite materials used on various aero structures across the globe. Also discussed are the possibilities of achieving stealth capability on our existing fleet of fighter and bomber aircrafts of our Indian Armed forces using composite and smart materials. Stealth technology also known as LOT (Low Observability Technology) is a technology which covers a range of techniques used with aircraft, ships and missiles, in order to make them less visible (ideally invisible) to radar, infrared and other detection methods. Stealth Technology essentially deals with designs and materials engineered for the military purpose of avoiding detection by radar or any other electronic system. Stealth aircraft are aircraft that use stealth technology to make it harder to be detected by radar and other means than conventional aircraft by employing a combination of features to reduce visibility in the visual, audio, infrared and radio frequency (RF) spectrum. Well known examples include the United States' F-117 Nighthawk (1980s-2008), the B-2 Spirit "Stealth Bomber," and the F-22 Raptor.

This study examines the selection of the best air gap to a model solar passive solar system chosen for heating in a cold climate based on instantaneous efficiency. The experiments have been performed on a passive solar system, which has been constructed from insulation sandwich panels in all sides except the south façade, which has been built from insulation sandwich panels on all sides except the south façade, where Trombe wall has been built in it, which is constructed from reinforced concrete and their exterior surface has been painted with dark black color, and covered with a single transparent glass layer. Five sets of experiments have been performed on the test system by changing the width of the air gap from 30 to 10 cm under the weather conditions in January 2017 in the city of Kirkuk (Iraq). The experimental results have showed that the 33 to 36% of the absorbs energy by Trombe wall has been converted to instantaneous energy provided to the heating space during the day. In addition, the results of the energy analysis of experimental equations have been produced to assess the efficiency of the system; they show that the 15 cm air gap has a better case when applying the same parameters, this result is consistent with an experimental study conducted by R. L. Casperson and C. J. Hocever, 1979. Nomenclature Trombe wall area [m 2 ] Vent area [m 2 ] A W Window area [m 2 ] B Width of the air gap [m] Specific heat of air [J/kg °C] Gravitational acceleration [9.81 m/s 2 ] Solar intensity incident on the absorbent surface [W/m 2 ] ℎ Average heat transfer coefficient on the glass side [W/m 2 °C] ℎ Average heat transfer coefficient [W/m °C] h o Surrounding heat transfer coefficient [W/m 2 °C] ℎ Radiant heat transfer coefficient within the air gap [W/m 2 °C] ℎ Average heat transfer coefficient on the absorbent side [W/m 2 °C] Distance between vents [m] Thermal conductivity of the air [W/m °C] k g Thermal conductivity of glass [W/m °C] ̇ Air mass flow rate [kg/s] Convection heat transfer [W] q L Heat loss to the surrounding [W] Useful energy [W] Ventilation energy [W] T a Ambient temperature [°C] T ab Absorbent temperature [°C] Inside surface of glass temperature [°C] Trombe wall temperature from the inside test system [°C] Mean air gap temperature [°C] Inside test system temperature [°C] Outlet temperature from the air gap [°C] u Wind speed [m/s] U L Overall heat transfer coefficient [W/m 2 °C] ̅ Average air velocity within the air gap [m/s] Glass thickness [m] The volume coefficient of expansion [K-1 ] Absorbent surface emissivity Glass emissivity Solar system efficiency Kinematic viscosity [m 2 /s] Air density [kg/m 3 ] Stefan-Boltzmann constant [5.669×10-8 W/m 2 K 4 ] Gr Grashof number Nu Average Nusselt number Pr Prandtl number Ra Rayleigh number

Low cyclic fatigue analysis at room temperature and crack growth rate under isothermal fatigue at 300-600 °C temperature ranges produced in AISI 420 martensitic stainless steel, using un-cracked solid cylinder specimen. The crack growth monitoring is obtained by using the DCPD machine. The research observes that the fatigue life reduces with increasing the surface roughness condition, while the behaviour of the material at room and high temperature to produce an initial hardening, followed by slow extension until fully plastic saturation then followed by crack initiation and growth eventually reaching the failure, and the effects of increasing temperature decrease the crack initiation period and also the crack length. The fatigue crack growth rate increase with stress intensity factor, and the crack growth rate at 600 °C test temperature less than 500 °C, due to the creep-fatigue taking place.