R134a (Hydrofluorocarbon refrigerant) is used in domestic refrigeration and other vapour compression system. R134a is having zero ozone depletion potential (ODP) and almost same thermodynamic properties as R12 (Chlorofluorocarbon refrigerant), but it has a high Global Warming Potential (GWP) of 1300. Hence an alternative for this refrigerant is to be identified. After reviewing the various literature for hydrocarbon refrigerants and their mixture gives good Performance in small capacity domestic refrigerators compared to R134a (Ref: Prafull V Chavan, Yarasu RB. A review on hydrocarbons as alternative refrigerants to R134a. Discovery Engineering, 2016, 4(12), 216-220); (Image: http://www.ff.up.pt/ monografias_toxicologia/).
Demand for higher production rate compels to operate machines at ever increasing speeds. With the advent of new manufacturing technologies now machine parts and mechanisms are also made of composite materials having high strength to weight ratio and high stiffness to weight ratio instead of homogeneous & isotropic materials such as carbon steels or aluminum metals. So, the members(Links) can also be fabricated from F.R.P.C. (fiber reinforced polymer composites) or simple P.M.M. (polymer matrix material) for very high speed of operations, this also result in weight savings up to 70% , thus less inertia forces , stresses, deflection, noise and vibration of links, therefore less chances of fatigue failure. These mechanisms are very often used in extreme atmospheric conditions with the requirement of high accuracy. In hygrothermal environment presence of moisture & high temperature affects the kinematic accuracy & precision of mechanism, also deviations in coupler curves are observed. In the present work F.R.O.M.(Full- Range-Of-Motion) computational simulative analysis has been done to find out the kinematic deviations mainly with reference to coupler curve of four bar mechanism made of neat polymer matrix material(Neat Resin)i.e. R-914 and 8551-7, when they are subjected to high temperature and high humidity environment i.e. hygrothermal environment with reference to dry atmosphere. It is found that due to structural deviations, coupler curve of four bar mechanism is altered under hygrothermal environment.
Thermal performance of solar air heater is very low due to the low heat transfer rate from absorber plate to air flowing through the air channel. So it has become a major intense for research work. In this context various methods have been proposed to enhance the heat transfer by convection. From all these methods artificial roughness provided on absorber plate is the most effective technique to increase the thermal performance of solar air heater. This paper is a review of various research work that has been done on solar air heater by using artificial roughness on absorber plate. In this study effect of different roughness element like ribs, baffles and dimples on heat transfer characteristics of solar air heater is discussed.
R134a (Hydrofluorocarbon refrigerant) is used in domestic refrigeration and other vapour compression system. R134a is having zero ozone depletion potential (ODP) and almost same thermodynamic properties as R12 (Chlorofluorocarbon refrigerant), but it has a high Global Warming Potential (GWP) of 1300.Hence an alternative for this refrigerant is to be identified. After reviewing the various literature for hydrocarbon refrigerants and their mixture gives good Performance in small capacity domestic refrigerators compared to R134a.
Solar updraft tower play an important role in the field of renewable energies. The solar updraft tower meets the crucial conditions and makes it possible to take the crucial step towards a global solar energy economy. Economic appraisals based on experience and knowledge gathered so far have shown that large scale solar updraft towers ( ≥ 100 MW) are capable of generating energy at costs close to those of conventional power plants. This reason is enough to further develop this form of solar energy utilization to encompass large, economically viable units. Solar updraft towers have typically assumed that they would be single use structures: solar to electricity via heat differentials between high altitude air and ground level greenhouse-enclosed air. The resulting system has marginal economic value. In a future energy economy, solar updraft towers could thus help assure the economic and environmentally benign provision of electricity in sunny regions. Therefore it is felt necessary to study the various geometric parameters of solar updraft tower to optimize the dimensional parameter for solar updraft power plant by means of experimental data to generate an exact mathematical model between different geometric. It has been decided to adopt qualitative experimental approach for this purpose in fact; more precisely field data based approach. For this, the inputs as well as corresponding responses are measured and the relationship is established between the responses and inputs using theories of experimentation for solar draft tower. Thus, the factors influencing the performance of the solar updraft tower activity have been identified, so as to optimize the performance of the solar updraft tower.
Solar seed dryer is basically designed for farmers for drying the seeds after harvesting. This project provides more efficient, safe (without contamination and dust) and eco friendly source for drying because it utilizes solar energy for its working. The basic principle of working of solar seed dryer is that the solar radiations are made to converge at focus of a parabolic reflector which is a parabola in extruded form. Due to this convergence the intensity of solar radiations gets increased. Then this heat of high intensity radiation is used to heat the air passing through a heat absorbing unit. The heated air is utilized to dry the seeds in a drying chamber. The major parts involved in this system are i) a parabolic reflector ii) a heat exchanger. Features of this project are: Reflecting surfaces required less material and are structurally simpler, because of the smaller area of heat exchanger the energy losses from the boundary is comparatively smaller, this project has the advantage of using both beam and diffuse solar radiation so it can even work in cloudy whether when the sun’s intensity is low. Parabolic reflector is designed with a mechanism to orient it in the direction of sun rays, so there is maximum utilization of solar energy.
Wear in a piston ring assembly occurs as a consequence of the sliding movement between the piston ring and the cylinder liner of the I C Engine. Wear is dependent on the friction between piston ring and cylinder liner. This leads to increased fuel consumption. The Piston Ring Assembly is a major contributor of friction. This review presents the detailed study of quantitative as well as qualitative models for predicting wear of a piston ring proposed by research scholars. It has been observed that the piston ring wears out unevenly throughout its circumference. All the proposed models are based on the assumption that the wear is uniform throughout the circumference. However, it has been observed that wear varies continuously along the circumference of the Piston Ring. This study tries to capture whether any research has been carried out to quantify the variability of the wear along the circumference.
This study has been carried out in the Hydraulic Laboratory, Department of Applied Mechanics, MNNIT Allahabad for Froude number ranged from 2 to 8 and incoming Reynolds number 8000 to 25000 to find out non – dimensional relationship for dissipation index and efficiency of free hydraulic jump in horizontal prismatic channels. The developed empirical computational models of dissipation index and efficiency of free hydraulic jump are validated using Bhutto (1987) data.
In the current scenario there is a considerable decrease in fossil fuels reserves, therefore, it is evident that biodiesel is destined to be an integral part of the future energy sources. In this regard, biodiesel is commercially and technically an alternative to fossil-diesel. There are different potential feed stocks for biodiesel production. This paper analyses the performance, emission and combustion characteristics of biodiesel from different feed stocks based up on composition and properties. Biodiesel has benefits like reduction of greenhouse gas emissions and many harmful pollutants (PM,HC,CO etc).The paper reviews the effect of injection timing on combustion and emission characteristics. The results of the study show the effect of different chemical composition leading to variations in its combustion, performance and emission characteristics. Biodiesel from different feed stocks reduces the pollutant emission and resistive to oxidation but exhibit poor atomization. To conclude, many research need to be carried out to understand the relationship between the type of biodiesel feed stock, performance and emission.
Heat exchanger is a device that facilitates the transfer of heat between two fluids that are at different temperatures and separated by a solid wall. The application of heat exchangers are found in many fields like space heating and air conditioning, power production, waste heat recovery, chemical processing etc. Double pipe (concentric tube) heat exchanger is one of the simplest heat exchanger in which the hot and cold fluids move in the same or opposite directions known as parallel flow and counter flow arrangements. An essential part of heat exchanger analysis is the determination of overall heat transfer coefficient and mean temperature difference between hot and cold fluids also known as log mean temperature difference (LMTD).In the present study, experimental work has been done on a double pipe heat exchanger in counter flow mode by using water as a hot fluid and cold fluid. Inside and outside convection heat transfer coefficients and LMTD are estimated for different hot fluid temperatures and mass flow rate for a given conditions of cold fluid. In each case, overall heat transfer coefficient and heat transfer rate were estimated. Experimental analysis has been carried with water as hot fluid and addition of radiator coolant (HP make) in water as cold fluid and effect of percentage addition of radiator coolant for different conditions on overall heat transfer coefficient and heat transfer rate has been studied. Double pipe heat exchanger has been modeled in CFD and analyzed using ANSYS CFX 14.0 solver. Effect of percentage addition of radiator coolant in water for 0.25/0.75v/v, 0.35/0.65v/v, 0.5/0.5v/v, 0.75/0.25 v/v, and 1.0/0.0 as cold fluid on overall heat transfer coefficient and heat transfer rate has been analyzed using CFD analysis. Theoretical analysis has been done by using CFD analysis for the cases for which the experimental data is not available. Finally, a comparison has been made between experimental results and results obtained from CFD analysis.
Homogenous charge Combustion ignition (HCCI) engines are being considered as an alternative to diesel engines. The HCCI concept involves premixing fuel and air prior to induction in to the cylinder (as is done in current spark- ignition engine) then igniting the fuel –air mixture through the compression process (as is done in current diesel engines). The combustion occurring in HCCI engine is fundamentally different from a spark ignition and Diesel engines in that of heat release occurs as a global auto ignition process, as opposed to the turbulent flame propagation or mixing controlled combustion used in current engines. The advantage of this global auto ignition is that the temperatures within the cylinder are uniformly low, yielding very low emission of oxides of Nitrogen (NOx, the chief precursors to photochemical smog). The inherent feature of HCCI combustion allows for design of engines with efficiency comparable to, or potentially higher than, diesel engines. This paper describes the results & Strategy proposed to control the combustion of HCCI engine. This is achieved by controlling air path & fuel path to maintain start of Combustion. An experimental result of Combustion Control analysis is presented to prove the strategy used for these experiments.
An innovative idea of extracting kinetic energy from man-made wind resources (chimney flue gases) with ducted horizontal axis turbine system for producing electricity is introduced in this paper. The turbine system is positioned beyond the chimney outlet, to avoid any negative impact on the chimney performance. The results from the CFD based simulation analysis indicate that a significant power can be harnessed from the chimney exhaust. The power extraction by the energy recovery system using a 6-blade ducted turbine with NACA4412 airfoil has been studied using CFD simulation. It is observed that the average flue gas velocity in the duct section at the throat is approximately twice that of the inlet velocity, whereas maximum velocity at the throat achieved is 2.6 times the inlet velocity. The system may be retrofitted to existing chimneys of thermal power plants, refineries and other industries. The market potential for this recovery system appears to be very high due to abundant chimneys, cooling towers and other unnatural exhaust air resources globally.
Identification of critical equipment from power plant is major and important step for defining maintenance strategy and making decisions. The criticality analysis is used to rank the risk associated with each failure mode identified during the Failure Mode Effect Criticality Analysis. The score of criticality index is used to categorize most critical equipment to least one. For maintenance planning higher the criticality the higher the level of effectiveness required for all actions performed to prevent the occurrence of the given failure mode. This paper describes methodology for identifying critical equipments of power plant based on criticality analysis using selected multiple criterions.
Optomechanical systems are facing two problems: one is heat control and other is noise control. This paper deals with cooling of optomechanical systems using quantum mechanics. In quantum mechanics, squeezed state shows amazingly different properties which are used in achieving steady states for these systems. Cooling of system is achieved by obtaining a steady state and by attaining the number of phonons required for a system as minimum as possible. Two different models for cooling of these systems are discussed and their merits and demerits are discussed.
This paper deals with the comparative study of two refrigerants namely, R134a and R404a. Refrigerant is the one which provides cooling to the food items and other stuffs in the refrigerator. Basically, there are two types of refrigeration cycle – Vapour Compression refrigeration cycle and Vapour Absorption refrigeration cycle. Most widely used cycle is Vapour Compression refrigeration cycle because it provides better Refrigerating Effect. The experimental analysis was carried out with Vapour Compression refrigeration cycle. Among the two refrigerants i.e. R134a and R404a, R404a is more eco-friendly and produces less global warming. The experiment was carried out with different helix coil diameters (3mm and 6.5mm) of expansion valve. It is also seen that with increase in temperature of evaporator, the compressor work decreases and the COP (Coefficient of Performance) increases. Refrigeration effect was observed to decrease with decrease in internal diameter of coil. When the comparative study of the two refrigerant was done using ‘COOLPACK’ software it was found that the compressor work required was more in case of R404a refrigerant than R134a. It was also found that refrigeration effect of R134a is more than R404a, and hence the COP is more in case of R134a than R404a.
Vapour absorption refrigeration systems (VARS) use natural refrigerants such as water or ammonia, they are environment friendly as they eliminate the use of CFC and HCFC refrigerants. This article presents thermoeconomic Input-Output analysis of a single stage vapor absorption refrigerant system (VARS) with water-LiBr pair whose energy source is waste steam. Thermoeconomic Input– Output analysis provides general relationships between the product and the resource with the efficiency for each component of an energy system. This model is a fundamental concept of symbolic thermoeconomics. In this work, authors have build a productive scheme from the physical structure of the VAR system that explains the resources distribution throughout the system. The definition of physical structure consists of indicating the pair of components that each flow of the system connects. The complete productive structure of the whole VAR system analyzed in this paper is shown graphically. This approach allows one to obtain the Fuel-Product [FP] table, a mathematical representation of thermoeconomic Input-Output model. The FP table shows, where the product of each component is used and the origin of the resources of each component. It includes the energy values of the flows in the productive components, and the external interactions with the other systems. The rows represent the destination of the production of each sub system as resource of other processes, as final product or as disposable waste, while the columns represent the source of the fuel of each sub system. Fuel-Product table provide results with clear interpretation because flows appearing in this table are not related to detailed flows of the physical structure but with productive flows related to the purpose of the components. FP table plays a key role in the various approaches of thermoeconomics like cost formation process and thermoeconomic diagnosis. The input data for performing the thermoeconomic Input-Output analysis are the energy of each flow of the system. Authors have modeled the Vapour Absorption Refrigeration System in TAESS (Thermoeconomic Analysis of Energy Systems Software). TAESS is developed in CIRCE (Center of Research for Energy Resources and Consumption) and the Department of Mechanical Engineering of the University of Zaragoza (Spain), to execute the thermoeconomic analysis of energy systems from their thermodynamic model and productive structure.
This paper is review of various research works that has been done on friction stir welding during the last decade. In this study, a comparison is done on various works that have been carried on friction stir welding by using finite element modeling. Study of thermal analysis is taken as the major point for discussion in this paper. Review of thermal analysis by using various softwares is studied. Transient thermal analysis of various metals has been discussed in this paper. Also the experimental investigations made by various researchers are also studied in the paper.
The experimental friction factor and Nusselt number data through a square twisted duct have been presented. Experiments were conducted for air as a working fluid with uniform wall flux boundary condition. The thermohydraulic performance has been evaluated. Reynolds number varies from 100 – 3,000. The major findings of this experimental investigation are that the square twisted duct of different twist ratio TR (y/W = 1.50 and 2.63) and length ratio LR (Ls/Lf = 1.0, 0.75 and 0.60) perform better than the straight square duct for laminar flow. The results show considerable increase in heat transfer and pressure drop in laminar region. Twist ratio of 1.50 with LR 1.0 shows higher heat transfer and pressure drop compared to other ducts.
Catalysts have come to occupy a prominent place in the reciprocating engine generated pollutants purifications. With the progressive tightening of the emission norms, there is a spurt in the research activity in this area. For the very survival of the piston engines in the new millennium, the engines have to adapt themselves to the challenges posed. As there is a vast population of single cylinder diesel engine powered irrigation pump sets in the rural areas of our country, it was thought fit to make these engines environmentally friendlier. As these engines are very rugged, by the fitment of fairly inexpensive exhaust gas treatment devices like the one discussed in this paper, the emission levels of major pollutants like oxides of nitrogen and particulate matter can be significantly brought down. There is only a marginal increase in the fuel consumption rate due to the add-on device. The details of a mixed oxides catalyst coated γ-alumina pellets filled converter system for the exhaust gases of a single cylinder, D.I. Diesel engine system are presented and discussed in this paper. It is believed that such systems have a role to play in the maintenance of the ecosystem of rural India. Effective reduction of NOx level will likely require exhaust after treatment devices such as catalytic NOx converters. The effects of aluminium-doped manganese and copper dioxide catalysts on the NOxemissions of the engine are presented and discussed in this paper.
Solar energy is a very large, inexhaustible source of energy with two main distinct advantages as follows; the first one is unlike fossil fuels and nuclear power, it is an environmentally clean source of energy and secondly it is free and available in lump in almost all the parts of world. Reducing the devices and energy efficiency are two major factors to find new materials and improving the designs of solar collectors. Nanofluides are innovative fluids getting worldwide attention due to their inherent characteristics. Nanofluides exhibits enhanced thermal conductivity and heat transport ability goes to nanoparticle suspension in based fluids. Nanofluides are nanoparticles suspended in base fluids. These nanofluides are now being used as working fluids to absorb solar radiation and transfer it to another fluid at higher rate as reported by many researchers and nano research labs all over the world. Our intention behind writing this review is to comprehensively and thoroughly investigate the research work done for improvement of efficiency in Direct Absorbing Solar Collectors using Nanofluides. Review of previous works based on experimental and theoretical studies have established that nanofluides have great potential to increase thermal efficiency of Direct Absorption Solar Collector. Recent trends also encourage towards applications of nanofluides on conventional solar flat plat collectors and concentrating collectors to increase overall efficiency of solar energy conversion.
In recent years, the high cost of energy and material has resulted in an increased effort aimed at producing more efficient heat exchange equipment. Furthermore, sometimes there is a need for miniaturization of a heat exchanger in specific applications, such as space application, through an augmentation of heat transfer. The main objective of this study is to review the different types of compact heat exchanger. This paper reviews the different methods and geometry to increases the effectiveness of heat exchanger and reduce the size of the compact heat exchanger.
This paper is review of various research works that has been done on Shell and Tube heat exchanger during the last few decades. Out of these, Helical Shell and Tube heat exchanger having significant effect on various parameters that improves the overall performance of Shell and Tube heat exchanger. This paper gives the main focus on the performance parameter of Helical shell and tube heat exchanger like baffle spacing, pressure drop, helix angle, fouling, shape of baffle and sealing strip.
Passive techniques, where inserts are used in the flow passage to augment the heat transfer rate, are advantageous compared with active techniques because the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger. In the past decade, several studies on the passive techniques of heat transfer augmentation have been reported. This paper is a review on progress with the passive augmentation techniques in the recent past and will be useful to designers implementing passive augmentation techniques in heat exchange. Twisted tapes, wire coils, ribs, fins, dimples, etc., are the most commonly used passive heat transfer augmentation tools. In the present paper, theemphasis is given to works dealing with twisted tapes and wire coils because, according to recent studies, these are known to be economic heat transfer augmentation tools.