The document discusses various topics related to chemical unit operations and heat transfer. It begins by covering chemical unit operations, including definitions of unit operations and the five main classes: fluid flow processes, heat transfer processes, mass transfer processes, thermodynamic processes, and mechanical processes. It then discusses heat transfer in depth, covering the three modes of heat transfer (conduction, convection, and radiation), equations governing each mode, and key aspects of convective heat transfer including boundary layers and Newton's Law of Cooling. Finally, it outlines the main steps in the thermal design procedure for a heat exchanger, including energy balancing, geometry selection, flow velocity choice, and design optimization.
Numerical Analysis of Heat Transfer Enhancement in Pipe-inPipe Helical Coiled...iosrjce
This document presents a numerical analysis of heat transfer enhancement in pipe-in-pipe helical coiled heat exchangers. Computational fluid dynamics (CFD) was used to analyze the effect of varying parameters like inner tube diameter, mass flow rates, and flow configuration (parallel vs. counter flow). The results show that overall heat transfer coefficients increase with increasing inner Dean number and mass flow rates. Heat transfer rates also increase with higher inner mass flow rates. Counter flow configuration provides better heat transfer than parallel flow. Increasing the inner tube size decreases the total heat transfer rate due to a reduction in annulus cross-sectional area. Measured inner Nusselt numbers agree reasonably well with existing correlations.
CFD Analysis of Heat Transfer in Helical CoilIRJET Journal
This document presents a computational fluid dynamics (CFD) analysis of heat transfer in a helical coil. The study aims to analyze the effect of coil diameter and inlet steam temperature on the heat transfer coefficient. CFD simulations are conducted for helical coils of different diameters with varying inlet steam temperatures and water flow rates. Results show that the heat transfer coefficient increases with increasing inlet steam temperature. Prior research on heat transfer in helical coils is also reviewed, focusing on studies utilizing CFD to analyze parameters like coil diameter, pitch, curvature ratio, and Reynolds number. The CFD methodology and boundary conditions used in this study are described. Contour plots of the simulated surface heat transfer coefficient are presented and discussed.
International Refereed Journal of Engineering and Science (IRJES)irjes
International Refereed Journal of Engineering and Science (IRJES)
Ad hoc & sensor networks, Adaptive applications, Aeronautical Engineering, Aerospace Engineering
Agricultural Engineering, AI and Image Recognition, Allied engineering materials, Applied mechanics,
Architecture & Planning, Artificial intelligence, Audio Engineering, Automation and Mobile Robots
Automotive Engineering….
This document provides a theoretical investigation of a solar energy driven combined power and refrigeration cycle that uses oil as the heat transfer medium. The cycle integrates a Rankine cycle for power production and an ejector refrigeration cycle for cold production. Thermodynamic analyses of the cycle were conducted to determine first law efficiency of 20% and second law efficiency of 11%. Key cycle components include a heliostat field, central receiver, heat recovery steam generator, turbine, evaporator, condenser and ejector. Effects of parameters such as steam temperature and evaporator temperature on cycle performance were examined.
The document summarizes the fabrication and testing of a heat exchanger test rig. Key points:
- The test rig was designed and built to study a counter-flow tube heat exchanger using aluminum sheets and tubes.
- Finite element analysis was performed on the rig design to analyze stresses. Water was heated to 40°C and pumped through one side while tap water entered the other side.
- Effectiveness-NTU method was used to calculate theoretical outlet temperatures which were compared to experimental readings to determine error percentages.
Optimization of a Shell and Tube Condenser using Numerical MethodIJERA Editor
The purpose of this study was to investigate the effect of installation of the tube external surfaces, their parameter and variable in a shell-and-tube condenser. Variation of heat transfer coefficient with each variable of shell and tube condenser was measured each test. The optimization tube outside diameter size was analyzed and use extended surface area attached tube with tube material and tube layout and arrangement (Number of tube a triangular or hexagonal arrangement) on shell-and tube condenser. The computer programming was used to get faster output in less time. Results suggest that mean heat transfer coefficient in variable condition were mainly at velocity is fixed. And also average additional surfaces and tube layout and the arrangement comparison with the quantity of the heat transfer.
Heat exchangers are used widely in industrial application such as chemical,
food processing, power production, refrigeration and air-conditioning
industries. Helical coiled heat exchangers are used in order to obtain a large
heat transfer per unit volume and to enhance the heat transfer rate on the inside
surface. In the present study, CFD simulations are carried out for a counter
flow tube in tube helical heat exchanger where hot water flows through the
inner tube and cold water flows through the outer tube. From the simulation
results heat transfer coefficient, pressure drop and nusselt number are
calculated. The heat transfer characteristics of the same are compared with that
of a counter flow tube in tube straight tube heat exchanger of same length
under same temperature and flow conditions. CFD simulation results showed
that the helical tube in tube heat exchanger is more effective than the straight
tube in tube heat exchanger.
Experimental Study of Heat Transfer Enhancement of Pipe-inPipe Helical Coil H...iosrjce
This document presents an experimental study of heat transfer enhancement in a pipe-in-pipe helical coil heat exchanger. Experiments were conducted with two different inner coil diameters (6mm and 8mm) under varying mass flow rates in the inner coil and annulus. The overall heat transfer coefficient and inner Nusselt number were found to increase with increasing mass flow rates. Counter-flow configuration resulted in higher heat transfer rates than parallel flow due to the larger log mean temperature difference, though overall heat transfer coefficients were similar between the two flow arrangements. Experimental results for inner Nusselt number agreed with established correlations in parallel flow but were higher in counter-flow.
Parallel flow heat exchanger is analysed with CFD tool. A comparative study of the analytical and experimental data is carried out to better understand the temperature profile, surface heat flux and heat transfer co-efficient parameters of the heat exchanger
The document summarizes an exergy and exergo-economic analysis of the Montazer Ghaem gas turbine power plant in Iran. The analysis finds that the combustion chamber has the highest exergy destruction due to the large temperature difference between the flame and operating fluid. The gas turbine's performance and efficiency are significantly affected by ambient temperature. An increase in ambient temperature decreases the net power output and exergy efficiency. The exergo-economic analysis determines that the combustion chamber also has the largest cost of exergy destruction.
IRJET- A Review on Basics of Heat ExchangerIRJET Journal
This document reviews the basics of heat exchangers. It discusses that heat exchangers are used to transfer heat between two or more fluids for heating and cooling processes. The three main types of heat exchangers are shell and tube, plate, and double pipe heat exchangers. It also discusses computational fluid dynamics as a method to analyze fluid flow and heat transfer in heat exchangers numerically. The document then reviews the basic design methods for two fluid heat exchangers, including the log-mean temperature difference method, effectiveness-NTU method, and other graphical methods.
Review on Comparative Study between Helical Coil and Straight Tube Heat Excha...IOSR Journals
The purpose of this study is to determine the relative advantage of using a helically coiled heat
exchanger against a straight tube heat exchanger. It is found that the heat transfer in helical circular tubes is
higher as compared to Straight tube due to their shape. Helical coils offer advantageous over straight tubes due
to their compactness and increased heat transfer coefficient. The increased heat transfer coefficients are a
consequence of the curvature of the coil, which induces centrifugal forces to act on the moving fluid, resulting in
the development of secondary flow. The curvature of the coil governs the centrifugal force while the pitch (or
helix angle) influences the torsion to which the fluid is subjected to. The centrifugal force results in the
development of secondary flow. Due to the curvature effect, the fluid streams in the outer side of the pipe moves
faster than the fluid streams in the inner side of the pipe. The difference in velocity sets-in secondary flows,
whose pattern changes with the Dean number of the flow.
In current work the fluid to fluid heat exchange is taken into consideration, Most of the investigations on heat transfer coefficients are for constant wall temperature or constant heat flux. The effectiveness, overall
heat transfer coefficient, effect of coldwater flow rate on effectiveness of heat exchanger when hot water mass
flow rate is kept constant and effect of hot water flow rate on effectiveness when cold water flow rate kept
constant studied and compared for parallel flow, counter flow arrangement of Helical coil and Straight tube
heat exchangers. The inner heat transfer coefficient calculated from Wilson plot method. Then Nusselt no and
correlation obtained on the basis of inner heat transfer coefficient. All readings were taken at steady state
condition of heat exchanger.
The result shows that the heat transfer coefficient is affected by the geometry of the heat exchanger.
Helical coil heat exchanger are superior in all aspect studied here.
The document presents information on helical baffle heat exchangers. It begins with introducing heat exchangers and defining a helical baffle heat exchanger. It then discusses the design of helixchangers, including thermal analysis of the helical baffles and tube side as well as hydrodynamic analysis of the shell side. Overall heat transfer coefficient is also examined. Key advantages of helixchangers are reduced bypass effects, fouling, vibration, and maintenance compared to traditional shell and tube exchangers. Future areas of research include CFD optimization and analysis of flow patterns and velocities.
This document provides an overview of cooling tower components and design. It describes the basic components of cooling towers including frames, fill materials, cold water basins, drift eliminators, air inlets, louvers, nozzles, and fans. It also discusses different types of cooling towers, factors that affect performance like wet bulb temperature, and efficient system operation through water treatment and use of efficient fans. The equipment used in this project includes a fan, DC centrifugal pump, sump, and tank. The fan and pump are powered by a DC motor.
NUMERICAL ENHANCEMENT OF HEAT TRANSFER OF FIN AND TUBE COMPACT HEAT EXCHANGER...anuragchoubey9
Heat exchangers are used in aero space engines have large heat transfer coefficient, large surface area per unit volume and low weight. The large surface area in compact heat exchangers is obtained by attaching closely spaced thin plate fins to the walls separating the two fluid. This study presents the airside performance of fin and tube compact heat exchangers with plain fin configuration. The effect of fin thickness, fin and tube material and fin spacing on the thermal-hydraulic characteristics is examined. Three-dimensional CFD simulations are carried out to investigate heat transfer and fluid flow characteristics of a plain fin and tube heat exchanger using the Commercial Computational Fluid Dynamics Code ANSYS fluent 16.0. Heat transfer and fluid flow characteristics with consideration of air property variability which is caused by the air temperature change of the heat exchanger are investigated for Reynolds numbers ranging from 2622 to 10498. Temperature drop and heat transfer rate is simulated using standard k-epsilon model with air flow is taken as steady and turbulent. Results are compared for two different material GH3044,S66280 and find out optimum heat transfer rate. After selecting best material GH3044 , we investigate the temperature variation and heat transfer characteristics of three different fin thickness 0.08 mm,0.1mm and 0.2 mm and three different fin spacing 0.8mm,1.1mm and 1.6 mm. domain having 0.8 mm fin spacing shows 5 % increase in heat transfer as compared to 1.1 mm fin spacing. Fin thickness 0.2 mm is better as compared to the other fin thickness and shows 8 % increment in heat transfer as compared to 0.1 mm fin thickness.
An experimental study of heat transfer in a corrugated plate heat exchangerIAEME Publication
1. The document discusses an experimental study of heat transfer in a corrugated plate heat exchanger. Experiments were conducted to analyze heat transfer characteristics for different flow arrangements of hot and cold fluids through the heat exchanger.
2. The effectiveness and exergy loss of the heat exchanger were calculated for parallel and counter flow arrangements. The average effectiveness was found to be 48% higher and exergy loss 33% lower in the counter flow arrangement compared to the parallel flow arrangement.
3. Maximum heat transfer was observed at the highest hot fluid inlet temperature of 70°C, being 5% greater in the parallel flow arrangement. However, the non-dimensional exergy loss and log mean temperature difference were both lower in the
IRJET- Multi Tube Heat Exchanger in Counter Flow by using CFD AnalysisIRJET Journal
The document discusses the design and analysis of a multi-tube heat exchanger using computational fluid dynamics (CFD). It describes a counter-flow heat exchanger with helical fins mounted on the outer surface of the inner tube to increase heat transfer area. Steel is used for the outer tube and copper for the inner tube due to their thermal and mechanical properties. The heat exchanger design is modeled using CREO software and analyzed using ANSYS to evaluate its heat transfer performance. Counter-flow configuration and helical fins are meant to enhance heat transfer while reducing vibration compared to a conventional double pipe heat exchanger.
This document summarizes a research paper that analyzed heat transfer in an economizer using computational fluid dynamics (CFD). It discussed how fins can be added to economizer tubes to increase the heat transfer surface area between flue gases and boiler feedwater. The document reviewed previous research on economizer design optimization and failures. It described the working of CFD analysis using equations of continuity, momentum, and energy to model fluid flow. The study used the k-ε turbulence model in CFD software to analyze heat transfer with and without fins on an economizer.
Design and analysis of plate heat exchanger with co2 and r134a as working fIAEME Publication
This document describes the design and analysis of a plate heat exchanger using CO2 and R134a as working fluids. The authors modeled the plate heat exchanger in Solidworks and analyzed it using computational fluid dynamics in ANSYS. They calculated the heat transfer coefficients, Nusselt number, Reynolds number, and overall heat transfer coefficient. The results from the CFD analysis matched closely with the theoretical calculations. The analysis showed a low pressure drop and the optimal design achieved a small temperature difference between the inlet and outlet of both fluids.
This document discusses heat exchangers and provides details about different types of heat exchangers classified based on heat exchange process, fluid flow direction, physical state of fluids, and constructional features. It describes double pipe heat exchangers and the objective of the study to compare the overall heat transfer coefficient of a double pipe heat exchanger without and with twisted sheet inserts of varying twist ratios. Key terms discussed include heat exchangers, regenerators, recuperators, parallel flow, counter flow, cross flow, condensers, and evaporators.
Heat exchangers are devices that transfer heat from one medium to another. The purpose of the heat transfer typically is to lower or raise temperatures in a device.
Heat transfer is the process of transferring thermal energy between objects due to a temperature difference. There are three main mechanisms of heat transfer: conduction, convection, and radiation. Conduction involves direct contact between objects, convection involves the mixing and movement of heated fluids, and radiation transfers heat through electromagnetic waves without a medium. Heat exchangers and heat interchangers are devices that facilitate heat transfer between different fluids and are widely used in industrial processes.
Thermodynamics deals with the amount of heat transfer between systems, while heat transfer determines the rates of energy transfer and temperature variations. Heat is transferred between objects by conduction, convection, or radiation. Conduction involves the transfer of kinetic energy between particles in direct contact. Convection combines conduction and fluid motion to transfer heat. Radiation emits electromagnetic waves and does not require a medium. Engineering applications include determining heat transfer rates and sizes of heat exchange equipment based on temperature differences and properties of materials.
1) The document discusses the key concepts and objectives of conduction heat transfer including understanding the basic mechanisms of heat transfer such as conduction, convection, and radiation.
2) It explains the differences between thermodynamics, which deals with the amount of heat transfer between equilibrium states, and heat transfer which determines the rates of energy transfers.
3) The three modes of heat transfer - conduction, convection and radiation - are defined and the governing equations for each are provided including Fourier's law of conduction, Newton's law of cooling, and Stefan-Boltzmann law of radiation.
Heat exchangers transfer heat between two or more fluids that are at different temperatures. They work by bringing the fluids into thermal contact through a conducting surface while preventing mixing. There are several types of heat exchangers classified by their heat exchange process, fluid flow direction, mechanical design, and physical state. A common type is the shell and tube heat exchanger, which consists of a shell with a bundle of tubes inside. One fluid flows through the tubes while another flows over the tubes to transfer heat between the fluids. Double pipe heat exchangers are a simpler design with one pipe inside a larger pipe, allowing fluids to flow within and between the pipes.
HT I&II - Copy-1.pdf all chapters are coveredamitbhalerao23
This document provides an overview of a course on heat transfer. The course is divided into 5 units that cover topics such as heat conduction, convection, radiation, and heat exchangers. Assessment includes continuous assessments, midterm and final exams. The course aims to explain heat transfer laws and analyze heat transfer problems involving various geometries and conditions. Key modes of heat transfer covered are conduction, convection, and radiation.
This document provides an overview of fundamentals of heat transfer. It discusses key objectives like understanding the relationship between thermodynamics and heat transfer. The main modes of heat transfer - conduction, convection and radiation - are introduced. Conduction involves energy transfer through direct contact of particles. Convection requires fluid motion, while radiation occurs via electromagnetic waves. Concepts like Fourier's law of conduction and Newton's law of cooling are also summarized.
Heat transfer is the movement of heat energy from warmer to cooler substances. The three main modes of heat transfer are conduction, convection, and radiation. Conduction involves the transfer of energy through direct contact of materials. Convection involves the transfer of energy by the movement of fluids like gases and liquids. Radiation involves the transfer of energy through electromagnetic waves without direct contact. Heat exchangers efficiently transfer heat between fluids or gases using various designs like double pipe, shell and tube, plate, and spiral configurations to conduct or convect heat between substances.
Introduction to Heat Transfer Mechanism.pptxhublikarsn
Heat transfer is the fundamental process by which thermal energy is exchanged between different materials or systems. This introduction explores the key concepts that govern the movement of heat, setting the stage for a deeper understanding of thermal systems and their applications.
Modes of Heat Transfer Conduction :Atomic Vibrations
In conduction, heat is transferred through the vibration of atoms and molecules within a material
Temperature Gradient
Conduction occurs due to a temperature gradient, where heat flows from the hotter region to the cooler region.
Thermal Conductivity
The rate of conduction depends on the material's thermal conductivity, which varies based on the atomic structure.
Convection:Fluid Motion
Heat is transferred by the movement of a fluid, such as air or water, over a surface
Natural Convection
Heat is transferred by the movement of a fluid, such as air or water, over a surface.
Forced Convection
Fluid motion is driven by an external force, such as a fan or pump
Radiation: Electromagnetic Waves
Heat is transferred through the emission and absorption of electromagnetic waves, even in a vacuum.
No Medium Required
Radiation can transfer heat even in a vacuum, unlike conduction and convection.
Emissive Power
The rate of radiation heat transfer depends on the emissive power of the surface.
Fourier's Law
Heat conduction is proportional to the temperature gradient and the material's thermal conductivity.
Newton's Law of Cooling
The rate of convective heat transfer is proportional to the temperature difference between the surface and the fluid.
Stefan-Boltzmann Law
The rate of radiative heat transfer is proportional to the fourth power of the absolute temperature.
Thermal contact resistance is the resistance to heat flow at the interface between two materials in contact. It arises due to surface irregularities and imperfect mating of the surfaces.
Accounting for thermal contact resistance is crucial in the design of efficient heat transfer systems, such as heat exchangers and electronic cooling applications
Contact pressure, surface roughness, and the presence of interfacial materials (e.g., thermal grease) can all influence the thermal contact resistance.
The critical radius of insulation is the thickness of insulation at which the heat loss from an insulated pipe or cylinder is minimized.
Knowing the critical radius is important for optimizing the insulation design to achieve maximum efficiency and cost-effectiveness.
The critical radius depends on the thermal conductivity of the insulation and the surrounding medium.
Heat transfer can be analogous to electrical circuits, with temperatures and heat fluxes corresponding to voltages and currents, respectively. This analogy helps in the analysis and design of thermal systems.
The overall heat transfer coefficient (U) is a measure of the overall effectiveness of heat transfer between a fluid and a solid surface. It accounts for various modes of heat transfer, such as conduction, c
This document discusses heat transfer and provides objectives and an overview of key concepts. It begins by defining heat transfer and its relationship to thermodynamics. It then outlines the main objectives, which are to understand the basic heat transfer mechanisms of conduction, convection, and radiation. It also discusses how heat transfer problems are used in engineering applications and provides background on the historical development of theories around heat and thermal energy.
This document provides an outline for a course on thermal unit operations. It begins with definitions of unit operations and thermal unit operations. The three main mechanisms of heat transfer are then described: conduction, convection, and radiation. Conduction involves heat transfer through direct molecular contact in solids or stationary fluids. Convection uses fluid motion to transfer heat. Radiation transfers heat via electromagnetic waves without a medium. Equations for calculating heat transfer via these different mechanisms are also provided.
This chapter introduces the concepts of thermodynamics and heat transfer. Thermodynamics deals with equilibrium states while heat transfer involves systems lacking thermal equilibrium. The three modes of heat transfer are conduction, convection, and radiation. Conduction involves the transfer of energy between adjacent particles in direct contact. Convection involves the combined mechanisms of conduction and fluid motion. Radiation transfers energy via electromagnetic waves without a medium. Fourier's law, Newton's law of cooling, and the Stefan-Boltzmann law govern conduction, convection, and radiation respectively. Example problems demonstrate applying conservation of energy to analyze various heat transfer processes.
This document discusses various topics related to heat and mass transfer. It begins by defining three modes of heat transfer: conduction, convection and radiation. It then explains key concepts like Fourier's law of heat conduction, natural and forced convection, the Stefan-Boltzmann law of radiation, and temperature gradients. Heat exchangers and their classifications are described. Finally, it covers methods of mass transfer like molecular diffusion and bulk flow, and briefly discusses temperature measurement techniques including mechanical, thermocouple, RTD and infrared pyrometers.
Heat is a form of energy that transfers from warmer objects to cooler ones. There are three main modes of heat transfer: conduction, convection, and radiation. Conduction involves the transfer of kinetic energy between adjacent particles in a substance. Convection refers to the movement of heated parts of fluids like gases and liquids. Radiation involves the emission and absorption of electromagnetic waves between objects and does not require a medium. Heat transfer aims to equalize temperatures and is driven by temperature differences between systems.
This document provides an overview of heat transfer and related topics. It discusses the three methods of heat transfer: convection, conduction, and radiation. It also covers factors that affect heat transfer like temperature and thermal resistance. The document outlines course contents on heat transfer equipment, fired process equipment, and combustion of fuels. It provides details on topics like heat exchangers, boilers, burners, and methods of heat exchange.
The document discusses heat transfer equipment and heat exchangers. It defines a heat exchanger as a device that transfers thermal energy between two or more fluids at different temperatures without mixing the fluids. Heat exchangers can be classified based on their transfer process, number of fluids, degree of surface compactness, construction, flow arrangement, and heat transfer mechanism. Common examples include shell-and-tube exchangers, radiators, condensers, evaporators, and cooling towers.
The document discusses kinetics of electrochemical reactions and mass transfer in electrochemical systems. It covers the following key points:
1) Chemical kinetics is the study of reaction rates and mechanisms. In industrial synthesis, reaction rates are as important as equilibrium constants. Kinetics answers how fast reactions occur, while thermodynamics addresses if they will occur.
2) Applying a potential increases the reaction rate by reducing the activation energy barrier. Current increases with increasing driving force from an applied potential. Catalysts also reduce the activation energy.
3) The rate of electrochemical reactions depends on parameters like materials, composition, and temperature. Increasing the reaction rate improves fuel cell performance. Reactions occur at electrode-elect
This document provides an overview of the methodology for heat exchanger design. It discusses that heat exchanger design is a complex, multidisciplinary process that involves specifying requirements, evaluating design concepts, detailed sizing and optimization. Key considerations in the design process include thermal and hydraulic design of the exchanger, mechanical design to ensure structural integrity, and manufacturing factors that influence cost. The methodology involves iterative thermal modeling, mechanical analysis, and consideration of manufacturing to arrive at an optimized design.
The document discusses batch and continuous processes. A batch process involves producing a product in stages over workstations, with a finite quantity produced at the end of each stage. Batch processes are commonly used in pharmaceuticals and other industries. Continuous processes involve constant material flow and processing without interruption. Continuous processes are used in capital-intensive industries and have advantages like lower costs and higher quality and consistency. The document also discusses flowcharts which visually represent process sequences and includes examples like swimlane, dataflow, and process flow diagrams.
Electrochemistry is the study of chemical reactions caused by the passage of an electric current and the production of electrical energy from chemical reactions. It encompasses phenomena like corrosion and devices like batteries and fuel cells. Electrochemical cells are either electrolytic cells, where an external power source drives non-spontaneous reactions, or galvanic/voltaic cells, where spontaneous reactions produce electricity. The kinetics and rates of electrochemical reactions, as well as mass transfer of reactants, influence current production in fuel cells and other devices.
Electrochemical energy storage systems convert chemical energy into electrical energy and vice versa through redox reactions. There are two main types: galvanic cells which convert chemical to electrical energy, and electrolytic cells which do the opposite. A basic electrochemical cell consists of two electrodes separated by an electrolyte. Primary cells cannot be recharged, while secondary cells are rechargeable through reversible chemical reactions. Lithium-ion batteries have become widely popular due to their high energy density and lack of memory effect.
The document discusses air pollution, including its definition, sources, classification of pollutants, effects, and control methods. It defines air pollution as the presence of foreign substances that adversely affect human health and the environment. Major sources include stationary sources like power plants and mobile sources like vehicles. Pollutants are classified as primary emitted directly or secondary formed through chemical reactions. Effects are discussed for human health, plants, and materials. Control methods include source prevention, air pollution control equipment like precipitators and scrubbers that collect pollutants, and laws regulating industrial emissions.
The document discusses various methods for analyzing experimental rate data from chemical reactions, including integral methods, differential methods, and the method of initial rates. It covers analyzing data from batch reactors as well as determining reaction orders and rate constants. Rate equations can be first-order, second-order, or nth-order depending on the mechanism and can be determined by plotting concentration or conversion versus time from batch reactor experiments.
1) Printing inks are made up of pigments, resins, solvents, and additives that are mixed and ground to impart color and bind the ink.
2) Inks are manufactured through a process of preparing varnishes from resins and solvents and then dispersing pigments evenly throughout the varnish.
3) Common printing processes include letterpress, screen, flexography, and gravure printing which utilize the inks to transfer images onto substrates through different techniques.
DNA controls the characteristics of cells and organisms. It is a large molecule composed of nucleotides with a sugar, phosphate, and organic base. DNA extraction involves breaking open cells, dissolving membranes, and precipitating the DNA from solution. Polymerase chain reaction (PCR) amplifies DNA by using primers, DNA template, DNA polymerase, nucleotides, and buffer solutions. It generates thousands to millions of copies of a DNA sequence.
ECONOMIC FEASIBILITY AND ENVIRONMENTAL IMPLICATIONS OF PERMEABLE PAVEMENT IN ...Fady M. A Hassouna
Permeable pavement is considered one of the sustainable management
options for roadway networks, which mitigates a number of problems associated with
stormwater, ground water pollution, and traffic safety. In this study, the economic
feasibility, vehicle operation, and environmental implications of implementing permeable
pavement in Nablus, Palestine have been determined by selecting the local roadways that
satisfy the permeable pavement requirement, such as low traffic volume, grade less than
5%, speed limit up to 50 km/h, and subgrade with good permeability. The total costs of
construction and maintenance for both conventional asphalt and permeable pavement have
also been compared based on the life cycle cost analysis (LCCA). Finally, the
environmental implications such as the expected increase in the amount of ground water
and the reduction in water pollutants have been investigated. The results of the analysis
show that the permeable pavement is applicable for the local roadways that have satisfied
the requirements, which are 61 roadways. Furthermore, it could lead to an annual
significant increase in ground water by 107,404.7 m3 and slightly reduce the cost of
construction and maintenance by up to 1,912,000 ILS during its life period compared to
conventional asphalt pavement. Moreover, applying porous asphalt could enhance
vehicular traffic safety by improving skid resistance.
Fix Production Bugs Quickly - The Power of Structured Logging in Ruby on Rail...John Gallagher
Rails apps can be a black box. Have you ever tried to fix a bug where you just can’t understand what’s going on? This talk will give you practical steps to improve the observability of your Rails app, taking the time to understand and fix defects from hours or days to minutes. Rails 8 will bring an exciting new feature: built-in structured logging. This talk will delve into the transformative impact of structured logging on fixing bugs and saving engineers time. Structured logging, as a cornerstone of observability, offers a powerful way to handle logs compared to traditional text-based logs. This session will guide you through the nuances of structured logging in Rails, demonstrating how it can be used to gain better insights into your application’s behavior. This talk will be a practical, technical deep dive into how to make structured logging work with an existing Rails app.
I talk about the Steps to Observable Software - a practical five step process for improving the observability of your Rails app.
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2. To be covered
• Chemical Unit operations
• Heat transfer
• Different mode of heat transfer
– Conduction
– Convection
– Radiation
• Multimode heat transfer
3. What is a unit operation?
A unit operation is any part of potentially multiple-step process which can
be considered to have a single function.
It is a basic step in a process because large processes can be broken into
unit operations in order to make them easier to analyze.
It can involve a physical change or chemical transformation such as
separation, crystallization, evaporation, filtration, polymerization,
isomerization, and other reactions..
4. Cont’d..
• Chemical engineering unit operations can be grouped into five general
classes:
1. Fluid flow processes
2. Heat transfer processes
3. Mass transfer processes
4. Thermodynamic processes
5. Mechanical processes
5. 1. Fluid Flow Process
Fluid flow processes: deals about fluids transportation and its
dynamics.
It includes fluids transportation (pump, compressor, blowers, pipes
and fittings,), gas-liquid two-phase flow, filtration, solids fluidization,
mixing, etc.
6. 2. Heat Transfer Processes
Heat transfer is the exchange of thermal energy between physical
systems, depending on the temperature and pressure, by dissipating
heat.
It includes heat exchange, evaporation, and condensation.
7. 3. Mass Transfer Processes
• Mass transfer is the net movement of mass from one location to
another.
• It occurs in many processes, such as absorption, distillation,
extraction, adsorption, and drying.
8. 4. Thermodynamics Process
A thermodynamic process may be defined as the energetic
development of a thermodynamic system proceeding from an initial
state to a final state.
It includes Refrigeration and Air Conditioning (AC), gas liquefaction.
9. 5. Mechanical Unit Operation
• Mechanical unit operation includes:
Solids transportation: different types of conveyors
Crushing and pulverization: reducing sizes
Screening and sieving: separation of different particles based on their
size.
10. • There are also some chemical engineering unit operations which
involves more than one class such as distillation, and reaction
crystallization
• A "pure" unit operation is a physical transport process, while a mixed
chemical/physical process requires modeling.
11. Heat transfer
• As you know from thermodynamics:
“Heat is defined as the energy-In-transit due to temperature difference.
• Heat transfer take place whenever there is a temperature gradient
within a system.
• Heat transfer cannot be measured directly, but the effects produced by
it can be observed and measured. E.g. temperature change
12. Heat transfer…
• All heat transfer process must obey the first and second laws of
thermodynamics.
• In addition to the laws of thermodynamics it is essential to apply laws
of heat transfer to estimate heat transfer rate.
• Estimating rate of heat transfer is a key requirement in the design and
analysis heat exchanger, refrigeration and air conditioning.
13. Modes of Heat Transfer
• The basic modes are:
Conduction
Convection , and
Radiation
• In most of the engineering problems, heat transfer takes place by more
than one mode simultaneously. Such kinds of heat transfer problems are
called multi-mode heat transfer.
14. Conduction Heat Transfer
• Conduction heat transfer takes place whenever a temperature
gradient exists in a stationary medium.
• By direct contact of two systems
• On a microscopic level, conduction heat transfer is due to:
The elastic impact of molecules in fluids
Molecular vibration and rotation about their lattice positions in solids, and
Free electron migration in solids
20. Convective Heat Transfer
• Convection heat transfer takes place between a surface and a moving
fluid, when they are at different temperature.
• It is the transfer of energy between an object and its environment, due
to fluid motion.
• All convective processes also move heat partly by
diffusion/conduction, as well.
• Convective heat transfer consists of two mechanisms operating
simultaneously:
21. 1. Energy transfer due to conduction through a fluid
layer adjacent to the surface
• Hydrodynamic boundary layer: when fluid flow on the surface, fluid layer
adjacent to surface attain velocity of surface. If surface is stationary, then
fluid layer is stationay.i.e.no slip condition
• Similarly, when a fluid flow on surface whose temperature is different from
fluid surface, then the fluid layer adjacent to the surface attain temperature of
surface. This is also no slip condition. This is called thermal boundary layer.
• And the heat transfer is initially from surface to fluid stationary layer by
conduction. Then the heat transfer will be by motion of the bulk fluid.
• This show similarity between momentum transfer and convective heat
transfer
22. 2. Energy transfer by macroscopic motion of fluid particles by
using of an external force (due to a fan/pump or buoyancy).
If you are using external force e.g. due to a fan/pump/ stirrers or other
mechanical means, this is called forced convection.
If it is without using any external force, it is called free/natural
convection.
Free, or natural, convection occurs when bulk fluid motions (streams
and currents) are caused by buoyancy forces that result from density
variations due to variations of temperature in the fluid.
23. • Convective heat transfer, or convection, is the transfer of heat from
one place to another by the movement of fluids, a process that is
essentially the transfer of heat via mass transfer.
• Convection is usually the dominant form of heat transfer in liquids and
gases.
Convective Heat Transfer…
24. Convective Heat Transfer…
• Heat transfer rate by convection is written as:
=> This is called Newton’s law of cooling (basic equation for convective heat
transfer/ Convective cooling).
Where, ℎc= the convective heat transfer coefficient,
Tw=is surface temperature, and
T∞=is temperature of fluid in the free stream
• Newton’s law of cooling states “The rate of heat loss of a body is
proportional to the temperature difference between the body and its
surroundings.”
25. Convective Heat Transfer…
• However, by definition, the validity of Newton's law of cooling
requires that the rate of heat loss from convection be a linear function of
("proportional to") the temperature difference that drives heat transfer,
and in convective cooling this is sometimes not the case.
• In general, convection is not linearly dependent on temperature
gradients, and in some cases is strongly nonlinear.
In these cases, Newton's law does not apply.
29. Radiation Heat Transfer
• Radiation heat transfer does not require a medium for transmission.
And it is more effective in vacuum.
• It is the transfer of energy from the movement of charged particles
within atoms which is converted to electromagnetic radiation.
• Energy transfer occurs due to the propagation of electromagnetic
waves such as microwave and light wave. A body due to its
temperature emits electromagnetic radiation.
• It is propagated with the speed of light in a straight line in vacuum. Its
speed decreases in a medium but it travels in a straight line in
homogenous medium.
31. Remember these;
What are the different types of chemical unit operations?
What is heat transfer?
What are the different mode of heat transfer?
What are the basic governing equation for each types of heat
transfer modes?
32. To be covered
HE Design considerations
Key steps of the thermal design procedure for HE
Overall energy balance
Selection of flow arrangement
Preliminary geometrical design
Choice of fluid flow velocities
The log-mean temperature difference
Baffle design
33. Design Considerations
The problem of heat exchanger design is complex and
multidisciplinary.
The major design considerations for a new heat exchanger include:
process/design specifications, thermal and hydraulic design,
mechanical design, manufacturing and cost considerations, and trade-
offs.
Most of the other major design considerations involve qualitative and
experience-based judgments, tradeoffs, and compromises.
Therefore, there is no unique solution for designing a heat exchanger
for given process specifications.
34. Cont’d..
• Two most important heat exchanger design problems are the rating
and sizing problems.
• Determination of heat transfer and pressure drop performance of either
an existing exchanger or an already sized exchanger is referred to as
the rating problem.
• In contrast, the design of a new or existing-type exchanger is referred
to as the sizing problem.
• Performance problem Vs Design problem
35. Step-by-step procedure for the "sizing" problem
to determine Exchanger dimensions
The key steps of the thermal design procedure for a serpentine tube heat
exchanger are as follows:
1. From given parameters calculate unknown inlet or outlet temperatures
and flow rates of fluids and heat transfer rate of heat exchanger using
overall energy balance
2. Select a preliminary flow arrangement (i.e. based on the common industry
practice).
3. Design preliminary geometry parameters of heat exchanger. The work
includes selection of tube diameter, layout and pitch.
4. Choose fluid flow velocities.
5. Estimate the log-mean temperature difference.
36. Cont’d..
6. Estimate an overall heat transfer coefficient using appropriate
methods for heat transfer calculation for designed type of heating
surface.
7. Estimate required heat transfer area.
8. Calculate length of tubes, the number of serpentines or passes,
baffles etc.
9. Estimate outside dimensions of heat exchangers.
10. Calculate pressure drops for both fluids.
11. Repeat, if necessary, steps 3 to 9 with an estimated change in design
until a final design is reached that meets specified requirements.
37. Overall energy balance
• Assumption; Energy losses to surrounding is neglected, i.e. heat energy
given off by hot fluid =heat energy absorbed by cold fluid
• Two energy conservation differential equations for an overall adiabatic two-
fluid exchanger with any flow arrangement are
dq = -ChdTh = +CcdTc
• The heat capacity rate is
Ci = mici
• The overall rate equation on a local basis is
dq = U(Th - Tc)dA = U∆TdA
• where dq=rate of HT,
• Ch and Cc =heat capacities of hot and cold fluid,
• ci - specific heat and
• U =heat transfer coefficient
38. .…Cont’d....
Integration of the above equations across the exchanger surface area
results in overall energy conservation and rate equations as follows.
q = Ch(Th,i - Th,o) = Cc(Tc,o - Tc,i)
and q = UA∆Tm
Here ∆Tm is the true mean temperature difference dependent on the
exchanger flow arrangement.
Aim of overall energy balance is to determine all external parameters
describing heat exchanger operation:
mass flow rates mh, mc
inlet temperatures Th,i, Tc,i
outlet temperatures Th,o, Tc,o
heat transfer rate
40. • Basic flow arrangements of two fluids in heat exchanger are
counterflow, parallelflow, single-pass crossflow, multipass crossflow
and various combinations.
Selection of flow arrangement
41. Preliminary geometrical design
The work includes selection of tube diameter, layout and pitch.
Choice depends on many conditions i.e. type of fluid, its velocity, pollution by
particles and chemical impurities, design limitations etc.
Two layouts of tubes in bundle are:
42. Tube Diameters:
• The most common sizes used are Ø3/4" and Ø1".
• Use the smallest diameter for greater heat transfer area with a
minimum of Ø3/4".
• For shorter tube lengths say < 4ft can be used Ø1/2" tubes.
43. Choice of fluid flow velocities
Choice of fluid flow velocity according to common practice allows
reasonable and compromise values of overall heat transfer coefficient
and pressure drop already in the first approach to heat exchanger
design.
Recommended velocities of fluid flows are:
44. The log-mean temperature difference
The driving force for any heat transfer process is a temperature
difference. For heat exchangers temperature difference between two
fluids across the heating area is not constant. It depends on heat
exchanger arrangement and value of Ch and Cc.
46. Evaluation of an average temperature difference is necessary for
calculation of heat transfer rate.
For cases with pure counter and parallel flow the temperature
difference is best represented by the log mean temperature difference
(LMTD or ΔTm ), defined in equation below.
where:
ΔT1 = the larger temperature difference between the two fluid streams
at either the entrance or the exit to the heat exchanger
ΔT2 =smaller temperature difference
48. Use of log mean temperature difference for evaluation of heat transfer
rate is valid on following conditions:
1. The heat exchanger is at a steady state.
2. Each fluid has a constant specific heat.
3. The overall heat transfer coefficient is constant.
4. There are no heat losses from the exchanger.
5. There is no longitudinal heat transfer within a given stream.
6. The flow is either parallel or counter.
49. And the main basic heat exchanger equation becomes;
For non-flow or batch heating the heat transfer rate is given by;
Q=m×cp×dT/t, where t is the time over which heating
process occurs
For flow or continuous heating process;
Q=cp×dT×m/t
50. In case of cross flow heat exchanger, fluid temperature differences are
illustrated as three-dimensional
In these heat exchangers, the temperature difference is not possible to
calculate by previous method, the correction factor is usually used
where the log mean temperature difference is expressed as
where Ψ is the correction factor and ΔTm,CF is the log mean temperature
difference for a cross flow heat exchanger. Value of correction factor is
usually determined from diagrams relating to crossflow heat exchanger
arrangement.
Cross flow heat exchangers
51. Baffles: are used to support tubes and enable a desirable velocity for
the fluid to be maintained at the shell side, and prevent failure of tubes
due to flow-induced vibration.
There are two types of baffles; plate and rod.
Plate baffles may be single-segmental, double-segmental, or triple-
segmental
BAFFLE DESIGN
52. The minimum spacing (pitch) of baffles normally should not be closer
than 1/5 of shell diameter (ID) or 2 inches whichever is greater.
The maximum spacing (pitch) does not normally exceed the shell
diameter. Tube support plate spacing determined by mechanical
considerations, e.g. strength and vibration.
No of baffles= (tube length/baffle spacing)-1
53. Remember these;
Major design consideration for a new heat exchanger
Key steps of thermal design procedure for heat exchangers
equations for energy balances in heat exchangers
Types of flow arrangements
Types of layouts of tubes
LMTD calculation
LMTD validity conditions
Baffle design