Code of Mechanical

The History of Electricity

2010-07-10T04:32:00.000-07:00

The History of Electricity

Collected By:

Abd-Alhady Mostafa Abd-Alhalem Abozeid

3^rd Year of Mechanical power branch (Mech. dep.)

1^st Group - Section: 6 - Bn#133

Contents

Georg Simon Ohm and Resistance

Gustav Robert Kirchhoff

Luigi Galvani and the Discovery of Nerve Excitation

Benjamin Franklin

Sir Charles Wheatstone

André Marie Ampère

Michael Faraday and the Field Concept

Magnetism and Electromagnetism

The Discovery of Electromagnetic Induction

Thomas Alva Edison

Charles Proteus Steinmetz

Henry Cavendish

Heinrich Rudolph Hertz

Hermann Ludwig Ferdinand von Helmholtz

William Bradford Shockley

Edwin Howard Armstrong—Radio Reception

Alexander Graham Bell

Nikola Tesla

George Westinghouse

Jean Baptiste Joseph Fourier

References

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Centrifugal Pumps

2010-07-10T04:24:00.000-07:00

Centrifugal Pumps

Basic Concepts of Operation, Maintenance, and Troubleshooting

Collected By:

Abd-Alhady Mostafa Abd-Alhalem Abozeid

3^rd Year of Mechanical power branch (Mech. dep.)

1^st Group - Section: 6 - Bn#133

Contents

Introduction

Working Mechanism of a Centrifugal Pump

Generation of Centrifugal Force

Conversion of Kinetic Energy to Pressure Energy

General Components of Centrifugal Pumps

Stationary Components

Rotating Components

Auxiliary Components

Definition of Important Terms

Capacity

Head

NPSH

Power and Efficiency

Specific Speed

The Affinity Laws

Understanding Centrifugal Pump Performance Curves

Developing a system curve

Developing a Pump performance Curve

Normal Operating Range

Two Basic Requirements for Trouble-Free Operation of Centrifugal Pumps

References

Attention

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The history of Measurements Report

2010-07-10T04:17:00.000-07:00

The history of

Measurements

Report

Some human-referenced units of measurements

Abd Al-hady Moustafa Abd Al-halem Abo-zeid Habib

3^rd Year of Mechanical power branch (Mech. dep.)

2^nd Group

Section: 6 - Bn#133

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The history of Fluid Mechanics Report

2010-07-10T04:10:00.000-07:00

Benha University

Mechanical Department

Power Branch

The history of

Fluid Mechanics

Report

The history of fluid mechanics, the study of how fluids move and the forces on them, dates back to the Ancient Greeks.

Submitted to

Prof. Dr. Osama Ezzat Abdel-Latif

Abd Al-hady Moustafa Abd Al-halem Abo-zeid Habib

3^rd Year of Mechanical power branch (Mech. dep.)

2^nd Group

Section: 6

Bn#133

Contents

1 Ancient and medieval era

1.1 Archimedes
1.2 The Alexandrian school
1.3 Sextus Julius Frontinus

2 Sixteenth, seventeenth and eighteenth century

2.1 Castelli and Torricelli
2.2 Blaise Pascal
2.3 Mariotte and Guglielmini
2.4 Studies by Isaac Newton

2.4.1 Friction and viscosity
2.4.2 Orifices
2.4.3 Waves

2.5 Daniel Bernoulli
2.6 Jean le Rond d'Alembert
2.7 Leonhard Euler
2.8 Pierre Louis Georges Dubuat

3 Nineteenth century

3.1 Gaspard Riche de Prony
3.2 Johann Albert Eytelwein
3.3 Jean Nicolas Pierre Hachette and others
3.4 Andreas Rudolf Harlacher and others

4 References

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Heat Exchangers & Concrete Pumps

2010-07-10T03:46:00.000-07:00

Heat Exchangers & Concrete Pumps

Collected By:

Abd-Alhady Mostafa Abd-Alhalem Abozeid

3^rd Year of Mechanical power branch (Mech. dep.)

1^st Group - Section: 6 - Bn#133

Contents

Heat Exchangers

Types of heat exchangers

Shell and Tube heat exchanger

Regenerative heat exchanger

Adiabatic Wheel heat exchanger

Fluid heat exchangers

Dynamic Scraped surface heat exchanger

Phase-change heat exchangers

HVAC air coils

Spiral Heat Exchangers

Self cleaning

Applications

Selection

Monitoring and maintenance

Fouling

Maintenance

Heat exchangers in nature

Counter current Heat Exchangers

Heat Exchangers in Industry

What Is a Concrete Pump?

Truck-mounted concrete pump

Hydraulic system features

Pictures

Main technical parameters

References

Some of Animated heat engines cycles

2009-12-05T05:07:00.000-08:00

Related flash animations found on the web

Carnot Cycle
http://www.cs.sbcc.net/%7Ephysics/flash/heatengines/Carnot

%20cycle.html
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The 2 Stroke Engine
http://www.cs.sbcc.net/

%7Ephysics/flash/heatengines/2stroke.html
T=420>

The 4 Stroke

Engine
http://www.cs.sbcc.net/

%7Ephysics/flash/heatengines/4stroke.html
T=420>

The Stirling Engine

http://www.cs.sbcc.net/

%7Ephysics/flash/heatengines/stirling.html
T=420>

The history of Fluid Mechanics

2009-12-03T11:21:00.000-08:00

Benha University

Mechanical Department

Power Branch

The history of

Fluid Mechanics

Report

The history of fluid mechanics, the study of how fluids move and the forces on them, dates back to the Ancient Greeks.

Submitted to

Prof. Dr. Osama Ezzat Abdel-Latif

Abd Al-hady Moustafa Abd Al-halem Abo-zeid Habib

Contents

1 Ancient and medieval era
1.1 Archimedes
1.2 The Alexandrian school
1.3 Sextus Julius Frontinus
2 Sixteenth, seventeenth and eighteenth century
2.1 Castelli and Torricelli
2.2 Blaise Pascal
2.3 Mariotte and Guglielmini
2.4 Studies by Isaac Newton
2.4.1 Friction and viscosity
2.4.2 Orifices
2.4.3 Waves
2.5 Daniel Bernoulli
2.6 Jean le Rond d'Alembert
2.7 Leonhard Euler
2.8 Pierre Louis Georges Dubuat
3 Nineteenth century
3.1 Gaspard Riche de Prony
3.2 Johann Albert Eytelwein
3.3 Jean Nicolas Pierre Hachette and others
3.4 Andreas Rudolf Harlacher and others
4 References

SooooooooooooooooooooooN ;-)

Fourier's law

2009-11-01T07:24:00.000-08:00

The law of Heat Conduction, also known as Fourier's law, states that the time rate of heat transfer through a material is proportional to the negative gradient in the temperature and to the area at right angles, to that gradient, through which the heat is flowing. We can state this law in two equivalent forms: the integral form, in which we look at the amount of energy flowing into or out of a body as a whole, and the differential form, in which we look at the flows or fluxes of energy locally.

Differential form

The differential form of Fourier's Law of thermal conduction shows that the local heat flux, , is equal to the product of thermal conductivity, k, and the negative local temperature gradient, . The heat flux is the amount of energy that flows through a particular surface per unit area per unit time.

where (including the SI units)

is the local heat flux, [W·m^−2]

is the material's conductivity, [W·m^−1·K^−1],

is the temperature gradient, [K·m^−1].

The thermal conductivity, k, is often treated as a constant, though this is not always true. While the thermal conductivity of a material generally varies with temperature, the variation can be small over a significant range of temperatures for some common materials. In anisotropic materials, the thermal conductivity typically varies with orientation; in this case k is represented by a second-order tensor. In nonuniform materials, k varies with spatial location

For many simple applications, Fourier's law is used in its one-dimensional form. In the x-direction,

Integral form

By integrating the differential form over the material's total surface S, we arrive at the integral form of Fourier's law:

where (including the SI units)

is the amount of heat transferred per unit time [W] and

is an oriented surface area element [m^2]

The above differential equation, when integrated for a homogeneous material of 1-D geometry between two endpoints at constant temperature, gives the heat flow rate as:

where

A is the cross-sectional surface area,
ΔT is the temperature difference between the ends,
Δx is the distance between the ends.

This law forms the basis for the derivation of the heat equation. Ohm's law is the electrical analogue of Fourier's law.

Conductance

Writing

where U is the conductance, in W/(m^2 K).

Fourier's law can also be stated as:

The reciprocal of conductance is resistance, R, given by:

and it is resistance which is additive when several conducting layers lie between the hot and cool regions, because A and Q are the same for all layers. In a multilayer partition, the total conductance is related to the conductance of its layers by:

So, when dealing with a multilayer partition, the following formula is usually used:

When heat is being conducted from one fluid to another through a barrier, it is sometimes important to consider the conductance of the thin film of fluid which remains stationary next to the barrier. This thin film of fluid is difficult to quantify, its characteristics depending upon complex conditions of turbulence and viscosity, but when dealing with thin high-conductance barriers it can sometimes be quite significant.

Intensive-property representation

The previous conductance equations written in terms of extensive properties, can be reformulated in terms of intensive properties.

Ideally, the formulae for conductance should produce a quantity with dimensions independent of distance, like Ohm's Law for electrical resistance:

Heat transfer

2009-10-31T19:15:00.000-07:00

Heat transfer

Heat transfer is the transition of thermal energy from a hotter object to a cooler object ("object" in this sense designating a complex collection of particles which is capable of storing energy in many different ways). When an object or fluid is at a different temperature than its surroundings or another object, transfer of thermal energy, also known as heat transfer, or heat exchange, occurs in such a way that the body and the surroundings reach thermal equilibrium. Heat transfer always occurs from a higher-temperature object to a cooler temperature one as described by the second law of thermodynamics or the Clausius statement. Where there is a temperature difference between objects in proximity, heat transfer between them can never be stopped; it can only be slowed.

Conduction

Conduction is the transfer of heat by direct contact of particles of matter. The transfer of energy could be primarily by elastic impact as in fluids or by free electron diffusion as predominant in metals or phonon vibration as predominant in insulators. In other words, heat is transferred by conduction when adjacent atoms vibrate against one another, or as electrons move from atom to atom. Conduction is greater in solids, where atoms are in constant contact. In liquids (except liquid metals) and gases, the molecules are usually further apart, giving a lower chance of molecules colliding and passing on thermal energy.

Heat conduction is directly analogous to diffusion of particles into a fluid, in the situation where there are no fluid currents. This type of heat diffusion differs from mass diffusion in behaviour, only in as much as it can occur in solids, whereas mass diffusion is mostly limited to fluids.

Heat conduction is directly analogous to diffusion of particles into a fluid, in the situation where there are no fluid currents. This type of heat diffusion differs from mass diffusion in behaviour, only in as much as it can occur in solids, whereas mass diffusion is mostly limited to fluids.

Metals (eg. copper, platinum, gold, iron, etc.) are usually the best conductors of thermal energy. This is due to the way that metals are chemically bonded: metallic bonds (as opposed to covalent or ionic bonds) have free-moving electrons which are able to transfer thermal energy rapidly through the metal.

As density decreases so does conduction. Therefore, fluids (and especially gases) are less conductive. This is due to the large distance between atoms in a gas: fewer collisions between atoms means less conduction. Conductivity of gases increases with temperature. Conductivity increases with increasing pressure from vacuum up to a critical point that the density of the gas is such that molecules of the gas may be expected to collide with each other before they transfer heat from one surface to another. After this point in density, conductivity increases only slightly with increasing pressure and density.

To quantify the ease with which a particular medium conducts, engineers employ the thermal conductivity, also known as the conductivity constant or conduction coefficient, k. In thermal conductivity k is defined as "the quantity of heat, Q, transmitted in time (t) through a thickness (L), in a direction normal to a surface of area (A), due to a temperature difference (ΔT) [...]." Thermal conductivity is a material property that is primarily dependent on the medium's phase, temperature, density, and molecular bonding.

A heat pipe is a passive device that is constructed in such a way that it acts as though it has extremely high thermal conductivity

Transient Conduction vs. steady state conduction

Steady state conduction is the form of conduction which happens when the temperature difference is constant, so that an equilibration time, the spatial distribution of temperatures in an object does not change (for example, a bar may be cold at one end and hot at the other, but the gradient of temperatures along the bar do not change with time).In short temprature at a section remains constant and it varies linearly along direction of heat transfer.In steady state the amount of heat entering a section is equal to amount of heat coming out.In steady state we can apply all laws of current electricity (direct current)for heat current as well. There also exist situations wherein the temperature drop or raise occurs more drastically, such as when a hot copper ball is dropped into oil at a low temperature, and the interest is in analysing the spatial change of temperature in the object over time. This mode of heat conduction can be referred to as unsteady mode of conduction or transient conduction. Analysis of these systems is more complex and (except for simple shapes) calls in for the application of approximation theories.

Lumped System Analysis

A common approximation in transient conduction, which may be used whenever heat conduction within an object is much faster than heat conduction across the boundary of the object, is Lumped system analysis. This is a method of approximation that suitably reduces one aspect of the transient conduction system (that within the object) to an equivalent steady state system (that is, it is assumed that the temperature within the object is completely uniform, although its value may be changing in time). In this method, a term known as the Biot number is calculated, which is defined as the ratio of resistance to heat transfer across the object's boundary with a uniform bath of different temperature, to the conductive heat resistance within the object. When the thermal resistance to heat transferred into the object is less than the resistance to heat being diffused completely within the object, the Biot number is small, and the approximation of spatially uniform temperature within the object can be used. As this is a mode of approximation, the Biot number must be less than 0.1 for accurate approximation and heat transfer analysis. The mathematical solution to the lumped system approximation gives Newton's law of cooling, discussed below.

This mode of analysis has been applied to forensic sciences to analyse the time of death of humans. Also it can be applied to HVAC (heating, ventilating and air-conditioning, or building climate control), to ensure more nearly instantaneous effects of a change in comfort level setting.

Convection

Convection is the transfer of heat energy between a solid surface and the nearby liquid or gas in motion. As fluid motion goes more quickly the convective heat transfer increases. The presence of bulk motion of fluid enhances the heat transfer between the solid surface and the fluid.

There are two types of Convective Heat Transfer:

Natural Convection: is when the fluid motion is caused by buoyancy forces that result from the density variations due to variations of temperature in the fluid. For example in the absence of an external source, when the mass of the fluid is in contact with a hot surface its molecules separate and scatter causing the mass of fluid to become less dense. When this happens, the fluid is displaced vertically or horizontally while the cooler fluid gets denser and the fluid sinks. Thus the hotter volume transfers heat towards the cooler volume of that fluid.
Forced Convection: is when the fluid is forced to flow over the surface by external source such as fans and pumps. It creates an artificially induced convection current.

Internal and external flow can also classify convection. Internal flow occurs when the fluid is enclosed by a solid boundary such as a flow through a pipe. An external flow occurs when the fluid extends indefinitely without encountering a solid surface. Both these convections, either natural or forced, can be internal or external as they are independent of each other.

The formula for Rate of Convective Heat Transfer:

q = hA(Ts − Tb)

A is the surface area of heat transfer. Ts is the surface temperature and while Tb is the temperature of the fluid at bulk temperature. However Tb varies with each situation and is the temperature of the fluid “far” away from the surface. The h is the constant heat transfer coefficient which depends upon physical properties of the fluid such as temperature and the physical situation in which convection occurs. Therefore, the heat transfer coefficient must be derived or found experimentally for every system analyzed. Formulae and correlations are available in many references to calculate heat transfer coefficients for typical configurations and fluids. For laminar flows the heat transfer coefficient is rather low compared to the turbulent flows, this is due to turbulent flows having a thinner stagnant fluid film layer on heat transfer surface.

Radiation

Radiation is the transfer of heat energy through empty space. All objects with a temperature above absolute zero radiate energy at a rate equal to their emissivity multiplied by the rate at which energy would radiate from them if they were a black body. No medium is necessary for radiation to occur; radiation works even in and through a perfect vacuum. The energy from the Sun travels through the vacuum of space before warming the earth.

Both reflectivity and emissivity of all bodies is wavelength dependent. The temperature determines the wavelength distribution of the electromagnetic radiation as limited in intensity by Planck’s law of black-body radiation. For any body the reflectivity depends on the wavelength distribution of incoming electromagnetic radiation and therefore the temperature of the source of the radiation. The emissivity depends on the wave length distribution and therefore the temperature of the body itself. For example, fresh snow, which is highly reflective to visible light, (reflectivity about 0.90) appears white due to reflecting sunlight with a peak energy wavelength of about 0.5 micrometres. Its emissivity, however, at a temperature of about -5C, peak energy wavelength of about 12 micrometres, is 0.99.

Gases absorb and emit energy in characteristic wavelength patterns that are different for each gas.

Visible light is simply another form of electromagnetic radiation with a shorter wavelength (and therefore a higher frequency) than infrared radiation. The difference between visible light and the radiation from objects at conventional temperatures is a factor of about 20 in frequency and wavelength; the two kinds of emission are simply different "colours" of electromagnetic radiation.

Clothing and building surfaces, and radiative transfer

Lighter colours and also whites and metallic substances absorb less illuminating light, and thus heat up less; but otherwise colour makes little difference as regards heat transfer between an object at everyday temperatures and its surroundings, since the dominant emitted wavelengths are nowhere near the visible spectrum, but rather in the far infrared. Emissivities at those wavelengths have little to do with visual emissivities (visible colours); in the far infrared, most objects have high emissivities. Thus, except in sunlight, the colour of clothing makes little difference as regards warmth; likewise, paint colour of houses makes little difference to warmth except when the painted part is sunlit. The main exception to this is shiny metal surfaces, which have low emissivities both in the visible wavelengths and in the far infrared. Such surfaces can be used to reduce heat transfer in both directions; an example of this is the multi-layer insulation used to insulate spacecraft. Low-emissivity windows in houses are a more complicated technology, since they must have low emissivity at thermal wavelengths while remaining transparent to visible light.

References :

From Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Heat_transfer

Mechanical Engineering

2009-10-23T03:50:00.000-07:00

Mechanical Engineering is an engineering discipline that was developed from the application of principles from physics and materials science. Mechanical engineering involves the analysis, design, manufacturing, and maintenance of various systems. It is one of the oldest and broadest engineering disciplines.

The field requires a solid understanding of core concepts including mechanics, kinematics, thermodynamics, fluid mechanics, materials science, and energy. Mechanical engineers use the core principles as well as other knowledge in the field to design and analyze manufacturing plants, industrial equipment and machinery, heating and cooling systems, motor vehicles, aircraft, watercraft, robotics, medical devices and more.

Development
Applications of mechanical engineering are found in the records of many ancient and medieval societies throughout the globe. In ancient Greece, the works of Archimedes (287 BC–212 BC) and Heron of Alexandria (c. 10–70 AD) deeply influenced mechanics in the Western tradition. In China, Zhang Heng (78–139 AD) improved a water clock and invented a seismometer, and Ma Jun (200–265 AD) invented a chariot with differential gears. The medieval Chinese horologist and engineer Su Song (1020–1101 AD) incorporated an escapement mechanism into his astronomical clock tower two centuries before any escapement could be found in clocks of medieval Europe, as well as the world's first known endless power-transmitting chain drive.

During the years from 7th to 15th century, the era called the Islamic golden age, there have been remarkable contributions from Muslims in the field of mechanical technology, Al-Jazari, who was one of them wrote his famous "Book of Knowledge of Ingenious Mechanical Devices" in 1206 presented many mechanical designs. He is also considered to be the inventor of such mechanical devices which now form the very basic of mechanisms, such as crank and cam shafts.

During the early 19th century in England and Scotland, the development of machine tools led mechanical engineering to develop as a separate field within engineering, providing manufacturing machines and the engines to power them. The first British professional society of mechanical engineers was formed in 1847, thirty years after civil engineers formed the first such professional society. In the United States, the American Society of Mechanical Engineers (ASME) was formed in 1880, becoming the third such professional engineering society, after the American Society of Civil Engineers (1852) and the American Institute of Mining Engineers (1871). The first schools in the United States to offer an engineering education were the United States Military Academy in 1817, an institution now known as Norwich University in 1819, and Rensselaer Polytechnic Institute in 1825. Education in mechanical engineering has historically been based on a strong foundation in mathematics and science. The field of mechanical engineering is considered among the broadest of engineering disciplines. The work of mechanical engineering ranges from the depths of the ocean to outer space.