Essays on Convection

Three phase induction motors

Introduction The three-phase induction machine is the most widely used among the rotating machines. An induction machine offers an almost constant speed within its normal operating range when operated off a constant-voltage, constant-frequency, and with the electric power source. The cost of purchasing these machines is very low, and they require little maintenance. However, speed control is difficult and very expensive. Therefore, the rotor current of the three phase induction motors is not induced by electrical connections, but rather the rotation of magnetic field.

Squirrel Cage Rotor construction

The rotor type of the motor is made up of a laminated core which is ...

I hereby certify that this material, which I now submit for assessment as a continuous assessment project in Heat and Mass Transfer on the course 4th year in BEng (Hons) Mechanical and Manufacturing Engineering, is entirely my own work and has not been submitted in whole or in part for assessment for any academic purpose other than in fulfilment for that stated above.

Abstract

Energy is a depleting resource, making it crucial for people to be knowledgeable in implementing conservation measures at the domestic dwelling level. Scientific advances had made effective energy conservation technology increasingly more accessible due to innovative ...

Abstract:

The principal intention of this study was to come up with the most conducive internal environment in a building. At any given moment, the internal temperature of a building is a function of the amount of heat produced by sources therein and the net heat transfer into or out of the building. The four heat transfer modes are convection, radiation, conduction, and phase- change. In executing this project, the researchers sought the relevant literature to establish the thermal properties of various materials. The properties are critical in determining the amount of heat inflow and exit from the building. The ...

Introduction

The main objectives of this report include; designing the operational principles of parallel and counter flow of heat exchangers. Improving the understanding of fluid temperature and flow rate heat exchangers and lastly to calculate and determine the overall heat transfer coefficient of a heat exchanger ("Superplastic duplex stainless steel heads for the heat exchanger market", 2010). The parallel flow of fluid is characterized by the flow of cold and hot fluids in the same direction; it, therefore, means that the entrance for the two fluids are in the same direction likewise their exit are also normally in the same ...

Roofing Ventilation

The need for ventilation in roofs and attics became apparent after it was observed that moisture inside attics, caused by the phenomenon of condensation, was deteriorating a large portion of the roofing materials and in extreme cases the insulation of the ceiling. Adding to this grief, wet attics became the breeding place for a variety of fungi and moulds . From then, wet attics had become the nightmare of many house owners. If roofing ventilations were a fancy contraption in the early days, in the modern world they are an integral part of any roofing solution. And gladly, there are ...

Thermal conductivity is defined as a material’s property to conduct heat. Heat transfer across materials occurs in materials that have lower thermal conductivity and transfers faster in materials with high conductivity. It is important to determine the thermal conductivity of materials since different materials are used for different applications. For instance, materials with high conductivity are more efficient when they are used as heat sinks since they can conduct heat away faster. Those with lower thermal conductivity are often used as insulators (Callister 78). The classical transfer of energy happens through conduction, radiation, convection or combination of all ...

This experiment is about heat transfer in a fin based on Fourier’s law of heat conduction and Newton’s Law of Cooling. The latter states that the rate of heat loss of a body is proportional to the differences in temperature between the environment and the body. On the other hand, Fourier’s law of heat conduction states that the time of heat transfer through a material is usually directly proportional to the negative gradient of temperature and the area, at right angles to the gradient, through which the heat flows (Liehnhard, 23). The two laws will be ...

Part one: Experimental procedure

The experiment to establish the extended surface heat transfer employed the use of two apparatus: Extended surface heat transfer accessory (HT15) and heat transfer service unit (HT10X). The extended surface heat transfer accessory heater was connected to the HT10XC. The thermocouples from the HT15 were then connected to the HT10XC. This was followed by setting the voltage control potentiometer to a minimum. The switch selector was then set to manual. The voltage of the heater was set to 6 V and the measurements were taken afterward. The above steps were repeated for heater voltage of 9 V and 12 ...

Introduction

The purpose of this experimental task was to investigate the possibility of using circular rods of different materials made from different materials and having different diameters as heat fins. Extend surfaces of heat fins allow for additional heating and cooling capacity in a cheap and passive way. The fins are intended for use in cooling a reactor by use of the surrounding air. Models were developed based on several assumptions for the simplification of the derivation of the steady and unsteady state temperature distribution state in a solid rod heated at one of the edges. The models derived shall ...

Explain the difference between the two statements mentioned below:

Spilling water on skin surface on a hot day will cool the body temperature. Spilling vegetable oil on skin surface on a hot day will not cool down the body temperature.

Strategy to Solve this Problem

The first step will be to discuss the temperature regulation mechanism of the human body. It will be followed by the cooling mechanisms adopted by the skin surface on a hot day to maintain the aforesaid body temperature. Next will be an overview of the inherent properties of water and vegetable oils. Finally, a correlation between the body mechanisms and cooling effects by water ...

Question #1

Three main layers of the interior of the Sun are convection zone, radiation zone and the core.The central part of the Sun with a radius of about 150-175 thousand km (ie, 20-25% of the radius of the Sun), in which are thermonuclear reactions, called a solar core. The density of material in the core is about 150 000 kg / m ³ (150 times higher than the density of water and ~ 6.6 times higher than the density of the densest metal on the Earth - osmium), and the temperature in the center of the core is over 14 million K. A ...

Assignment 4

4. Describe the three (3) main layers of the Sun's interior. The three (3) main layers of the Sun’s interior are the Core, Radiation Zone, and Convection Core. First, the Sun’s Core or innermost part, is tightly packed and with a temperature of about 1.5x107 K. It extends from the Sun’s center to the photosphere (that is, approximately 0.25 solar radius or 1.75x105 km). It is at the Sun’s Core that thermonuclear reactions occur because of the enormous temperature and pressures. Second, the Sun’s Radiation Zone or the middle interior part, where energy ...

Q1. Describe the three main layers of the Sun’s interior.

The three main layers of the Sun’s interior are the core, the radiative envelope and the connective envelope.

The core is the center of the Sun, with a density of 150 g/cc and a temperature of 15 million K. This is the region where high energy fusion reactions take place and energy is produced. The energy produced is mainly in the form neutrino and gamma rays, which are actually high energy protons which travel several light years and supply energy to the Earth and other planets. The energy produced in the core then radiates outwards through the radiative zone. The ...

Explain how the outward flow of energy from the Earth’s interior drives the process of plate Tectonics

All the earth processes are a result of energy flow and mass circulation in and outside of the earth system. Plate tectonics is an earth process that involves the movement of the lithosphere caused by internal processes inside the earth’s mantle (Kent C 154). This is as a result of convection currents within the earth’s crust caused by the heat in the crust. This heat in the crust is due to the initial heat during the earth’s formation and through the radioactive process. The earth’s core is made of radioactive elements such as uranium which decay and ...

1) Explain how the outward flow of energy from the Earth’s interior drives the process of plate tectonics?

The outermost layer of earth, or lithosphere, is broken up into tectonic plates. The boundaries of the plates and their movement leads to the formation of earthquakes, volcanic activity, creation of mountains, and the formation of oceanic trenches. Tectonic plates are formed from either oceanic crust or continental crust, with many containing both. The movement of the plates varies from 0-100mm in a given year. The movement of these plates comes from the outward energy of flow that comes from earth’s central core. Radioactivity produced from elements within earth’s core, such as uranium, decay and release energy. The ...

1) Explain how the outward flow of energy from the Earth’s interior drives the process of plate tectonics?

The earth’s composition consists of a crust, mantle and core. The earth’s core consists of elements like uranium which are radioactive. Due to the phenomenon of radioactivity, these elements decay and trigger a reaction. Because of this a large amount of energy is produced in the core and inner core of the earth. Because of this energy, the core of the earth is very hot and in a molten state. This heat is transferred from the core to the crust by the process convection currents formed in the molten core, creating a cycle of rising and falling of the molten material. This ...

2) There are justifications on the presence of the moon. Perhaps, collision-ejection theory of the moon gives an explains on the issues. The theory asserts that the moon exists due to the formation of debris ejected from the earth, especially when objects crushed. Collision-ejection theory claims that the newly formed earth collided with mars at an angle, which splashed the layers of the earth surface into the orbit around it. This implies that the Earth crust and mantle formed the moon though condensation. There are various facts on the moon that the theory is consistent with. Some of the ...

Kinetic theory of matter tries to explain all molecules in terms of motion. The theory posits that every substance consists of many small particles referred to as molecules. Substances in this case are called matter and are in three forms; solids, liquids, and gases. Solids have molecules that are closer to each other by intermolecular forces. Liquids on the other hand have molecules slightly far apart with gases the furthest apart. Furthermore, according to this theory all the molecules are in constant random motion referred to as Brownian motion (Chang, 2004).

The study of heat relates to kinetic theory ...

Introduction

Building simulation methods should focus on the effect that occurs between convective heat repulsion between external air circulation and the given wall surfaces. This study will take a closer look on the effects of heat transfer on a brick surface. A tetrahedral mesh will be used to scertain for the effects that are caused on the walls. A brick wall is known for its thermal characteristic of absorbing heat. Therefore, this thermal property will also be studied in this study. Most authors have attributed this norm to behavior of the different correlations that are used to estimate the exact value of ...

Methods of Heat Transfer

Conduction The first method through which heat is transferred from one object to another is conduction. Conduction occurs in liquids and solids through transfer of kinetic energy present in one particle to the immediate particle(s) in its surrounding. By considering the bonds existing between atoms and molecules in solids as elastic links, the vibration of one particle due to increase energy level caused by heat, the next in its line vibrate too. This process is replicated in adjacent particles thereby allowing transfer of thermal energy from a body with a higher temperature as compared to the one with low ...

Literature review

Heat transfer and friction characteristics in a square duct roughened by various shaped ribs on one wall [Aliaga, b, 1994]. Liquid crystal thermograph is used to measure local and average heat transfer coefficient of ribbed surface. The ribs height to duct hydraulic diameter ratio is fixed to 0.1. The rib pitch to height ratio varies from 8 to 15 and Reynolds number spans from 8000 to 20,000[Aliaga, b, 1994]. The experiment consists of heat transfer test and pressure test. The test experiment consists of 750mm long smooth duct followed by a rib-roughened section of equal length. Plexiglas plates are applied to ...

Annotated Bibliography: Definition of a Monster

Introduction Considering that particular focus of this research is defining what a monster is. The sources incorporated herein essentially work to define the term monster in relation to film literature, and personal perceptions. In a bid to accomplish this, sources that are to be used in the research establishes the chronology of the term monster, culture perception of the term monster, and finally the relation of monstrous characteristics to human behaviour. The most important ideas in understanding the subject of the research evident from the sources below include myths, history of monsters, magic and believes. Asma, Stephen T. On ...

Article Research

Introduction In the late 1820’s, the Northern Carolina became more industrialized as the Southern remained non-developed. The Congress had passed a high protective tariff in 1828 that made the southern states more furious because they thought the tariff only benefited the northern states. The southern claimed that high tariff on imports were imposed to them leading to increased costs of importing products. Bradley Hays saw the Southern states sympathy to South Carolina’s position on the tariff rejected as the cause of federalism (Hays 221). Eventually, the doctrine of nullification was introduced that provided an insight to the ...

INTRODUCTION

Climate change in the Arctic region can be considered to be the most serious environmental issue that is threatening the Arctic environment. Apparently, the annual average temperature in this region has been gradually increasing by approximately double the total global average temperature (Symon, Lelani and O W, 123). It has become evident that human activities are the single most cause of climate change, even the government of US has at last admitted to this fact. During the past few years, the Arctic environment has warmed at alarming rate, and scientist predict that it is still going to continue by ...

SiRNA also known as small interfering RNA is a set of double-stranded RNA molecules. SiRNA is also termed as silencing RNA or short interfering RNA. Most of the SiRNA molecules are 20 to 25 base pairs in length. SiRNA is known to have many distinct roles but has a crucial role in the RNA interface pathway (RNAi). Small interference RNA (siRNA) represents a promising therapeutic strategy and its clinical evaluation began in 2004.

Slide 4

It is important to understand the barriers associated in SiRNA delivery. The barriers to siRNA delivery are multiple and depend on the targeted organs and the administration routes (locoregional ...

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The Sun has been with us for 4 billion years, and is the nearest star to the Earth. The Sun is comprised of about 74% of hydrogen, 25% of helium, and 1% of other elements. The surface of the Sun has a temperature of about 5800 K. The core of the Sun has a temperature ranging from 10 – 15 million Kelvin. This temperature range is high enough to activate nuclear fusion within the Sun. Here, four protons will fuse together to obtain a helium nucleus containing two protons and two neutrons via a proton-proton chain. The core of the ...

The sun is about 864000 miles wide and filled with sweltering hot gases. Hydrogen is the most abundant element present in the Sun, composition of the Sun by its constituent mass is 71% hydrogen (H), 27% helium (He) and 2% other heavier elements. Inside the Sun the gravitational pull compresses the gases, and increase the temperature and pressure at the core. (CAIN, F., 2009) The temperature is about 10000°F on the surface and more than 28 million degrees Fahrenheit at the core of the sun. The pressure at the core of the sun is 250 billion times the ...

The constitutional scholar and radio host presenter Mark Levin culminates as an author of the book, “The Liberty Amendments: Restoring the American Republic.” The author of the book invokes Article V of the constitution that sets out methods for amendments that intend to rein in a reckless, unruly, and usurpations federal government highlighted in the 10th Amendment. McCarthy, (2013) assert that Levin undertakes this project to preserve and restore the constitutional republicanism and the civil society and prevent federal Leviathan authoritarianism. According to Levin, Statists achieved the process of disfiguring the compact constitutional order (Levin, 2014). Framers of the ...

(Check the 7_Main_Sequence) - What is a main sequence star?

Answer: Stars that combines hydrogen into helium in their cores are called main sequence stars

- What are the different types of main sequence stars and what distinguishes them (size, colour, lifetime, luminosity)? Answer: The Upper main sequence stars (Stars above 1.5 the mass of the sun) and the Lower main sequence stars (Stars below 1.5 the mass of the sun). The distinguishing features of these types of stars are mass, temperature, brightness and elemental composition. - What is an HR Diagram and what does it reveal to astronomers? Answer: HR Diagram is a scatter graph showing the relationship between a star ...

Introduction

Physics is an abstract field of science that influences our lives in more ways than we can imagine. From waking up every morning, to the water we drink; from driving to work, to the music we listen to; from the internet, to the cell phones that we use so often, physics governs all their basic operating principles. Many natural phenomena throw questions whose answers lie deep in physics. Why are lightning flashes so spectacular? How long does it take for light from a star to reach us? How is a rainbow formed? What causes a boomerang to swirl back? Many of these ...

- Pressure= 1000 x (0.5)5.6/5.6 Pressure=500 mb Pressure=1000 x (0.5)8.85/5.6 Pressure=334.40 mb Pressure=1000 x (0.5)11.2/5.6 Pressure=250 mb Pressure= 1000 x (0.5)50/5.6 Pressure=2.05 mb - The temperature of the upper stratosphere is greater than that of the lower stratosphere due to the presence of the ozone layer. It is here where ozone absorbs ultraviolet light, which triggers chemical reactions. These chemical reactions produce heat, a process which is not found in the lower stratosphere. - Conduction is the transfer of heat through solid objects such as metal and ...

1. Introduction Agriculture and other food products are dried for use. The agriculture grains are dried for future use or production process, in order to dry the agriculture products the sun drying has been used for many years. The sun drying dries the products in a open air condition with the help of hot sun rays. In past centuries the sun drying systems has been used. Most of the industries use mechanized drying instead of sun drying system. The mechanized drying uses boilers and fan to heat and force the air to the required part. The time taken for ...

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Geothermal energy (GE): An Introduction Geothermal energy can be termed as a heat found inside the Earth. This type of heat is an uncontaminated, renewable fuel resource that supplies the energy needs of millions of people in the USA as well as all over the world for various utilizations and applications. Though domains like hot springs are more noticeable and are generally the first source of GE resources, the heat underneath the earth is accessible universally, and the scientists are able to utilize in a wide variety of circumstances. ...

Introduction

There has been an increase in the intensity of the relationship between domestic law and international law (Samaha, 2010). The above topic has led into a burning debate concerning how different domestic legal systems should face challenges in arising because of incorporation of international norms/laws. Different nations have their own jurisdictions governed by their constitutions. By definition, jurisdiction refers to practical authority given to a formal legal body defining specific areas of responsibility within which that the body can administer justice. Different nations have different jurisdictions depending on their constitutional demands. For example, in United States, the federal government has jurisdiction ...

Introduction and terminologies

A cloud is a mass of liquid drops or frozen crystals of water or any other chemicals in the atmosphere over the surface of the earth (merriam-webster.com, erh.noaa.gov). Clouds are mainly formed as a result of vertical movement of air due to convection, forced gain in height over highlands or large scale vertical ascent due to merging of hot and cold air masses in the mid-latitudes. Clouds form and important part the water cycle, because they are the source of rain and snow, which transport water from the atmosphere to the surface of the earth. This maintains the water cycle on ...

During 1800's women were dominated by men. By this time, women were relegated to household duties and taking care of their families. They were property to their husbands and many of them were subjected to horrendous treatment devoid of reprimand from the law. They could neither vote nor make financial decision or own property. However, there came up some women who struggled for equity and equality such as Lucretia Mott and Elizabeth Cady Stanton who questioned both political and religion authority that comprised of men. This essay discusses how women exerted political influence in the 1800s in US history. ...

Introduction

With people becoming more conscious of the detrimental effects of fossil fuel, the demand for green sources of energy is on a rise. The Sun is the source of all the energy in this world. Even if a small percentage of solar irradiance is collected every day then all the problems related to the scarcity of sufficient energy will be solved. However, it is not very easy to collect and store solar energy in an effective way. Solar Collectors also known as Solar Thermal Collectors are designed to absorb solar energy from solar radiation which is then reduced to heat water ...

Bill of Rights was first drafted as a compromise from the constitutional convection in 1791 (Donnelly 72). While the idea of Bill of Rights had been raised towards the end of Constitution Convention the delegates at time thought the suggestion pointless (Donnelly 72). As such, omission of Bill of Right raised argument of anti-federalist against the constitution. At thi point no state had conditioned for constitution ratification on Bill of Right, although there were a few that came close, a subject that almost prevented the entire constitution from being ratified (Donnelly 73). Anti-federalist fight to the issue continued even after the constitution ...

Outdoor Play in Early Childhood Education and Care Ireland

Childhood is a very important stage in the development of each individual. It is in this stage that permanent traits and behaviours are nurtured and acquired. This stage plays a crucial role in ensuring that children develop to desired individuals in the society. In this stage, several activities are incorporated to ensure that a child is fully equipped to face the next stage of life. Some of the activities include playing, schooling, and other distinct activities varying with social status of the family. Research as shown that childhood influences greatly the future life of the individual this is because values instilled in ...

Abstract

This paper clearly presents and defines the numerical study on how hollow building block operates to suppress the convectional currents and reduce the amount of heat flux transferred across the petition of the building wall. The configuration and weight of these blocks have made them to fully be utilized in building the facades. The air filled cavities (hollow cells) together with the small cross-sectional area geometry provides an appropriate elevation for the building block. The hollow polythene bars inserted in this bricks also helps to reduce the heat by about 36% depending on the petition number (Mejad 2006). ...

Question 1

Juvenile transfer laws are the laws that allow the court to try young people as the adult. They are three main types of juvenile transfer laws. They include Automatic Legislative Exclusion, Prosecution-Discretionary and Judicial-Discretionary. In addition to juvenile transfer laws some states only single transfer law is applicable while other states combines two transfer laws.

Question 2

Judicial-discretionary The law allows the court to determine whether the juvenile is should be considered as young adult or should be tried as an adult. Juvenile judge have to provide a formal support for the juvenile to be moved into adult court out of ...

American is a superpower thus so many countries look up to it. Any event that happens in America today is watched through a lens by the world be it a third world country or otherwise. The United States is an important superpower and ever since time immemorial, she has been at the forefront of development throughout the world. Most of American historians do not go unnoticed. They created history to reckon with and what has made most policies and shaped most world decisions in today’s world. Among the historical figures to reckon with are Benjamin Franklin, Thomas Jefferson and George ...

Heat and Temperature

The transfer of energy from a high temperature body to a lower temperature body is known as heat. Heat travels in form of waves and like any other form of energy it has the potential to bring change into the matter it contacts. This process is usually accompanied by the transfer of entropy, the energy per unit temperature that goes unused. Heat transfer is usually generated by three types of thermal interaction, mainly, conduction, convection and radiation. Conduction is mostly related to the transfer of heat in solids, wherein the materials are in direct contact with each other and the heat ...

Abstract

Heat transfer through a cylindrical pin fin s studied. For the purposes of this study, thermal conductivity, heat transfer coefficient and the source terms and the sink terms are assumed to depend on the temperature. In the model being used for the study, the source and sink terms are given as arbitrary functions. We therefore employ techniques on symmetry to find the forms of the source and the sink terms which the extra lie point symmetries are admitted. The method of separating variables is used in the study to get the exact solutions when the equation for the equation is ...

CHAPTER 2: FIRE SPREAD

Chapter 2: Fire spread 2.1 Introduction The chapter discusses aspects of fire spread so as to understand spread of fire, fire transfer, and how fire moves or escapes. Most fires spread quickly in buildings because of the presence of combustible materials like furniture, and flammable gases. Controlling of fire spread is easy in the first stage also referred to as the insipient fire. Nevertheless, fire can move swiftly and even reach higher speed limits in the presence of assistant factors found in gaps or penetration inside a building. Internally, spread of fire is common in obscured spaces, ...

Executive summary

When deciding a good venue to hold annual general meetings, planners face a lot of problems in coming up with the best location that has all the requirements related to space, security, catering, and cost. Below is a consideration of three locations, chosen within Perth, in Australia. The three locations are analyzed accordingly and a recommendation on the best location given.

1.0 Introduction When planning for an annual general meeting for a big organization, the site should meet the following requirements. To start with, the room should be big enough to accommodate all the people. Secondly, it should be in a central location with ...

Introduction

Fire is described as the visible result of an oxidation process in the chemical reaction known as combustion. Combustion occurs between an oxidant (source of fuel) and oxygen which results in the release of heat and the source of fuel being converted into another form (Grimwood et al., 2010). When heat is released, light is produced either as a flame or glowing. The fuels which bring about combustion are mainly organic compounds like hydrocarbons which may be in the solid, liquid, or gaseous phase. The part of the fire which is visible is known as the flame. It is ...

Abstract

Several accounting principle have been put in place to ensure that the financial statement presented to users are free and fair. The principle of consistency ensures financial statements are prepared using the same principle year after year. Materiality concept ensures that only valuable information is included in financial statement. Principle of disclosure ensures that all valuable information is included in preparation of financial statement. Then the principle of conservatism makes sure that losses are recorded when foreseen while profits must be earned before recording. The fixed asset register keeps eye on all fixed assets of a firm. The assets ...