...Heat Transfer: Conduction, Convection, & Radiation 1 Heat Transfer Basics Tami L. Donnell Humanities 300, History and Methods of Science Professor Datte February 7, 2007 Heat Transfer: Conduction, Convection, & Radiation 2 Heat Transfer Basics What is Heat Transfer? Heat Transfer is the movement of energy due to a temperature difference. In my paper I will discuss Heat Transfer Basics and will address three physical mechanisms of the movement of heat. The three modes are conduction, convection, and radiation. I will offer examples of the three in hopes that you will gain a better understanding of what each one means. By the end of my essay paper you will have gain the knowledge, skills and abilities to define and understand how heat transfer occurs in our daily living. I will begin by given some small information about heat. Heat as some of you may know flows from an area of higher temperature to a region of lower temperature. Heat can also be made to flow from a cooler area to a hotter area in order to do this function; heat is controlled via a system such as a heat pump. Heat is basically made up of molecules as most anything. Molecules are constantly moving so the hotter something maybe the faster the molecules are moving. Eventually, they move at the same speed which means that any object that is hot will become cold. As mentioned previously heat moves from one object to another in three ways: conduction, convection...
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...Air Conditioning and Heat Pump Systems Clinton Ward COM155 February 17, 2013 Joyce Keeling Air Conditioning and Heat Pump Systems Air conditioners and heat pump systems are used by most people in the world today. They are used to cool in the summer time and to heat in the winter time. These machines are bought and used when most people do not even understand the principle on which they work. The machines are expected do what they are designed to do, and when they cease to do this, they can be costly to repair. Air conditioners and heat pumps are similar in appearance and operation, but while using the same components they can perform completely different tasks. Knowing the difference between the two and the principle in which they perform their tasks will enable each person to make an informed decision when the time comes to repair or replace a piece of equipment. Air conditioners and heat pumps have several components that work in the same way. The compressor is the heart of the system. It is present in both an air conditioner and a heat pump. The compressor pumps the refrigerant throughout the system and enables the system to heat and cool. A few other components in an air conditioner and a heat pump are the metering device, the indoor coil, and the outdoor coil. These four basic components must be present for the cooling process to take place. There are a few components in heat pumps that do not show up in air conditioners. These devices are what make the...
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...The most important concept to understand within the fire phenomena is heat transfer. Heat transfer is everywhere within the aspects of fire, such as fire development. Before the three types of heat transfer can be explained, a few more things need to be understood. Such as heat is the transfer of energy based on a temperature difference between two objects. Also that temperature is a measure of kinetic energy of the molecules in an object. Now the three types of heat transfer and first up is Conduction which is the transfer of energy in the form of heat by direct contact through excitement of molecules with driven by a temperature difference. Energy travels from a high to a low and the same thing happens with heat. When the high temperature molecules collide with the low temperature molecules, a transfer of energy occurs from the hot, more energetic molecules to the colder, less energetic molecules and this is recognized as conduction. Conduction is most prevalent in solids but it can also be found in liquids and gases. The rate at which heat is transmitted through a material by conduction depends on thermal conductivity which is a characteristic of a material and its mass. The easiest way to think of conduction is to hold a metal rod by one end and put the other over a fire. Eventually the hot energetic molecules from the fire will transfer to the cold, less energetic molecules of the metal rod and slowly creep up the rod to the cold end where it is being held and then...
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...Cork. the thermal environment • Metabolism and comfort • Bodily mechanisms of heat transfer and thermostatic control • Metabolic rates • Clothing • Environmental influences on comfort • Fanger's comfort equation • Measuring Instruments • The choice of inside design conditions 1. metabolism and comfort [pic] Metabolism is the mechanism whereby the body converts food into different forms of energy by digesting food in the presence of oxygen. This energy takes the following forms: 1. Work 2. Thermal Energy 3. Waste products Work The amount of bodily energy converted into work is not very great - 0% for a body at rest, 20% when walking up a one in four gradient at 10km/h. Thermal Energy Most of the energy produced by the bodily metabolism is dissipated as heat to the environment. The mechanism for this is seen in the next overhead. Waste Products The remainder of the energy produced is dissipated in waste products. thermal energy Thermal energy is released through an interaction of chemical changes occurring within the body and muscular contractions. [pic] The purpose of the body's thermo-regulatory system is to keep the temperature of the body's deep tissue at 37.2ºC by maintaining a thermal balance with the external environment through heat dissipation. comfort ASHRAE (American Society for Heating Refrigeration and Air Conditioning...
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...HEAT TRANSFER Essay 1 Heat is one of many forms of energy that can be transformed into each other in accordance with the First Law of Thermodynamics. However, it is important to note that the energy contained within any substance cannot be regarded as heat. In fact, heat only exists when it is transferred between two media and then only due to a temperature difference between those media. There are many misuses of the word “heat”. It is not uncommon to describe the temperature in an oven as being 350 degrees of heat. Also, the energy contained in a medium is sometimes said to be the heat contained within that medium. These uses, as well as other misuses, are excluded by the definition: heat is energy in transit due to a temperature difference. Heat transfer is one of the most ubiquitous processes in nature. It is also commonly encountered in virtually all devices, machines, instruments, and living creatures. With such a broad range of application, heat transfer becomes a key part of the engineering knowledge base. Like most undergraduate subjects, the subject matter taught in heat transfer courses represents the academic view of the topic. That view is highly sanitized and drastically simplified compared with reality. The homework problems in the typical undergraduate course are also contrived to be solvable by use of the knowledge base that is conveyed in standard textbooks and in the classroom. Expertise in solving such problems is misleading because those problems...
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...Title: Forced Convection Objective: To demonstrate the use of extended surface such as fin and pin to improve the heat transfer in forced convection. Introduction: Convection is the study of conduction in a fluid as enhanced by its "convective transport", that is, its velocity with respect to a solid surface. It thus combines the energy equation, or first law of thermodynamics, with the continuity and momentum relations of fluid mechanics. The causes of convection are generally described as one of either natural or forced. However the distinction between natural and forced convection is particularly important for convective heat transfer. Forced convection or also known as heat advection studies the heat transfer between a moving fluid and a solid surface. There are various types of forced convection, such as flow in a tube or across a flat plate and so on. In forced convection, the fluid has a nonzero streaming motion in the field away from the body surface, caused perhaps by a pump or fan or other driving force independent of the presence of the body. Also in this class are bodies moving through a still fluid, since fluid velocities are forced and may be large, heat transfer via forced convection will usually be significantly larger. It should be considered as one of the main methods of useful heat transfer as significant amounts of heat energy can be transported very efficiently and this mechanism is found very commonly in everyday life, including central heating, air...
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...trODuct ION tO G rO u N D S O u rc e Heat P uMP SyS teM S chris arkins This note TEC 6, originally published in February 1999, was reviewed by Chris Arkins in January 2004. This summary page includes recent updates to the topic since publication. SUMMARY OF actIONS tOwarDS SuStaINable OutcOMeS Introduction Alternative low energy air conditioning solutions are now commonly sought in preference to typical air conditioning systems for both residential and commercial applications. The industry has seen a growing emergence of ground source heat pump (GSHP) installations throughout Australia over the last five years. A broad spectrum of facilities ranging from domestic housing, hospitals, education facilities, commercial offices and civic buildings to name a few, are now realising the environmental benefits offered by GSHP systems over more commonly used air conditioning systems. This summary note provides a brief overview of the previous note and provides an update on changes that have occurred since. basic Strategies Heat rejection is fundamental to all air conditioning systems. Typically, unsightly roof mounted air cooled condensers and cooling towers are by far the most commonly used method for rejecting heat from a building. Ground source heat pumps are somewhat different to the norm. Basically GSHP are refrigeration machines that provide heating and cooling by using ground water and the earth as a medium to reject and/or absorb heat and as such do not require air cooled...
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...Mike Voss PCT 105 Equipment April 5, 2012 Heat Exchangers There are many types of heat exchangers used in a wide variety of industrial applications including power plants, boilers for industrial steam, chemical plants, and many types of manufacturing facilities. Several different configurations are used to accomplish the function of transferring heat from one fluid to another without mixing the two fluids together. The two most common industrial heat exchangers, the shell and tube heat exchanger and the double pipe heat exchanger, along with information about spiral heat exchangers, flat plate heat exchangers, flat plate heat exchangers, fin-tube heat exchangers, and condensers. Calculations for heat exchanger design use heat transfer parameters such as convection heat transfer coefficients, overall heat transfer coefficients, and log mean temperature differences. These calculations are needed for shell and tube and double pipe heat exchangers, as well as other types. The flow pattern through a heat exchanger affects the required heat exchanger surface. A counter flow heat exchanger needs the lowest heat transfer surface area. It gives a higher value for log mean temperature difference than either a parallel flow heat exchanger or a cross flow heat exchanger. A heat exchanger can have several different flow patterns. Counter flow, parallel flow, and crosss flow are common heat exchanger types. A counter flow heat exchanger is the most efficient flow pattern...
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...set body temperature. How does this happen? How do we generate additional heat when our body is too cold, and how do we cool off when we are too hot? Although part of this response is voluntary, how do we really know that we are cold, and what is our brain doing involuntarily to keep temperatures constant. At times our temperature will move away from the set point, whether through environmental effects such as exposure to cold or internal processes including fever and exercise. How is Heat Distributed Throughout the Body? Humans are homeotherms, maintaining an average core temperature of 37 +/- 0.5 degrees Celsius. Core temperature varies slightly due to environmental and metabolic factors. Exercise or fever may raise core temperature by up to three degrees, while exposure to cold may lower core temperature by a degree. Beyond these boundaries, the human is susceptible to heat stroke (elevated temperature) or hypothermia, both of which are life threatening conditions. While core temperature is tightly regulated, skin temperature varies greatly in response to metabolism and the environment. Temperature receptors in the skin (cold and hot) detect these changes, initiating compensatory mechanisms through the central nervous system. How Does the Body Produce Heat? Energy in the form of heat is gained by two methods: production (metabolic) and acquisition (environmental). Heat production and retention are elevated by a number of factors. 1. Muscular...
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...2. BASICS OF ENERGY AND ITS VARIOUS FORMS Syllabus Basics of Energy and its various forms: Electricity basics - DC & AC currents, Electricity tariff, Load management and Maximum demand control, Power factor. Thermal basics -Fuels, Thermal energy contents of fuel, Temperature & Pressure, Heat capacity, Sensible and Latent heat, Evaporation, Condensation, Steam, Moist air and Humidity & Heat transfer, Units and conversion. 2.1 Definition Energy is the ability to do work and work is the transfer of energy from one form to another. In practical terms, energy is what we use to manipulate the world around us, whether by exciting our muscles, by using electricity, or by using mechanical devices such as automobiles. Energy comes in different forms - heat (thermal), light (radiant), mechanical, electrical, chemical, and nuclear energy. 2.2 Various Forms of Energy There are two types of energy - stored (potential) energy and working (kinetic) energy. For example, the food we eat contains chemical energy, and our body stores this energy until we release it when we work or play. 2.2.1 Potential Energy Potential energy is stored energy and the energy of position (gravitational). It exists in various forms. Chemical Energy Chemical energy is the energy stored in the bonds of atoms and molecules. Biomass, petroleum, natural gas, propane and coal are examples of stored chemical energy. Nuclear Energy Nuclear energy is the energy stored in the nucleus of an atom - the energy that holds...
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...This page intentionally left blank SEVENTH EDITION Fundamentals of Heat and Mass Transfer THEODORE L. BERGMAN Department of Mechanical Engineering University of Connecticut ADRIENNE S. LAVINE Mechanical and Aerospace Engineering Department University of California, Los Angeles FRANK P. INCROPERA College of Engineering University of Notre Dame DAVID P. DEWITT School of Mechanical Engineering Purdue University JOHN WILEY & SONS VICE PRESIDENT & PUBLISHER EXECUTIVE EDITOR EDITORIAL ASSISTANT MARKETING MANAGER PRODUCTION MANAGER PRODUCTION EDITOR DESIGNER EXECUTIVE MEDIA EDITOR PRODUCTION MANAGEMENT SERVICES Don Fowley Linda Ratts Renata Marchione Christopher Ruel Dorothy Sinclair Sandra Dumas Wendy Lai Thomas Kulesa MPS Ltd. This book was typeset in 10.5/12 Times Roman by MPS Limited, a Macmillan Company and printed and bound by R. R. Donnelley (Jefferson City). The cover was printed by R. R. Donnelley (Jefferson City). Founded in 1807, John Wiley & Sons, Inc. has been a valued source of knowledge and understanding for more than 200 years, helping people around the world meet their needs and fulfill their aspirations. Our company is built on a foundation of principles that include responsibility to the communities we serve and where we live and work. In 2008, we launched a Corporate Citizenship Initiative, a global effort to address the environmental, social, economic, and ethical challenges we face in our business. Among the issues we are addressing...
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...Chapter 1 INTRODUCTION The project ‘Heat Transfer Studies on a 7.5 Watt LED Lighting Load using Finite Element Analysis’ is mainly concerned with the heat generated by an LED lighting load and its dissipation to the surrounding such that the LED junction temperature is maintained low. The LED chosen for this project is 7.5 Watt, which has a maximum operating temperature of around 80°C, exceeding which the LED will fail. The LED is best operated at room temperature conditions and may be just above. The project implements a specific method of cooling or rather maintaining the LED junction temperature as low as possible by using a Thermo Electric Cooling device, more specifically known as the Peltier device. The project looks into the various methods by which a Peltier cooler can be implemented such as, with or without a fan or simply a fan would provide sufficient cooling for the LED module. A Heat sink is a necessary component which is always associated with cooling electronic components. Before getting into the depth of the project detailing we will look into the basic components that have been used in the project setup which include: a. LED Module b. Peltier Cooler c. Heat Sink d. Cooling Fan 1.1 Light Emitting Diode: Light-emitting diodes (LEDs) are small but powerful devices in terms of their diverse applications. LED lights assume greater significance in the context of need for electrical energy conservation and pollution control world over. LED is basically...
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...1. PELTIER CELL • A Peltier Cell is device which directly convert heat energy into electric energy. Peltier device consist several of thermocouples. The thermocouple have two thermo elements that spreads between the hot side and cold side of the device. Fig. 1.1 • The efficiency of this device is around 5-8 % (Wikipedia.org).Generally, older devices are made from bimetallic junctions.it was very bulky. But, now a days highly doped semiconductors are used which is made from bismuth telluride (Bi2Te3) and lead telluride (PbTe). Practically Peltier cell working based on three effects 1) Peltier effect. 2) Thomson effect. 3) Seebeck effect. 1) Peltier Effect: • If we applied voltage to peltier unit then the heat is transferred from...
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...No. Information on Every Subject 1. Unit Name: Physics I 2. Code: FHSP1014 3. Classification: Major 4. Credit Value: 4 5. Trimester/Year Offered: 1/1 6. Pre-requisite (if any): No 7. Mode of Delivery: Lecture, Tutorial, Practical 8. Assessment System and Breakdown of Marks: Continuous assessment: 50% - Theoretical Assessment (Tests/Quizzes/Case Studies) (30%) - Practical Assessment (Lab reports/Lab tests) (20%) Final Examination 9. 10. 50% Academic Staff Teaching Unit: Objective of Unit: The aims of this course are to enable students to: • appreciate the important role of physics in biology. • elucidate the basic principles in introductory physics enveloping mechanics, motion, properties of matter and heat. • resolve and interpret quantitative and qualitative problems in an analytical manner. • acquire an overall perspective of the inter-relationship between the various topics covered and their applications to the real world. • acquire laboratory skills including the proper handling and use of laboratory apparatus and materials. 11. Learning Outcome of Unit: At the end of the course, students will be able to: 1. Identify and practice the use of units and dimensional analysis, uncertainty significant figures and vectors analysis. 2. Apply and solve problems related to translational and rotational kinematics and dynamics in one and two dimensions. 3. Apply and solve problems related to the...
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...nuclear. Even mass can be considered a form of energy. Energy can be transferred to or from a closed system (a fixed mass) in two distinct forms: heat and work. For control volumes, energy can also be transferred by mass flow. An energy transfer to or from a closed system is heat if it is caused by a temperature difference. Otherwise it is work, and it is caused by a force acting through a distance. We start this chapter with a discussion of various forms of energy and energy transfer by heat. We then introduce various forms of work and discuss energy transfer by work. We continue with developing a general intuitive expression for the first law of thermodynamics, also known as the conservation of energy principle, which is one of the most fundamental principles in nature, and we then demonstrate its use. Finally, we discuss the efficiencies of some familiar energy conversion processes, and examine the impact on energy conversion on the environment. Detailed treatments of the first law of thermodynamics for closed systems and control volumes are given in Chaps. 4 and 5, respectively. Objectives The objectives of Chapter 2 are to: • Introduce the concept of energy and define its various forms. • Define the nature of internal energy. • Define the concept of heat and the terminology associated with energy transfer by heat. • Discuss the three...
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