Energy Harvesting for Wireless Switch—Power Reference Design
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Estimation of the Dissipation Rate of Turbulent Kinetic Energy: a Review
Chemical Engineering Science 229 (2021) 116133 Contents lists available at ScienceDirect Chemical Engineering Science journal homepage: www.elsevier.com/locate/ces Review Estimation of the dissipation rate of turbulent kinetic energy: A review ⇑ Guichao Wang a, , Fan Yang a,KeWua, Yongfeng Ma b, Cheng Peng c, Tianshu Liu d, ⇑ Lian-Ping Wang b,c, a SUSTech Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology, Shenzhen 518055, PR China b Guangdong Provincial Key Laboratory of Turbulence Research and Applications, Center for Complex Flows and Soft Matter Research and Department of Mechanics and Aerospace Engineering, Southern University of Science and Technology, Shenzhen 518055, Guangdong, China c Department of Mechanical Engineering, 126 Spencer Laboratory, University of Delaware, Newark, DE 19716-3140, USA d Department of Mechanical and Aeronautical Engineering, Western Michigan University, Kalamazoo, MI 49008, USA highlights Estimate of turbulent dissipation rate is reviewed. Experimental works are summarized in highlight of spatial/temporal resolution. Data processing methods are compared. Future directions in estimating turbulent dissipation rate are discussed. article info abstract Article history: A comprehensive literature review on the estimation of the dissipation rate of turbulent kinetic energy is Received 8 July 2020 presented to assess the current state of knowledge available in this area. Experimental techniques (hot Received in revised form 27 August 2020 wires, LDV, PIV and PTV) reported on the measurements of turbulent dissipation rate have been critically Accepted 8 September 2020 analyzed with respect to the velocity processing methods. Traditional hot wires and LDV are both a point- Available online 12 September 2020 based measurement technique with high temporal resolution and Taylor’s frozen hypothesis is generally required to transfer temporal velocity fluctuations into spatial velocity fluctuations in turbulent flows. -
Turbulence Kinetic Energy Budgets and Dissipation Rates in Disturbed Stable Boundary Layers
4.9 TURBULENCE KINETIC ENERGY BUDGETS AND DISSIPATION RATES IN DISTURBED STABLE BOUNDARY LAYERS Julie K. Lundquist*1, Mark Piper2, and Branko Kosovi1 1Atmospheric Science Division Lawrence Livermore National Laboratory, Livermore, CA, 94550 2Program in Atmospheric and Oceanic Science, University of Colorado at Boulder 1. INTRODUCTION situated in gently rolling farmland in eastern Kansas, with a homogeneous fetch to the An important parameter in the numerical northwest. The ASTER facility, operated by the simulation of atmospheric boundary layers is the National Center for Atmospheric Research (NCAR) dissipation length scale, lε. It is especially Atmospheric Technology Division, was deployed to important in weakly to moderately stable collect turbulence data. The ASTER sonic conditions, in which a tenuous balance between anemometers were used to compute turbulence shear production of turbulence, buoyant statistics for the three velocity components and destruction of turbulence, and turbulent dissipation used to estimate dissipation rate. is maintained. In large-scale models, the A dry Arctic cold front passed the dissipation rate is often parameterized using a MICROFRONTS site at approximately 0237 UTC diagnostic equation based on the production of (2037 LST) 20 March 1995, two hours after local turbulent kinetic energy (TKE) and an estimate of sunset at 1839 LST. Time series spanning the the dissipation length scale. Proper period 0000-0600 UTC are shown in Figure 1.The parameterization of the dissipation length scale 6-hr time period was chosen because it allows from experimental data requires accurate time for the front to completely pass the estimation of the rate of dissipation of TKE from instrumented tower, with time on either side to experimental data. -
Work and Energy Summary Sheet Chapter 6
Work and Energy Summary Sheet Chapter 6 Work: work is done when a force is applied to a mass through a displacement or W=Fd. The force and the displacement must be parallel to one another in order for work to be done. F (N) W =(Fcosθ)d F If the force is not parallel to The area of a force vs. the displacement, then the displacement graph + W component of the force that represents the work θ d (m) is parallel must be found. done by the varying - W d force. Signs and Units for Work Work is a scalar but it can be positive or negative. Units of Work F d W = + (Ex: pitcher throwing ball) 1 N•m = 1 J (Joule) F d W = - (Ex. catcher catching ball) Note: N = kg m/s2 • Work – Energy Principle Hooke’s Law x The work done on an object is equal to its change F = kx in kinetic energy. F F is the applied force. 2 2 x W = ΔEk = ½ mvf – ½ mvi x is the change in length. k is the spring constant. F Energy Defined Units Energy is the ability to do work. Same as work: 1 N•m = 1 J (Joule) Kinetic Energy Potential Energy Potential energy is stored energy due to a system’s shape, position, or Kinetic energy is the energy of state. motion. If a mass has velocity, Gravitational PE Elastic (Spring) PE then it has KE 2 Mass with height Stretch/compress elastic material Ek = ½ mv 2 EG = mgh EE = ½ kx To measure the change in KE Change in E use: G Change in ES 2 2 2 2 ΔEk = ½ mvf – ½ mvi ΔEG = mghf – mghi ΔEE = ½ kxf – ½ kxi Conservation of Energy “The total energy is neither increased nor decreased in any process. -
Middle School Physical Science: Kinetic Energy and Potential Energy
MIDDLE SCHOOL PHYSICAL SCIENCE: KINETIC ENERGY AND POTENTIAL ENERGY Standards Bundle Standards are listed within the bundle. Bundles are created with potential instructional use in mind, based upon potential for related phenomena that can be used throughout a unit. MS-PS3-1 Construct and interpret graphical displays of data to describe the relationships of kinetic energy to the mass of an object and to the speed of an object. [Clarification Statement: Emphasis is on descriptive relationships between kinetic energy and mass separately from kinetic energy and speed. Examples could include riding a bicycle at different speeds, rolling different sizes of rocks downhill, and getting hit by a wiffle ball versus a tennis ball.] MS-PS3-2 Develop a model to describe that when the arrangement of objects interacting at a distance changes, different amounts of potential energy are stored in the system. [Clarification Statement: Emphasis is on relative amounts of potential energy, not on calculations of potential energy. Examples of objects within systems interacting at varying distances could include: the Earth and either a roller coaster cart at varying positions on a hill or objects at varying heights on shelves, changing the direction/orientation of a magnet, and a balloon with static electrical charge being brought closer to a classmate’s hair. Examples of models could include representations, diagrams, pictures, and written descriptions of systems.] [Assessment Boundary: Assessment is limited to two objects and electric, magnetic, and gravitational interactions.] MS-PS3-5. Engage in argument from evidence to support the claim that when the kinetic energy of an object changes, energy is transferred to or from the object. -
The Mechanical Equivalent of Heat
THE MECHANICAL EQUIVALENT OF HEAT INTRODUCTION This is the classic experiment, first performed in 1847 by James Joule, which led to our modern view that mechanical work and heat are but different aspects of the same quantity: energy. The classic experiment related the two concepts and provided a connection between the Joule, defined in terms of mechanical variables (work, kinetic energy, potential energy. etc.) and the calorie, defined as the amount of heat that raises the temperature of 1 gram of water by 1 degree Celsius. Contemporary SI units do not distinguish between heat energy and mechanical energy, so that heat is also measured in Joules. In this experiment, work is done by rubbing two metal cones, which raises the temperature of a known amount of water (along with the cones, stirrer, thermometer, etc,). The ratio of the mechanical work done (W) to the heat which has passed to the water plus parts (Q), determines the constant J (J = W/Q). THE EXPERIMENT CAUTION: The apparatus must not be operated without oil between the cones. The cones have to be cleaned and a tiny drop of oil put between the rubbing surfaces (caution! too much oil will reduce the friction excessively and make the experiment impossible). The apparatus is shown in Figure 1. The heat generated in the system is absorbed by different parts: the water, the inner and outer cones, the stirrer and the immersed part of the temperature probe. The total increase in heat, including all these contributions, is therefore: Q = (MCw + M′Cbr + v Cth) ∆T = constant1 × ∆T (1) -1 -1 Cw = specific heat of water = 1.00 cal g C (by definition of the calorie) -1 ° -1 Cbr = specific heat of brass (cones and stirrer) = 0.089 cal g C -3 ° -1 Cth = heat capacity per unit volume of temperature probe = 0.013 cal cm C M = mass of water (in g) M′ = mass of cones and stirrer (in g) v = volume of the immersed part of the temperature probe (in cm3). -
Fuel Wise Or Fuelish? Grades 9 to 12
LESSON PLAN Fuel Wise or Fuelish? Grades 9 to 12 SUMMARY LESSON OBJECTIVES In this lesson, the students will explore the different impacts Upon completing this lesson the students will: using alternative fuels has on the economy. • Learn how world events affect supply and demand for The students will research and compare different cars. petroleum; They will determine the cost of operation for one year to • Explore why it is important for South Carolinians to use include price, fuel, insurance, property taxes, title, tag, and alternative fuels; and maintenance, as well as determine the most cost-effective choice of vehicle, based on their research. • Make decisions pertinent to choosing a fuel-efficient car. ESSENTIAL QUESTION How have alternative fuels impacted the economy? DURATION The activity requires about one to two weeks to complete. 2014 S.C. SCIENCE STANDARDS CORRELATIONS Standard H.P.3: The student will demonstrate an understanding of how the interactions among objects can be explained and predicted using the concept of the conservation of energy. CONCEPTUAL UNDERSTANDING H.P.3A.: Work and energy are equivalent to each other. Work is defined as the product of displacement and the force causing that displacement; this results in the transfer of mechanical energy. Therefore, in the case of mechanical energy, energy is seen as the ability to do work. This is called the work-energy principle. The rate at which work is done (or energy is transformed) is called power. For machines that do useful work for humans, the ratio of useful power output is the efficiency of the machine. -
Mechanical Energy
Chapter 2 Mechanical Energy Mechanics is the branch of physics that deals with the motion of objects and the forces that affect that motion. Mechanical energy is similarly any form of energy that’s directly associated with motion or with a force. Kinetic energy is one form of mechanical energy. In this course we’ll also deal with two other types of mechanical energy: gravitational energy,associated with the force of gravity,and elastic energy, associated with the force exerted by a spring or some other object that is stretched or compressed. In this chapter I’ll introduce the formulas for all three types of mechanical energy,starting with gravitational energy. Gravitational Energy An object’s gravitational energy depends on how high it is,and also on its weight. Specifically,the gravitational energy is the product of weight times height: Gravitational energy = (weight) × (height). (2.1) For example,if you lift a brick two feet off the ground,you’ve given it twice as much gravitational energy as if you lift it only one foot,because of the greater height. On the other hand,a brick has more gravitational energy than a marble lifted to the same height,because of the brick’s greater weight. Weight,in the scientific sense of the word,is a measure of the force that gravity exerts on an object,pulling it downward. Equivalently,the weight of an object is the amount of force that you must exert to hold the object up,balancing the downward force of gravity. Weight is not the same thing as mass,which is a measure of the amount of “stuff” in an object. -
A Review on Thermoelectric Generators: Progress and Applications
energies Review A Review on Thermoelectric Generators: Progress and Applications Mohamed Amine Zoui 1,2 , Saïd Bentouba 2 , John G. Stocholm 3 and Mahmoud Bourouis 4,* 1 Laboratory of Energy, Environment and Information Systems (LEESI), University of Adrar, Adrar 01000, Algeria; [email protected] 2 Laboratory of Sustainable Development and Computing (LDDI), University of Adrar, Adrar 01000, Algeria; [email protected] 3 Marvel Thermoelectrics, 11 rue Joachim du Bellay, 78540 Vernouillet, Île de France, France; [email protected] 4 Department of Mechanical Engineering, Universitat Rovira i Virgili, Av. Països Catalans No. 26, 43007 Tarragona, Spain * Correspondence: [email protected] Received: 7 June 2020; Accepted: 7 July 2020; Published: 13 July 2020 Abstract: A thermoelectric effect is a physical phenomenon consisting of the direct conversion of heat into electrical energy (Seebeck effect) or inversely from electrical current into heat (Peltier effect) without moving mechanical parts. The low efficiency of thermoelectric devices has limited their applications to certain areas, such as refrigeration, heat recovery, power generation and renewable energy. However, for specific applications like space probes, laboratory equipment and medical applications, where cost and efficiency are not as important as availability, reliability and predictability, thermoelectricity offers noteworthy potential. The challenge of making thermoelectricity a future leader in waste heat recovery and renewable energy is intensified by the integration of nanotechnology. In this review, state-of-the-art thermoelectric generators, applications and recent progress are reported. Fundamental knowledge of the thermoelectric effect, basic laws, and parameters affecting the efficiency of conventional and new thermoelectric materials are discussed. The applications of thermoelectricity are grouped into three main domains. -
Chapter 7 Electricity Lesson 2 What Are Static and Current Electricity?
Chapter 7 Electricity Lesson 2 What Are Static and Current Electricity? Static Electricity • Most objects have no charge= the atoms are neutral. • They have equal numbers of protons and electrons. • When objects rub against another, electrons move from the atoms of one to atoms of the other object. • The numbers of protons and electrons in the atoms are no longer equal: they are either positively or negatively charged. • The buildup of charges on an object is called static electricity. • Opposite charges attract each other. • Charged objects can also attract neutral objects. • When items of clothing rub together in a dryer, they can pick up a static charge. • Because some items are positive and some are negative, they stick together. • When objects with opposite charges get close, electrons sometimes jump from the negative object to the positive object. • This evens out the charges, and the objects become neutral. • The shocks you can feel are called static discharge. • The crackling noises you hear are the sounds of the sparks. • Lightning is also a static discharge. • Where does the charge come from? • Scientists HYPOTHESIZE that collisions between water droplets in a cloud cause the drops to become charged. • Negative charges collect at the bottom of the cloud. • Positive charges collect at the top of the cloud. • When electrons jump from one cloud to another, or from a cloud to the ground, you see lightning. • The lightning heats the air, causing it to expand. • As cooler air rushes in to fill the empty space, you hear thunder. • Earth can absorb lightning’s powerful stream of electrons without being damaged. -
Mechanical Energy Kinetic Energy 1 2 Ek = 2 Mv Where Ek Is Energy (Kg-M2/S2) V Is Velocity (M/S) Gravitational Potential Energy
Mechanical Energy Kinetic Energy 1 2 Ek = 2 mv where Ek is energy (kg-m2/s2) v is velocity (m/s) Gravitational Potential Energy Eg = W = mgz where w is work (kg-m2/s2) m is mass (kg) z is elevation above datum Pressure of surrounding fluid (potential energy per unit volume) Total Energy (per unit volume) 1 2 Etv = 2 r v + r gz + P Total Energy (per unit mass) or Bernoulli equation 1 P 2 Etm = 2 v + gz + r For a incompressible, frictionless fluid v2 P 2g + z + r g = constant This is the total mechanical energy per unit weight or hydraulic head (m) Groundwater velocity is very low, m/yr, so kinetic energy can be dropped 2 P h = z + r g Head in water of variable density hf = (r p/r f)hp where hp = pressure head hf = freshwater head Force Potential P F = gh = gz + r Darcy's Law dh KA dF Q = -KA dl = - g dl Applicability of Darcy's Law (Laminar Flow) r vd R = m < 1 where v = discharge velocity (m/s) d = diameter of passageway (m) R = Reynold's number Specific Discharge (Darcy Flux) and Average Linear Velocity Q dh v = A = -K dl Q K dh v = = - x neA ne dl 3 Equations of Ground-Water Flow Confined Aquifers Flux of water in and out of a Control Volume ¶ inMx = r wqxdydz; outMx = r wqxdydz + ¶x (r wqx) dx dydz; ¶ netMx = - ¶x (r wqx) dx dydz ¶ netMy = - ¶y (r wqy) dy dxdz ¶ netMz = - ¶z (r wqz) dz dxdy ¶ ¶ ¶ netMflux = - ( ¶x (r wqx) + ¶y (r wqy) + ¶z (r wqz) ) dxdydz From Darcy's Law ¶h ¶h ¶h qx = - K ¶x qy = - K ¶y qz = - K ¶z and assuming that w and K do not vary spatially ¶2h ¶2h ¶2h M = K + + r dxdydz net flux ( ¶x2 ¶y2 ¶z2 ) w Note hydraulic head and hydraulic conductivity are easier to measure than discharge. -
3. Energy, Heat, and Work
3. Energy, Heat, and Work 3.1. Energy 3.2. Potential and Kinetic Energy 3.3. Internal Energy 3.4. Relatively Effects 3.5. Heat 3.6. Work 3.7. Notation and Sign Convention In these Lecture Notes we examine the basis of thermodynamics – fundamental definitions and equations for energy, heat, and work. 3-1. Energy. Two of man's earliest observations was that: 1)useful work could be accomplished by exerting a force through a distance and that the product of force and distance was proportional to the expended effort, and 2)heat could be ‘felt’ in when close or in contact with a warm body. There were many explanations for this second observation including that of invisible particles traveling through space1. It was not until the early beginnings of modern science and molecular theory that scientists discovered a true physical understanding of ‘heat flow’. It was later that a few notable individuals, including James Prescott Joule, discovered through experiment that work and heat were the same phenomenon and that this phenomenon was energy: Energy is the capacity, either latent or apparent, to exert a force through a distance. The presence of energy is indicated by the macroscopic characteristics of the physical or chemical structure of matter such as its pressure, density, or temperature - properties of matter. The concept of hot versus cold arose in the distant past as a consequence of man's sense of touch or feel. Observations show that, when a hot and a cold substance are placed together, the hot substance gets colder as the cold substance gets hotter. -
Work, Power, & Energy
WORK, POWER, & ENERGY In physics, work is done when a force acting on an object causes it to move a distance. There are several good examples of work which can be observed everyday - a person pushing a grocery cart down the aisle of a grocery store, a student lifting a backpack full of books, a baseball player throwing a ball. In each case a force is exerted on an object that caused it to move a distance. Work (Joules) = force (N) x distance (m) or W = f d The metric unit of work is one Newton-meter ( 1 N-m ). This combination of units is given the name JOULE in honor of James Prescott Joule (1818-1889), who performed the first direct measurement of the mechanical equivalent of heat energy. The unit of heat energy, CALORIE, is equivalent to 4.18 joules, or 1 calorie = 4.18 joules Work has nothing to do with the amount of time that this force acts to cause movement. Sometimes, the work is done very quickly and other times the work is done rather slowly. The quantity which has to do with the rate at which a certain amount of work is done is known as the power. The metric unit of power is the WATT. As is implied by the equation for power, a unit of power is equivalent to a unit of work divided by a unit of time. Thus, a watt is equivalent to a joule/second. For historical reasons, the horsepower is occasionally used to describe the power delivered by a machine.