PHYSICS PROJECT TOPIC: HEAT TRANSFER NAME: MALEIK WRIGHT GRADE 11O TEACHER: A. TIMOLL SUBJECT: PHYSICS TABLE OF CONTENTS WHAT IS HEAT TRANSFER? 1 METHODS OF HEAT TRANSFER CONDUCTION CONVECTION RADIATION 2 3 4 FACTORS AFFECTING: ABSORPTION RADIATION 5 6 GOOD AND BAD ABSORBERS OF HEAT 7-8 EMITTERS OF HEAT 9-10 PRINCIPLES OF THERMAL ENERGY TRANSFER TO: 11-12 SOLAR PANEL VACCUM FLASK GREENHOUSE EFFECT (CO2 AND GLOBAL WARMING) REFERENCES 13 WHAT IS HEAT TRANSFER? Heat transfer is defined as the movement of heat across the border of the system due to a difference in temperature between the system and its surroundings. CONDUCTION Conduction is defined as the process of transmission of energy from one particle of the medium to another with the particles being in direct contact with each other. An area of higher kinetic energy transfers thermal energy towards the lower kinetic energy area. High-speed particles clash with particles moving at a slow speed, as a result, slow-speed particles increase their kinetic energy. CONVECTION Convection is the movement of particles through a substance, transporting their heat energy from hotter areas to cooler areas. An example of convection include: Boiling of water, that is molecules that are denser move at the bottom while the molecules which are less dense move upwards resulting in the circular motion of the molecules so that water gets heated. RADIATION In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or a material medium. When a person positions their hands in proximity to the fire, their skin absorbs this infrared radiation, resulting in an increase in skin temperature and the sensation of warmth. This process continues until there is thermal equilibrium, at which point the person's hands reach a temperature consistent with their surroundings. FACTORS AFFECTING ABSORPTION OF HEAT Heat energy is dependent on mass, specific heat, and changes in the temperature of the body: Mass: The larger the surface area, the more heat can be absorbed. For example, a broad metal sheet exposed to sunlight will absorb more heat than a small metal object of the same material. Temperature: The quantity of heat energy is directly proportional to the rise in temperature. If a body is initially at a lower temperature than its surroundings or a heat source, it will absorb heat from those sources and gradually increase in temperature. As a body absorbs heat, it will continue to rise in temperature until it reaches a state of thermal equilibrium. This means that the body's temperature will stabilize when it is in balance with its surroundings, and there is no net heat transfer. Specific Heat: A substance with a high specific heat will experience a smaller temperature increase for a given amount of heat input, while a substance with a low specific heat will experience a greater temperature increase. FACTORS AFFECTING RADIATION The hotter the temperature of an object the more radiation emitted. If the color of an object is black, more radiation is emitted, but if the object is white, less radiation will be emitted. The surface area of the object (greater surface area = more area for radiation to be emitted from) GOOD AND BAD ABSORBERS OF HEAT A good absorber of heat is a material or surface that efficiently absorbs and retains thermal energy when exposed to heat sources or thermal radiation. A poor absorber of heat is a material or surface that is less efficient at absorbing and retaining thermal energy when exposed to heat sources or thermal radiation. Good Absorbers of Heat Poor Absorbers of Heat Dark-colored materials Light-colored materials Rough or matte surfaces Smooth or polished surfaces Materials with high thermal conductivity Materials with low thermal conductivity Common examples: asphalt, blackened metal, water, and wood Common examples: polished metal, glass, and some plastics Efficiently absorb and retain heat Less efficient at absorbing and retaining heat Often used in heating systems, cooking, and solar Used in applications where heat retention is not panels desirable EMITTERS OF HEAT A heat emitter is any product that sends out heat. Heat emitters are used to distribute heat around an area to maintain required set points within spaces. Examples include: 1. Radiators: Radiators use convection and radiation to heat spaces. They're cost-effective and easy to install but may not work efficiently with renewable energy sources like heat pumps and solar. 2. Warm Air Heaters: These systems heat air with a burner or heating elements and use fans to distribute it. They're less common in the UK and are generally less efficient due to the air’s lower heat capacity. 3. Radiant Heating: Radiant heating emits infrared energy that warms objects and occupants directly. It's efficient, provides instant heat, and reduces temperature differences. It's suitable for commercial spaces with higher ceilings. 4. Underfloor Heating: Provides consistent thermal comfort but is expensive to install and slow to respond to changing heat demands. It's well-suited for renewable heat sources and can significantly improve heat pump efficiency. 5. Electrical Space Heaters: These heaters provide localized heat and are quick to warm up rooms. They have low capital and installation costs but can be expensive to run. PRINCIPLES OF HEAT TRANSFER TO: SOLAR PANELS: Solar thermal systems harness the sun's energy and convert it into heat, typically using solar collectors like solar panels or solar tubes. This heat is then transferred to a building's heating system, providing hot water and space heating. It's an eco-friendly and renewable energy source that can help reduce reliance on conventional heating methods, thereby saving energy and reducing greenhouse gas emissions. VACCUM FLASK: A vacuum flask or a thermos works by using a combination of vacuum insulation, reflective surfaces which reflect the radiant heat back into the flask, preventing it from escaping, and sealed construction to minimize heat transfer through conduction, convection, and radiation. This design allows the flask to maintain the temperature of its contents, keeping them hot or cold for an extended period. The Earth receives energy from the sun in the form of visible light. This energy passes through the Earth's atmosphere and warms the surface.. It emits heat in the form of infrared radiation. Greenhouse gases, like CO2, trap some of this heat, preventing it from escaping into space. This trapped heat contributes to the greenhouse effect, which keeps our planet habitable. However, human activities have increased greenhouse gas levels, intensifying this effect and causing global warming. REFERENCES https://news.climate.columbia.edu/2021/02/25/carbon-dioxide-cause-globalwarming/#:~:text=As%20CO2%20soaks%20up%20this,' https://byjus.com/question-answer/p-name-the-3-factors-affecting-the-radiated-energy-bythe-hot-body-p/ https://www.metoffice.gov.uk/weather/learn-about/weather/how-weather-works/what-isconvection#:~:text=Convection%20is%20the%20movement%20of,another%20upon%20c ontact%2C%20transferring%20heat. https://byjus.com/physics/heat-transfer-conduction-convection-and-radiation/ http://energy.asu.edu.jo/index.php/r-d/solar-thermalsystems#:~:text=The%20basic%20principle%20of%20solar,hot%20water%20and%20spa ce%20heating.
