Heating And Cooling Van Nuys are about raising and lowering the temperature inside homes and buildings. This can be done using central systems that heat and cool many rooms or by electric space heaters.
Students investigate how heating and cooling can cause changes in matter. They watch an animation showing how heating butter causes the molecules to move faster and come apart and then see how cooling butter makes them move slower and connect again.
Heat transfer is the exchange of thermal energy (heat) between physical objects. There are three primary methods of heat transfer: conduction, convection and radiation. Engineers consider all three mechanisms of heat transfer when designing systems for heating and cooling buildings and other structures like ductwork, water heaters and solar panels.
When two objects that are at different temperatures come into contact, heat transfers from the warmer to the cooler object until the temperature of the bodies are identical, a state called thermal equilibrium. Heat transfer can occur at a microscopic level between molecules in solids and at a bulk level in liquids or gases.
The process of heat transfer can happen slowly, such as when a pot of hot water cools down in the sink. It can also happen rapidly, such as when a wood fire warms up your house. The speed at which heat moves through a system depends on the temperature difference and the materials used in construction.
A metal is a good conductor of heat because it has a high thermal coefficient. This means that heat flows through the metal easily, but it does not flow as quickly through a plastic cup. Heat flow can also depend on the size of the objects involved and their relative positions in relation to each other.
Convection is the dominant mode of heat transfer in liquids and gases. In this case, the heat is transferred from the hotter to the colder material because heated liquids and gases expand more than their cooler counterparts. This expansion causes the atoms and molecules to move faster, which results in vibrations of the fluid that carries them.
This kinetic energy is emitted as electromagnetic waves, or radiant heat. Radiation can take place across a vacuum or through a transparent medium such as air or glass.
Engineers use their knowledge of heat transfer to make buildings more energy efficient and sustainable. They also optimize the use or dissipation of heat in products such as cell phones, heavy machinery and cars. The thermal characteristics of materials, including their conductivity, viscosity and surface area, are considered to determine how well they will function in a system.
Convection is the bulk, macroscopic flow of heat from a hot to a cool region. This is a separate process from the microscopic transfer of energy between atoms involved in conduction. Convection occurs in liquids and gases (fluids) on a larger scale than conduction, and is the mechanism of heat transfer for a large part of the Earth’s atmosphere, oceans, and planetary mantles. On even larger scales, the movement of gas and dust in the accretion disks of black holes is thought to be driven by convection.
Convective heating and cooling takes place in a pot of boiling water, for example. As the water heats, molecules in the heated portion of the pot vibrate faster than those in the cooler portion of the pot. This causes the warmer molecules to spread out, making them less dense. Since a fluid rises according to its density, this allows the hotter portion of the water to rise and be replaced by colder water that has been drawn up into it by buoyancy. This process continues as long as there is a temperature difference between the two regions of the liquid or gas.
Natural convection is responsible for much of the global circulation in the atmosphere, oceans, and planetary mantles, as well as for some weather phenomena such as fog and storm clouds. The movement of wind over the surface of the Earth is also due to convection. Warm air over land typically rises while cool air sinks, and this creates the large prevailing winds that affect our weather.
The physics behind convection is based on thermal expansion. When a fluid is heated from below, the lower layers of the fluid become less dense as the molecules expand to fill more space. This makes them float above the denser, colder upper layer of the fluid. As the hotter, less dense fluid rises it loses heat to the colder surrounding water and eventually descends again. This cycle can repeat as many times as needed.
The resulting convection cells can take on an almost geometric form, with the up- and down-moving portions of the fluid often forming stripes or hexagons in shape. If the number of the fluid increases, however, this symmetry breaks down and the convection cell tends to be more chaotic in appearance.
Radiation is energy in the form of waves or particles that travel through space. All objects give off radiation, and it is one of the main ways heat is transferred from one object to another. The type of radiation that is emitted from an object depends on the temperature of the object. Radiation can take the form of radio waves, visible light, X-rays and ultraviolet radiation. Radiation is also used for medical diagnostic imaging tests such as X-rays and CT scans.
All matter is made of tiny particles called atoms. The nucleus of an atom has a positive electrical charge, while its outer layer contains negative electrons. Forces within the atom work toward a balance of these charges, but sometimes the nucleus or electrons may have too much energy. When the atoms have too much energy, they give off a portion of it in the form of radiation. Radiation can be classified as ionizing or non-ionizing, depending on how much energy it carries.
Ionizing radiation is capable of breaking molecular bonds and removing electrons from atoms. This makes it able to cause chemical changes in living cells. Ionizing radiation is found naturally in some materials such as radon gas, X-rays and cosmic rays. However, ionizing radiation is also produced by man-made sources such as nuclear reactors, medical X-ray machines and nuclear medicine studies.
Thermal radiation, on the other hand, does not carry enough energy to ionize atoms or break chemical bonds. This type of radiation deposits its energy in the material that is absorbing it, raising the temperature of the material. Thermal radiation also radiates heat in all directions, unlike X-rays which are directional.
Radiation is the source of the heat we feel when standing in front of a stove or fireplace, and it is the reason we can see our shadows on a wall when sitting in the sun. We are also subjected to a natural amount of radiation on a daily basis, most of which comes from the sun and the ground. In general, the higher the surface temperature of an object, the more it will radiate.
Ventilation refers to the intentional movement of clean air into a space and stale air out of it. It may be done through natural or mechanical means. Ventilation systems are the heart of your home’s heating, ventilation and air conditioning (HVAC) system. They are what keeps you feeling warm and cozy in the winter and cool and comfortable in the summer. They are also the systems that filter and clean indoor air to keep you healthy and your humidity levels at optimal comfort levels.
Ventilation works through convection, radiation and perspiration. As hot air rises, it absorbs heat from walls and ceilings in your home. This heat is then transferred to objects in the room and the cooling process begins. Ventilation increases the speed at which this heat moves and makes it easier for cooler air to flow past your body.
Natural ventilation is controlled by outdoor climatic conditions and the thermal properties of the building and its enclosure. It is a stochastic process, and varies as environmental conditions change. The air-change rate can be uncomfortably high or stagnant in some areas, and the direction of the flow can be difficult to control. The flow of stale air can also carry contaminants such as lead and other hazardous materials from nearby sources.
The air-flow rates of naturally ventilated buildings can be increased by designing the building envelope to provide a higher porosity and by providing inlet ventilation through vents, louvers and other openings that are integrated into the building design. This allows for the natural driving forces of wind and temperature differences to overcome the resistance of building surfaces. However, a building’s thermal properties and occupant behavior may make these methods impractical or undesirable.
Intentional ventilation can be achieved by using fans to move the air through the building. These can be supplied by external air or from the internal spaces of the building itself. Increasing the supply of fresh air through these means can reduce pollutants and humidity levels, and can also increase energy efficiency by reducing the load on the heating and cooling systems. This approach is also more effective than relying on passive means of ventilation alone to improve the quality of indoor air.