Heat travels by radiation, conduction and convection. Where there is no medium for heat to travel through, such as the heat from the sun moving through space, heat travels by radiation. When heat enters a medium or strikes an object or substance, it travels by either conduction or convection.Know More
When heat travels by radiation through a vacuum, it is carried by subatomic particles moving in the form of electromagnetic waves. When an electromagnetic wave hits an object or substance, it transfers energy to its molecules. The molecules become excited by the transfer of energy and begin moving faster. This causes the object or substance to increase in temperature. An example of heat transfer by radiation is the energy from the sun reaching the Earth's atmosphere after traveling through space as waves. When those waves strike and excite the molecules of the gases in the Earth's atmosphere, the excited and vibrating molecules cause the air to warm.
In conduction, heat travels across molecules in a solid substance or between two substances by direct contact between them. Because the molecules are in direct contact with each other, vibrating molecules cause adjacent molecules to also vibrate.
Convection refers to the transfer of heat energy in liquids and gases in contact with each other. Unlike solids, the molecules in liquids and gases are not held in place tightly and can move about. This enables heat to move across and between liquids and gases by an actual transfer of excited molecules from a location of higher excitation to another of lesser vibration until a uniform temperature is achieved. For example, pouring cold water into hot water will result in a uniform temperature which is somewhere between the two original hot and cold extremes.Learn more about Thermodynamics
Although absorption rates vary from one type of radiation to the next, dark exteriors—especially black, matte surfaces—are particularly good absorbents of infrared radiation. Infrared radiation is heat radiation that travels by way of electromagnetic waves.Full Answer >
Styrofoam keeps things cold because it is made from polystyrene, a substance known for its low thermal conductivity, which is its ability to transfer heat. Styrofoam also uses millions of microscopic air bubbles as insulation to slow the progress of heat.Full Answer >
Everything in the universe that is above absolute zero gives off heat. Only a hypothetical substance that is perfectly ordered having zero enthalpy and entropy at absolute zero and whose atoms are stationary gives off no heat.Full Answer >
The overall heat transfer coefficient represents the total resistance experienced as heat is transferred between fluids or between a fluid and a solid. The overall heat transfer coefficient is calculated by dividing heat flux by the temperature difference between the two materials where heat is being transferred.Full Answer >