The purpose of this glossary is that the new concepts that we are learning throughout the subject are as clear as possible.
Boundary conditions
Noun
The solution to a heat conduction problem depends of the conditions at the surfaces, and the mathematical expressions for the thermal conditions at the boundary are called boundary conditions.
Example: In order to fully describe a heat transfer problem, two boundary conditions must exist for each direction of the coordinate system along which heat transfer is significant. Therefore, you need to specify two boundary conditions for one-dimensional problems, four for two-dimensional problems, and six for three-dimensional ones. For example, in the case of the wall of a house, you need to specify the conditions in two places (the interior and exterior surfaces) since, in this case, the heat transfer is one-dimensional. But in the case of a parallelepiped, you need to specify six boundary conditions (one on each face) when heat transfer is significant in all three dimensions.
ko: condiciones de frontera
Emissivity
Noun
The emissivity whose value is in The interval (electrical permittivity is between 0 and 1), is a measure of how close a surface is to being a black body, for which electrical permittivity is equal to 1.
Example: In many practical applications, Surface and incident radiation source temperatures are of the same order of magnitude, and the average absorptivity of a surface is considered equal to its average emissivity.
ko: Emisividad
Energy balance
Noun
An energy balance is a consideration of the energy input, output, and consumption or generation in a process or stage.
Example: 1. In establishing an energy balance, all sources of thermal energy are put on the input side, and all items of heat utilization on the output side.
2. When determining an energy balance, you need to know what energy is being transferred in and out of the system.
3. An energy balance is a consideration of the energy input, output, and consumption or generation in a process or stage.
ko: Balance de energía
Heat conduction equation
Noun
Heat conduction is said in a medium is stationary (or stable) when the temperature
does not vary with time and is not stationary or transient when yes you have this variation. Heat conduction in a medium is one-dimensional when conduction is significant only in one dimension and negligible in the other two dimensions. It is said to be two-dimensional when conduction in the third dimension it is negligible and three-dimensional when driving in all dimensions is significant.
Example: The heat conduction equation can be obtained by perform an energy balance on a differential element of volume. The one-dimensional heat conduction equation in rectangular, cylindrical and spherical coordinate systems, for the case of constant thermal conductivities, express as: (shown in the picture).
ko: Ecuación de conducción de calor.
Heat flux
Heat is a verb and can also act as a noun.
Heat flow is defined as the heat transfer per unit time per unit area, that is, the rate of heat transfer per unit of area.
Example: A heat flow meter attached to the inside surface of a refrigerator door that is 3 cm thick indicates that you have a flow of 25 W / m2 through that door. Also, interior surface temperatures are measured and outside of the door and turn out to be 7 ° C and 15 ° C, respectively. Determine the average thermal conductivity of the refrigerator door. Response: 0.0938 W / m ° C
ko: Flujo de calor
Heat generation
Noun
In a medium through which heat is transferred, the conversion of mechanical, electrical, nuclear or chemical energy into heat (or thermal energy). In the analysis of heat conduction, these conversion processes are characterized as generation of heat (or thermal energy).
Example: For example, the temperature of a wire resistor rises rapidly when an electric current passes through it, as a result of the electrical energy that is being converted into heat.
Initial condition
Noun
Is called the initial condition, which is a mathematical expression for the temperature distribution in the medium, initially
Example: An initial condition is needed for a heat conduction problem, regardless of dimension, since the equation of conduction is of the first order in time (contains the first derivative
temperature versus time). In rectangular coordinates, the initial condition can be specified in the general form as shown in the equation.
ko: Condición inicial
Insulation
Noun
Isolation reduces the transfer of heat but does not eliminate it in its entirety, unless its thickness is infinite. However, heat transfer through a properly insulated surface can be taken as zero, since proper insulation reduces heat transfer through a surface to negligible levels. Therefore, a well-insulated surface can be thought of as one with a specific heat flux of zero.
Example: adding more insulation to a wall or attic always decreases heat transfer. The thicker the insulation, the lower it is the reason for the heat transfer. This is foreseeable since area A of heat transfer is constant and adding insulation always increases the thermal resistance of the wall without increasing the resistance to convection.
ko: Aislamiento
Internal energy
Noun
The sum of all microscopic forms of energy is called internal energy of a system and is denoted by U (or u in terms of unit mass).
Example: Internal energy can be considered as the sum of the kinetic energies and potential of molecules. The part of the internal energy of a system that is associated with the kinetic energy of molecules is known as energy sensible or sensible heat. The average speed and degree of activity of molecules are proportional to temperature. Consequently, at higher temperatures, the molecules have higher kinetic energy and, as a result, the system has a higher internal energy as well. Internal energy is also associated with the forces exerted on each other by the molecules of a system.
ko: Energía interna
Specified temperature
Noun
The specific temperature boundary condition is the most Simple one of this kind to deal with.
Example: For a one-dimensional heat transfer through a planar wall of thickness L, the specific temperature boundary conditions on both the left and the left surface right, they can be expressed as shown in the figure.
ko: Temperatura especifica
Steady
Is a verb and can also act as a noun, an adjective, an adverb, and an exclamation.
The term stationary means no change over time in a location specific.
Example: Heat transfer through the walls of a house will be stationary when conditions in the inside it and outside remain constant for several hours.
ko: Estacionario
Thermal conductivity
Noun
the thermal conductivity of a material can be defined as the rate of heat transfer to through a unit thickness of the material per unit area per unit of temperature difference.
Example: The thermal conductivity of a material is a measure of the material's ability to conduct heat. A high value for thermal conductivity indicates that the material is a good conductor of the heat and a low value indicates that it is a poor conductor or that it is an insulator.
ko: Conductividad térmica
Thermal diffusivity
Noun
the thermal diffusivity of a material can be conceived as the ratio between the heat conducted through the material and the heat stored per unit volume.
Example: A material that has a high thermal conductivity or a low heat capacity it has a great thermal diffusivity. The higher the thermal diffusivity, faster is the propagation of heat towards the medium. A small value of the Thermal diffusivity means that, for the most part, heat is absorbed by the material and a small amount of that heat will be conducted further.
ko: Difusividad térmica
Thermal symmetry
Noun
Some heat transfer problems have thermal symmetry such as result of symmetry in imposed thermal conditions.
Example: For instance, the two surfaces of a large hot plate, of thickness L, suspended vertically in the air, will be subject to the same thermal conditions and, therefore Therefore, the temperature distribution in one of its halves will be equal to that of the other half. That is, the heat transfer on this plate will possess thermal symmetry with respect to the central plane in x L / 2.
ko: Simetría térmica
Transient
It can act as a noun and an adjective.
Transient implies variation with time or dependence with respect to time.
Example: Cooling an apple in a refrigerator is a transitory process of heat transfer, since the
temperature at any fixed point within that block will change with the time while cooling occurs. During heat transfer transient, the temperature normally varies both with time and with
position.
