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Brief description of thermal design of power adapter
Add time:2019-05-28    Click:720
1) Wen Sheng
Temperature rise refers to the difference between the temperature of the power adapter and the ambient temperature. If the non-linear effect of temperature change on objects in the air is neglected, the approximate temperature of the power adapter at the highest possible ambient temperature can be obtained by directly adding the temperature rise measured at the general ambient temperature to the maximum possible ambient temperature. For example, when the temperature of a power adapter is measured to be 40 C, the temperature of the adapter will be 95 C at the highest ambient temperature of 55 C.
2) heat consumption
Heat consumption refers to the heat generated by the power adapter during normal operation. Heat consumption is not equal to power consumption, which refers to the input power of the power adapter. Generally, the efficiency of power adapters is relatively low, and most of the power is converted into heat. When calculating the temperature rise of power adapter, the heat consumption should be calculated according to its power consumption and efficiency. When only the approximate power consumption is known, the heat consumption can be regarded as equal to the power consumption for low-power equipment and 75% for high-power equipment. In order to leave a margin for design, power consumption is sometimes used directly.

3) Heat flux
Heat flux density refers to the heat transfer per unit area of power adapter, which is W/m2.
4) Volume power density
Volume power density refers to the heat flux per unit volume of power adapter, which is W/m3.
5) thermal conductivity
The thermal conductivity coefficient is a parameter to characterize the thermal conductivity of materials. It shows the thermal conductivity per unit time, per unit area and at a negative temperature gradient, in units of W/(m.K) or W/(m.C).
6) Convection heat transfer coefficient
Convective heat transfer coefficient reflects the intensity of convective heat transfer process between two media. It shows that when the temperature difference between the fluid and the wall is 1 C, the heat passing through the unit area in unit time is W/(m2.K) or W/(m2.C).
7) blackness
The blackness represents the degree to which the radiation force of the object is close to the absolute blackbody radiation force. It is the ratio of the radiation force of the actual object to the radiation force of the blackbody at the same temperature, between 0 and 1. It depends on the type of object, surface condition, surface temperature and surface color. Rough surface, no luster, the blackness is large, radiation heat dissipation ability is strong. Blackness is generally expressed in terms of epsilon, no unit.
8) Thermodynamics
Thermodynamics studies the thermal equilibrium state of matter and determines the total heat required for the system to change from one equilibrium state to another.
9) Heat Transfer Science
Heat transfer studies the transfer rate of energy, which is an extension of thermodynamics. The problem of heat transfer must be solved based on thermodynamics and heat transfer.
10) Thermal Convection
Heat convection refers to the heat exchange of fluid caused by relative displacement of particles. The displacement of natural convective particles is caused by the density difference inside the fluid, which makes the light floating and the heavy sinking.
11) Thermal radiation
Thermal radiation refers to the transfer of electromagnetic wave in space due to the heat (temperature difference). Thermal radiation is not only energy transfer, but also accompanied by the transfer of energy form. Radiation heat transfer does not need any medium as a medium and can be propagated in vacuum.
12) thermal resistance
Thermal resistance refers to the resistance of heat on the heat flow path. It is generally expressed by R, i.e. R=t/Q, in units of (?) C/W.
13) Characteristic size
Characteristic dimension refers to the geometrical dimension representing the hot surface in the convective heat transfer criterion number, which is generally expressed in D and in M.
14) Reynolds number
This number reflects the ratio of inertia force to viscous force in fluid flow. It is a similar criterion for describing fluid flow pattern. It is generally expressed by Re and has no unit.
15) Plante number
This number is a similar criterion for explaining the effect of fluid physical properties on heat transfer. It is generally expressed in Pr and has no unit.
16) Grashov Number
This number reflects the relative magnitude of buoyancy and viscous force on the fluid. It is a similar criterion for describing the intensity of natural convection heat transfer. Generally, it is expressed by Gr and has no unit.


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