Calculation of total power selection of electric heater
The electric heater chooses the power to meet the heating requirement of the heating medium. It is the first choice to ensure the heating of the heater and the normal operation.
Since the thermal efficiency of electric heating is approximately 1, we can say that the power of an electric heater is calorific.
1, the power options are considered
The power calculation options should consider the following three:
From the initial state, according to the provisions of the time requirements of the heating medium to set temperature (temperature);
In the condition of heat to maintain the temperature of the medium;
It should have a certain safety margin, generally 1.2.
Obviously, from the first, the choice of a greater power, multiplied by the safety margin is elected power.
2, the calculation of the power required for heating from the initial state
(1) static fluid heating
(2) flow fluid heating
(3) the air duct heater is heated by atmospheric air
In the above three formulas
P meter - the power required for an electric heater (KW);
Q dispersion - the heat dissipation of the vessel at the set temperature (KW);
C1 - specific heat of a heated medium (Kcal/ (kg DEG C)
C2 - specific heat of a container (system) (Kcal/ (kg DEG C)
M1 - the quality of the heated medium. (Kg);
M2 - container (system) quality (Kg);
T71 - a set temperature and the initial temperature difference (c);
T - the time from the initial temperature to the setting temperature of the heating medium (H);
F - heating medium flow (usually taking maximum flow). (m, /min);
S - heat dissipation area. (M2);
Q loss - thermal loss of material per unit area at setting temperature (Kwh/m)
3. the calculation of the power required to maintain the medium temperature
P dimensional electric heater to maintain the medium temperature required power (KW)
M1 increase - the quality of media added per hour. (Kg/h)