The power of the electric heater is selected to meet the heating value required by the heating medium, and it is the first choice to ensure that the heater can achieve the heating purpose and operate normally.
Since the thermal efficiency of electric heating is close to 1, it can be considered that the power of the electric heater is the amount of heat.
1, the consideration of power selection
The calculation and selection of power should consider the following three:
⑴ From the initial state, realize the heating medium to the set temperature (working temperature) according to the specified time;
⑵ Under working conditions, the calorific value is sufficient to maintain the temperature of the medium;
⑶ There should be a certain safety margin, generally 1.2.
Obviously, choose the larger power from Article ⑴ and ⑵, and multiply it by the safety margin to get the power that should be selected.
2. Calculation of the power required for heating from the initial state
(1) Static fluid heating
(2) Flowing fluid heating
(3) Atmospheric air heating by duct heater
In the above three formulas
P meter-power required by electric heater (KW);
Q scattered-the heat dissipation of the container at the set temperature (KW);
Generally have
C1 — Specific heat of the heated medium. (Kcal/(kg·℃)
C2 — Specific heat of container (system). (Kcal/(kg·℃)
M1 — The mass of the heated medium. (Kg);
M2 — container (system) mass (Kg);
ΔТ — The difference between the set temperature and the initial temperature. (℃);
t — the time required to heat the medium from the initial temperature to the set temperature. (h);
F-heating medium flow rate, (usually the maximum flow rate). (m /min);
S — heat dissipation area. (m2);
q Loss — (Insulation) The amount of heat loss per unit area of the material at the set temperature. (Kwh/m)
3. Calculation of the power required to maintain the temperature of the medium
Where:
P dimension-the power required by the electric heater to maintain the temperature of the medium. (KW)
M1 increase-the medium mass increased per hour. (Kg/h)
