The power selection of electric heater is to meet the heat generation required by the heating medium, which is the first choice to ensure that the heater can achieve heating purposes and normal operation.
Since the thermal efficiency of electric heating is approximately 1, it can be considered that the power of the electric heater is the heat generation.
1. Consideration of power selection
The following three items should be considered in the choice of power calculation:
(1) From the initial state, realize the heating medium to the set temperature (working temperature) according to the specified time requirements;
(2) Under working conditions, the heat generation is sufficient to maintain the temperature of the medium;
(3) There should be a certain safety margin, generally take 1.2.
Obviously, the greater power selected from clauses (1) and (2) is the power to be selected by the safety margin.
2, the calculation of the power required for heating from the initial state
(1) Static fluid heating
(2) Flow fluid heating
(3) Air duct heater atmospheric air heating
In the above three formulas
P-meter - the power required for the electric heater (KW);
Q dispersion - the amount of heat dissipation (KW) of the container at the set temperature;
Generally there is
C1 — specific heat of the heated medium. (Kcal/(kg·℃)
C2 — specific heat of the container (system). (Kcal/(kg·℃)
M1 — mass of the medium being heated. (Kg);
M2 — container (system) mass (Kg);
ΔТ — the difference between the set temperature and the initial temperature. (℃);
t — the time from the initial temperature to the specified time of the set temperature. (h);
F — flow rate of heating medium, (generally take the maximum flow). (m /min);
S — heat dissipation area. (m2) ;
Q loss — (insulation) The amount of heat loss per unit area of the material at a set temperature. (Kwh/m )
3. Calculation of the power required to maintain the temperature of the medium
In the formula:
P-dimensional — The power required by the electric heater to maintain the temperature of the medium. (KW)
M1 increase — increased media mass per hour. (Kg/h)
Knowledge Development:
Electric air heaters are mainly used to heat the required air flow from the initial temperature to the required air temperature, up to 850°C. It has been widely used in aerospace, ordnance industry, chemical industry and colleges and universities and many scientific research and production laboratories. It is especially suitable for automatic temperature control and high flow high temperature combined system and accessory test. Air electric heater has a wide range of use: it can heat any gas, and the hot air produced is dry and waterless, non-chemically corrosive, non-polluting, non-conductive, non-combustible, non-explosive, safe and reliable, and the heated space heats up quickly (controllable).
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