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Explosion-proof electric heater is a device that converts electrical energy into thermal energy to heat the required materials. Its design has low surface power load and adopts multiple protections, greatly increasing the safety and lifespan of the explosion-proof electric heater. And according to requirements, through the circuit design of the explosion-proof electric heater, it can conveniently achieve active control of parameters such as outlet temperature, flow rate, and pressure, with significant energy-saving results, and almost 100% of the heat generated by electricity is transferred to the heating medium.
How to choose a suitable explosion-proof electric heater, first consider the power size of the explosion-proof electric heater. Under the condition of meeting time parameters, selecting power is to meet the heat required by the heating medium, ensuring that the explosion-proof electric 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 explosion-proof electric heater is the heat output.
1. Considerations for power selection
The calculation and selection of power should consider the following three points:
⑴ From the initial state, heat the medium to the set temperature (working temperature) within the specified time;
⑵ Under working conditions, the heat output is sufficient to maintain the medium temperature;
⑶ There should be a certain safety margin, generally taken as 1.2.
Obviously, choose the larger power from points ⑴ and ⑵, multiplied by the safety margin, that is the selected power.
2. Calculation of power required for heating from initial state
(1) Static fluid heating
(2) Flowing fluid heating
(3) Duct-type explosion-proof electric heater for atmospheric air heating
In the above three formulas
P_calc —— Required power of explosion-proof electric heater (KW);
Q_diss —— Heat dissipation of the container at set temperature (KW);
Where:
C1 — Specific heat of the heated medium. (Kcal/(kg?℃)
C2 — Specific heat of the container (system). (Kcal/(kg?℃)
M1 — Mass of the heated medium. (Kg);
M2 — Mass of the container (system) (Kg);
ΔT — Difference between set temperature and initial temperature. (℃);
t — Time required to heat the medium from initial temperature to set temperature. (h);
F — Flow rate of the heating medium (generally take the maximum flow rate). (m /min);
S — Heat dissipation area. (m2);
q_loss — Heat loss per unit area of (insulation) material at set temperature. (Kwh/m)
3. Calculation of power required to maintain medium temperature
Where:
P_main — Power required to maintain medium temperature of explosion-proof electric heater. (KW)
M1_inc — Increased mass of medium per hour. (Kg/h)
Explosion-proof electric heater in operation, low-temperature fluid medium enters its inlet under pressure through the pipeline, flows along the specific heat exchange channel inside the electric heating container, using the path designed based on fluid thermodynamics principles, takes away the high-temperature thermal energy generated during the operation of the electric heating element, causing the temperature of the heated medium to rise, and the outlet of the explosion-proof electric heater obtains the high-temperature medium required by the process.
The internal high-voltage system of the explosion-proof electric heater can provide alarm signals such as operation, high temperature, fault, and shutdown to the DCS system, and can also accept automatic and shutdown operation commands from the DCS. Moreover, reliable and safe monitoring devices have been added to the explosion-proof electric heater system, but the price reference for explosion-proof electric heaters is relatively higher.
Note: The above information and technical parameters are from Yangzhou Darui Electric Co., Ltd.
