With the development of the power industry and the increasing scale of chemical plants, the occasions for designing and applying circulating electric heaters in China will become more and more numerous. This article mainly introduces the characteristics and applications of circulating electric heaters.
I. Advantages of Circulating Electric Heaters:
1. Small size, high power: The circulating electric heater mainly uses bundled tubular heating elements inside, which can accommodate more tubular electric heating elements per unit volume, increasing the heat exchange area per unit volume and greatly reducing the device size. Each bundled tubular electric heating element group has a maximum power of.
2. Fast thermal response, high temperature control accuracy, high overall thermal efficiency: Since the circulating electric heater directly transfers heat energy to the heated medium, its electrical energy conversion efficiency reaches above. In traditional processes, heat exchangers use heat media such as hot oil from thermal oil furnaces or steam from steam heat exchangers, which involve secondary thermal conversion. Additionally, the characteristics of fast thermal response and high temperature control accuracy of this electric heater not only reduce process auxiliary time and effectively ensure process temperature control accuracy but also improve overall thermal efficiency and reduce unnecessary process energy loss.
3. Wide application range, strong adaptability: Circulating electric heaters can heat various gases and fluids, whether acid, alkali, or oil and gas, whether in explosion-proof or general environments, whether in high-pressure circulation or atmospheric devices. This electric heater can adapt, with explosion-proof levels up to class and class, and pressure resistance up to.
4. High heating temperature: The maximum working temperature of the circulating electric heater design can reach "℃", which is not achievable by ordinary heat exchangers.
5. Fully automatic control: Through the circuit design of the circulating electric heater, automatic control of parameters such as outlet temperature, pressure, and flow can be easily achieved, and it can be connected to a computer network for human-machine interaction.
6. Long life, high reliability: The circulating electric heater is made of special electric heating materials, and the design power load is relatively conservative. The electric heater adopts multiple protections, greatly increasing the safety and lifespan of the circulating electric heater.
Due to the many advantages mentioned above, circulating electric heaters have been used as conventional chemical process equipment abroad.
The foreign academic name for the circulating electric heater is "circulation heater". The so-called "circulation" means that the heated medium is heated by forced convection, that is, one end of the circulating electric heater uses a pump to inject fluid into the heating chamber, and after heating, it flows out from the other end of the electric heater, forming a cycle to achieve the goal. This circulation method can be pump convection circulation or natural circulation. The circulating electric heater consists of electric heating elements, a container, a junction box, control elements, etc.
The application range of circulating electric heaters is wide, but their usage environment, medium process parameters, and other technical conditions vary. This requires a comprehensive design of the heater to reduce manufacturing costs, ensure use effectiveness, extend service life, and meet process requirements.
II. Applications of Circulating Electric Heaters:
Circulating electric heaters can be used for heat preservation, temperature rise, preheating, and process heating of various liquids and gases, with wide application fields in commercial, industrial, and military sectors.
According to the application scenarios of circulating electric heaters, they can be roughly divided into three types of heating forms:
1. Closed-loop circulation
Closed-loop circulation means that the heated medium flows through the heater under a certain pressure, undergoes the process, and then returns to form a closed loop. Closed-loop circulation can be further divided into direct heating and indirect heating based on the characteristics of the medium being heated.
1.1 Direct heating
As the name implies, direct heating is a method where the heater directly heats the medium. When using this method, the selection of power density is particularly important. If the power density is too high, such as for heavy oil, the medium may carbonize, affecting the heater's lifespan.
Typical applications: Some testing equipment that requires relatively uniform medium temperature and occasions requiring similar applications in laboratories.
1.2 Indirect heating
Indirect heating means that the heater first heats a medium, such as thermal oil, ethylene glycol solution, water, steam, etc., and then these media exchange heat with the heated body through coils in the container or reactor.
Typical applications include:
① Various fluids and fluids sensitive to temperature, such as hot melt adhesive, asphalt, chocolate, etc.
② Media that directly corrode electric heating tubes, such as acids and chemical solvents.
③ Mold heating for injection molding machines and extrusion machines, and other flat plate heating.
2. Sidewall heating
Sidewall heating means that the medium in the storage tank flows through the heater beside it and then returns to the container. It is heated by natural convection. If higher temperature uniformity or closer control temperature is required, adding a pump between the tank and the heater for forced convection is ideal.
Compared with direct heating, sidewall heating has the following advantages:
① Easy to clean the container
② Convenient heater maintenance without draining the medium in the container.
Typical applications: Anti-freezing of water tank cooling towers, maintaining appropriate temperature and viscosity of lubricating oil.
3. Open-loop heating
Open-loop heating means that the heated medium is heated by the heater only once and then directly released to the application site.
Typical application: Preheating of fuel oil.
