Water boilers require high efficiency in heating because they provide boiling water for drinking. In general, the usual heating element is built-in SS ordinary tubular heating elements. The second heating element is external aluminum plates. The final one is thick film heating elements. We can consider they are direct or indirect heating. This article will introduce these three heating elements in detail.
1. Built-in stainless steel heating tubular
Stainless steel heating tubular is a stainless steel tube for the shell, along the central axis of the tube evenly distributed spiral electric heating alloy wire (nickel-chromium, iron-chromium alloy) its gap-filling compacted with good insulation and thermal conductivity of magnesium oxide sand, the two ends of the tube mouth with silicone or ceramic seal. Stainless steel electric heating rod is specialized in the conversion of electrical energy into heat electrical components, its high thermal efficiency, easy to use, simple installation, is widely used in a variety of water heaters, boilers, water boilers. Stainless steel electric heaters have a long service life, generally designed to last more than 10,000 hours. Usually, it is in I type, U type or W type, and O type for the shape.
At present, ISE and QUOOKER use the built-in heating rod heating method.
1.1 Comprehensive Features
a. small volume, large power
the electric heater mainly uses the internal cluster type tubular heating element, each cluster type tubular electric heating element has a maximum power of up to 5000KW.
b. Fast thermal response
high precision of temperature control, high comprehensive thermal efficiency.
c. wide range of applications
It is applicated to the electric heating boiler, electric heating oven, chemical equipment, plastic molding and auxiliary equipment, hot press molding machinery, cigarette machinery, quick sealing machine, pharmaceutical machinery, sauna equipment, electric water boiler, kitchen equipment, industrial cleaning equipment, commercial air conditioning and drinking water dispenser.
d. High heating temperature
The maximum working temperature of the heater can reach 850℃, which is not available for general heat exchangers.
e. fully automatic control
through the heater circuit design, can easily realize the export temperature, pressure, flow and other parameters of automatic control, and can be networked with the computer, to achieve man-machine dialogue.
f. long life, high-reliability
the heater is made of special electric heating materials, plus the design power load is more reasonable, the heater uses multiple protection, making this heater’s safety and life greatly increased.
What is the best material for SS heating elements?
The same stainless steel electric heating tube, the difference in quality performance is also very large. The difference between good and bad stainless steel electric heating elements material is mainly the difference in the amount of nickel, nickel is excellent corrosion-resistant material, in stainless steel with chromium to make certain improvements in corrosion resistance and process performance of stainless steel. But low-carbon nickel steel to obtain pure austenite organization, nickel content to reach 24%, and as long as the nickel content of 27% to make the steel in some media corrosion resistance significantly changed. Thus, from the material 800, 840, 316L is the relatively good corrosion resistance and high-temperature stainless steel electric heating tube, 800 stainless steel tube nickel content to 30%, 840 tube nickel content to 20%, if the use of poor 304 tubes stainless steel nickel content as long as 8%. Therefore, 316L stainless steel bright bar using high nickel content of high temperature and corrosion-resistant stainless steel heating tube products are also very advantageous.
1.2 What are the disadvantages of stainless steel heating pipes?
The main problem with built-in heating elements is limescale deposits.
In heavy water areas, scale deposits tend to lead to reduced heating performance and also very much affect water quality. Therefore, it is very important to clean the limescale regularly, but the cleaning of the built-in heating rod is more troublesome, the picture below is the picture of Quooker’s water boiler heating rod limescale deposit following the video of how to clean it.
2. External heating plate
The heating plate is composed of heating tubes and an upper and lower aluminum heat-conducting sheet, three independent heating tubes are wrapped in an aluminum heat-conducting sheet, after high-frequency brazing technology weld the heating plate and boiler tank bottom into one, and then with the control unit, it constitutes a heating plate with heating function.
2.1The working principle of the heating plate
A heating plate is a combination of a heating tube and a heat-conducting sheet formed, the heating source is generated by the heating tube inside the heating plate, the heating tube is a U-shaped high-temperature resistant aluminum tube, the internal center of the heating tube is distributed with a spiral electric heating wire, the heating tube is filled with crystalline magnesium oxide powder with good thermal conductivity and insulation in the gap part, the heating tube has ceramic insulating terminals in two sections, there are terminals in the middle, when the electric heating wire has current through, it will produce the Heat, heat through the magnesium powder to the heating tube surface, and then conduct to the heating plate heat-conducting piece and the tank, at this time the water in the tank will be heated. This structure has high thermal efficiency, fast heating, uniform heating, and good stability, when the heating tube is energized and heated, the magnesium powder insulation, the surface of the heating tube is not charged, safe and reliable use.
2.2Control unit of the heating plate
The heating plate is the only heating function, needs to be equipped with a control unit to control its work and protect its safe use, not be burned, the main control component of the heating plate is the thermostat when the temperature exceeds the safe temperature, the thermostat will automatically power off, and so the temperature is reduced to the safe temperature thermostat energized, the heating plate continues to heat, the thermostat can effectively protect the heating plate will not work over-temperature, will not be burned.
2.3 Advantages of aluminum tube chassis heating
In addition to having the advantage of a built-in SS heating rod, it avoids the undesirable disadvantages of limescale deposits on the heating rod.
Hcdrink water boiler with boiling water faucet, no need to disassemble the water boiler, directly from the spout of the boiling water faucet to inhale lemon descaling water, easy to descale, the operation is very simple, the following video is the operation method of HCDRINK water boiler descaling.
2.4 Disadvantages of aluminum tube chassis heating
Since the heating is outside the water tank, the noise when heating will be relatively loud, about 55 decibels.
3. Thick film heating elements
3.1 The history of thick file heating elements.
Thick film heating element means: using screen-printing technology to print insulating medium, resistance, conductor, protective glaze, and other materials on the substrate and sintered by high temperature. This technology is the end of the nineties, the United States Dupont, Germany Heraeus, and other giant companies developed a new high-power stainless steel substrate thick film electric heating element, its high strength, high efficiency, high life of excellent performance and safety, environmental protection, the use of flexible features soon popularized in the field of industrial and household electric heating products, known as the industrial revolution in the field of electric heating elements.
3.2 What materials are available for thick film heating
Thick film heating is made of superconducting ceramic material micronized with organic bonding solvent and blended into a paste, and the paste is printed on the substrate material in the form of circuit wiring or pattern by screen leakage printing technology, and sintered by a strict heat treatment procedure to make a superconducting thick film, the thickness can be in the range of 15-80μm. The superconducting transition temperature of this film layer is above 90K, and the zero resistance temperature is above 80K.
3.3 Advantages of Thick Film Heating elements
a. High surface power density
We can also call extremely low thermal capacity. It means thick-film elements have a quick temperature rise or rising temperature instantly.
b. Adequate heat transfer
It heats water to boil not only fast but also heats evenly. Compared with ordinary heating elements, it has minimum temperature fluctuations. The basis on it, it heats water without noise.
3.4 Lifetime of thick film heating elements
Thick film heater heating element from inside to outside mainly by the stainless steel tube substrate, the inner insulating medium layer, resistance heating layer and outer insulating medium layer, water flowing through the stainless steel tube, where the inner insulating medium layer thickness is about 100 microns, due to the short distance from the resistance heating layer to the stainless steel substrate heat conduction, so the thermal resistance is very small, fast thermal response. This application advantage is stronger is the thick film heating tube, barrel-shaped structure, natural water channel, 360 degrees overall channel heating, the overall heating is more uniform, will not produce a large number of bubbles on the surface of the heater to reduce the heating efficiency. Because the heat can be conducted away in time, the entire heating tube surface temperature is not high, which will not cause an open fire. Good safety and long service life.
3.5 Application for thick film heating elements
These heating elements can be applied for several applications such as home appliances, railway transport, restaurants, machinery, etc. in the industry. The heat components of the thick film are manufactured in large volumes and in individual units. Thick film heating components can help with contact heating of plan surfaces as well as heating other materials by means of vesselling. New products with thick film heating elements for tubes were introduced in recent years that can also be applied when the fluid is heated in the application.
Hcdrink is trying to apply the thick film heating technology to the water boiler, and the data from the pilot test so far shows that the effect is better than that of the traditional built-in heating rod and external heating plate. The biggest problem is that the cost of thick film heating is too high. We expect the thick film heating technology to be more widely used and applied to more living appliances, bringing more convenience to people’s lives.
