Introduction to Electric Heaters
Electric heating is the process of converting electrical energy into thermal energy. Since the discovery that electric current passing through a conductor produces a heating effect, many inventors around the world have been engaged in the research and manufacturing of various electric heating appliances. The development and widespread application of electric heating, like other industries, follows a pattern: gradually spreading from advanced countries to the rest of the world; from cities to rural areas; from collective use to household and personal use; and from low-end to high-end products. In the 19th century, electric heating appliances in their infancy were mostly crude. The earliest electric heating appliances were for domestic use. In 1893, the prototype of the electric iron first appeared and was used in the United States. Then in 1909, the electric stove came into use, where an electric heater was placed inside the stove, meaning heating shifted from firewood to electricity—that is, converting electrical energy into thermal energy. However, the rapid development of the electric heating appliance industry truly began after the invention of nickel-chromium alloy as a heating element. In 1910, the United States first successfully developed an electric iron using nickel-chromium alloy heating wire, which fundamentally improved the structure of the iron and led to its rapid popularization. By 1925, products with heating elements installed in pots appeared in Japan, becoming the prototype of modern rice cookers. During this period, industrial electric heating products such as laboratory electric furnaces, glue melting furnaces, and heaters also emerged. The years from 1910 to 1925 were a major development period in the history of electric heating appliances. In both households and industries, various types of electric heating appliances emerged and were rapidly popularized, especially in households. Thus, the invention of nickel-chromium alloy laid the foundation for the development of the electric heating appliance industry.
After the 1920s, there were not as many new applications as in the previous period, but during this stage, all kinds of electric heating appliances were redesigned and continuously improved, marking a period of advancement in the history of electric heating appliances. In household electric heating appliances, various devices were designed to be more aesthetically pleasing, durable, and robust, and most were equipped with automatic temperature and time control, thus eliminating the risks of improper use, incorrect temperature, and accidents. Appliances such as electric stoves, toasters, and waffle irons all had automatic controls. Meanwhile, manufacturing materials were also improved, such as using high-quality grade A nickel-chromium wire and using magnesium oxide or zirconium oxide as insulators. In industry, similar to household heating appliances, automatic control devices were adopted and better materials were used. For example, wax melting pots, lead melting furnaces, various large ovens, and heat treatment furnaces were all widely improved and applied. After the 1940s, due to the advancement of science and technology in the United States, cheap electricity, war profits, and relatively high incomes, electric heating appliances entered a stage of widespread adoption. In 1940, the electric iron reached a certain penetration rate in American households. Before liberation, due to imperialist aggression and reactionary rule, China's electric heating appliance industry remained very backward. After liberation, it began to develop continuously, especially entering a stage of rapid progress in terms of product variety, quantity, and application penetration.
