The difference between electric heating efficiency and heat exchange efficiency

The difference between electric heating efficiency and heat exchange efficiency

In the current trend of energy conservation and emission reduction as the core of society, various energy-saving measures are also becoming mandatory with the strengthening of testing and supervision. Electric heating elements are the core components of energy conversion in many small household appliances, and their energy consumption and actual utilization directly affect the detection results of the electric heating power of the entire machine. Due to the increasing supervision of high-energy consumption products, Here is a summary of common knowledge and engineering methods commonly faced in the electric heating element industry for selection:

1, The difference in the definition concepts of electric heating efficiency and heat exchange efficiency

As an electric heating element, if only the heat generated by the consumption of electrical energy by the heating wire is directly utilized, the electric heating efficiency and heat exchange efficiency are the same concept in data; In fact, this kind of exception is very rare. Generally, the heating wire consumes electrical energy to generate heat energy, which is transferred to the absorbing medium through magnesium powder and metal shell. This is the detailed process of the entire electric heating exchange and heat transfer. It is not difficult to prove that the electric heating efficiency only refers to the process of heat generated when the heating wire consumes electrical energy, while the ability of heat exchange refers to the data that overcomes thermal resistance throughout the entire process of heat transfer and ultimately reaches the pipe surface. Before conducting analysis and calculation, in addition to a rational understanding of the concepts of electric heating efficiency and heat exchange efficiency, there is also sufficient basis for analyzing and judging the engineering phenomena of electric heating tubes. We hope to have a correct understanding and mastery.

In the process of discussing its issues with relevant colleagues in daily life, there is a basic concept worth elaborating on here. Many colleagues believe that even though the fact that some heat transfer is lost due to the thermal resistance relationship of the heat transfer path is recognized, they mistakenly understand that the heat that has not been transferred is completely accumulated in the pipe, and even believe that when the surface temperature of the pipe reaches a constant, the heat generated by the heating wire is completely transferred, For the former, the depth of understanding of the problem is not sufficient. Heat energy is transmitted through a transmission path with thermal resistance, and its value must be attenuated. The consumed energy is not all accumulated inside the heating tube, but some of the heat energy has been converted into other energy and consumed. For example, in a dry burning tube, although the surface temperature of the tube reaches a constant state during operation, the high temperature characteristics of the magnesium sand inside the tube have expanded the geometric volume of the tube shell, The experimental process has similar characteristics to other electric heating elements such as water cooker tubes, which means that some of the thermal energy has already evolved into mechanical energy, and this energy consumption is an integral of a continuous function as long as the electric heating element is in working condition. Therefore, this objectively recognizable special case can be used to explain to people that as long as there is thermal resistance in the heat transfer path of the electric heating element, Its electric heating efficiency cannot reach 100%, and of course, the level of this thermal efficiency can be artificially changed; Secondly, it has a significant impact on the comprehensive performance indicators of electric heating elements; The third is a reflection of the technical strength of electric heating component manufacturers.

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