SU970731A2 - Electric heater - Google Patents

Description

The invention is related to the electrotermine, in particular to devices for electrically heating the air.

According to the main author. St. And 425374 an air heater is known, which contains a grid heater consisting of longitudinal conductors fixed in current leads and transverse support conductors made with ends that are extended beyond the longitudinal conductors and rigidly fixed in the electrically insulating material 1.

However, this heater does not allow to increase the temperature of the heated gas generator while maintaining the reliability and life of the heater, since in this case the heater walls overheat.

The purpose of the invention is to increase the reliability of the heater.

The goal is achieved by the fact that in the electric heater the extreme transverse longitudinal conductors with electrically insulating material and the extreme longitudinal conductors with current leads are installed with a gap of 2-3 steps of the heater.

FIG. 1 schematically depicts a heating element assembled from flat layers of a grid; in fig. 2, section A-A in FIG. one; in fig. 3 mesh elements rolled up; in fig. 4 is a graph of the distribution of weight velocity across the channel cross section; in fig. 5 is a graph of air temperature distribution

10 across the channel cross section.

The longitudinal conductors 1 are connected to the current source by means of current leads 2. The cross conductors 3 are made with the longitudinal conductors 4, which are out of the extreme, 15, which are rigidly fixed in the wall 5 in an electrically insulating material. Distance from The walls to the extreme longitudinal conductor 1 and from the current-carrying conductor to the nearest transverse conductor 3 comprise two or three grid steps, which leads to an increase in the grid permeability along the channel perimeter by about one and a half times.

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The heater works as follows.

The grid is heated by the current passing along the longitudinal conductors 1. The gas flow is heated, washing successively all the layers of the grid. Because

Along the edges of the grid, its permeability is higher than on the rest of it, then at the walls of the channel 5 air moves with greater speed and lower temperature than the rest of it, which ensures cooling of wall 5 at elevated temperature of the heated gas. This is well supported by experimental data carried out on three model grid-type electric heaters of various sizes. As shown in FIG. Figures 3 and 4 show that increasing the distance from the channel walls to the outer wires by 2-3 steps results in an increase in the air flow rate at the wall by 1.5 times and a decrease in temperature at the channel wall by 2.3 times compared to the temperature in the middle of the grid.

A further increase in the gap between the channel walls and the conductors is impractical, since it causes too much unevenness of the velocity fields and temperatures in cross-sections) and. it is undesirable from a more accurate view of strength, since this increases the vibration of the grids and wires, and also, as a result of this, the service life of the electric heater decreases.

Reducing the gap between the walls {sangla and grid wires Up to 1-1.5 step5: Figure /

ha of the grid leads to a decrease in the air flow rate near the wall and to an increase in the wall temperature and, consequently, to overheating of the electrical insulation and to the exit from the electric heater.

Thus, the proposed heater makes it possible to increase the temperature of the heated gas about two times while maintaining the reliability and resource of the heater and, conversely, with the same operating parameters as that of the prototype, the life of the heater increases several times.

Claims (1)

1. USSR author's certificate 425374, cl. H 05 B 3/26, 1967. K-A - FIG. 2 M f f f