What Are The Heating Methods for Glass Tempering Furnaces? How To Heat The Glass inside Glass Tempering Furnace?

Tempered glass is often used in our daily lives, and these tempered glass are processed and made by glass tempering furnaces. Glass tempering furnaces are mainly processed through chemical or physical methods. So, what are the heating methods of glass tempering furnaces?

Heating method of glass tempering furnace

1. Convective heating

1.1. There is a heat balance tube inside the heating furnace, and the direction of the heat balance tube is perpendicular to the direction of the heating furnace wire. Below the heating furnace wire, there is a 1mm small hole in the heat balance tube, while adjacent ones are the opposite. The distance between the holes is 120 millimeters, which is equal to the distance between adjacent furnace wires. The compressed air sprayed from the hole passes through the upper heating element and is blown to the upper surface of the glass, forming convective heating to ensure uniform heating of the upper and lower surfaces of the glass.

1.2. If the temperature inside the heating furnace is uneven, air flows from low temperature to high temperature, and heating the glass requires the air temperature to be higher than the temperature of the glass.

1.3. The opening of the furnace door can cause the heating furnace to be poorly sealed and allow cold air to enter. The cold air locally lowers the furnace temperature and glass temperature. In actual production, the opening of the furnace door still has an impact on the temperature. Corner furnace wires are added to the upper and lower parts of the heating furnace to balance the temperature. In the rear furnace door, air curtains are often used to isolate the exchange of cold and hot air due to the fear of cold air blowing into the furnace by the wind grid.

1.4. Hot air is extracted from the heating furnace and blown on both sides of the glass with a nozzle. The hot air is sealed and circulated to effectively prevent cold air from entering the furnace. At this point, two separate convective heating systems are used for the upper and lower surfaces of the glass, allowing them to heat towards the center of the glass at the same heating rate.

2. Radiation heating

2.1. The heating wire in the glass tempering furnace transfers thermal energy radiation to the glass. During the heating process, controlling the radiation heat is a technology to ensure that the glass is uniformly heated. However, due to the different reflection effects of the layers on the surface of coated Low-E glass on radiation heat, the challenge is to control radiation heat in the tempering furnace.

2.2. Radiation is everywhere. If a cold glass is placed in a heating furnace, various heating elements will emit radiation heat to heat the glass. From the spectral curve of the glass, it is less than 2.5 μ Most of the radiation heat of m will penetrate the glass, and when the wavelength of the radiation heat is greater than 3.2 μ The furnace temperature at m is only around 630 ° C, making it difficult to quickly heat the glass. The absorption of radiant heat is also related to blackness.

3. Conduction heating

Conduction heating can be divided into two aspects. Firstly, radiation and convection heating transfer heat to the surface of the glass, and then enter the inner layer through conduction heating, thereby achieving heating of the glass; The second is that the ceramic roller in the furnace contacts the lower surface of the glass to transfer heat to the glass. It is important to ensure the stable temperature of the ceramic roller conveyor during the glass heating process. The ceramic roller conveyor is made of quartz and added auxiliary materials, which is very heat-resistant. The coefficient of thermal expansion is 0, the thermal conductivity is low, and the contact area with the glass is very small. Therefore, the heating process of thermal conduction is not the main way. In the heating furnace, less than 10% of the heat absorbed by the glass comes from thermal conduction.