- January 25, 2022 at 10:01 pm #6172MartinKeymaster
What are The Advantages of Convection Technology in Windshield Glass Bending?
Convection technology is the most efficient way to transfer heat according to physical laws. But, in practice, what arguments support it? Let us go deeper and look beyond the laws of physics to see what convection heating can offer users in the glass industry especially when its used in convectional glass tempering furnaces.
1. There is No Glass Breakage As a Result of Temperature Differences
Glass breakage during heating is avoided by maintaining an even temperature between the glass pair and the mold. Glass breakage in radiation-heated furnaces is caused by the fast heating speeds inherent in radiation heating. The mold cannot heat as quickly as the glass, resulting in a significant temperature difference between them. As a result, the glass cracks due to thermal shock before it can be bent. What a squander!
Convection heating circulates hot air in the heating chamber, simultaneously heating the glass and the mold. As a result, heating rates can be much higher – and glass breakage is avoided.
2. Improved Optical Quality
Convection heating is unaffected by the surface materials of glass. It makes no difference whether the glass is clear, printed, or coated.
Consider the wide black printed areas on a windshield’s sides, bottom, and top. Consider the large black printed areas designated for the ADAS camera, which is mounted near the top of the windshield. To avoid overheating those black printed areas, you must spend a significant amount of time determining the proper size and position for heat suction plates or radiation shields between the glass and the heaters.
Overheating the printed area is a well-known issue that causes the “burn line,” which is visible just above the printed surface of the windshield.
Convection heating does not have this issue. There is almost no temperature difference between the black printed area and the clear glass area next to it. You don’t waste time experimenting with heat suction plates or radiation shields. Convection heating consistently delivers.
3. Increased Heating Rates for Greater Capacity
The glass is heated at a rate of 40–50 °C per minute by a traditional infrared radiation heating furnace. The only constraint is the mold’s slower heating. Convection heating can reach 75 °C per minute.
A faster heating rate allows you to use a shorter furnace, a smaller furnace footprint, fewer molds, and less energy while producing the same capacity.
Furthermore, with fast convection heating at the start of the process, glass heating speeds in the bending chambers can be relatively slow. As a result, convection heating allows for more time to shape the windshields.
4. Millions of Dollars in Savings
As previously stated, convection is the most efficient method of heat transfer. Let us perform some simple calculations to demonstrate this.
The power used in a test with a convection furnace filled with windshield compositions in sizes 2.1 + 2.1 mm and 3 + 3 mm was measured to be 5 kWh/m2. That is far less power than the best non-convection furnaces, which typically use around 10 kWh/m2.
To account for measurement errors, suppose the glass processing furnace with convection technology uses 4 kWh/m2 less energy than conventional machines without convection.
Now comes the math. Assume your annual output is 300,000 windshields. One windshield is typically 1.2 m2 in size. As a result of 300,000 x 1.2 m2, the annual output of glass is 360,000 m2.
Assume the price of energy is 0.12 EUR/kWh.
Annual savings of 360,000 m2 x 4 kWh/m2 x EUR 0.12/kWh = EUR 172,800.
That’s right – in less than six years, convection furnaces can save you a million euros!
You may interest to read our “The Best 8 Ways to Reduce Glass Tempering Furnace Energy Consumption” article to get more information energy saving in glass tempering furnaces.
5. Visible Outcomes
Convection technology holds numerous promises, ranging from improved glass quality to lower costs. The most important promise, however, is that the benefits will be noticed. Your customers will notice an improvement in the optical quality of the windshields they receive. You may also save a digit or two on your energy bills.
The laws of physics cannot be challenged. And glass processors can determine the efficiency of convection heating for themselves.
I hope that this “Convection Technology in Windshield Glass Bending” article will help you to understand how convection technology helps your production by means of energy savings. If you have any recommendation to our readers or questions, please freel free to reply.
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