Is Electric Heating More Energy-Intensive for Drying Single-Layer Wood Panels? Suggestions for Enhancing Four Design Parameters

In recent years, there has been in-depth global research on the drying characteristics of plywood veneers, primarily focusing on hot air drying. Advances have been made in accelerating the drying process by increasing temperature and airflow speed. Among the more advanced systems, Germany has developed jet speeds up to 60m/s, with temperature control ranging from 210°C to 290°C, achieving thermal efficiency of up to 38%. Energy consumption equivalents indicate 1.9 kWh per kg of water evaporated. Historically, low energy utilization rates of alloy wire electric heating elements in drying equipment have resulted in high comprehensive energy consumption rates, equivalent to 5 kWh per kg of water evaporated. Therefore, electric heating drying has not been widely promoted.

The primary reason for the limited promotion of electric heating drying for single-layer panels is high energy consumption. Modern jet-type single-layer drying machines have suppressed the development of infrared drying machines in the short term. However, infrared drying theory is more advanced than hot air drying theory. Any theory accepted by the market requires time, ranging from a few years to several decades. The advantages of infrared drying can be theoretically analyzed. Compared with the thermal circulation system, the air temperature is 100°C, relative humidity is approximately 5%, and airflow velocity is 2m/s. If the surface temperature of the infrared radiation source reaches 600°C, its heat flux is 30 times that of convective drying, making infrared drying methods promising.

The first challenge to address is improving energy utilization efficiency. This primarily involves two aspects: enhancing the electrical-to-thermal conversion of electric heating elements and increasing the absorption rate of heat by single-layer panels. Similarly, reducing energy consumption requires efforts in two areas: lowering equipment heat loss rates and enhancing heat recovery rates. Achieving these goals could pave the way for electric heating drying systems to replace hot air drying systems in the field of single-layer panel drying.

1. Enhancing Electrical-to-Thermal Conversion Rate of Heating Elements

To improve energy efficiency, consider using carbon fiber heating elements, which boast a conversion rate of 95% to 98%. During heating, they emit infrared or far-infrared radiation of different wavelengths. This makes carbon fiber heating elements a favorable choice for single-layer panel drying. In contrast, tungsten wire infrared heating elements achieve approximately 90% conversion, while alloy resistance wire stands at around 65%. Both have drawbacks: gradual power loss over time and require soft start devices due to high initial current impact.

2. Improving Wood Panel Heat Absorption Rate

There are two drying mechanisms: passive and active heating. Passive heating involves absorbing heat in a high-temperature environment, warming from the outside in, as seen in thermal circulation drying mechanisms. Active heating involves absorbing energy to heat from the inside out, such as microwave and infrared radiation heating. The latter method offers higher thermal efficiency. Microwave heating’s high initial investment costs make it less viable, but infrared radiation heating offers better cost-effectiveness by actively heating wood panels with infrared radiation.

3. Reducing Equipment Heat Loss Rate

Effective insulation measures are crucial to reducing heat loss. Adequate insulation prevents external surface temperatures of well-insulated equipment from exceeding 50°C. Choose insulation materials based on regional and site-specific requirements, opting for quality without necessarily the highest cost or the lowest price. Additionally, minimize heat loss through reducing heat dissipation holes and implementing insulation measures at product entry and exit points to minimize heat flow.

4. Enhancing Equipment Heat Utilization Rate

Efficient heat recovery is critical in hot air drying equipment, where maximizing heat reuse significantly improves overall utilization rates. Similarly, using carbon fiber heating elements for infrared radiation drying also requires heat recovery. Implement heat recovery devices at exhaust emission points after on-site inspection and design by appropriate equipment manufacturers.

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