Side channel blower with air knife energy-efficient alternative to compressed air
Compressed air is used in industry not only as a drive technology, but also often for cooling, drying or cleaning products. A side channel blower with air knife provides an energy-efficient, easy-to-install alternative.
Using compressed air to cool, dry or clean products is a rather expensive solution in terms of energy consumption. An air knife can also be used for these applications with less energy. This is a cylindrical tube with a smooth outlet slot that, due to its specific design and aerodynamics, carries a very evenly directed, non-turbulent airflow to the product being treated. By tailoring the design, an optimal solution can be created for each application.
Dovac in Zevenhuizen promotes the industrial use of air knives as an alternative to compressed air. The company specializes in vacuum and blower technology, supplying vacuum pumps, blowers and accessories. The supplied air knives, also known as “air knives,” produce a laminar airflow suitable for drying, cooling or cleaning a variety of parts and products. This airflow also sucks ambient air with it, further increasing the effectiveness of the air knife. A popular application is blowing cars dry at the car wash.
Air knives are more energy-efficient and thus cheaper than compressed air
Low pressure, high efficiency
An air knife operates with relatively low input pressure. This is much more energy-efficient, and therefore cheaper, than (high-pressure) compressed air reduced to low pressure. The sizing of the exit slot relative to the cylindrical tube is critical to obtaining uniform, efficient airflow along the entire length of the air knife. Dovac has calculation methods for determining the correct combination of exit velocity, air blade length and blower type.
Side channel blower
The trading company combines an air blade with its own brand of side channel blower (or regenerative blower). “We have had our blowers produced by the same manufacturer for 20 years,” says owner Ferry Jansen. “The blower is designed for high efficiency, low maintenance and low noise, which means energy consumption is much lower than with a blower system working with compressed air. On top of that, a blower with air knife is a local solution, while compressed air requires more infrastructure and long pipelines.”
Clean and maintenance-free
His company offers a complete solution: blower, air knife, intake filter and mounting components. “Our air knives deliver clean, oil-free, dry air, are easy to assemble and safe to use because of the low operating pressure.” An additional advantage is that an air knife has no moving parts, making it maintenance-free in that respect. Contamination of air filter and air gap is, of course, a concern. The air knives are available in various lengths up to a maximum of three meters, made of aluminum or stainless steel.
An air knife blower requires less infrastructure and piping than compressed air
Air knives multifunctional
The combination air knife-blower is used in a variety of industries, from metal and plastics, galvanic and food industries to agriculture, horticulture and medical clinics and laboratories. Examples of applications include chip removal, rapid cooling of injection molded parts, streak-free coating of doors and dry blowing of products that should not stick to a conveyor belt (such as paste), be labeled or glued. A version with air cannon can be used more focused on a smaller product and/or aerate galvanic baths. In short, air knives are suitable for many applications.
Air knives in practice
An air knife (also called a blower knife, air curtain, transvector, airflow amplifier or string knife) is available in a variety of designs to suit the specific application. The dimensions of the area to be blown off determine the required length of the air knife and the force to be delivered by the air knife. This force is the product of air flow and velocity (exit velocities of 50 to 250 m/sec are achievable) and is determined by the volume of the cylindrical tube and the width of the air gap. As the distance from the blowhole increases, the force decreases. Air knives are designed for fixed mounting and permanent use; they should be mounted to allow adjustment for different products. Accurate adjustment of the airflow direction is crucial to blowing results. Air blades are preferably placed at a distance of 25 mm for best results and at an angle of 10° to 15° to the product flow – with the blowing direction against the flow. If necessary, obstacles in a production line or conveyor belt at the level of the air knife are removed. Ultimately, the optimum distance and blow-off angle should be determined experimentally. Factors include possible noise pollution at high air velocities and the turbulence that can occur when using multiple air blades blowing against each other. A slight twisting of the air knives often helps greatly reduce a problem. When mounting, the line between the blower and the air knife should be as short as possible and any bends should be as wide as possible. This is to reduce any possible loss in this already energy-efficient blowing technology.