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Plug & play axial fans for applications with high back pressure

Axial fans are normally used for situations when strong air flow with relatively low back pressure is required. That is why they have not yet been the fan of choice for devices that require a high pressure increase. But now that has all changed: ebm-papst's new axial fans are also suitable for applications with high back pressure, meaning that these types of applications can also benefit from their higher air flow rates.

At the start of 2020, ebm-papst introduced its AxiEco Protect axial fans with guard grills, which are able to overcome high back pressure. The fan and motor specialist is now going a step further by expanding its existing AxiEco series with the AxiEco Perform (Fig. 1) axial fans. These achieve even greater efficiency and pressure stability and come with an easy-to-install housing made of composite material.

Fig. 1: Extract from the product range: new AxiEco Perform EC axial fan in size 350 with housing made of composite material. (Photo | ebm-papst)

The air performance curve is much steeper than that of comparable axial fans, and efficiency remains high, even when back pressure rises (Fig. 2). As a compact plug & play solution with CE marking, the fans are easy to integrate into applications. Users won’t have to worry about nozzles or distance to the impeller, nor concern themselves with conducting their own ErP assessment.

Thanks to the addition of the new fans, the AxiEco series now covers a very broad range of applications. For example, the AxiEco Protect fan with guard grill is particularly well-suited for noise-sensitive applications, as its noise emissions are very low. By contrast, the AxiEco Perform fan with housing is recommended when a ready-to-install fan is needed. With air flows of up to 12,000 m³/h and pressures of up to nearly 500 Pa, they are ideal for a broad spectrum of applications, ranging from heat pumps and evaporators to industrial ventilation systems and the cooling of air compressors. The new fans with housing come in sizes 300, 350, 400, 450, and 500 and are available in EC and AC design. Both the EC and AC variants of this series also meet the requirements of the future ErP Directive and can be used for both exhaust and suction.

Fig. 2: The air performance curve of the AxiEco Perform is much steeper than that of the HyBlade, and it offers all that at a high efficiency. (Graphic| ebm-papst)

Aerodynamic design increases efficiency and air throw

Optimized aerodynamics lie at the heart of the fan’s design and are what help to increase efficiency and pressure: the impeller, integrated diffusor ring and hub form a compact unit and the blade tips pass over straight into the integrated diffusor ring. This eliminates the head gap between the nozzle and the impeller, which also prevents air from flowing over the tips of the blades, as seen in conventional axial fans. The new design both increases efficiency and reduces noise. The integrated diffusor ring also functions as a diffuser that is directly integrated into the impeller. It increases the pressure, resulting in reduced exit loss and less noise. Thanks to the inlet ring that immerses in the impeller and a larger outlet opening, the fan has an optimal flow (Fig. 3).

Fig. 3: Thanks to the inlet ring that immerses in the impeller, the large outlet opening, and the housing design, the AxiEco Perform fan has an optimum flow. (Graphic| ebm-papst)

The fan also features an aerodynamically optimized housing with integrated guard grill and guide blades. Cavities in the housing corners improve the flow; the guide blades ensure that the swirl in the outflow field of the fan, and thus the dynamic losses, are reduced to a minimum. The air throw is also higher compared to conventional axial fans (Fig. 4). This means that in large refrigerated warehouses for example, there is an even distribution of cold air, so fewer fans may suffice.

Application-compatible design details

Fig. 4: The air throw from the AxiEco Perform is considerably better than from the HyBlade. (Graphic| ebm-papst)

In terms of exhaust-based applications, an optional guard grill can be attached to the intake side of the housing. If the fans are used for evaporators, an air bag that closes the air outlet opening during defrosting and when the fan is switched off can be easily installed. It is fixed to the cylinder-shaped housing using the standard tensioning belt.

The air bag keeps the trapped heat in the evaporator housing during the defrosting process. This significantly reduces the defrosting time and makes for a low final defrosting temperature, thus saving a considerable amount of energy.

The flow profile at the outlet of the AxiEco Perform fan ensures that the integrated guard grill does not freeze over as quickly, as there is backflow – even at high back pressures. And the impeller with the integrated diffusor ring has been produced in highly resistant composite material, a material that, in and of itself, discourages icing. The grooves on the rear of the fan blades provide the necessary mechanical strength for achieving the high impeller speeds for the impressively high pressures. They also ensure that any water present can easily drain away in applications in which the fan has been installed with a vertical motor shaft.

Fig. 5: Different installation methods for intake and exhaust operation. (Graphic| ebm-papst)

Different installation options and needs-based control

The sophistication of the housing design makes the fan easier to install and enables a number of potential installation methods (Fig. 5). For example, for intake operation, the fans can be installed “on top”, i.e. on top of the customer’s device, or “semi-top” (recessed into the device). For exhaust operation, the entire fan unit is installed in the customer’s device the other way around using the central flange and fitted with the intake-side guard grill. When used in ventilation pipes, the central flange makes it easier to install the fan directly on the pipe system. This makes it easy to integrate the fans into ventilation applications.

Fig. 6: The fans come in sizes 300, 350, 400, 450, and 500 and are available in EC and AC design. With air flows of up to 12,000 m³/h and pressures of up to nearly 500 Pa, they are ideal for many different applications in refrigeration, air conditioning, ventilation technology and mechanical engineering. (Graphic| ebm-papst)

The new AxiEco Perform fans satisfy the requirements of the next ErP stage, regardless of the motor technology they have. And the fans with EC motors offer many more advantages. In comparison to AC motors, EC motors function with considerably higher efficiency. They also generate less waste heat, an important advantage for chilling applications. It is also possible to control and monitor the fans on a needs basis using a 0-10 V signal or MODBUS. These features help the EC fans to work very efficiently, particularly in the partial-load range, and significantly reduce energy consumption. This facilitates individual adaptation to particular cooling requirements.

Typical examples include the maturing of cheese and the ripening of sensitive fruit and vegetables in storage, and varying day and night operation. The new features enable needs-based air flow to be easily set in ventilation applications as well. The high speeds of the EC motors also provide much higher air performance, which are hugely welcomed for many industrial applications (Fig. 6).

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Best under pressure

The pressure-resistant AxiEco series