Selection of the right fan on the basis of an application-specific operating point is only possible with reliable data and is generally performed with the aid of appropriate product selection software. The properties of the RadiPac centrifugal fans are documented in product data sheets and printed catalogues (Fig. 1a, b, c) as well as in a product selection program, the Product Selector. At ebm-papst, the origin of the fan performance data contained in the software can always be traced back to measurements as described above. The required air flow and the static pressure increase which the fan subsequently has to achieve in practical use are the minimum criteria employed for the selection process.
Because the required operating points are not always identical to the measured operating points, there is a need for interpolation between the measured values. Use is often made for this purpose of the familiar affinity laws for flow machines. These are sufficiently accurate in cases where fans merely consist of a flow machine, in other words an impeller. As we already know however (ARTICLE THE FAN), ebm-papst fans also include a motor and control electronics. These two assemblies do not conform to the fan affinity laws, but rather exhibit completely different performance characteristics, particularly in the partial load range. The selection software has been appropriately optimised to obtain a highly accurate forecast of the operating behaviour of the fan unit at any conceivable operating point.
The Product Selector from ebm-papst provides a particularly user-friendly means of finding the right fan. The selection program makes it possible to check fans at various operating points and determine the performance data. It additionally permits dynamic comparisons closely resembling actual operating conditions. The influence of temperature, altitude and installation space can also be incorporated. If there are several fans in the specified performance range, the aerodynamic and acoustic data displayed can be used to help select the most suitable model. Another option available is calculation of the life cycle costs for the fans selected. The performance data are also output at the specified operating point with suction and pressure side sound power level values over the octave band. The software can be incorporated into customer device configuration programs by way of a DLL interface.
The performance data output is extremely accurate, as confirmed by the inspection authorities (TÜV Süd). Validation measurements performed on all 38 models in the RadiPac product range show that on average the efficiency level indicated by the Product Selector tends to be slightly too low! What procedure was employed for the validation measurements? 15 reference points (Fig. 2) were chosen for each fan in the RadiPac product range. These were measured on the certified chamber test rig and the performance data were then compared to the data from the Product Selector. This revealed that the calculated values from the Product Selector are almost identical to the values actually measured. In accordance with AHU guideline 01, the best possible accuracy class 0 is thus obtained for RadiPac fans (Fig. 3). In other words, ebm-papst RadiPac fans in as-delivered condition tend to exhibit a higher level of efficiency than that indicated by the Product Selector. This guarantees true planning reliability for customers.