Nowa­days, data centers are springing up wher­ever you look. So much waste heat is gener­ated in each of these data centers that around half of the required elec­trical energy must be used for cooling the hard­ware alone. Yet the infor­ma­tion age has only just “warmed up”; the larger the volume of data is, the higher the required cooling capacity and thus the energy consump­tion will also be. These facts are accom­pa­nied by the desire for higher compu­ta­tional capacity over the same floor space, which results in the fans needing to move more air without increasing in diam­eter. In today’s preci­sion air-condi­tioning units, for example, air-duct cross-sections are designed for larger quan­ti­ties of air, which improves cooling and mini­mizes flow losses.

Opti­mized for new require­ments

Figure 2: A CRAC unit with a diag­onal heat exchanger: The blue areas repre­sent low-speed air flows, while the red areas accord­ingly repre­sent high-speed air flows.

Preci­sion air-condi­tioning units are usually deployed in data centers. These units – also referred to as Computer-Room Air-Condi­tioning (CRAC) units – guar­antee a constant temper­a­ture and humidity in data centers and network control centers. CRAC units with heat exchangers are used in this case (Fig. 2). The design of the CRAC units signif­i­cantly influ­ences the choice of suit­able fans. In light of the consid­er­ably lower back-pres­sure require­ments, these are now also required to work at the optimum oper­ating point to ensure that they can run energy-effi­ciently and save on oper­ating costs. After all, every watt counts during round-the-clock oper­a­tion in data centers. To this end, motor and fan specialist ebm-papst Mulfingen has expanded the tried-and-tested RadiCal model series (Fig. 3).

In order to tailor the oper­ating point of the RadiCal fans to the higher air flow desired by the market, the aero­dy­namics of the impeller were over­hauled.

In order to tailor the oper­ating point of the RadiCal fans to the higher air flow desired by the market, the aero­dy­namics of the impeller were over­hauled. Powerful simu­la­tion tool Compu­ta­tional Fluid Dynamics (CFD) was a great help in doing so: In conjunc­tion with numeric opti­miza­tion approaches, this resulted in a number of indi­vidual detail improve­ments that make a real differ­ence overall. As such, the width of the impeller, the size of the intake area, the blade contour and blade thick­ness were all adapted to the higher air flow and lower head. Like its prede­cessor, the new impeller is made of glass-fiber-rein­forced polypropy­lene. The outer diam­eter and instal­la­tion height have remained the same in spite of the opti­miza­tion. This enables the limited space avail­able in CRAC units to be utilized to best effect.

Figure 3: The new RadiCal has been tailored to the changed market require­ments.

A higher air flow with high effi­ciency

For this partic­ular advanced devel­op­ment, the engi­neers in Mulfingen set their sights on the aero­dy­namics, and the results are plain to see: The new RadiCal not only delivers a higher air flow than its prede­cessor, but also oper­ates more effi­ciently (Fig. 4). Thanks to the computer-assisted opti­miza­tion methods used, the new RadiCal impeller is not only consid­er­ably better than the prede­cessor model, but is currently also the best impeller in the world for this appli­ca­tion, i.e. for this air perfor­mance range and degree of effi­ciency. Its prede­cessor achieves its maximum static overall effi­ciency of 61.5% at an air flow of 12,000 m³/h. The maximum of 68.5% for the RadiCal is achieved at an air flow of 13,000 m³/h. The new RadiCal impeller can lead to effi­ciency improve­ments in other appli­ca­tions, too.

The maximum static overall effi­ciency of 68.5% for the RadiCal is achieved at an air flow of 13,000 m³/h.

The effi­ciency advan­tage of the new RadiCal impeller also shows itself in an installed state. In a CRAC unit, three RadiCal fans running in parallel were compared using the previous and new solu­tion. The result was a reduc­tion of more than 10% in the fans’ elec­trical power consump­tion. Thanks to lower flow losses in the impeller, lower turbu­lence and less laminar sepa­ra­tion, the fans also have more pleasant noise char­ac­ter­is­tics.

Figure 4: The new RadiCal (green) not only supplies a higher air flow than its prede­cessor (blue), but also oper­ates with higher effi­ciency.

Effi­cient Green­Tech EC tech­nology

The impeller is perfectly tailored to the like­wise opti­mized Green­Tech EC motor and is bolted directly onto the motor’s rotor. Due to the aero­dy­namic shape of the fan impellers and the EC motor inte­grated into the impeller itself, the centrifugal fans comprise an effi­cient and space-saving unit (Fig. 5). The power elec­tronics inte­grated into the Green­Tech EC motors enables the speed to be adjusted to meet require­ments by means of a 0–10 V control signal or via Modbus RTU. The high level of effi­ciency is even main­tained in partial-load oper­a­tion.

Figure 5: The width of the impeller, the size of the intake area, the blade angle and blade thick­ness have all been adapted to the higher air flow.

When using the Modbus RTU inter­face, numerous oper­ating para­me­ters can also be queried and moni­tored in ongoing oper­a­tion along­side the control signals. When needed, the oper­ator can quickly modify oper­ating para­me­ters in order to promptly react to changing require­ments. Simul­ta­ne­ously recording oper­ating hours facil­i­tates preven­tive main­te­nance for effec­tive mini­miza­tion of servicing time. Should servicing still be needed, the affected fans are easily iden­ti­fied thanks to the Modbus RTU commu­ni­ca­tion. Fail-safe func­tion­ality enables safe oper­a­tion, even in the event of a bus commu­ni­ca­tion failure; the fans simply continue to run at the currently set speed.

Prac­tical and future-proof

RadiCal centrifugal fans are avail­able for all common line volt­ages and frequen­cies. In addi­tion, instal­la­tion is simple and prac­tical. As such, the instal­la­tion posi­tion of the fans can be varied due to the optional fixing bracket: It is possible to install them with the motor shaft in either a hori­zontal or vertical orien­ta­tion. The new RadiCal fans there­fore repre­sent a prac­tical and future-proof solu­tion for powerful, energy-effi­cient CRAC units.