Low-noise Data Center cooling systems
Thanks to its wide-ranging benefits, the concept is now also becoming established in other sectors as a genuine cross-industry innovation. Demands in terms of reliability, availability and energy efficiency are particularly high in a Data Center. So it is no wonder that other industries are keen to enjoy the benefits of low-noise cooling. In this blog article on chillers we will be taking a look at one very special benefit: The comprehensive sound-proofing makes such a chiller highly attractive for many different sectors and projects.
The noise dilemma
Our customer in the scenario we describe had no idea that noise might become a problem. An industrial manufacturer, the company operates a large site with production running round the clock. Noise had not previously been an issue. It was only when a particular construction project was carried our that an industrial chiller needed to be installed directly adjacent to an office building. But it was essential for the chiller to meet a number of requirements: The system first had to be highly efficient, as the company's self-imposed CO2 limits could not be exceeded. Other crucial factors were that the chiller should operate as quietly as possible, and take up minimal space. Compact size and low noise emissions are contradictory demands in chiller design however. Even with identical cooling capacity, large chillers are usually more efficient and quieter than small ones. Data Centers are often sited in locations of mixed residential and commercial usage, and operate round the clock.
So a Data Center chiller has to adhere to more stringent noise limits, particularly at night. And Data Centers have changed significantly in recent years: Increasing packing densities have led to a continuous rise in heat loads inside Data Centers, though the footprint remains virtually the same as existing centers are upgraded or new ones built. As a result, the space available to install chillers on a roof or next to a building is rapidly shrinking. This means in order to achieve the required cooling capacity smaller chillers need to be installed, but they tend to be overly loud and not efficient enough.
Sound-proofing as a development concept
The running noise emissions of components such as compressors, fans and pumps were tested in great detail right at the start of the development process when designing the CyberCool 2 chiller. The outcome of this development work was that the CyberCool 2's compressors were housed in a special sound-proofed chamber. This first step in itself greatly reduced noise emissions. Sound-proofing the fans proved rather more complex however. Being small, they have to rotate faster in order to propel more air. This inevitably makes them louder, and they consume more power. To resolve this problem, the STULZ development team decided to fit the largest sized fans possible, while making optimum use of the space available on the chiller. They did so by ensuring that there was literally no room for even a sheet of paper to fit between the individual fans. To enable the new fan system to deliver its full power, it was necessary to redesign the entire air conduction system, from the intake, via the heat exchangers, to the fans.
Large free cooling coil as the key factor in sound-proofing
The combination of large condenser surface areas (with low air-side pressure losses) and maximum-sized fans permits an overall reduction in fan speed – thereby also reducing noise levels without any significant loss of efficiency. This comprehensive sound-proofing was made possible in the first place by extensive CFD analysis of the air conduction system. It provided the only means of achieving an ideal balance between thermodynamic performance and noise emissions.
The STULZ development team painstakingly investigated all potential weakspots, determined to eke out every square millimeter of coil area. They were well aware that only large-area free cooling coils would enable early switching to free cooling mode, or to the mixed compressor cooling and free cooling mode. Their successful design means that the compressors can be shut down earlier. Correspondingly large-sized coils additionally provide for a low condensation temperature in DX mode as well as a low air flow speed.
This does, however, mean that it is essential to utilize the full coil area. There must be no zones or corners with turbulence, nor must there be any zones of the coil which the air does not reach. Special air baffles ensure optimal flow to the inner coil elements. In conclusion, it can be stated: If a chiller system is properly planned in detail, the noise emissions can be reduced in such a way that no loss of efficiency should be expected. It is not enough merely to make purely cosmetic modifications to individual components however. Rather, the complete chiller system must be considered and analyzed as a single unit. The optimization must be coordinated in all aspects, and positively support the downstream cooling process.