New technology often takes time to overcome teething trouble and ‘bed in’ to become an industry standard. Steve Warnock, managing director of the Coolmation Group, explains how the Turbocor compressor chiller has now come of age offering a significantly higher efficiency ratings, allowing end-users to cut both their carbon emissions and fuel costs.
When Turbocor compressor chillers were launched a few years’ ago they received rapturous applause, offering contractors and end-users a highly efficient chiller that could significantly cut both carbon emissions and fuel costs in one fell swoop. Their introduction was timely with the ACR industry facing increasing pressure from EU regulations, including the F-Gas, as well as a raft of building legislation introduced by the Government to reduce the UK’s carbon output, in line with Kyoto.
However, the Turbocor compressor was huge technological leap, so it was not surprising that the technology took time to overcome teething problems as the industry familiarised itself with the product. The Turbocor compressor brought huge efficiency savings but its innovative design was so dramatically different from previous compressors that it took time produce the optimum relationship between chiller and compressor. This refining process has now resulted in proven Turbocor chiller technology which offers all the efficiencies that the prototype compressor promised.
According to recent data from BSRIA the compressor market is currently in a state of flux with the sector continuing to experience shifts in compressor type, refrigerant and size. However, BSRIA has also noticed growth in recent technologies such as the Turbocor. This is being driven by a number of factors including: the existence of proven Turbocor chiller technology, by energy efficiency regulation and the desire to reduce carbon emissions. The compressor is generally the single, largest energy consumer within the HVACR system and is at the heart of chiller operation, it’s for this reason Turbocor chillers are such an important step forward for energy efficiency. In its target capacity range, there is no other compressor currently on the market that produces better efficiency in operation.
So how do Turbocor chillers achieve such high operating efficiencies? Let me explain. The Turbocor, oil-free compressor incorporates an inverter-driven, permanent magnet motor and magnetic bearings. Within the compressor, efficiency is affected by the compressor’s isentropic efficiency (the efficiency of the impellers), the motor and the bearings. Typically, traditional induction motors of this size are in the 92% efficiency range. The Turbocor compressor’s permanent magnet DC motor, with its completely integrated variable-speed drive, provides an efficiency of between 96 to 97%. The variable-speed drive (VSD) varies the frequency between 300 and 800 Hz, providing a compressor-speed range from 18,000 to 48,000 rpm and at the same time eliminating the need for an energy consuming gear set.
Efficiency is further enhanced by the use of magnetic bearings which have friction losses typically 500 times less than traditional oiled bearings, reducing starting current to just 2A and removing the transient starting spikes frequently associated with screw compressors, the need for expensive soft start arrangements, as well as eliminating the risk of penalty charges for exceeding maximum power demands.
However, it is the seamless integration of the Turbocor compressor within the chiller as a whole, which is now providing new outstanding and reliable operating efficiencies. Following the initial launch of the Turbocor compressor to the UK market years of research and development have resulted in proven future ready technology, which enables end-users to cut both their carbon and fuel costs.
For instance, Coolmation, has launched Rhoss’ new series of Eurovent-certified Turbocor R134A cooled chillers which are available from 150kW to 2,100kW and have been developed through a unique partnership between Rhoss and the University of Udine. The result is that Coolmation’s Turbocor chillers include innovative design features which complement the Turbocor compressor to offer even higher efficiencies.
Turbocor chillers, such as Coolmation’s range, now offer significantly higher operating efficiencies than chillers using scroll, screw or reciprocating compressors. Compared with screw compressors, Coolmation’s Turbocor range has an EER of up to 4.0 at full load conditions and in excess of 8.0 at part load, representing an efficiency increase of 10% and more than 100% respectively.
These efficiencies are due to a number of new chiller design elements which complement the Turbocor compressor. Features include: electronic expansion valves, innovative heat exchange technology, highly intelligent control systems and “micro channel” parallel flow air cooled condenser coils. For instance, the revolutionary “micro channel” parallel flow air cooled condenser coils is designed to increase performance by up to 45%, making it possible to drastically reduce condenser dimensions for a given capacity. Constructed entirely of aluminium, the coils’ weight is also reduced by as much as 45% while the manufacturing method considerably reduces the potential for refrigerant leakage. These factors not only make the chillers easier to install but the high standard of workmanship means that the reduction in potential refrigerant leaks makes it easier for end-users to comply with the F-Gas Regulation.
Other benefits of micro channel condenser coils include a reduction in coil depth which reduces air pressure drop providing further energy savings through reducing the capacity or number of fans required to create the design air flow rate. The smaller coils also result in a 30% reduction in the refrigerant volume and a reduction in refrigerant pressure drop across the coil of 65%, enhancing energy efficiency still further.
In addition, the condenser fans feature low noise sickle blades which are arranged so that when the Turbocor compressor cycles off, they have the ability to reverse, to blow out dust which has gathered on the coil surfaces. This feature helps to maintain coil efficiency and overall energy consumption.
Another benefit of the new generation of Turbocor chillers is a flooded type evaporator which is more efficient than a shell and tube direct expansion evaporator. The flooded type is designed and optimised specifically for R134A featuring specially finned tubes along with a cleverly sited refrigerant level sensor, which makes it possible to take full advantage of the total heat exchange surface area. This helps to create higher saturated suction gas temperatures and higher EER values while lowering energy consumption. Again adding to better operating performance. The Turbocor compressor is thus optimised by using a flooded type of evaporator showing how important chiller design is a whole when utilising a Turbocor compressor.
Meanwhile, a patented heat exchange device further increases the overall energy performance levels by interchanging heat between the saturated suction gas and condensed liquid refrigerant, raising the temperature of the suction gas while sub cooling the liquid, improving the cooling efficiency and EER values.
It is the symbiotic relationship between the compressor and chiller as a whole that offers contractors and end-users increased benefits. Low maintenance is one another key feature of this type of chiller which is partly due to the simplicity of the compressor - it comprises only one moving component - the compressor shaft. Magnetic bearings keep this high-speed shaft suspended in the air and frictionless, so reducing wear, extending the chiller’ lifetime and keeping maintenance to an absolute minimum. The compressors are also oil-free. This not only helps to keep maintenance costs down but is also the key to sustainability by improving heat exchange performance through the elimination of oil film between the coolant and heat exchange surfaces. Oil management, particularly in relation to the lubrication of compressor bearings, is always a critical issue in refrigeration system design. But with magnetic bearings, this issue is effectively eliminated. Avoiding oil management systems also avoids the capital cost of oil pumps, sumps, heaters, coolers, and oil separators, as well as the labour and time required to perform oil-related services.
When selecting a Turbocor chiller it is important for contractors and end-users to consider the chiller as a whole, weighing up the Turbocor compressor’s efficiency and how it operates reliably and in harmony with the entire chiller. Offering great reliability with low maintenance the Turbocor compressor is manufactured from aircraft grade aluminium castings with high strength thermoplastic electronics enclosures. A rugged Designed to operate at extremely low sound levels, the low noise frequency is possible thanks to zero-vibration, even at start-up, and the elimination of the tonal problems typically found in screw compressor chillers.
