Tuesday, 1 October 2013

Maximum efficiency at full and part loads

UK: McQuay has launched a new air-cooled chiller which is said to maximise performance at both part and full loads by incorporating both a built-in inverter and variable volume ratio.

Based on the J&E Hall single screw compressor running on R134a, the ATS chiller is available in three versions from 170 to 730kW and is said to offer the highest efficiencies and smallest footprint of any chiller on the market.

The chillers have a capacity range three times as wide as the units they replace. On top of this, full load efficiency (EER) is 35% better, seasonal efficiency (ESEER) is 26% higher, and the unit is 30% smaller.

The ATS solves the dilemma of choosing between an inverter-driven chiller offering high efficiency at part loads or a non-inverter-driven unit for high efficiencies at full loads.

“The ATS unit gives you the best of both worlds in a single chiller with no need to compromise on efficiency or reliability,” says McQuay UK’s chiller technical manager James Henley.

A twin circuit offers redundancy and the in-built inverter design ensures a power factor constantly higher than 0.95 at full load. All the unit’s electronic components and boards are sealed by special coating that protects them against moisture and vibrations.

In-built temperature control maintains a constant 40°C throughout the entire functional envelope by means of a regulating valve, controlled by a solid-state relay. Heaters are switched on during stand-by hours at low ambient temperatures to eliminate moisture and prevent freezing.

The VVR controller’s moveable slide is positioned by the controller in two possible positions. This, along with advanced controller software, ensures a variation in the discharge side geometry. The result is an optimised pressure ratio depending on the compressor’s working conditions.

Thanks to a dynamic condensing pressure management system, the controller is able to modulate the chiller’s running conditions to achieve the optimum working point.

The ATS chiller also features high efficiency condenser coils made with internally enhanced seamless copper tubes arranged in a staggered row pattern to improve the efficiency still further.

Other features and benefits include an integrated sub-cooling circuit, economised refrigerant circuits and inverter-driven, brushless axial condenser fans with superior aerodynamic wing-profile blades for enhanced performance and acoustic efficiency.

Payback is said to be, typically, around three years or as little as one year in process cooling applications.

The chillers and compressors have been tested for more than 12,000 hours in factories, on selected job-sites in Europe and Middle-East, and at extreme ambient temperatures of up to 50°C in Dubai.

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