Chiller Sets New Benchmarks For Energy Efficiency, Tight Control

To be launched in July, the new line will start with small portable chillers of 1 to 15 tons, with larger portable models up to 30 tons and central models to follow thereafter. Initial models will be air cooled, though water-cooled units will not be far behind.

SAVING ENERGY, BIG TIME
Perhaps the most important innovation in these new chillers is variable-speed compressor technology, which has been used for 20 years in the HVAC industry but rarely before in process chilling. (The only other known example is NQV series of 10- and 20-ton portable chillers introduced by Thermal Care, Niles, Ill., at NPE2015. See June '15 Keeping Up.)

The new Delta T system monitors the process temperature and signals the drive to speed up or slow down the compressor. It eliminates the wear and tear of on/off cycling of the compressor or energy- wasting hot-gas bypass valves. Compared with conventional fixed- speed compressors with hot-gas bypass, the new technology uses up to 50% less energy, according to Delta T Systems, or 30-50% of the initial investment, and thereby pays for itself in two to three years. Naujokat says these estimated savings are conservative because “Most chillers are selected based on the peak-usage time of the year, which means the chiller is oversized for the average use.”

According to Naujokat, variable-speed compressors have historically been designed for HVAC use, and only recently have models tailored for industrial chilling become available. A key requirement for industrial versions is a wider operating envelope, Holzhauer explains. Another element critical to the development of the new chillers was that Delta T Systems Inc. worked with controls manufacturers to create a system specifically for use with these compressors.

The controller continuously monitors the suction and discharge pressures to ensure the compressor stays within its operating envelope. However, that operating envelope is now between 10% and 100% of rated capacity, which means that a 10-ton chiller can operate efficiently at loads of 1 to 10 tons. That compares with a 30% to 100% operating range for conventional chillers, says Naujokat.

Another new energy-saving feature is an electronic expansion valve, which works with the variable-speed compressor to tune the valve to the system needs based on data from temperature and pressure sensors. The valve is driven by a DC stepper motor, which moves a pin up or down to allow more or less refrigerant to flow through the valve. Up to now, this technology has been available mainly on larger chillers of 20 tons or more capacity. (It is also used on Thermal Care's NQV series small portable chillers.)