Originally, New Frontiers was planning to use a different product. However, Hill Phoenix regional sales manager Jack Ryan educated his customer on the benefits of the hybrid condenser technology.
New Frontiers has two Hill Phoenix refrigeration systems. The medium-temperature system uses glycol, and the low-temperature system uses R-507 DX. These were connected to two air-cooled condensers located on the roof. The design considerations for these systems are shown in Table 1.
The installation of the new condensers was very much like an air-cooled system, the manufacturer said, except that the footprint is smaller and the weight is lighter. In addition, because water is used during upper ambient periods, a water line must be brought to the unit and a waste line must be run to a drain.
UTILITY INCENTIVESPacific Gas and Electric provided a significant energy rebate to New Frontiers for using this condenser. It helped reduce the company’s out-of-pocket costs and decrease its payback period.
New Frontiers VP Jake Collier said he appreciates the environmental benefits that are expected. “We are continuously striving to positively impact the planet. We were initially attracted … because of the promised energy savings, reduced power plant emissions, and the increased peak ambient cooling capacity.
“This installation has validated those expectations,” he said. “It is also of great environmental importance that the 3C allows us to reduce the refrigerant charge, and that the unit can be recycled at the end of its useful life. Benefits like these can only help us make a more positive impact in the communities we serve.”
THE HYBRID CONDENSERThe condenser was developed by Muller Industries to eliminate the energy penalty and capacity losses experienced under high ambient conditions, and is said to reduce water usage by about 75 percent. It is well suited for supermarkets, with their narrow profit margins and continuous need for refrigeration, the manufacturer pointed out.
The unit is essentially an air-cooled condenser that rejects its heat to ambient air drawn by fans across condenser coils (heat exchangers). However, there are some key differences:
• The standard horizontal condenser coils have been replaced with vertically mounted aluminum microchannel heat exchangers that allow increased heat rejection and a lower refrigerant charge.
• Evaporative cooling pads have been mounted to the outside of the heat exchangers. Under high ambient conditions, water flowing across the pads evaporates into the condenser air, thereby lowering its temperature and increasing heat rejection. To minimize water use, water that is not evaporated is recirculated over the pads, then flushed to drain at the end of each day. With no standing water, chemical treatment is not required.
• The 3C runs in the dry mode the majority of the time, only using water when the ambient temperature rises above a predetermined set point. That allows for a reduction in water use of up to a 90 percent versus other water-based systems.
• The low-efficiency fans typically found in air-cooled condensers have been replaced with high-efficiency, quiet EC fans with integral variable-speed drives. This can reduce fan energy use by up to 75 percent depending on ambient conditions. Additional energy savings can be achieved, because the cooling systems are able to run at lower, steadier head pressures. (During peak ambient periods, as the water flows through the evaporative pads on the condensers, head pressures are lowered, which causes the compressors to draw less power.)
• The all-aluminum construction makes it durable, lightweight, supportable, and recyclable.
OBSERVATIONSAs shown in Table 2, with the 3C in operation, condensing temperatures were lowered by 25° and 15°F, respectively. Manufacturer data suggest that this will lower energy use by approximately 20 percent, and will substantially increase cooling capacity.
Additional energy savings can be achieved at the condenser where standard-efficiency fans have been replaced by high-efficiency EC fans with integral VFD. Fan speed is reduced as the ambient temperature falls, so additional savings are achieved.
As a result of the unit’s microchannel heat exchangers, New Frontiers was able to reduce its refrigerant charge by approximately 406 pounds.
For more information, visit www.mullerna.com.