Magnetic Bearing Centrifugal Chiller Development

Mainstream developed and patented the world's first high-efficiency, lubricant-free 120-ton centrifugal chiller that uses centrifugal compressors with dual 24,000 rpm magnetic-bearing supports. While developing this project, Mainstream made significant technological advances in dynamic control, high-speed rotating machinery and magnetic bearings. As a result, substantial improvements were made in efficiency and dramatic savings were made in both operating and maintenance costs.

The engineers at Mainstream incorporated other unique features into the chiller, such as variable speed control to provide load following, environmentally safe non-toxic HFC refrigerant to improve performance, and integrated electronic diagnostics to provide condition monitoring and predictive maintenance capabilities.

Low Lift Heat Pump for Satellites

Mainstream decided to demonstrate the space-based applications of a low-lift heat pump thermal control system for heat rejection. As part of the project, our engineers performed a detailed design and experimental optimization of an innovative magnetic-bearing centrifugal compressor (including impeller, diffuser, and shroud). We then designed and fabricated a prototype heat pump thermal control system that contained prototypical cold plates and condensers.

The prototype system was extensively tested to measure key performance parameters such as power consumption and cooling capacity. The experimental performance of this system validated a prior trade study that compared the performance of a low-lift heat pump to a single-phase pumped loop. The results of the low-lift heat pump experiments demonstrated that the system has lower total mass than a single-phase pumped loop at the conditions compared. This makes an extremely compelling case for using the low-lift heat pump over a single-phase pumped loop for spacecraft thermal management systems.

Oil-less Compressor for Refrigerated Centrifuge at the International Space Station

Conventional refrigeration compressors need gravity to assist in their oil lubrication systems. In a microgravity environment such as the one on NASA's International Space Station (ISS), these compressors would not be adequately lubricated. Mainstream developed an oil-less compressor for Lockheed-Martin Space Operation's refrigerated centrifuge to be used on-board the ISS. This unique compressor requires no oil for lubrication; instead it uses self-lubricating materials and permanently greased bearings.

Mainstream's oil-less refrigeration compressor was recently transported to the ISS on NASA's Space Shuttle Mission STS-114 to begin service in the ISS refrigerated centrifuge. The compressor provides similar performance to terrestrial-based refrigeration compressors and has been life tested for over 1000 hrs. New designs are planned that will increase the life of the compressor by an order-of-magnitude.

Hydrocarbon Environmental Control Unit for Military Shelters

Mainstream has a long history of investigating the use of alternative refrigerants, including hydrocarbon refrigerants in heat pumps, air conditioners and other vapor compression systems. Our experimental data demonstrated the performance of some hydrocarbon refrigerants to be about 7% better than R-410A and 10% better than HCFC-22. Experiments also demonstrated that hydrocarbon blends can be formulated to match the saturation temperature/pressure behavior of HCFC-22. In addition, compressor tests showed that the hydrocarbons are compatible with conventional mineral-oil refrigeration oils.

Mainstream is now focusing on demonstrating a full-scale optimized prototype 5-ton lightweight ECU using a hydrocarbon refrigerant (HECU), along with comparing of the performance of this improved ECU with Mainstream's commercial MECU.

QwikChill™ Instant Beverage Cooler

QwikChill Animation: High Bandwidth    Dial-up
Maintaining vending machines filled and operational within the U.S. Navy is extremely labor intensive. Shipboard logistical problems are further complicated by lengthy distances from storerooms to vending machines, lack of transportation aids, and the high per capita consumption rate of those onboard the ship. As manpower needs increase, devoting large amounts of labor (up to six man-years for large ships) to stock these vending machines becomes a problem. An ideal solution is Mainstream's compact QwikChill™ Instant Beverage Cooler, conveniently located around the ship. Mainstream's QwikChill™ cools a can of soda from room temperature to refrigeration temperature in 10 seconds. QwikChill™ eliminates wasted man-hours required to fill and maintain vending machines ship wide. Instead of maintaining hundreds of soda cans at cold temperatures for days until they are needed, QwikChill™ only cools soda cans as they are needed, that is, immediately before consumption. The Ships Store would sell room temperature soda, in bulk if desired, to the sailors who could cool the soda before they leave the Ship Store for immediate consumption, or store the cans as personal items and cool them just before consumption. Mainstream has already successfully fabricated and demonstrated a prototype QwikChill system that exceeds all of the Navy's performance, size, weight and cost objectives. Mainstream is currently developing the finished commercial product.