New machine pumps fluids efficiently

Tom Shelley reports on a novel machine that offers energy and cost economies in refrigeration, heat pumps and engines

A novel compressor-expander is efficient, simple, lubricated by working fluid and cheap to manufacture using robotic methods. Invented to make refrigeration systems more efficient, it also shows great additional potential as a hydraulic pump, heat pump and engine supercharger, possibly turning four-stroke engines into more efficient two-stroke engines. The principle breakthrough in the machine invented by Ron Driver, and being developed by his company, EA Technical Services, is its simple mechanism. This combines a hinging vane and an eccentrically mounted rolling piston. Encountered at the Clean Energy Investment Showcase, organised by the Centre for Sustainable Engineering, Driver told Eureka: “We have been testing a 20kW prototype of this for two years.” Designed to compress standard refrigerant R134A, he said: “We have managed to eliminate manufacturing tolerances. It does this by having polymer in little slots to bridge the manufacturing gap. On the first few rotations, the polymer wears away to make a good fit. We have also run it for 100 hours using only the refrigerant as a lubricant.” Tests have been carried out at the University of Ulster, which has expertise in refrigeration. The device can be used as an expander as well as a pump. “All expanders waste energy, but we recover 20-40% of the energy by expanding it through a separate part of the machine, working in the same way as the compressor,” said Driver. “Others who have tried to do this only recover 5%, but ours is a positive displacement machine rather than a small turbine.” The machine can also be used in heat pumps, since these machines are essentially refrigerators run in reverse. Heat pumps deliver more heat than the amount of energy used to run them – since they move heat from one place to another rather than generate it – the project has been supported with £149,466 from the Carbon Trust and £40,000 from a Shell Springboard Award. “We are due to finish tests in the middle of January 2007,” Driver told us. As well as refrigerators and heat pumps, it could also sit in the intake of a petrol engine. “It could either recover pumping losses or act as a supercharger,” said Driver. “We found we could put it well away from the engine and inject air and fuel – so that the engine becomes a two-stroke instead of a four-stroke with a variable expansion ratio.” The design has been extensively modelled using ProE/Mechanica’s FEA facility to calculate bearing fatigue life. Fluid flow was modelled using Ansys CFD software. The total cost of the test programme has been £500,000, with 70% provided by the private sector. Ron believes his technology has, “The realistic potential to reduce UK CO2 emissions by 7.2 million tonnes per year at 10% market penetration and save 20% for the consumer. E.A.Technical Services Pointers * Machine works as a refrigeration or heat pump with an integral expander that recovers 20-40% of input energy * It is simple in design, lubricated by the working fluid and designed for robotic manufacture * Polymer rubbing strips wear in the first few rotations to ensure efficient sealing without the need for tight manufacturing tolerances