The reversed Brayton process can be used in drying, air conditioning and cooling. The research started at early 90's and the laboratory designed and produced two test facilities to demonstrate the function of the process for drying purposes.
Applying high speed technology makes the machine practically service free and very compact; the drying and air conditioning can be done without big heat exchangers.
First test facility, 12 kW, 20 000 rpm
In the early stage of the design, it was clear that a prototype was needed to verify the process calculations of the Reversed Brayton Cycle and its components. The first facility was based on the Reversed Brayton Cycle with partial high speed technology. The goals of the first facility (1992-93) were to verify the calculation model and to check the results of the design parameters in favourable operation regions.
Second test facility, 2 kW, 87 000 rpm
The second test facility was built with high speed technology in the years 1994-95. It was designed to function as an air drier in the operational range of commercial air driers, and it was planned to be a serious reference for further development of commercial Reversed Brayton Cycles. The reversed Brayton process consists of a compressor, expansion turbine and high speed machine.
The rotating speed of this second gas- and magnetic bearing test apparatus is 87 000 rpm and the small size is reflected with a match.
In the early stage of the research, the process calculations proved to be very iterative and time consuming to accomplish the required accuracy. The researchers, and later the product development and marketing personnel, could benefit from a reliable process calculation programme that provides explicit data about the performance and the components of the machine.
The extensive theoretical and experimental research at LUT has resulted in one doctoral thesis (Backman) and one licentiate’s thesis (Sahlberg).