SBIR Phase I: High Efficiency Multi-fluid Jet Refrigeration

This Small Business Innovation Research Phase I project will demonstrate a highly efficient supersonic ejector vapor compression technology that converts low-to-medium grade thermal energy (200-400F) into useful refrigeration (20F-50F) at high condenser temperatures (100-120F). The proposed multi-fluid jet cooler maximizes heat transfer efficiency by using a propellant with relatively low latent to continuously entrain and compress an immiscible low temperature refrigerant of relatively high latent heat. Initial prototypes have 400% higher efficiencies than conventional single-fluid ejectors. Phase I research will extend these gains while operating at elevated condenser temperatures. Specific research foci are: 1) Highly efficient jet nozzles to supersonically expand a high molar mass, low specific heat ratio propellant without the expansion/compression losses observed when using conventional nozzle designs; 2) Mixing of subsonic refrigerant into the supersonic propellant with minimal kinetic energy loss by avoiding sonic choking of the refrigerant; and 3) Maximum pressure recovery diffusers utilizing weak, oblique compression waves instead of strong, normal shock waves to transition the mixed supersonic flow to subsonic velocity. Potential applications for the two-fluid ejector compression technology include natural gas powered air conditioning, concentrated solar thermal chiller plants, lower cost combined heating power and cooling plants, and thermally-driven water desalination. The broader impact/commercial potential of this project is reduced economic and climate burden associated with the world?s growing demand for space cooling. Air conditioning is the leading usage for peak-time electricity in the U.S. and largest energy expense for commercial buildings. Globally, the $65billion air conditioning equipment market is growing at 5% p.a.; and because it is dominated by the electrically-driven mechanical vapor compression cycle the strain on electrical grids - and by extension the environment and economy - is rising likewise. A quiet, clean, reliable and cost effective heat-driven solution would greatly reduce these risks. Unfortunately, status quo technologies suffer low efficiencies, large form factors, and require expensive water-cooled condensers. Initial R & D efforts have proven an ejector vapor compressor using optimized fluid pairs built with low cost components can operate at efficiencies competitive with electric compressors when operating in moderate ambient conditions. Massmarket adoption, however, requires efficient operation at extreme outside temperatures. Phase I research will maximize cooling power and discharge pressure (thus operability at high condenser temperatures) by minimizing irreversible losses incurred during supersonic expansion and compression of the immiscible fluid pairs. Project findings will benefit adjacent fields of hypersonic avionics and low atmosphere jet propulsion