This Small Business Technology Transfer (STTR) Phase II project seeks to continue the research and analysis of condensing ejectors for second stage compression in a refrigeration cycle. A condensing ejector is a two-phase jet device that produces outlet pressure higher than either of inlet pressures. The project combines theoretical and experimental models in order to design the condensing ejector for use in more efficient refrigeration systems. The results thus far show that the new design is capable of improving the efficiency of vapor compression refrigeration cycle by approximately one-third with R22 refrigerant. The goal is to draw closer to this ideal value with environmentally friendly refrigerants like R410A. The application of critical two-phase flow devices will lead to development of more efficient thermodynamic cycles for refrigeration and A/C and in the future possibly for propulsion and power generation.
The broader impact/commercial potential from this project will bring considerable economic and societal benefits by reducing our nation's dependence on foreign oil, improving safety of nuclear reactors and natural gas pipelines, and better understanding of phenomena of two-phase flow. Applications of the condensing ejector theory in heat pumps might promote use of renewable geothermal energy sources in the remote communities with limited energy choices. This project leads to enabling technologies by providing the technology platform for a new approach to evaluating two-phase flows. The capability to handle rapid phase change simulations has generated interest from the automotive industry to simulate flash boiling in automotive fuel injection. This project also provides the basis for establishing fundamentally new engineering and designing methods for equipment operating on two-phase flow.
Cheaper, more efficient, and less polluting solutions are required for our Nation’s future air conditioning (A/C) and refrigeration because as of now, they account for almost 25% of all U.S. electricity consumption and create two sources of environmental pollution and global warming: 1) the ozone-depletion effect of traditional refrigerants and 2) the emission of greenhouse gases connected with the generation of electricity. In response to these needs we developed under the STTR project a "condensing ejector", which can work in various applications to improve efficiency and reduce energy usage in refrigeration and A/C systems. A condensing ejector is a device that compresses gas or vapor without using any mechanical energy. It can be used in refrigeration systems to either "help" a mechanical compressor by providing a portion of compression, or as a stand-alone compressor. The principle of a condensing ejector, shown in Fig. 1 is based on a mixing of vapor and liquid refrigerant. The vapor, which is hotter than liquid, rapidly condenses, producing a high pressure due to a "condensation shock". During Phase I we demonstrated in a laboratory the feasibility of this concept and obtained the actual pressure rise. In a follow-up Phase II, we developed the methodology for practical design of such ejector and have built a working prototype shown in Fig. 2. Consequently, the US Patent No. 7,559,212 B2 was obtained for this invention. Further, we developed following practical applications for our ejector: 1. Ejector used as a second step compressor in geothermal heat pumps to improve their efficiency by up to 40%. 2. Ejector-based A/C system powered by solar and waste heat. This application eliminates a mechanical compressor and the A/C can operate without any need for electricity. 3. Miniature cooling system for computers, powered by the heat produced by microprocessor. These new systems are well suited for natural refrigerants, which do not create any ozone depletion effect. In the future we can envision many other attractive products based on the same technology, for example automobile A/C powered by the engine exhaust, cooling cabins in tanks and helicopters by engine heat, cooling data centers by utilizing the heat generated by computers, mobile solar-powered refrigerated storage for medicines, etc. Our first design was for a solar-powered A/C for residential dwellings. The model of 3 Ton unit per schematics of Fig.3 was fabricated and installed in a laboratory . Sustainable operation of the system was achieved and we were able to lower the outside temperature by 30F, utilizing solar heat at temperature of 170F. We believe this was the first practical demonstration of a working ejector-based, heat-driven cooling system in the world. The developed system reduces the consumption of electric energy by over 90% as compared to current technology - due to elimination of the mechanical compressor. Heat rather than electricity is the main source of energy and it is either very cheap (waste heat) or free (solar heat). Such system is best suited for Southern US States. If only 10% of houses in those states adopt our technology, the electricity savings may reach $2.65Bln per year and the emission of greenhouse gases decreased by 36 Million Tons/year. In Phase IIB, we were able to attract an investment from the leading US computer manufacturer to develop a cooling system for laptop computers utilizing the heat generated by the microprocessor as a main source of energy. This technology could be attractive for the Dept of Defense, especially in the Middle East, for cooling field hospitals, command centers and/or data centers. It can be used for refrigeration and air-conditioning purposes in Third World countries and in remote areas where electric energy is unavailable. Small solar-based units can be developed for storage of medicines and perishable food. Magnetic Development, Inc. has previously developed an inexpensive mobile solar unit, shown in Fig. 4, which together with our new cooler can produce about 1/3 Tons of refrigeration without any need for outside electricity. Summarizing, this innovation has following benefits as compared to conventional A/C systems: 1) utilizes solar or waste heat as a main source of energy, 2) eliminates the mechanical compressor, which is a main user of electricity and the main contributor to maintenance and reliability issues in cooling systems and 3) operates without any ozone depletion effects and any greenhouse gas (GHG) emissions, when used with natural refrigerants. Further benefits are: 1. Expanded availability of A/C and refrigeration in Third World countries. 2. Potential applications for Dept. of Defense. 3. Creation of well–paid professional jobs for production, installation and maintenance. 4. Advancement in technology, stimulating other institutions to undertake related research.
