Enhancement of Heat and Mass Transfer in Mechanically Contstrained Ultra Thin Films

Oregon State University (OSU) and the Pacific Northwest National Laboratory (PNNL) were funded by the U.S. Department of Energy to conduct research focused on resolving the key technical issues that limited the deployment of efficient and extremely compact microtechnology based heat actuated absorption heat pumps and gas absorbers. Success in demonstrating these technologies will reduce the main barriers to the deployment of a technology that can significantly reduce energy consumption in the building, automotive and industrial sectors while providing a technology that can improve our ability to sequester CO{sub 2}. The proposed research cost $939,477. $539,477 of the proposed amount funded research conducted at OSU while the balance ($400,000) was used at PNNL. The project lasted 42 months and started in April 2001. Recent developments at the Pacific Northwest National Laboratory and Oregon State University suggest that the performance of absorption and desorption systems can be significantly enhanced by the use of an ultra-thin film gas/liquid contactor. This device employs microtechnology-based structures to mechanically constrain the gas/liquid interface. This technology can be used to form very thin liquid films with a film thickness less then 100 microns while still allowing gas/liquid contact. When the resistance to mass transfer in gas desorption and absorption is dominated by diffusion in the liquid phase the use of extremely thin films (<100 microns) for desorption and absorption can radically reduce the size of a gas desorber or absorber. The development of compact absorbers and desorbers enables the deployment of small heat-actuated absorption heat pumps for distributed space heating and cooling applications, heat-actuated automotive air conditioning, manportable cooling, gas absorption units for the chemical process industry and the development of high capacity CO{sub 2} absorption devices for CO{sub 2} collection and sequestration. The energy potential energy savings associated with these technologies is estimated to ultimately be 2.88 quads per year. It has become clear that commercial application of these technologies depends on a deeper understanding of the thermal phenomena encountered in a mechanically constrained ultra-thin film device. Our lack of understanding is currently limiting both the performance of these devices and the potential for further size reductions. Barriers to successful commercial applications of the mechanically-constrained ultra-thin film contactors include poorly understood single and two phase flow phenomena in the thin film, the need for improved micromachined contactors and a poor understanding of the phenomena effecting the dimensional stability of the thin film. The research included in this proposal is focused on research associated with resolving and removing these technical barriers to commercialization. The results of the research will significantly advance the prospects for the commercialization of the whole range to technologies that depend on improved gas/liquid contacting