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Oklahoma State University

Optimal A/C cycles for 21st Century Refrigerants

Sponsors: Oklahoma Center for the Advancement of Science and Technology, Quantum Construction Technologies, Inc., and the York Unitary Products Group

Description: The proposed project will consist of a joint effort between the York Advanced Technology Group and the Building Environmental and Thermal Systems Research Group (BETSRG) in the Department of Mechanical and Aerospace Engineering at Oklahoma State University.  The two groups bring complementary expertise and resources to the project and will work closely together in a synergistic research environment to develop innovative unitary air conditioning equipment that uses advanced and natural refrigerants.

Over the last decade refrigerant research has focused on the thermodynamic and kinematic properties of binary and ternary zeotropic blends of HFCs and, more recently, on possible applications of natural refrigerants.  Experimental research is currently underway to determine the transport and heat transfer properties of these refrigerants in the components of the vapor compression cycle.  In addition, numerical analysis and simulation have been employed to use experimentally determined refrigerant properties in the analysis of cyclic performance under various conditions.  However, no work has been done to extend the current research to the synthetic development of innovative systems that use advanced and natural refrigerants.  To achieve this objective a simulation environment must be developed that couples cutting-edge vapor compression component models with realistic transient environmental boundary conditions and detailed physical and transport property information for advanced refrigerants.

This research advances the state-of-the-art in three significant ways.  First, cutting-edge component technologies will be modeled by the research team and linked to the simulation environment.  Second, heat-balance based models of environmental boundary conditions for enclosed HVAC equipment will be developed and experimentally validated.  Finally, existing physical and transport property data for advanced and natural refrigerants will be linked to the simulation environment.  In most cases, this will require the development of correlations that are suitable for system simulation.  Component models, some of which will represent new and emerging technologies, refrigerant property correlations and environmental boundary models will be linked to an existing simulation engine that supports a dynamically variable simulation time step.

The proposed research also achieves the main objective of a Phase I Applied Research project by developing the R&D capabilities of the York Unitary Products Group (UPG).  The result of this project will place a synthetic design research tool in the hands of the Unitary Products Group.  This tool will greatly expand the York’s capacity for technological innovation.  Its development is not only timely, but also critical to the development of new product lines at the Oklahoma City facility.  Existing steady state cycle simulations cannot be used in design applications, and the “trial and error” method used successfully for incremental improvement of existing designs cannot be successfully used to design new cycles for advanced refrigerants.  A synthetic design and analysis research tool is the critical “missing link” in UPG’s R&D chain.  The research program outlined in this proposal provides this missing link.

Keywords: air-conditioning, energy, ozone, refrigerants, simulation

Product Description:

The seven York UPG product lines can be broadly described as air-conditioner systems operating on a standard vapor compression cycle.  These systems, which currently use low level ozone-depleting refrigerants, range in capacity from 1.5 to 40 tons of cooling.  The new products will be designed utilizing the simulation technology developed under this proposal and will include state-of the art components and alternate/natural refrigerants.

The 1.5 to 5 ton residential air-conditioning unit shown in Figure 24.1 is an example of  one of the seven product lines targeted for the application of the new technology.

Residential A/C Unit


Nathan Weber's  M.S. Thesis (pdf)

Iu, I., Bansal, P.K., Rees, S.J., Fisher, D.E., Weber, N.A. and Spitler, J.D. Energy efficiency analysis of a unitary heat pump system. Proc. of International Conference on Building Systems and Facilities Management - Integrating Innovations and Technologies for a Built Environment, Singapore, October 2003.