Assessment Of Heat Pump With Carbon Dioxide/Low-Global Warming Potential Working Fluid Mixture For Drying Process: Energy And Emissions Saving Potential

Drying is one energy-intensive process in the industry. Heat pump system for drying process by employing carbon dioxide/low-global warming potential working fluid mixture is proposed and compared with traditional boiler drying systems. A life cycle thermodynamic and environmental evaluation model is developed to assess the energy consumption, gaseous and particulate matter emissions saving potential by using the new heat pump drying solutions. With the help of carbon dioxide/low-global warming potential working fluid mixtures, the coefficient of performance of heat pump dryer is obviously enhanced and the discharge pressure is reduced. The highest coefficient of performance of 4.29 is achieved by using carbon dioxide/R32 under the mass fraction of 0.1/0.9, which is increased by 7.42% in contrast to pure carbon dioxide. The specific moisture extraction rate is improved and the primary energy consumption throughout the lifetime is dramatically reduced. The life cycle climate performance is also reduced and the equivalent carbon dioxide emissions from energy consumption are the dominant category. Carbon dioxide-based mixture heat pump dryer can also reduce the pollutant emissions. Compared with natural gas-fired boiler system, oxynitride emissions are decreased by 81.66%, and particulate matter emissions are less than a quarter of the electric boiler. Carbon dioxide/low-global warming potential working fluid mixtures with low or medium-temperature glide, and high-temperature glide carbon dioxide/lowglobal warming potential working fluid mixtures with extremely low (-0.1) or very high (-0.9) carbon dioxide mass concentrations are recommended. The heat pump dryer charged with carbon dioxide/low-global warming potential working fluid mixtures is a promising solution to substitute traditional boilers for energy-saving and environmentally-friendly industrial drying.