Abstract
A novel two stage compressor for CO2 heat pump water heater was developed. CO2 as a working fluid has high operating pressure and high pressure difference, which brings decrease in efficiency and reliability. Therefore, it is especially important for a development of CO2 compressor to make a proper selection of its basic structure. The developed two stage compressor equips intermediate pressure housing, intermediate gas injection and both rotary and scroll compression chambers as first and second stage respectively. For the efficiency improvement, loss classifications based on the cylinder pressure measurements were conducted and 6% reduction in the indicative efficiency in the second stage was obtained by stiffness enhancement of the fixed scroll. The developed compressor resulted in over 15% improvement of efficiency compared with conventional single stage compressor. Moreover, 25% and 50% improvement of heating capacity and COP respectively is archived on deep frozen condition by employing two stage intermediate gas injection system with the developed compressor.
