Rotary transcritical heat pump feasibility

The concept of a transcritical cycle rotating heat pump is modelled. In this, the centripetal force of rotation creates the compression pressure of the working fluid, replacing the conventional positive displacement or turbine compressor. The rotating heat pump was conceived over five decades ago yet the first know realization is a reverse Brayton cycle heat pump proven in early commercialization. In this, both the low and high temperature heat exchangers rotate, meaning the entire fluid cycle is rotating. In this work, the rotating concept is applied to a transcritical cycle with only the compressor tube, high temperature heat exchanger, and expander are rotating, with the evaporator external to rotation. This arrangement is modelled in EES, assessing rotor radius and rpm required for the transcritical cycle for various fluids to include natural refrigerants and modern refrigerants meeting the latest F-Gas regulation. The model is assessed over various heat pump applications, domestic heat pump, freezer system, and high temperature industrial heat pump. The modelling shows the pressures that are relatively easy to achieve with this arrangement allow the high pressures required for transcritical cycles of not only R744, but also R600, R290, R1224yd(Z), and significantly, R717 Ammonia. The new possible range of transcritical cycles offer high COP and significantly greater volumetric and specific power compared to the commercial reverse Brayton cycle rotating system. The rotating system also allows a compressor heat exchanger, allowing simulations compression and heat exchange, greatly reducing compression work of isentropic, towards isothermal compression. The resultant compression pressure and temperature to be as desired for a particular application by design of the compressor heat exchanger and rotating system. The rotating system with a single rotating heat exchanger and transcritical cycle does present mechanical design challenges that are discussed.