Basic study on new cryogenic refrigeration using CO2 solid–gas two phase flow

In this paper, a cryogenic refrigeration method is described, which utilizes CO2 solid–gas two phase flow and the dry ice. The CO2 solid–gas two phase flow is achieved by expanding liquid CO2 and thus refrigeration process less than CO2 triple point −56.6 °C can be available. The experimental work is divided into two parts and two experimental set-ups were designed, constructed and tested. The interest of the first experiment test is the feasibility of expanding liquid CO2 into CO2 solid–gas flow in a horizontal circular tube by expansion valve. The second experiment focuses on the feasibility of the refrigeration of liquid CO2 expanding into solid–gas two phase flows used in a prototype CO2 heat pump system. The results show that solid–gas two phase flows can be achieved by expanding liquid CO2 by expansion valve in a closed CO2 heat pump system loop and low temperature refrigeration below −56.6 °C is achieved in the experiments, which give greater possibility to create a cryogenic refrigeration process below −56.6 °C for food industries, bio-medical engineering, etc.