Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.
Transcritical expansion through coiled adiabatic
capillary tubes having CO2 as the refrigerant is
numerically simulated and the performance is
compared with R22 flow through such tubes. Mori
and Nakayama friction factor correlation in
combination with Churchill equation, which is fitted
into Blasius type equation, is used to calculate the
friction factor. Results indicate that reduction in mass
flow rate with a coiled capillary tube compared to a
straight one is more pronounced in case of CO2 in
comparison to R22. Mass flow rate of refrigerant
increases as the coil diameter increases, but changes
little beyond a coil diameter (D) of 180 mm. A
shorter capillary tube will be required to match the
requisite system mass flow rate when coiled capillary
tubes are employed.
