Open Access

ARTICLE

A COMPARISON OF THE EQUILIBRIUM AND THE DROPLETS BASED NON-EQUILIBRIUM COMPRESSIBLE PHASE CHANGE SOLVERS FOR CONDENSATION OF CARBON DIOXIDE INSIDE NOZZLES

by

Birla Institute of Technology and Science, Pilani, Rajasthan, 333031, India
† Corresponding author. Email: ss.yadav@pilani.bits-pilani.ac.in

Frontiers in Heat and Mass Transfer 2021, 16, 1-10. https://doi.org/10.5098/hmt.16.14

Abstract

In the current work, we simulate the condensation of supercritical CO₂ during its high speed flow inside two different converging-diverging nozzles. We use the homogeneous equilibrium method and the classical nucleation theory based non-equilibrium phase change model for this purpose. The simulation results indicate significant influence of the nozzle inlet condition, nozzle shape and the fluid thermophysical behaviour on the nonequilibrium conditions prevailing inside the nozzles. We observe very low, ∼0.15 K, supercooling for the flow of CO₂ inside the Claudio Lettieri nozzle compared to the supercooling of ∼3 K observed for the Berana nozzle. Very high nucleation rate (∼ 10³⁵ nucleation per m³ per second) is observed before the throat of the nozzles which remains confined to a very small axial distance. The nucleation rate takes much smaller values (∼ 10⁷ nucleation per m³ per second) in rest of the nozzle. A maximum of 70 nano meter sized droplets with number densities of the order of 10²¹ droplets per m³ are predicted inside the nozzles. Liquid mass fraction values between 0.2 to 0.4 are predicted by the solvers inside the nozzles. These results will be useful to the engineering community involved in the design and fabrication of CO₂ based systems.

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