TY  - EJOU
AU  - Chen, Yan 
AU  - Li, Xuefang 

TI  - MODELING OF THE HEAT TRANSFER IN A SUPERCRITICAL  CO<sub>2</sub>/DME MIXTURE FLOWING IN COOLED HELICALLY COILED  TUBES
T2  - Frontiers in Heat and Mass Transfer

PY  - 2021
VL  - 16
IS  - 1
SN  - 2151-8629

AB  - The heat transfer of supercritical CO<sub>2</sub>/DME mixtures was modeled in this study for a mass ratio of 95/5 for cooling in horizontal helically coiled 
tubes. The CO<sub>2</sub>/DME heat transfer coefficient was higher in the high-temperature zone than with pure CO<sub>2</sub>. The heat transfer of CO<sub>2</sub>/DME (95/5) 
was predicted for various mass fluxes, heat fluxes and pressures. The CO<sub>2</sub>/DME heat transfer coefficient increased with the mass flux due to the 
increased turbulent diffusion, and first increased but then decreased with the heat flux. The peak heat transfer coefficient of CO<sub>2</sub>/DME shifted toward 
the high-temperature region as the operating pressure increased. The effects of buoyancy and the centrifugal force were also analyzed to better 
understand the heat transfer mechanisms in helically coiled tubes. The gravitational buoyancy effect on the heat transfer decreased with mass flux 
while increased with heat flux. Higher heat fluxes strengthened the centrifugal buoyancy effect on the heat transfer at the beginning of the cooling 
process but weakened the centrifugal buoyancy effect later in the cooling process. The present study gives insight into the flow and heat transfer 
processes in helically coiled tubes which is useful for heat exchanger designs and refrigerant selection.
KW  - CO<sub>2</sub>/DME mixture
KW  -  trans-critical system
KW  -  heat transfer
KW  -  heat pump

DO  - 10.5098/hmt.16.18