TY - JOUR
T1 - Heat rejection in condensers close to critical point-de-superheating, condensation in superheated region, and condensation of two-phase fluid
AU - Kondou, Chieko
AU - Hrnjak, Pega
N1 - Copyright:
Copyright 2013 Elsevier B.V., All rights reserved.
PY - 2013/11/14
Y1 - 2013/11/14
N2 - Conventional modeling of condensers typically assumes three zones: de-superheating, condensation, and subcooling zone, even though it is clear that condensation occurs in the de-superheating zone at some conditions and subcooling occurs during condensation. This article discusses the actual situation and provides experimental validation of the hypothesis. The experimental results show heat transfer coefficients (HTC) of CO2 and R410A at mass fluxes from 100 to 240 kg m-2 s-1, heat fluxes from 3 to 25 kW m-2, and reduced pressures from 0.68 to 1.00 in a horizontal smooth tube of 6.1 mm inner diameter. Data are compared to correlations proposed for other working fluids or other conditions. Results show much higher values of HTC than the correlation proposed for single-phase turbulent flow in the superheat zone. The occurrence of condensation in the superheat zone is evident when tube wall temperature is below saturation temperature. The results suggest that simplified calculations of heat rejection in a superheated zone could oversize condensers. The semi-empirical correlation, which is here proposed as the combination of existing correlations for single-phase turbulent and saturated condensation, satisfactorily predicts HTC of the superheat zone condensation.
AB - Conventional modeling of condensers typically assumes three zones: de-superheating, condensation, and subcooling zone, even though it is clear that condensation occurs in the de-superheating zone at some conditions and subcooling occurs during condensation. This article discusses the actual situation and provides experimental validation of the hypothesis. The experimental results show heat transfer coefficients (HTC) of CO2 and R410A at mass fluxes from 100 to 240 kg m-2 s-1, heat fluxes from 3 to 25 kW m-2, and reduced pressures from 0.68 to 1.00 in a horizontal smooth tube of 6.1 mm inner diameter. Data are compared to correlations proposed for other working fluids or other conditions. Results show much higher values of HTC than the correlation proposed for single-phase turbulent flow in the superheat zone. The occurrence of condensation in the superheat zone is evident when tube wall temperature is below saturation temperature. The results suggest that simplified calculations of heat rejection in a superheated zone could oversize condensers. The semi-empirical correlation, which is here proposed as the combination of existing correlations for single-phase turbulent and saturated condensation, satisfactorily predicts HTC of the superheat zone condensation.
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U2 - 10.1080/01457632.2013.776883
DO - 10.1080/01457632.2013.776883
M3 - Article
AN - SCOPUS:84878686035
SN - 0145-7632
VL - 34
SP - 1180
EP - 1190
JO - Heat Transfer Engineering
JF - Heat Transfer Engineering
IS - 14
ER -