Effect of sensible heat, condensation in superheated and subcooled region incorporated in unified model for heat rejection in condensers in horizontal round smooth tubes

• Review of current models for condensation and proposal of 5 zones for heat rejection.
• Discussion of proposed model which includes the effect of sensible heat rejection in condensation.
• Validation of model with experimental data for three fluids R1234ze(E), R134a and R32 at various operating conditions.
• Qualitative discussion of condensation in superheated, two-phase and subcooled zone separately by comparing experimental data with model results.

Heat transfer in condensers is typically divided into 3 zones: superheated, two-phase and subcooled. The heat transfer coefficients (HTC) for these zones show discontinuity at qualities of 0 and 1, where two-phase correlations meet single phase flow correlations. The paper presents a model that bridges that discontinuity. It takes into account the condensation in de-superheating zone and subcooled liquid in two-phase zone which results in condensation in subcooled region. Cavallini et al. (2006) and Gnielinski correlations have been used as a baseline correlations in the model to calculate HTC in two-phase and single phase zone respectively. The model has been compared to experimental data in condensation for R1234ze(E), R134a and R32 conducted from superheated to subcooled region and predicts the HTC satisfactorily within an accuracy of 16% for these fluids.