Empirical study of heterogeneous refrigerant condensation in pipe minichannels

• R134a, R404A, R410A and R407C refrigerant condensation in pipe minichannels.
• Experimental investigation results.
• Own model for calculation pressure drop and heat transfer during condensation in minichannels.
• The short review of knowledge about condensation in minichannels.

This paper concerns the experimental test results of homogeneous refrigerant R134a and zeotropic solutions R404A, R407C and R410A condensation in pipe minichannels with an internal diameter d = 0.90–3.30 mm. The paper presents experimental thermal and flow characteristics of condensation in comparable ranges. The experimental results were compared to the calculated results of other authors' correlations. It was found that the discrepancy between the results of tests and calculations is large, especially for zeotropic solutions, and in excess of the range of ±50%. The authors developed their own correlations, providing compatibility within ±25% for all of the tested refrigerants. Correlations are proposed for annular and annular-stratified two-phase flow structures.