Air-side heat transfer and pressure drop in spiral wire-on-tube condensers

The air-side thermal-hydraulic performance of spiral wire-on-tube condensers is investigated experimentally in this paper. Sixteen prototypes have been manufactured and tested in an open-loop wind tunnel calorimeter. The influence of the following geometric parameters has been evaluated: the number of tube passes, the radial and longitudinal tube spacings and the wire spacing. Measurements of the air-side thermal conductance and pressure drop were carried out for air flow rates ranging from 70 to 220 m3 h−1. The data were correlated using empirical relationships for the Colburn j-factor and the Darcy friction factor. The agreement with the experimental data presented RMS deviations of 0.9% for the air-side heat transfer and 1.3% for the frictional pressure drop dimensionless parameters. A quantitative analysis based on the core volume goodness factors for heat transfer and pressure drop is presented to provide the most viable configuration from the point of view of application in a refrigerator.

► Evaluation of air-side performance of spiral wire-on-tube condensers in forced convection.
► All sixteen condenser prototypes have the same total tube length, tube diameter and wire diameter.
► The wire spacing is the most significant parameter in the thermal performance of the condenser.
► The pressure drop is more strongly influenced by the radial tube spacing.
► Empirical correlations were proposed for the Colburn j-factor and for the Darcy friction factor.