Effect of inserting coiled wires on pressure drop of R-404A condensation

•The insertion of coiled wires causes pressure drop increase up to 1300%.•Pressure drop is increased with the increase of coiled wire diameter.•A correlation was proposed to predict the pressure drop of coiled wire inserted tubes.

In this study, an experimental investigation was carried out to determine the increase of pressure drop during convective condensation of R-404A vapor inside coiled wire inserted tubes. Experiments were performed for a plain tube and five coiled wire inserted tubes. Data were collected for four mass velocities. For each mass velocity, six different vapor qualities were considered. From the results, it is found that the coiled wire inserts increased the pressure drop up to 1200% compared to plain tube values. An empirical correlation is also developed to predict the pressure drop of coiled wire inserted tubes during R404-A condensation with accuracy of ±20%.