Ammonia condensation in the horizontal and vertical smooth tubes

Abstract

The paper proposes the experimental study of ammonia condensation in aluminium tubes with 8 mm and 11 mm internal diameters. The new study aimed to compare and extend the existing ammonia in-tube condensation data. The lines were tested mainly in horizontal configuration at mass velocities of 20 to 160 kg·m−2s−1, saturation temperature of 35 to 65 °C and inlet vapour quality of 0.1 to 0.9. Shah (1979), laminar-laminar Dobson and Chato (1998), and Cavallini et al. (2001) models predict well ammonia condensation HTCs at mass velocities of 120 to 160 kg·m−2s−1. A new phenomenological model has been proposed for the mass velocities of 20 to 120 kg·m−2s−1, predicting the test data with an accuracy of ±20%. Similar ammonia condensation HTCs have been obtained for horizontal and upstream flows at a mass velocity above 120 kg·m−2s−1. The lowest condensation HTCs at the considered boundary conditions characterise the downstream configuration of an in-tube condenser at a mass velocity below 120 kg·m−2s−1. However, inclining the ID 8 mm tube by 15° from the normal substantially increases the condensation HTCs by 10 to 30%, depending on vapour quality. At the inclinations of 15 to 45° from the horizontal line toward the downstream flow, the condensation HTCs exceed the ones of horizontal flow by 10 to 15% at the vapour quality of <0.5 and low mass velocity of 80 kg·m−2s−1.