پيش بيني افت فشار در جريان چرخشي- جوششي مبردR- 134 a در لوله ي افقي

PREDICTION OF PRESSURE DROP DURING SWIRL FOLW BOILING OF R-134A INSIDE A HORIZONTAL TUBE

In the present work, an investigation into prcssuie drop during swirl flow boiling of refrigerant R-134a inside a horizontal tube has been undertaken. To do so, twisted tape inserts, with twist ratios of 6, 9, 12 and 15 were employed inside the evaporator tube. The test set-up used in this investigation was a well instrumented va­por compression refrigeration system. This set-up con­sisted of three electrically heated evaporators called pre- evaporat.or, test evaporator and after evaporator. First, a correlation was developed to prcdict the pressure drop inside the plain tube by using the experimental data, Then, based on the collected data for the plain tube and the tubes with twisted tape inserts, two correla­tions were developed to predict the pressure drop inside the twisted tape inserted tubes. The predicted pressure drop by these correlations, fell with an error band of ± 15% of the experimental pressure drop data. Generally, the insertion of twisted tape inside a horizontal tube, increases the pressure drop. In the worst condition, the flow boiling pressure drop increases up to 180% and, as an average, up to 100% relative to plain tube values on a nominal area basis