630/22. evaluacion mediante strain longitudinal global automático de largos supervivientes de leucemia aguda linfoblástica en edad pediatrica

Ammonia is an environment-friendly natural refrigerant and working fluid with negligible global warming and ozone depletion. Nowadays, ammonia is widely used in industrial refrigeration systems, heat pumps and thermal control systems, including heat pipes, loop heat pipes and two-phase mechanically pumped loops. In perspective, “green” ammonia is considered an energy carrier and carbon-free fuel. In two-phase systems, the void fraction is one of the critical factors determining the frictional and local pressure losses, boiling and condensation heat transfer and phase separation. The experimental study of ammonia void fraction in the tubes with inner diameters of 8.5 mm and 15 mm is proposed in this paper. The quick-closing valve method has been chosen. Three flow configurations are considered: vertical downward, vertical upward and horizontal. The tests were provided for the two-phase ammonia at a mass velocity of 50…500 kg·m−2s−1, saturation pressure of 15…30 bar, and vapour quality of 0.05…0.30. One hundred and five points have been tested. No existing single correlation predicts the ammonia void fraction well at the considered boundary conditions for at least two orientations in the gravity field. A new single correlation has been proposed based on the Rouhani drift model with the tube inclination angle-dependent distribution parameter allowing the adequate prediction of void fraction in a tube with ammonia flow at horizontal, upward and downward orientations.