Pressure losses investigation at boiling two-phase flow movement in inclined pipes of a marine refrigeration machine evaporator

Abstract

The study of pressure losses at boiling two-phase flow movement in vertical and inclined pipes of evaporators of ship refrigeration units is carried out. The study of the ascending two-phase flow is promising from the point of view of practical application. Such a movement is typical for various types of industrial heat exchange equipment, including for the development of promising types of evaporators, for example, vertical apparatuses for ships in which internal boiling of the refrigerant occurs. A methodology has been developed and an experiment has been set up to study the processes in the steam generating channels of refrigeration units at various angles of inclination with a fixed height. At the same time, the length of the channel changed, it became possible to analyze friction losses. A new approach has been applied that brings the model as close as possible to the actual boiling process, taking into account the constant increase of steam in the channel. Experimental studies have been carried out and data on pressure losses have been revealed when the angle of inclination of the steam generating channel changes. The main dependences and various components of hydraulic resistances during the movement of a boiling two-phase flow are presented. Based on the data obtained, the justification of ship evaporators transition of refrigeration units to the vertical arrangement of the heat exchange steam generating beam is proved. The results obtained indicate that an increase in the slope of the pipe, provided that the height is maintained, leads to an increase in pressure losses. Applicability to marine refrigerating machines has been determined – the transition to vertical apparatuses has advantages, primarily in reducing pressure losses. The obtained set of data allows to recommend the design of vertical evaporators for auxiliary ship installations.

Research of boiling flow parameters in vertical evaporators of marine refrigeration machines

“…Из рисунка видно, что рост давления в показанном диапазоне изменяет температуру кипения от 1 градус для R410a и до 1,6 градусов для R600a. Такое изменение необходимо будет компенсировать понижением температуры кипения хладагента, что, снижает холодопроизводительность машины примерно на 4 процента за каждый градус [14][15]. Тем не менее такое повышение температуры кипения будет наблюдаться только в самой нижней части трубы и будет снижаться по мере приближения к её верхней части.…”