Open AccessCHANGING INTENSITY OF HEAT TRANSFER IN THE PIPE SECTION DURING REFREGERANT BOILING IN THE EVAPORATORS OF SHIP REFRIGERATING PLANTS
Author(s) -
Александр Букин,
Vladimir Grigorievich Bukin
Publication year - 2019
Publication title -
vestnik astrahanskogo gosudarstvennogo tehničeskogo universiteta. seriâ: morskaâ tehnika i tehnologiâ
Language(s) - English
Resource type - Journals
eISSN - 2225-0352
pISSN - 2073-1574
DOI - 10.24143/2073-1574-2019-2-80-84
Subject(s) - heat transfer , boiling , evaporator , mechanics , thermodynamics , heat transfer coefficient , refrigerant , intensity (physics) , micro loop heat pipe , slug flow , materials science , nucleate boiling , heat exchanger , flow (mathematics) , plate heat exchanger , two phase flow , physics , optics
The article describes the experimental evaporator as a research object, the evaporator model being given with boiling refrigerant R4O6A inside the pipe. The experiment in heat transfer was performed on a special stand inside a smooth pipe made of 1X18H9T grade steel with a diameter of 0.013 mm, a length of 3.3 m, and a wall thickness of 0.5 mm. There has been studied the influence of the two-phase regimes of the working medium movement on heat exchange where it is boiling both along the length of the pipe and in its section. The comparison between heat transfer coefficients has been given. The visual observations over the flow structure were held. There were determined four regimes of two-phase flow: emulsion, slug, wavy, and stratified. Changing heat transfer coefficients in the upper, medium and bottom parts of the tube section has been shown. Changing of heat transfer was identified in the dependence of developing of the regimes. There has been proved the existence of dry wall in the upper part of the pipe under wave and stratified regimes, where the minimal heat transfer was recorded. Graphic dependences of changing the heat transfer coefficients in the pipe section for various regimes are presented. It has been stated that the intensity of heat transfer to steam depends on the speed of its movement, and the heat transfer to a boiling liquid depends on two components: boiling intensity and speed of the liquid movement. It has been inferred that the refrigerant enters the evaporators of the ship refrigeration units after throttling with initial mass of steam content from 0.1 to 0.15 kg/kg, which corresponds to the projectile or wave mode; emulsion mode is possible only in pumping circuits; the length of the stratified regime with low heat transfer intensity will be the most significant.