Open AccessHydraulic resistance of pipes under refrigerant boiling in horizontal and vertical evaporators in ship refrigerating machines
Author(s) -
Vladimir Grigorievich Bukin,
Aleksander Ivanovich Andreev,
Александр Букин
Publication year - 2020
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 - 10.24143/2073-1574-2020-2-92-99
Subject(s) - boiling , head (geology) , mechanics , evaporator , refrigerant , flow resistance , hydraulic head , flow (mathematics) , horizontal and vertical , refrigeration , tube (container) , environmental science , materials science , geotechnical engineering , geology , mechanical engineering , engineering , thermodynamics , heat exchanger , physics , geodesy , geomorphology
The article presents the comparison of the head losses under the boiling refrigerant flow in horizontal and vertical evaporators. The values of all the components of the hydraulic resistance, such as the friction losses, local resistance, flow acceleration and leveling head have been calculated, compared and analyzed. Graphic dependences of the pressure loss of the two-phase flow on the mixture density and the apparatus height, as well as the effect of hydraulic resistances on the changes in boiling temperature have been obtained. It has been stated that studying the effectiveness of vertical evaporators comprises two main components: defining heat transfer and hydraulic resistance in the course of working fluids boiling in the vertical pipes. The second part of the study is under consideration. Vertical evaporators are higher than horizontal ones, which leads to greater losses when overcoming the leveling head of a larger column of a two-phase flow. Other components of the hydraulic resistance in the horizontal and vertical apparatus are comparable, although the friction losses and local resistance losses in the vertical evaporators may be less. In a vertical apparatus the main losses appear due to overcoming the leveling head, the remaining losses are smaller than in the horizontal apparatus. Therefore, when designing vertical apparatuses, one must not use the ratio of the apparatus length to its diameter, which is recommended for the horizontal apparatuses (L/d ratio for horizontal and vertical is 6). The ratio for the vertical apparatus should be significantly less. The experiments performed on the air-water model proved that L/d ratio of vertical evaporators should be within 1.0 ÷ 2. More precise values of this parameter can be found after testing R410A refrigerant.