Selected thermal and flow issues in a reversed thermosiphon with a steam liquid lifter

Abstract

The work presents initial studies of a reversed thermosiphon with a steam liquid lifter and a minigap evaporator. The main interest of the authors is the evaporator, especially the heat exchange efficiency and flow issues, such as maldistribution and pressure drop. However, because the thermosiphon circuit of such a construction is characterized by cyclic working conditions, which are quite difficult in analysis the authors focused on this specificity first. The article presents the concept of a test circuit and preliminary results for distilled water and for a minigap evaporator with a smooth heat exchange surface 100 x 200 mm and minigap thickness of 1 mm. Visualizations of the separator's work and the minigap boiling structures are presented.

Flow Boiling in Minigap in the Reversed Two-Phase Thermosiphon Loop

“…The heat transfer intensification in passive methods is of interest to authors again [17]. A good example of passive method is the thermosiphon loop, which has been used widely before and is now the focus of research attention again [18]. There were about 200 publications on the topic in 1995 and, 5 years later, only half the number.…”

“…Those kinds of systems give the heat flow from the top to bottom, generally using two-phase flows. The usage of reverse systems results in emerging new research issues [18].…”

“…Klugmann et al [18] presented the research of a reversed thermosiphon with a vapor-liquid lifter and a minigap evaporator of 1 mm thickness gap, working with distilled water. The pulsatile mean of the system operation was described, as well as the way of system self-adjustment to the varying heat fluxes.…”

“…Temperatures in evaporator (blue (lower) -inlet, red (higher)-outlet) for average heat flux supplied to the minigap: Left = 7.6 kW/m 2 ; right = 14 kW/m 2[18].Energies 2019, 12, x FOR PEER REVIEW 10 of Temperatures in condenser (blue (higher)-inlet, red (lower)-outlet) for average heat flux supplied to the minigap: left = 7.6 kW/m 2 ; right = 14 kW/m 2[18].…”

“…12, x FOR PEER REVIEW 12 of Mass flow rate: blue-at evaporator inlet, red-at separator outlet (liquid pipeline) for average heat flux supplied to minigap: left = 7.6 kW/m 2 ; right = 14 kW/m 2[18].…”