What is it about?
Vapordynamic thermosyphon (VDT) is an efficient heat-transfer device. The two-phase flow generation and dynamic interaction between the liquid slugs and vapor bubbles in the annular mini-channel of the VDT condenser are the main features of such thermosyphon, which aloud to increase its thermodynamic efficiency. They can transfer heat flow in horizontal position over a long distance. The condenser is nearly isothermal with the length of tens of meters. The VDT evaporators may have different forms. Some practical applications of VDT are considered.
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Why is it important?
One of the variety of thermosyphons is a vapordynamic thermosyphon (VDT) developed in the Porous Media Laboratory of the Luikov Heat & Mass transfer Institute (Minsk, Belarus). This device holds high heat-transmitting ability, low sensibility to odd a quantity of a working liquid, presence of a noncondensing gas, gives a possibility of various embodiments with an extensive zone of evaporation including bent or flexible modifications. The first principal distinction of VDT from conventional thermosyphons of the same diameter is related with its horizontally oriented annular condenser and the two phase flow of the working fluid inside it. They can transfer heat flow in horizontal position over a long distance. The condenser is nearly isothermal with the length of tens of meters. The VDT evaporators may have different forms. The second principal distinction consists in the fact that the vapor flow and two-phase liquid flow are separated spatially (tube in tube heat exchanger). This makes it possible to avoid a negative hydrodynamic interaction between the opposite flows of the vapor and liquid typical for the conventional thermosyphons.
Perspectives
1. Horizontal vapordynamic thermosuphons (VDT) have a unique possibility to transfer the heat flow on the long distance (tens of meters) with very high uniformity of the temperature distribution along the condenser due to the original design of the annular evaporator. 2. Micro/nano porous coating of the evaporator and vapor pipe inside the condenser of VDT increase the intensity of the heat transfer and substantially decrease its total thermal resistance. Vapordynamic thermosuphons with porous coating and small distance between the vapor pipe and condenser envelope (less the capillary constant) can be used at the low gravity cases due to the dynamic bubble pressure on the liquid in the annular channel inside the VDT condenser. 3. Given device can successfully be used in various fields of technology both for heating and cooling and improve the quality of the industrial product. VDT can substitute electrical heaters and boilers in snow melting devices for roads and sidewalks, etc. The VDT based recuperative heat exchangers development could be technology applicable to vapor-compression, direct-expansion and chilled-water air-handling-unit coils; heat-powered desiccant dehumidification equipment (supermarket, ice-rink) and natatorium air-conditioning and dehumidification systems. VDT assisted solid sorption coolers and heaters are suggested and experimentally tested as thermal control system in solar refrigerators. Burning gas driven VDT are suggested for the solid sorption heat pumps with natural gas consumption savings, when compared to the traditional technologies.
Professor, Dr.Sci. Leonard L.eonidovich Vasiliev
Luikov Institute
Read the Original
This page is a summary of: Vapordynamic thermosyphon – heat transfer two-phase device for wide applications, Archives of Thermodynamics, January 2015, De Gruyter,
DOI: 10.1515/aoter-2015-0033.
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