Three-dimensional CFD simulation of geyser boiling in a two-phase closed thermosyphon

Abstract

This paper examines the application of CFD modelling to simulate the complex multiphase characteristics inside a wickless heat pipe (thermosyphon). Water and refrigerant R134a were selected as working fluids. A novel and comprehensive threedimensional CFD model of a wickless heat pipe was developed to simulate both the complex multiphase heat and mass transfer characteristics of boiling and condensation and the heat transfer characteristics of the cooling fluid in the condenser -heat exchanger. The CFD simulation has successfully predicted, for the first time, a boiling regime and two phase flow pattern that takes place with water at low power throughput, known as geyser boiling. The effects of the power throughput on the characteristics of the geyser boiling were investigated. The CFD simulation was also successful in modelling and visualising the multiphase flow characteristics, emphasising the difference in pool boiling behaviour between these working fluids.Temperature profiles and visual validation of the resulting 3D CDF findings were conducted using two experimental facilities.

Investigation of Separated Two-Phase Thermosiphon Loop for Relieving the Air-Conditioning Loading in Datacenter

“…The vapor plugs then pushes the liquid slug upwards and eventually breaks up to spread around the tube periphery to yield annular flow zone as depicted in Figure 5b. This phenomenon was also numerically verified by Jouhara et al [20].…”

“…The indoor temperature = 27 • C and outdoor temperature = (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22) • C The optimal filling ratios for CO 2 , R22 and R134a are 120%, 100% and 90%, respectively Han et al [3] Integrated air conditioner with thermosyphon (dual mode direct expansion evaporator) Feng et al [7] T.S was built to use ambient energy to cool a typical data center, the volume of T.S = (0.75 × 0.32 × 0.29) mm 3…”

Effects of humidified enriched air on combustion and emissions of a diesel engine

“…The potential of EA in Diesel engines was already considered by the Authors by a preliminary study [16], analysing the effects of oxygen enriched air on the exhaust emissions and performance of a high-speed direct-injection Diesel engine, by means of 3D Computational Fluid Dynamics (CFD) simulations. The numerical approach has been selected since up-to-date CFD software are able to provide realistic simulations and reliable results of complex phenomena with costs that are very low in comparison with experiments in many engineering fields [17] [18] [19]. The preliminary CFD simulations demonstrated that EA mixture allows to increase engine thermal efficiency up to 8 %, thanks to a faster and more complete combustion, and drastically reduces soot emissions.…”

Specifics in the operating modes of thermosyphon air heater of steam generators №1 and №2 in TPP "Republika" at fuel switch from coal to natural gas

“…А number of developments exist in literature related to the numerical study of the heat and mass transfer processes in two phase thermosyphons. In [1,2] a detailed analysis of the processes in a horizontal thermosyphon is presented. The effects of the two-phase flow regime along with the degree of filling of the thermosyphon on the heat and mass transfer processes are examined.…”

“…The vapour velocity and temperature distributions of the flat twophase thermosyphon are obtained by numerically solving the equations of continuity, momentum and energy. A detailed numerical analysis of the heat and mass transfer processes in a multiphase thermosyphon is presented in [7]. [8] presents a CFD analysis of a two-phase thermosyphon using the commercial software ANSYS-CFX.…”