New Variants to Theoretical Investigations of Thermosyphon Loop

Abstract

The purpose of this chapter is to present three variants of the generalized model of thermosyphon loop, using a detailed analysis of heat transfer and fluid flow (Bielinski & Mikielewicz, 2011). This theoretical investigation of thermosyphon loop is based on analytical and numerical calculations. The first variant of thermosyphon loop (HHVCHV) is composed of two heated sides: the lower horizontal and vertical sides and two cooled sides: the upper horizontal and vertical opposite sides. This variant is made for conventional tubes and has a one-phase fluid as the working substance. The second variant of thermosyphon loop (2H2C) is consisted of two lower evaporators: horizontal and vertical and two upper condensers: horizontal and vertical and is made for minichannels. The third variant of thermosyphon loop has an evaporator on the lower horizontal section and a condenser on the upper vertical section. This variant contains minichannels and a supporting minipump (HHCV+P). A two-phase fluid is used as the working substance in the second and third variants. The new variants reported in the present study is a continuation and an extension of earlier work “Natural Circulation in Single and Two Phase Thermosyphon Loop with Conventional Tubes and Minichannels.” published by InTech (ISBN 978-953-307-550-1) in book “Heat Transfer. Mathematical Modelling, Numerical Methods and Information Technology”, Edited by A. Belmiloudi, pp. 475-496, (2011). This previous work starts a discussion of the generalized model for the thermosyphon loop and describes three variants. In the first variant (HHCH) the lower horizontal side of the thermosyphon loop was heated and its upper horizontal side was cooled. In the second variant (HVCV) the lower part of vertical side of the thermosyphon loop was heated and its upper part at opposite vertical side was cooled. In the third variant (HHCV) a section of the lower horizontal side of the thermosyphon loop was heated and its upper section of vertical side was cooled. A oneand two-phase fluid were used as a working substance in the first and in both second and third variants of the thermosyphon loop, respectively. Additionally, the first variant was made for conventional tubes and the second and third variants were made for minichannels. It was necessary in case of the thermosyphon loop with minichannels to apply some new correlations for the void fraction and the local two-phase friction coefficient in both two-phase regions: adiabatic and diabatic, and the local heat transfer coefficient in flow boiling and condensation. Some other variants to theoretical investigations of the generalized model for thermosyphon loop are demonstrated in (Bielinski & Mikielewicz, 2004, 2005, 2010).