Natural convection heat transfer of high temperature gas in an annulus between two vertical concentric cylinders

Abstract

Water cooling panels have been adopted as the vessel cooling system of the High Temperature Engineering Test Reactor (HTTR) to cool the reactor core indirectly by natural convection and thermal radiation. In order to investigate the heat transfer characteristics of high temperature gas in a vertical annular space between the reactor pressure vessel and cooling panels of the HTTR, we carried out experiments and numerical analyses on natural convection heat transfer coupled with thermal radiation heat transfer in an annulus between two vertical concentric cylinders with the inner cylinder heated and the outer cylinder cooled. In the present experiments, Rayleigh number based on the height of the annulus ranged from 2.0 × 10 7 to 5.4 × 10 7 for helium gas and from 1.2 × 10 9 to 3.5 × 10 9 for nitrogen gas. The numerical results were in good agreement with the experimental ones regarding the surface temperatures of the heating and cooling walls. As a result of the experiments and the numerical analyses, the heat transfer coefficient of natural convection coupled with thermal radiation was obtained as functions of Rayleigh number, radius ratio, and the temperatures and emissivities of the heating and cooling wall surfaces.

Development of a Thermal Wellbore Simulator With Focus on Improving Heat Loss Calculations for SAGD Steam Injection

“…Thus the formula for calculating heat loss is given by: (10) where U to is the overall heat transfer coefficient, r to is the outside radius of tubing, T f is the fluid temperature and T cf is the temperature at the cement/formation interface. The overall heat transfer coefficient developed by Willhite (1967) can be written as: (11) where r ti , r to , r ins , r ci , r co , and r cf represent the radii of inside tubing, outside tubing, tubing insulation, inside casing, outside casing and cement/formation interface, respectively. k t , k ins , k cas , and k cem are the thermal conductivities of the tubing wall, tubing insulation, casing wall and cement.…”

“…Particularly after 2000, the research on annulus heat transfer has more relied on numerical simulation. Complete models for describing heat transfer phenomenon in annulus were built and software (e.g., FLUENT) that can simulate heat transfer in annulus was used (Hamad et al 1998;Inaba et al 2005). There are some widely-used correlations for calculating convective heat transfer in annulus such as Raithby and Hollands (1974) and Churchill (1983).…”

Development of a Thermal Wellbore Simulator With Focus on Improving Heat-Loss Calculations for Steam-Assisted-Gravity-Drainage Steam Injection

“…Pourafshary et al (2008) developed a thermal compositional wellbore simulator that was coupled with a reservoir simulator. Livescu et al (2008aLivescu et al ( , b, 2010) developed a series of fully coupled thermal multiphase (black oil and compositional) wellbore-flow models. Bahonar (2011) further developed a nonisothermal wellbore simulator for steam-injection wells.…”