High-Rayleigh heat transfer flow: Thermal stratification analysis and assessment of Boussinesq approach

CORZO SANTIAGO; RAMAJO DAMIAN; NIGRO NORBERTO

INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID FLOW

EMERALD GROUP PUBLISHING LIMITED

Año: 2017 vol. 27 p. 1928 - 1954

0961-5539

pre { direction: ltr; color: rgb(0, 0, 0); }pre.western { font-family: "Liberation Mono","Courier New",monospace; }pre.cjk { font-family: "Liberation Mono","Courier New",monospace; }pre.ctl { font-family: "Liberation Mono","Courier New",monospace; }p { margin-bottom: 0cm; direction: ltr; color: rgb(0, 0, 0); text-align: justify; }p.western { font-family: "Times New Roman",serif; font-size: 11pt; font-weight: bold; }p.cjk { font-family: "Times New Roman",serif; font-size: 11pt; font-weight: bold; }p.ctl { font-family: "Times New Roman",serif; font-size: 10pt; }a:link { color: rgb(0, 0, 255); }Purpose The purpose of this paper is to assess the Boussinesq approach for a wide range of Ra (10 × 6to 10 × 11) in two-dimensional (square cavity) and three-dimensional(cubic cavity) problems for air- and liquid-filled domains.Design/methodology/approach The thermal behavior in ?differentiallyheated cavities? filled with air (low and medium Rayleigh) andwater (high Rayleigh) is solved using computational fluid dynamics(CFDs) (OpenFOAM) with a non-compressible (Boussinesq) andcompressible approach (real water properties from the IAPWSdatabase). Findings The results from the wide range of Rayleighnumbers allowed for the establishment of the limitation of theBoussinesq approach in problems where the fluid has significantdensity changes within the operation temperature range and especiallywhen the dependence of density with temperature is not linear. Forthese cases, the symmetry behavior predicted by Boussinesq is farfrom the compressible results, thus inducing a transient heatimbalance and leading to a higher mean temperature. Researchlimitations/implications The main limitation of the present researchcan be found in the shortage of experimental data for very highRayleigh problems. Practical implications Practical implications ofthe current research could be use of the Boussinesq approach bycarefully observing its limitations, especially for sensible problemssuch as the study of pressure vessels, nuclear reactors, etc.Originality/value The originality of this paper lies in addressingthe limitations of the Boussinesq approach for high Rayleigh watersystems. This fluid is commonly used in numerous industrialequipment. This work presents valuable conclusions about thelimitations of the currently used models to carry out industrialsimulations.