Hongtao Xu

Numerical Simulation of Steady Mixed Convection Around Two Heated Circular Cylinders in a Square Enclosure

In this paper, a numerical study has been carried out to investigate the steady-state mixed convection around two heated horizontal cylinders in a square two-dimensional enclosure. The cylinders are located at the middle of the enclosure height and the walls of the cavity are adiabatic. Streamlines and isotherms are produced and the effects of cylinder diameter, Reynolds number, and Richardson number on the heat transfer characteristics are numerically analyzed. The average Nusselt number over the surface of cylinders and average nondimensional temperature in the enclosure are also presented. The results show that both heat transfer rates from the heated cylinders and the dimensionless fluid temperature in the enclosure increase with increasing Richardson number and cylinder diameter. However, the trend of average Nusselt number and nondimensional temperature variation is completely opposite when Reynolds number increases. In addition, by increasing the cylinders diameter and Richardson number, the left cylinder is less affected by the inlet flow than right one.

Numerical Investigation of Thermal Characteristics in a Solar Chimney Project

In order to create interior multiclimate zones suitable for plant cultivation in a solar chimney project proposed for the World Horticultural Exposition 2016 in China, the numerical investigation is performed to a solar chimney with 2 km radius and 1 km height. The simulation methodology is validated by experimental data. The impacts of inlet height and radius to interior thermal characteristics are evaluated. It is found that the temperature field is much similar when the inlet height decreases from 3.8 m to 0.5 m. With further decrease of the inlet height to 0.2 m, its impact to temperature field is significant. The temperature field is similar though the radius of solar chimney decreases from 2.0 km to 1.725 km. Further decrease to 1.13 km results in much lower temperature field as less radiate heat is obtained. The procedure of soil surface temperature calculation is also proposed to obtain the supplementary heat amount maintaining the required temperature for plant cultivation.

Numerical simulation of transient forced convection in a square enclosure containing two heated circular cylinders

Purpose – Unsteady simulation of forced convection of two heated horizontal cylinders confined in a 2D squared enclosure. The paper aims to discuss this issue. Design/methodology/approach – The finite-volume method is used to solve the transient heat transfer problem by employing quadrilateral mesh type. To solve the governing equations (conservations of mass, momentum and energy) on unstructured control volumes, a second-order quadratic upwind interpolation of convective kinematics scheme for the convection terms and the semi-implicit method for pressure-linked equations pressure correction algorithm were used. Findings – The results indicate that the variation of the area-averaged Nusselt number strongly depends on the Reynolds number. On the contrary, the effect of cylinders’ space on heat transfer was found to be nearly negligible for Re < 460. It is also observed that steady state flow and heat transfer shift to periodical oscillation, and ultimately chaotic oscillation in non-dimensional cylinders d...

Numerical study of the thermal characteristics of a solar chimney for creating interior multi-climate zones

In order to create the interior multi-climate zones suitable for plant cultivation in a solar chimney proposed for the World Horticultural Exposition 2016 in China, the numerical study is performed to investigate the interior thermal characteristics of a solar chimney with 2km radius and 1km height. The simulation methodology is validated by experimental data. Available heat from radiation, steel plant and underground water are taken as the sources for multi-climate zone generation. The interior thermal characteristics in summer season (SS) and winter season (WS) scenarios are predicted to evaluate the impacts of inlet height and radius. It is found the temperature increment is around 6t and 17t for SS and WS with 3.8m inlet height. The air velocity in SS is much larger than WS. The decrease of the inlet height from 3.8m to 0.5m has minimal impact for interior thermal field. However, further decrease to 0.2m brings less air flow rate and higher temperature. The temperature field remains almost the same when the radius of solar chimney decreases from 2.0km to 1.725km. Further decrease to 1.13km results in much lower temperature. The current numerical analysis can provide preliminary suggestions for the plant cultivation in the solar chimney.

Numerical Investigation of Natural Convection Characteristics in a Water Tank

In this paper, the numerical study is performed to investigate the natural convection characteristics in a 2D water tank model. The hot water flows in horizontal cylinder, heating the water stored in a water tank. The effects of different aspect ratios are numerically analyzed to inspect the natural convection characteristics in the 2D water tank model. The average and local Nusselt number over the cylinder surface at different aspect ratios and cylinder surface temperature are also discussed.Copyright