Heat Transfer Experiment

Heat transfer by mixed convection of air inside a rectangular enclosure is investigated numerically. Different placement configurations of inlet opening are considered. A constant flux heat source was heated vertical wall. The fluid considered is air. The other side walls including the top and bottom of the enclosure were assumed to be adiabatic. The inlet opening, located on the left vertical wall, was placed at varying locations. The outlet opening was placed on the opposite heated wall at a fixed location. The basis of the investigation was the two–dimensional numerical solutions of governing equations by using Finite Difference Method (FDM).Significant parameters considered were Richardson number (Ri) and Reynolds number (Re). Results are

The computational results indicate that heat transfer is strongly affected by Reynolds and Richardson numbers. As the value of Ri increases, there occurs a transition from forced convection to buoyancy dominated flow at Ri >1. A detailed analysis of flow pattern shows that natural or forced convection is based on the parameter Ri.

Key words: Richardson number (Ri), Reynolds number (Re), partial differential equations (pdes), finite difference method (FDM), The heated vertical wall.

I.INTRODUCTION AND LITERATURE REVIEW

1.1 Background of study

Thermal buoyancy forces play a significant role in forced convection heat transfer when the flow velocity is relatively small and the temperature difference between the surface and the free stream is relatively large. The buoyancy forces modify the flow and temperature fields and hence the heat transfer rate from the surface.Problems of heat transfer in enclosures by mixed convection has been the subject of investigations for many years. Numerous experimental and numerical studies of mixed convection in a cavity have been conducted by a great number of researches. Mixed convection occurs in many heat transfer devices

Three heating modes were considered: assisting flow, opposing flow and heating from below. Results for Richardson numbers equal to 0.1 and 100, Re= 100 and 1000 and aspect ratio in the range 0.1 -1.5 were reported. It was shown that that maximum temperature values were decreased as the Reynolds and the Richardson number increased. The effect of the ratio of channel height to the cavity height was found to play a significant role on streamline and isotherm patterns for different heating configuration. The investigation showed that opposing forced flow configurations had the highest thermal performance in terms of both maximum temperature and average Nusselt number. Later, similar problems for the case of the assisting forced flow configuration were tested experimentally by Manca et al (2006) and based on the flow visualization results, they pointed out that for Re=1000, there are two nearly distinct fluid motions: a parallel forced flow in the channel and a recirculation flow inside the cavity. For Re=100, the effect of a stronger buoyancy force determined the penetration of thermal plume from the heated plate wall into the upper