Volume No. 3 Issue No.: 2 Page No.: 464-471 Oct-Dec 2008

 

HEAT TRANSFER AND FRICTION FACTOR CHARACTERISTICS OF COMPOUND TURBULATORS IN RECTANGULAR DUCTS OF SOLAR AIR HEATER

 

C.B.Pawar*, K.R.Aharwal1 and Alok Chaube2

1. Department of Mechanical Engineering, Shri G.S. Institute of Technology & Science, Indore (INDIA)
2. Rajiv Gandhi Technical University, Bhopal (INDIA)

 

Received on : August 2, 2008

 

ABSTRACT

 

The demand of energy is increasing day by day because of increase in the population and increase in the living standards of the people. As the existing conventional sources of energy only is not sufficient enough to meet the growing demand of energy, it becomes mandatory to opt for the non-conventional sources of energy like solar, wind, bio-mass etc., to fulfil the growing demand of the energy. Amongst the various alternative energy sources, solar energy is a clean renewable resource of energy with zero emission, and has got tremendous potential which can be harnessed using a variety of devices e.g. solar cooker, solar water heater, solar photovoltaic cell and solar air heating systems etc. Solar air heating systems are used for drying foods and other agricultural crops, seasoning of wood and in air-conditioning systems. The performance of solar air heater being low due to the low value of convective heat transfer coefficient between the flowing air and the absorber plate. The convective heat transfer can be increased by increasing the level of turbulence by breaking the laminar viscous sub layer. The use of artificial roughness or turbulators on heated surface is one of the passive techniques which is used mostly for enhancing the heat transfer. In the present work artificial roughness in the form of integral wedge shaped rib with and without groove has been employed to enhance the heat transfer. The Nusselt number and friction factor for the same was determined experimentally and the corresponding values were compared with the smooth plate for Reynolds number in the range of 3000-20000. The wedge roughened surface enhances the Nusselt number and the friction 1.5-2.3 times and 2-2.5 times respectively in comparison to the smooth plate in the range of parameters investigated. The investigations on wedge shaped transverse compound turbulator (rib

 

Keywords : Artificial roughness, Aspect ratio, Compound turbulators, Thermo-hydraulic performance.

 

 

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