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ABSTRACT
This work deals with the experimental investigation on heat transfer, friction factor, and thermal hydraulic performance of V-pattern dimpled obstacles in an air passage. The experiments were conducted in a turbulent flow regime with Reynolds number ranging from 5,000 to 17,000 using air as the working fluid under uniform wall heat flux boundary condition. The experimental investigation encompassed the geometrical parameter, namely relative dimpled obstacles width
varying from
to
, ratio of dimpled depth to print diameter (
) from 0.50 to 2.0, relative dimpled pitch (
) from 8.0 to11.0, relative dimpled height
of 0.037, and the angle of attack (
) varying from 35° to 75°. The experimental results revealed that both heat transfer and friction factor of the air passage fitted with the V-pattern dimpled obstacles were significantly higher than those of the smooth-surface air passage. The optimum data of thermal and hydraulic performance were obtained at
,
1.0,
= 9.0,
= 0.037, and
= 55°. The current study shows that the thermal hydraulic performance of multi-type V-pattern dimpled obstacles shape is around 7% higher as compared to other obstacles shapes air passage.
Nomenclature
| = | Surface area of heated plate, | |
| = | Area of orifice, | |
| = | Coefficient of discharge | |
| = | Specific heat of air, | |
| = | Hydraulic diameter of air passage, | |
| = | Print diameter of dimpled obstacles | |
| = | Friction factor of dimpled obstacles | |
| = | Friction factor without dimpled obstacles | |
| = | Convective heat transfer coefficient, | |
| = | Height of air passage, | |
| = | Height of dimpled obstacles, | |
| = | Thermal conductivity of air, | |
| = | Length of test section, | |
| = | Relative dimpled obstacles height | |
| = | Ratio of dimpled depth to print diameter | |
| = | Mass stream rate of air, | |
| = | Nusselt number of dimpled obstacles air passage | |
| = | Nusselt number of air passage without dimpled obstacles | |
| = | Pitch of dimpled obstacles, | |
| = | Relative dimpled obstacles pitch | |
| = | Pressure drop across test section, | |
| = | Pressure drop across orifice plate, | |
| = | Useful heat gain, | |
| = | Reynolds number | |
| = | Mean air temperature, | |
| = | Inlet temperature of air, | |
| = | Outlet temperature of air, | |
| = | Plate temperature of air, | |
| = | Velocity of air, | |
| = | Width of air passage, | |
| = | Width of dimpled obstacles | |
| = | Relative dimpled obstacles width | |
| = | Relative width ratio | |
| = | Passage aspect ratio | |
| = | Solar air heater | |
| SAC | = | Solar air channel |
Greek symbols
| = | Angle of attack, | |
| = | Ratio of orifice meter to pipe diameter | |
| = | Density of air, | |
| = | Kinematic viscosity of air, | |
| = | Thermo-hydraulic performance |