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ABSTRACT
This paper presents an experimental study carried out to investigate the influence of different performance parameters on heat transfer and fluid flow characteristics of a roughened double pass duct provided with combination of discrete multi V and staggered shaped ribs. The investigation has covered the range of operating parameter, i.e. Reynolds number (Re) from 3000 to 21000, and roughness parameters, i.e. relative inclined gap distance (Ig/Lv) from 0.4 to 0.8, and angle of attack (α) from 30° to 75° while the other roughness parameters are kept as constant. The Nusselt number, friction factor, and thermohydraulic performance for the artificially roughened double pass duct have been investigated. The results of the study have been compared with that of double-pass channel without roughness and considerable enhancement in the performance of the duct has been achieved. Based on the experimental results, the optimum values of roughness and operating parameters have also been identified. Further, the pumping power reduction to circulate the air has also been investigated.
Nomenclature
| = | Air flow rate, kg/s | |
| A | = | Area, m2 |
| H | = | Height of the duct, m |
| Dh | = | Hydraulic diameter of duct, m |
| h | = | Heat transfer coefficient, W/m2-K |
| L | = | Length of the collector, m |
| V | = | Velocity of flow, m/s |
| p | = | Pitch of the roughness pattern, m |
| Sp | = | Pitch of the staggered rib, m |
| ΔP | = | Pressure drop, Pa |
| e | = | Rib height, m |
| Sr | = | Staggered rib size, m |
| T | = | Temperature, °C |
| K | = | Thermal conductivity of working fluid, W/m-K |
| g | = | Gap width, m |
| Q | = | Total heat collection, W |
| Dimensionless numbers | = | |
| f | = | Friction factor |
| Nu | = | Nusselt number |
| Pr | = | Prandtl number |
| Re | = | Reynolds number |
| Cd | = | Discharge coefficient |
| Greeks symbols | = | |
| α | = | Angle of attack, ° |
| ρ | = | Density of air, kg/m3 |
| ν | = | Kinematic viscosity of air, m2/s |
| Cp | = | Specific heat of air, J/kg-K |
| μ | = | Dynamic viscosity of air, Pa-s |
| β | = | Ratio of orifice diameter to pipe diameter |
| Subscripts | = | |
| a | = | Inlet |
| fm | = | Average fluid |
| pm | = | Average plate |
| b | = | Outlet |
| p | = | Plate |
| s | = | Smooth |
| r | = | Roughened |
| o | = | Orifice |