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ABSTRACT
In this work, a numerical and experimental study on flow-dynamics and heat transfer in a solar air heater (SAH) provided with dimpled and dimple with v-miniature as roughness element over plate (absorber). For experimental study a staggered dimple was created on the plate (absorber) as a roughness element and ANSYS was used for the simulation. By providing the relative longway length (L/d), relative depth of dimple, and relative short way length (S/d) range from 15–25, 0.024–0.036, and 10–15, respectively. The RNG k-ε model was used to model turbulence, and Nusselt number and friction factor values are estimated for a proposed roughness. The simple duct was validated using Dittus Boelter along with this comparison is also made for roughened plate with experimental and numerical values. The thermal and hydraulic performance parameter of the proposed roughness was also studied by varying the Reynolds numbers from 5000 to 20,000. Results revealed that dimple with v-miniature at relative short way lengths (S/d) value of 15 shows the highest heat transfer at Reynolds number value of 20,000. It was observed that maximum thermal and hydraulic performance parameter has achieved value of 1.73 at α = 45°, L/d = 20 and S/d = 15 at Reynolds number 20,000 for the dimple with v-miniatures roughness.
Disclosure statement
No potential conflict of interest was reported by the author(s).
Nomenclature
| Cp | = | Specific heat (J/Kg k) |
| D | = | dimple printed diameter (mm) |
| e | = | V-miniatures height (mm) |
| d | = | depth of dimple (mm) |
| TKE | = | Turbulent kinetic Energy (m2/s2) |
| u | = | inlet air velocity (m/sec) |
| w | = | length of V-miniature wire (mm) |
| SAH | = | solar air heater |
| Nu | = | average Nusselt number |
| RSL | = | Relative short way length |
| RLL | = | Relative longway length |
| THPP | = | Thermohydraulic performance parameter |
| Ti | = | inlet air temperature |
| Re | = | Reynolds number |
| ∆P | = | Pressure drop (N/m2) |
| fr | = | friction factor for rough channel |
| fp | = | friction factor for plain channel |
| Greek Letters | = |
|
| α | = | angle of attack of V miniature,o |
| ε | = | dissipation rate (m2/s3) |
| λ | = | thermal conductivity (W/mK) |
| μt | = | eddy viscosity (m2/s) |
| ρ | = | air density, kg/m3 |
| µ | = | air dynamic viscosity (Pa.s) |
| δ | = | dimple depth (mm) |
Author contributions
Navneet Arya: Writing, Software; Varun Goel: Supervision, Review and Editing
Additional information
Notes on contributors
Navneet Arya
Navneet Arya completed his master degree in Thermal Engineering. And currently, he is a research fellow in the Department of Mechanical Engineering, National Institute of Technology, Hamirpur, Himachal Pradesh, India, PIN-177005.
Varun Goel
Varun Goel received his PhD from National Institute of Technology, Hamirpur, India. His area of interests includes Renewable Energy (Small Hydro, Solar thermal and Bioenergy), Turbo-machines, Computational Fluid Dynamics, Heat Transfer, Life Cycle Assessment. He is presently associate professor in the Department of Mechanical Engineering, National Institute of Technology, Hamirpur, Himachal Pradesh, India, PIN-177005.