Browsing by Author "Allauddin, Usman"

Now showing 1 - 4 of 4
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    Heat transfer and fluid flow characteristics investigation using detached ribs in an axisymmetric impinging jet flow
    (Springer, 2022-10-15) Rasheed, Adnan; Allauddin, Usman; Ali, Hafiz Muhammad; Uzair, Muhammad; Verdin, Patrick G.; Siddiqui, Yasir H.
    This research work is directly concerned with the heat transfer involved in a single jet flow covering a heated surface having detached ribs present above the surface. A computational study has been conducted to check the effect due to the presence of such detached ribs. The generalized k−ω (GEKO) turbulence model with Reynolds-averaged Navier–Stokes equations formulation has been adopted after validation with the relevant experimental data from the literature. A rectangular rib design was selected for which rib width, height, clearance, pitch and first rib radial distance were varied to study their effect on heat transfer. Local heat transfer distributions were investigated over the target surface, especially focusing on the ribs-based region for different nozzle positions. The thermal performance with and without ribs is compared. A maximum increase in heat transfer of 64% was observed for a normalized nozzle to plate spacing z/d = 0.5.
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    Heat transfer enhancement investigation in jet impingement system of a single and array of square jets using numerical tools
    (Begell House, 2023-04-16) Allauddin, Usman; Sohail, Muhammad U.; Sohaib, Muhammad; Siddiqui, Muhammad A.; Khan, Muhammad H. U.; Khan, Kashif; Verdin, Patrick G.
    Computational Fluid Dynamics (CFD) techniques can predict complex fluid flow structures and the thermal performance of jet impingement systems. Numerical studies can complement extensive and time-consuming experimental studies, where local parameter measurements are difficult and costly to obtain. In the current work, a single and an array of four and nine square jets impingements were numerically investigated with CFD, for mass flow rate (m) ranging from 2.71x10-4to 7.40x10-4kg/s. The effects of the jet’s outlet-to-target plate distance (Z) were assessed as a function of the width of a single square nozzle (B). The flow field features of different nozzle configurations were also studied. It was shown that the Nusselt number increases as the mass flow rate increases, but increases inversely as the dimensionless jet’s outlet-to-target plate spacing Z/B increases. The numerical investigation also demonstrated that when increasing the number of nozzles under a constant mass flow rate, the Nusselt number significantly increases. The effect of nozzle configuration is not that significant at Z/B > 7. The present impinging jet system offers about 63% enhancement in thermal efficiency was found while the pumping power increased by 3.7 times. All simulations were successfully validated with experimental data.
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    Investigation of the Thermo-hydraulic performance of a roughened Parabolic trough collector
    (Elsevier, 2022-10-28) Allauddin, Usman; Rafique, Muhammad U.; Malik, Osama; Rashid, Osama; Waseem, Ashir; King, Peter; Karim, Mounia; Almond, Heather
    Parabolic trough collectors (PTC) are an already established technology set to prove its competitiveness. Recently, a lot of research is ongoing to further enhance the thermal performance of PTC systems. Computational Fluid Dynamics (CFD) can help in the design and development of PTCs with optimized thermal efficiency. In the current work, a combined enhancement in the performance of a PTC is evaluated, involving modifications to the geometry of the absorber tube and the use of a heat transfer fluid (HTF) (Syltherm800). Absorber tube geometries involving dimpled protrusions (d-PTC) and circumferential inclined ribs (IR-PTC) are used. The performance of PTC with and without turbulators is compared with that of a smooth absorber tube by calculating the Nusselt number (Nu), friction factor (f) and performance evaluation criterion (PEC). PEC values of 1.46 and 1.18 are observed by using inclined ribs and dimpled protrusions, respectively at an absorber tube inlet temperature (Tin) of 500 K and mass flow rate (m) of 0.5 kg s−1. Thus, a significant enhancement in thermo-hydraulic performance of PTC is observed with inclined rib turbulators.
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    Numerical investigation of fluid flow and heat characteristics of a roughened solar air heater with novel v-shaped ribs
    (Canadian Science Publishing, 2022-03-24) Allauddin, Usman; Khan, Waqar; Ali, Saim E.; Haider, Syed Muhammad Mehdi; Ahmed, Abdul S.; Rehman, Abdur; Verdin, Patrick G.
    Solar air heaters convert clean solar energy into useful heat and have a wide range of applications. Computational Fluid Dynamics (CFD) can aid in the design and development of solar air heaters with optimized thermal efficiency. A detailed numerical study was conducted to investigate the fluid flow and heat transfer characteristics of a roughened solar air heater with novel V-shaped ribs having staggered elements. Three dimensional steady-state numerical simulations were performed using the k– RNG turbulence model, and results were found in excellent agreement with experimental data. The effect of ribs spacing were studied through varying the rib pitch to rib height ratio P/e= 6 to 14, for Reynolds numbers (Re) in the range of 4000-14,000. A significant enhancement in the ribs-roughened solar air heater’s thermal performance was observed. It was also established that an increment in P/e from 6 to 10 increases the Nusselt number (Nu) for all Re values investigated. About 72.6% Nu enhancement was predicted for P/e=10 at Re = 12,000. It was further observed that an increment in p/e from 10 to 14 decreases Nu for all Re values considered.