Nozzle exit conditions and the heat transfer in non-swirling and weakly swirling turbulent impinging jets

İkhlaq, Muhammad; Al-Abdeli, Yasir M.; Khiadani, Mehdi

doi:10.1007/s00231-019-02710-1

Cited by 11 publications

(5 citation statements)

References 58 publications

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“…53 This model has shown to predict results comparable to experimental data. 54 Details about the constants used in the above equations and their values can be found elsewhere. 55,56…”

Section: Methodsmentioning

confidence: 99%

“…53 This model has shown to predict results comparable to experimental data. 54 Details about the constants used in the above equations and their values can be found elsewhere. 55,56 Numerical results from different numerical models applied in the current study were compared with the experimental results of velocity data obtained using CTA for Q s / Q t = 0.25 at h/D = 0.76, 0.84 and 0.94.…”

Section: Numerical Modelling and Validationmentioning

confidence: 99%

See 1 more Smart Citation

Secondary air induced flow structures and mixing in a fixed bed combustor

Junejo

Chapela

Porteiro

et al. 2023

Proceedings of the Institution of Mechanical Engineers, Part A:

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Air staging features widely in biomass combustion from small space heaters to industrial-scale moving grate systems. Whilst studies have been conducted into the impact of air staging on emissions and combustion performance, there is little or no insight into the exact flow dynamic and physical mechanisms that are induced by secondary air under such conditions. This paper uses experimental data to validate numerical predictions before investigating the flow field structures and mixing characteristics in a fixed bed air staged combustor. The study utilizes Constant Temperature Anemometry (CTA) experiments to establish boundary conditions for a lab-scale fixed bed combustor. Results from numerical simulations obtained using [Formula: see text] l- 𝜔 model were in good agreement with experimental data. Conditions tested cover five different secondary to total air ratios (Qs/Qt) and two different locations of secondary air injection. Results show that at Qs/Qt = 0.50, 0.25 and 0.18 one strong recirculation zone is induced upstream of the secondary air injection and one downstream. Varying the point of injection of secondary air from h/D = 0.64 to h/D = 0.40 also had an effect on the size of the upstream recirculation zone. Qs/Qt = 0.50 had the highest values of mixing index among all spatially located planes at the upstream of secondary air injection. The overall findings shed light on the possible flow interactions between secondary air and the top layers of fuel bed. They also highlight the significance of secondary air on inducing both upstream and downstream flow structures.

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“…53 This model has shown to predict results comparable to experimental data. 54 Details about the constants used in the above equations and their values can be found elsewhere. 55,56…”

Section: Methodsmentioning

confidence: 99%

Section: Numerical Modelling and Validationmentioning

confidence: 99%

Secondary air induced flow structures and mixing in a fixed bed combustor

Junejo

Chapela

Porteiro

et al. 2023

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…Among other things, researchers have tested inserts in jets as well. Ikhlaq et al [71] numerically investigated a swirl insert inside the impingement orifice. This paper had an exhaustive list of papers related to swirl jets.…”

Section: Jet Orificementioning

confidence: 99%

Opportunities in Jet-Impingement Cooling for Gas-Turbine Engines

Dutta

Singh

2021

Energies

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Impingement heat transfer is considered one of the most effective cooling technologies that yield high localized convective heat transfer coefficients. This paper studies different configurable parameters involved in jet impingement cooling such as, exit orifice shape, crossflow regulation, target surface modification, spent air reuse, impingement channel modification, jet pulsation, and other techniques to understand which of them are critical and how these heat-transfer-enhancement concepts work. The aim of this paper is to excite the thermal sciences community of this efficient cooling technique and instill some thoughts for future innovations. New orifice shapes are becoming feasible due to innovative 3D printing technologies. However, the orifice shape variations show that it is hard to beat a sharp-edged round orifice in heat transfer coefficient, but it comes with a higher pressure drop across the orifice. Any attempt to streamline the hole shape indicated a drop in the Nusselt number, thus giving the designer some control over thermal budgeting of a component. Reduction in crossflow has been attempted with channel modifications. The use of high-porosity conductive foam in the impingement space has shown marked improvement in heat transfer performance. A list of possible research topics based on this discussion is provided in the conclusion.

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“…Heat transfer rates were enhanced by 27.7%, 25.0%, 21.6%, and 19.3% by using a twisted tetra-lobed nozzle with twisted ratios of 2.0, 3.0, 4.0, and 5.0, respectively, as compared to a circular nozzle (non-swirling jet). Ikhlaq et al [92] numerically studied the impact of the weak swirling jet (S = 0.31) on a heated plate for heat transfer characteristics. The study was performed for jet-plate spacing (H/D) = 2, 4, and 6.…”

Section: Excited Jetsmentioning

confidence: 99%

Heat Transfer Augmentation through Different Jet Impingement Techniques: A State-of-the-Art Review

et al. 2021

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Jet impingement is considered to be an effective technique to enhance the heat transfer rate, and it finds many applications in the scientific and industrial horizons. The objective of this paper is to summarize heat transfer enhancement through different jet impingement methods and provide a platform for identifying the scope for future work. This study reviews various experimental and numerical studies of jet impingement methods for thermal-hydraulic improvement of heat transfer surfaces. The jet impingement methods considered in the present work include shapes of the target surface, the jet/nozzle–target surface distance, extended jet holes, nanofluids, and the use of phase change materials (PCMs). The present work also includes both single-jet and multiple-jet impingement studies for different industrial applications.

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Nozzle exit conditions and the heat transfer in non-swirling and weakly swirling turbulent impinging jets

Cited by 11 publications

References 58 publications

Secondary air induced flow structures and mixing in a fixed bed combustor

Secondary air induced flow structures and mixing in a fixed bed combustor

Opportunities in Jet-Impingement Cooling for Gas-Turbine Engines

Heat Transfer Augmentation through Different Jet Impingement Techniques: A State-of-the-Art Review

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