Generation of longitudinal vortices in internal flows with an inclined impinging jet and enhancement of target plate heat transfer

Impinging jet heat transfer on a target plate was enhanced by using two parallel confining plates mounted between a rectangular nozzle end plate and a jet target plate. The target plate was set equal to 2, 3, 4, and 5 times the jet exit width, h, and the gap ratio of two parallel confining plates, W/h, were changed from 2.7 to 8.0 only by impinging length H=5h and from 2.7 to 6.7 by H≠5h. Two confining parallel plates mounted near the jet exit produced swing-type flow under some conditions. As a result, the maximum Nusselt number attained around the stagnation point was augmented by about 50% compared to the one for normal impinging jet without the two parallel plates and then spatial mean Nusselt number was increased by about 40%.

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Parametric Design and Optimization for Impingement Jet Heat Transfer Over Dimpled Topologies

Volume 7: Fluids and Heat Transfer, Parts A, B, C, and D ◽

10.1115/imece2012-87487 ◽

2012 ◽

Cited By ~ 1

Author(s):

Deepchand Singh Negi ◽

Arvind Pattamatta

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Average Nusselt Number ◽

Parametric Design ◽

Turbulence Models ◽

Impinging Jet ◽

Initial Section ◽

Geometric Parameters ◽

Complex Flow ◽

Target Plate

A large number of experimental and theoretical studies investigating heat transfer of impinging jet and jet arrays exist in the literature. However, there are only a few experimental and numerical studies that consider the heat transfer performance of the impinging jet and jet array over complex impinging surface topologies. In spite of these studies, several other factors concerning the dimpled target plate configuration such as dimple height, diameter, pitch spacing between dimples, and their effects on the heat transfer coefficient have not yet been well apprehended. The purpose of the present study is to address some of these aspects through a detailed computational investigation of 3D impinging jet interaction on dimpled target plates. The initial section of the study is focused on the evaluation of different turbulence models in capturing the complex flow features associated with dimpled topology. These models are validated for Nusselt number against previous experimental data in literature. This is followed by a parametric study in which geometric parameters of the dimpled target plate such as dimple diameter, pitch spacing between dimples and dimple height are varied to understand their role on heat transfer enhancement. The final section of the study deals with the optimization of the above geometric parameters based on three factorial design of parametric space. Results from these designed simulations are used to construct a surrogate model based on response surface analysis and the optimized configuration is determined. The objective functions for optimization include maximizing the average Nusselt number, Nuavg, and minimizing the deviation of maximum Nusselt number, Numax-sd. With respect to the reference configuration there is 12% and 8.58 % increase in the average Nusselt number values for the optimized case corresponding to Reynolds number of 3000 and 8200 respectively. Enhancement in terms of Nusselt number is observed with the dimpled target plate over corresponding non dimpled target plates.

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Effect of Reynolds Number, Hole Patterns and Hole Inclination on Cooling Performance of an Impinging Jet Array: Part I — Convective Heat Transfer Results and Optimization

Volume 5B: Heat Transfer ◽

10.1115/gt2016-56205 ◽

2016 ◽

Cited By ~ 1

Author(s):

Weihong Li ◽

Xueying Li ◽

Jing Ren ◽

Hongde Jiang ◽

Li Yang ◽

...

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Nusselt Number ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Convective Heat Transfer ◽

Convective Heat ◽

Impinging Jet ◽

Target Plate ◽

New Correlation

This study comprehensively illustrates the effect of Reynolds number, hole spacing, jet-to-target distance and hole inclination on the convective heat transfer performance of an impinging jet array. Highly resolved heat transfer coefficient distributions on the target plate are obtained utilizing transient liquid crystal over a range of Reynolds numbers varying between 5,000 and 25,000. Effect of streamwise and spanwise jet-to-jet spacing (X/D, Y/D: 4–8) and jet-to-target plate distance (Z/D: 0.75–3) are employed composing a test matrix of 36 different geometries. Additionally, the effect of hole inclination (θ: 0°–40°) on the heat transfer coefficient is investigated. Optical hole spacing arrangements and impingement distance are pointed out to maximize the area-averaged Nusselt number and minimize the amount of cooling air. Also included is a new correlation, based on that of Florschuetz et al., to predict row-averaged Nusselt number. The new correlation is capable to cover low Z/D∼0.75 and presents better prediction of row-averaged Nusselt number, which proves to be an effective impingement design tool.

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Effect of Reynolds Number, Hole Patterns, and Target Plate Thickness on the Cooling Performance of an Impinging Jet Array—Part II: Conjugate Heat Transfer Results and Optimization

Journal of Turbomachinery ◽

10.1115/1.4036297 ◽

2017 ◽

Vol 139 (10) ◽

Cited By ~ 7

Author(s):

Weihong Li ◽

Li Yang ◽

Xueying Li ◽

Jing Ren ◽

Hongde Jiang

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Boundary Conditions ◽

Conjugate Heat Transfer ◽

Plate Thickness ◽

Impinging Jet ◽

Measured Temperature ◽

Temperature Uniformity ◽

Target Plate ◽

Jet Array

This study comprehensively illustrates the effect of Reynolds number, hole spacing, nozzle-to-target distance, and target plate thickness on the conjugate heat transfer (CHT) performance of an impinging jet array. Test models are composed of a specific thermal-conductivity material which exerts a matched model Biot number to that of engine condition. High-resolution temperature measurements are conducted on the impinging-target plate utilizing steady liquid crystal (SLC) with Reynolds numbers ranging from 5000 to 27,500. Different streamwise and spanwise jet-to-jet spacing (i.e., X/D and Y/D: 4–8), nozzle-to-target plate distance (Z/D: 0.75–3), and target plate thickness (t/D: 0.75–2.75) are employed to compose a total of 108 different geometries. Experimental measured temperature is utilized as boundary conditions to conduct finite element simulation. Local and averaged nondimensional temperature and averaged temperature uniformity of target plate “hot side” are obtained. Optimum hole spacing arrangements, impingement distance, and target plate thickness are pointed out to minimize hot side temperature, amount of cooling air and to maximize temperature uniformity. Also included are 2D predictions with different convective boundary conditions, i.e., local 2D distribution and row-averaged heat transfer coefficients (HTCs), to estimate the accuracy of temperature prediction in comparison with the conjugate results.

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Effect of Reynolds Number, Hole Patterns, Target Plate Thickness on Cooling Performance of an Impinging Jet Array: Part II — Conjugate Heat Transfer Results and Optimization

Volume 5B: Heat Transfer ◽

10.1115/gt2016-56768 ◽

2016 ◽

Cited By ~ 2

Author(s):

Weihong Li ◽

Xueying Li ◽

Jing Ren ◽

Hongde Jiang ◽

Li Yang

Keyword(s):

Heat Transfer ◽

Reynolds Number ◽

Boundary Conditions ◽

Conjugate Heat Transfer ◽

Plate Thickness ◽

Impinging Jet ◽

Test Model ◽

Temperature Uniformity ◽

Target Plate ◽

Jet Array

This study comprehensively illustrates the effect of Reynolds number, hole spacing, jet-to-target distance and target plate thickness on the conjugate heat transfer performance of an impinging jet array. Test model is constructed with a relatively high conductivity material so that the Biot number of the models match engine condition. Highly resolved temperature distributions on the target plate are obtained utilizing steady liquid crystal over a range of Reynolds numbers varying between 5,000 and 27,5000. Effect of streamwise and spanwise jet-to-jet spacing (X/D, Y/D: 4–8), jet-to-target plate distance (Z/D: 0.75–3) and target plate thickness (t/D: 0.75–2.75) are employed composing a test matrix of 108 different geometries. Measured data are utilized as boundary conditions to conduct finite element simulation. Local and averaged non-dimensional temperature and averaged temperature uniformity of target plate “hot side” are obtained. Optimum hole spacing arrangements, impingement distance and target plate thickness are pointed out to minimize hot side temperature, the amount of cooling air and maximize the temperature uniformity. Also included are 2D predictions with different convective boundary conditions, i.e. row-averaged and local heat transfer coefficients, to estimate the accuracy of temperature prediction in comparison with the conjugate results.

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Influence of capsule length and width on heat transfer in capsule-type plate heat exchangers

Advances in Mechanical Engineering ◽

10.1177/1687814019895742 ◽

2019 ◽

Vol 11 (12) ◽

pp. 168781401989574 ◽

Cited By ~ 1

Author(s):

Chen Jiang ◽

Wenxue Zhou ◽

Xiaoying Tang ◽

Bofeng Bai

Keyword(s):

Heat Transfer ◽

Heat Exchangers ◽

Low Flow ◽

Width Ratio ◽

Plate Heat ◽

Longitudinal Vortices ◽

Wake Vortices ◽

Capsule Type ◽

Numerical Studies ◽

Length Width

Capsule-type plate heat exchanger has the advantages of less deposition and low flow resistance. Based on previous research, numerical studies of capsule-type plate heat exchangers with different capsule lengths and widths for the Reynolds number ranging from 600 to 10,000 are performed. The results show that wake vortices, transverse vortices, and longitudinal vortices generate in the channels by the flow shearing and separation. The vortices promote the swirl and flow destabilization, exchange the fluid between the boundary layer and the mainstream, and thus enhance the heat transfer in the capsule-type plate channels. Wake vortices transform to longitudinal vortices with increasing Re. The number of the longitudinal vortices decreases and the size of the longitudinal vortices increases with increasing Re or the decreasing length−width ratio of the capsule. In addition, Nusselt number and friction factor decrease with the increasing length−width ratio of the capsule.

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