scholarly journals Enhancing the Thermal Performance of Slender Packed Beds through Internal Heat Fins

Processes ◽  
2020 ◽  
Vol 8 (12) ◽  
pp. 1528
Author(s):  
Nico Jurtz ◽  
Steffen Flaischlen ◽  
Sören C. Scherf ◽  
Matthias Kraume ◽  
Gregor D. Wehinger
Keyword(s):  
Heat Transfer ◽  
Heat Transport ◽  
Thermal Performance ◽  
Internal Heat ◽  
Spherical Particles ◽  
Reactor Wall ◽  
Packed Beds ◽  
Radial Heat ◽  
Simulation Results ◽  
The Impact

Slender packed beds are widely used in the chemical and process industry for heterogeneous catalytic reactions in tube-bundle reactors. Under safety and reaction engineering aspects, good radial heat transfer is of outstanding importance. However, because of local wall effects, the radial heat transport in the vicinity of the reactor wall is hindered. Particle-resolved computational fluid dynamics (CFD) is used to investigate the impact of internal heat fins on the near wall radial heat transport in slender packed beds filled with spherical particles. The simulation results are validated against experimental measurements in terms of particle count and pressure drop. The simulation results show that internal heat fins increase the conductive portion of the radial heat transport close to the reactor wall, leading to an overall increased thermal performance of the system. In a wide flow range (100<Rep<1000), an increase of up to 35% in wall heat transfer coefficient and almost 90% in effective radial thermal conductivity is observed, respectively.

scholarly journals Numerical Analysis on Thermohydraulic Performance of the Tube Inserted with Rectangular Winglet Vortex Generators

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 179
Author(s):  
Yicong Li ◽  
Zuoqin Qian ◽  
Qiang Wang
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Transfer Performance ◽  
Circular Tube ◽  
Vortex Generators ◽  
Transfer Performance ◽  
Empirical Formulas ◽  
Influence Mechanism ◽  
Simulation Results ◽  
The Impact

The aim of this design was to improve the heat transfer performance significantly due to larger turbulent region and much vortices formed by tube inserted. In this article, the BSL k-ω model was chosen as turbulence model to simulate the thermohydraulic performance of the proposed tubes inserted with rectangular winglet vortex generators (RWVGs) when the Re was set as 5000 to 15,000. The reliability of the simulation results was obtained by comparing with the empirical formulas and experimental results. By means of numerical simulation, the influence mechanism of geometric parameters of RWVGs on thermal-hydraulic performance in tubes was analyzed. And the impact of three configurational parameters on the thermal performance was studied, namely the angle α, the height H and the number N of the RWVGs, respectively. The results revealed that the capacity of heat transfer in tubes with RWVG inserts was obviously larger than that in ordinary circular tube. In addition, it could be seen from the results that both Nu and f increased with the increase of H and N. At the same time, the case of α = 135° showed the greatest enhancement of thermal performance than the case of α = 45° and α = 90°.The PEC achieved the highest value of 1.23 when the height H of RWVG was 0.7 mm, the number N was 20, and angle α was 135°.

Experimental study of thermohydraulic characteristics and irreversibility analysis of novel axial corrugated tube with spring tape inserts

2020 ◽  
Vol 92 (3) ◽  
pp. 30901
Author(s):  
Suvanjan Bhattacharyya ◽  
Debraj Sarkar ◽  
Ulavathi Shettar Mahabaleshwar ◽  
Manoj K. Soni ◽  
M. Mohanraj
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Working Fluid ◽  
The Novel ◽  
Heat Exchanger Tube ◽  
Heat Transfer Augmentation ◽  
Corrugated Tube ◽  
The Impact ◽  
Exchanger Tube

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.

scholarly journals Influence of Macroscopic Wall Structures on the Fluid Flow and Heat Transfer in Fixed Bed Reactors with Small Tube to Particle Diameter Ratio

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 689
Author(s):  
Thomas Eppinger ◽  
Nico Jurtz ◽  
Matthias Kraume
Keyword(s):  
Heat Transfer ◽  
Fixed Bed ◽  
Particle Diameter ◽  
Diameter Ratio ◽  
Spherical Particles ◽  
Reactor Wall ◽  
Entry Length ◽  
Fixed Bed Reactors ◽  
Wall Structures ◽  
Small Tube

Fixed bed reactors are widely used in the chemical, nuclear and process industry. Due to the solid particle arrangement and its resulting non-homogeneous radial void fraction distribution, the heat transfer of this reactor type is inhibited, especially for fixed bed reactors with a small tube to particle diameter ratio. This work shows that, based on three-dimensional particle-resolved discrete element method (DEM) computational fluid dynamics (CFD) simulations, it is possible to reduce the maldistribution of mono-dispersed spherical particles near the reactor wall by the use of macroscopic wall structures. As a result, the lateral convection is significantly increased leading to a better radial heat transfer. This is investigated for different macroscopic wall structures, different air flow rates (Reynolds number Re = 16 ...16,000) and a variation of tube to particle diameter ratios (2.8, 4.8, 6.8, 8.8). An increase of the radial velocity of up to 40%, a reduction of the thermal entry length of 66% and an overall heat transfer increase of up to 120% are found.

The Study on the Impact of Recycled Fine Aggregate and Powder on the Mechanics and Thermal Performance of Recycled Concrete Hollow Blocks

2012 ◽  
Vol 509 ◽  
pp. 119-122
Author(s):  
Wei Zhou ◽  
Ling Huan Lu ◽  
Zhen Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Thermal Performance ◽  
High Strength ◽  
Recycled Concrete ◽  
Fine Aggregate ◽  
Ordinary Concrete ◽  
Recycled Fine Aggregate ◽  
The Impact ◽  
The Heat Transfer Coefficient

The impact of recycled fine aggregate and powder on the mechanics and thermal performance of recycled concrete hollow blocks was discussed in this paper. The results showed that 30% recycled fine aggregate and powder have slight affect on the strength of recycled concrete hollow blocks. But the strength reduced significantly when the replacement is above 50%. The impact of recycled fine aggregate and powder on the performance of concrete hollow blocks with high strength grade is notable . The heat transfer coefficient of recycled concrete hollow blocks with 30% recycled fine aggregate and powder was equivalently to ordinary concrete hollow blocks.

scholarly journals Effect of Rotational Speed Modulation on the Weakly Nonlinear Heat Transfer in Walter-B Viscoelastic Fluid in the Highly Permeable Porous Medium

Mathematics ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1448
Author(s):  
Anand Kumar ◽  
Vinod K. Gupta ◽  
Neetu Meena ◽  
Ishak Hashim
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Prandtl Number ◽  
Heat Transport ◽  
Viscoelastic Fluid ◽  
Rotational Speed ◽  
Weakly Nonlinear ◽  
Speed Modulation ◽  
The Stability ◽  
The Impact

In this article, a study on the stability of Walter-B viscoelastic fluid in the highly permeable porous medium under the rotational speed modulation is presented. The impact of rotational modulation on heat transport is performed through a weakly nonlinear analysis. A perturbation procedure based on the small amplitude of the perturbing parameter is used to study the combined effect of rotation and permeability on the stability through a porous medium. Rayleigh–Bénard convection with the Coriolis expression has been examined to explain the impact of rotation on the convective flow. The graphical result of different parameters like modified Prandtl number, Darcy number, Rayleigh number, and Taylor number on heat transfer have discussed. Furthermore, it is found that the modified Prandtl number decelerates the heat transport which may be due to the combined effect of elastic parameter and Taylor number.

On the Heat Transfer and Flow Structures’ Characteristics of the Turbine Blade Tip Underside With Dirt Purge Holes at Different Locations by Using Topological Analysis

2019 ◽  
Vol 141 (7) ◽  
Author(s):  
Lei Luo ◽  
Zhiqi Zhao ◽  
Xiaoxu Kan ◽  
Dandan Qiu ◽  
Songtao Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Topological Analysis ◽  
Internal Heat ◽  
Gas Turbine Blade ◽  
Transfer Enhancement ◽  
Cooling Passage ◽  
The Impact

This paper numerically investigated the impact of the holes and their location on the flow and tip internal heat transfer in a U-bend channel (aspect ratio = 1:2), which is applicable to the cooling passage with dirt purge holes in the mid-chord region of a typical gas turbine blade. Six different tip ejection configurations are calculated at Reynolds numbers from 25,000 to 200,000. The detailed three-dimensional flow and heat transfer over the tip wall are presented, and the overall thermal performances are evaluated. The topological methodology, which is first applied to the flow analysis in an internal cooling passage of the blade, is used to explore the mechanisms of heat transfer enhancement on the tip wall. This study concludes that the production of the counter-rotating vortex pair in the bend region provides a strong shear force and then increases the local heat transfer. The side-mounted single hole and center-mounted double holes can further enhance tip heat transfer, which is attributed to the enhanced shear effect and disturbed low-energy fluid. The overall thermal performance of the optimum hole location is a factor of 1.13 higher than that of the smooth tip. However, if double holes are placed on the upstream of a tip wall, the tip surface cannot be well protected. The results of this study are useful for understanding the mechanism of heat transfer enhancement in a realistic gas turbine blade and for efficient designing of blade tips for engine service.

scholarly journals On parameterization of heat conduction in coupled soil water and heat flow modelling

2012 ◽  
Vol 7 (No. 4) ◽  
pp. 125-137 ◽  
Author(s):  
J. Votrubová ◽  
M. Dohnal ◽  
T. Vogel ◽  
M. Tesař
Keyword(s):  
Thermal Conductivity ◽  
Soil Water ◽  
Heat Transport ◽  
Preferential Flow ◽  
Thermal Conditions ◽  
Industrial Applications ◽  
Soil Thermal Conductivity ◽  
Vegetation Season ◽  
Simulation Results ◽  
The Impact

Soil water and heat transport plays an important role in various hydrologic, agricultural, and industrial applications. Accordingly, an increasing attention is paid to relevant simulation models. In the present study, soil thermal conditions at a mountain meadow during the vegetation season were simulated. A dual-continuum model of coupled water and heat transport was employed to account for preferential flow effects. Data collected at an experimental site in the &Scaron;umava Mountains, southern Bohemia, during the vegetation season 2009 were employed. Soil hydraulic properties (retention curve and hydraulic conductivity) determined by independent soil tests were used. Unavailable hydraulic parameters were adjusted to obtain satisfactory hydraulic model performance. Soil thermal properties were estimated based on values found in literature without further optimization. Three different approaches were used to approximate the soil thermal conductivity function, &lambda;(&theta;): (i) relationships provided by Chung and Horton (ii) linear estimates as described by Loukili, Woodbury and Snelgrove, (iii) methodology proposed by C&ocirc;t&eacute; and Konrad. The simulated thermal conditions were compared to those observed. The impact of different soil thermal conductivity approximations on the heat transport simulation results was analysed. The differences between the simulation results in terms of the soil temperature were small. Regarding the surface soil heat flux, these differences became substantial. More realistic simulations were obtained using &lambda;(&theta;) estimates based on the soil texture and composition. The differences between these two, related to neglecting vs. considering &lambda;(&theta;) non-linearity, were found negligible.

Throughflow and G-Jitter Effects on Oscillatory Convection in a Rotating Porous Medium

2020 ◽  
Vol 12 (6) ◽  
pp. 781-791
Author(s):  
S. H. Manjula ◽  
Palle Kiran ◽  
B. S. Bhadauria
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Heat Transport ◽  
Landau Equation ◽  
Nonlinear Stability Analysis ◽  
Periodic Mode ◽  
Ginzburg Landau ◽  
Weakly Nonlinear ◽  
Weakly Nonlinear Analysis ◽  
The Impact

The impact of vertical throughflow and g-jitter effect on rotating porous medium is investigated. A feeble nonlinear stability analysis associate to complex Ginzburg-Landau equation (CGLE) has been studied. This weakly nonlinear analysis performed for a periodic mode of convection and quantified heat transport in terms of the Nusselt number, which is governed by the non-autonomous advanced CGLE. Each idea, rotation and throughflow is used as an external mechanism to the system either to extend or decrease the heat transfer. The results of amplitude and frequency of modulation on heat transport are analyzed and portrayed graphically. Throughflow has dual impact on heat transfer either to increase or decrease heat transfer in the system. Particularly the outflow enhances and inflow diminishes the heat transfer. High centrifugal rates promote heat transfer and low centrifugal rates diminish heat transfer. The streamlines and isotherms area portrayed graphically, the results of rotation and throughflow on isotherms shows convective development.

scholarly journals Internal Heat Transfer Coefficient Determination in a Packed Bed From the Transient Response Due to Solid Phase Induction Heating

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
David Geb ◽  
Feng Zhou ◽  
Ivan Catton
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Internal Heat ◽  
Temperature Response ◽  
Packed Bed ◽  
Spherical Particles ◽  
Fluid Temperature ◽  
The Core ◽  
Internal Heat Transfer

Nonintrusive measurements of the internal heat transfer coefficient in the core of a randomly packed bed of uniform spherical particles are made. Under steady, fully-developed flow the spherical particles are subjected to a step-change in volumetric heat generation rate via induction heating. The fluid temperature response is measured. The internal heat transfer coefficient is determined by comparing the results of a numerical simulation based on volume averaging theory (VAT) with the experimental results. The only information needed is the basic material and geometric properties, the flow rate, and the fluid temperature response data. The computational procedure alleviates the need for solid and fluid phase temperature measurements within the porous medium. The internal heat transfer coefficient is determined in the core of a packed bed, and expressed in terms of the Nusselt number, over a Reynolds number range of 20 to 500. The Nusselt number and Reynolds number are based on the VAT scale hydraulic diameter, dh=4ɛ/S. The results compare favorably to those of other researchers and are seen to be independent of particle diameter. The success of this method, in determining the internal heat transfer coefficient in the core of a randomly packed bed of uniform spheres, suggests that it can be used to determine the internal heat transfer coefficient in other porous media.

scholarly journals Prediction of the impact of climate change on the thermal performance of walls and roof in Morocco

2021 ◽  
Author(s):  
Yassine Kharbouch ◽  
Mohamed Ameur
Keyword(s):  
Climate Change ◽  
Heat Transfer ◽  
Heat Loss ◽  
Thermal Performance ◽  
Building Energy ◽  
Building Envelope ◽  
Heat Gain ◽  
Impact Of Climate Change ◽  
Summer Heat ◽  
The Impact

Abstract Climate change has become a real challenge in different fields, including the building sector. Understanding and assessing the impact of climate change on building energy performance is still necessary to elaborate new climate-adaptive design measures for future buildings. The building energy consumption for heating and cooling is mainly related to the building envelope thermal performance. In this study, the winter heat loss and summer heat gain indicators are proposed to assess and analyse the potential impact of climate change on opaque building envelope elements for different climate zones in Morocco over the next 40 years. For that purpose, a one-dimensional heat transfer model is used to simulate the heat transfer through the multi-layer structure of the wall/roof. A medium climate change scenario is considered in this study. The results showed that the current average walls and roof summer heat gain is expected to increase of about 19.2–54.3% by the 2060s depending on the climate zone, versus a less important decrease in winter heat loss varies between –10.6 and –20.6%. This paper provides a reliable evaluation of the climate change impact on building envelope thermal performance, which leads to better adjustments in future building envelope designs.

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