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Ho CD, Tu JW, Chang H, Lin LP, Chew TL. Optimizing thermal efficiencies of power-law fluids in double-pass concentric circular heat exchangers with sinusoidal wall fluxes. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2022; 19:8648-8670. [PMID: 35942729 DOI: 10.3934/mbe.2022401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Effect of external-recycle operations on the heat-transfer efficiency, specifically for the power-law fluid flowing in double-pass concentric circular heat exchanger under sinusoidal wall fluxes, is investigated theoretically in the developed countries. Given that the fluid is heated twice on both sides of the impermeable sheet, four flow patterns proposed in recycling double-pass operations are expected to make substantial improvements in the performance of heat exchanger device in this study. Theoretical predictions point out that the heat-transfer efficiency increases with the ratio of channel thickness of double-pass concentric circular heat exchanger for all new designs under the same working dimension and the operational condition. The fluid velocity within the double-pass heat exchanger is increased by the fluids flowing through divided subchannels, which contributed to the higher convective heat-transfer efficiency. A simplified mathematical formulation was derived for double-pass concentric circular heat exchangers and would be a significant contribution to analyze heat transfer problems with sinusoidal wall fluxes at boundaries. The results deliver the optimal performance for the proposed four configurations with the use of external recycle compared to those conducted in single-pass, where an impermeable sheet is not inserted. The influences of power-law index and impermeable-sheet position on average Nusselt numbers under various flow patterns are also delineated. The distribution of dimensionless wall temperature was lower at the level of relative smaller thickness of annular channel, and the average Nusselt numbers for four external-recycle configurations and single-pass device were more suitable for operating under same condition. The ratio of the power consumption increment to heat-transfer efficiency enhancement demonstrates the economic feasibility among various configurations of double-pass concentric circular heat exchanger. The results also show that the external-recycle configuration (say Type B in the present study) serves as an important economic advantage in designing concentric circular heat exchangers for heating power-law fluids due to the smaller volumetric flow rate in annular channel with exiting outlet temperature.
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Affiliation(s)
- Chii-Dong Ho
- Department of Chemical and Materials Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui, New Taipei, Taiwan 251
| | - Jr-Wei Tu
- Department of Chemical and Materials Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui, New Taipei, Taiwan 251
| | - Hsuan Chang
- Department of Chemical and Materials Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui, New Taipei, Taiwan 251
| | - Li-Pang Lin
- Department of Chemical and Materials Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui, New Taipei, Taiwan 251
| | - Thiam Leng Chew
- Department of Chemical Engineering, Faculty of Engineering, Universiti Teknologi Petronas, 32610 Seri Iskandar, Perak Darul Ridzuan, Malaysia
- CO2 Research Center (CO2RES), Institute of Contaminant Management Universiti Teknologi Petronas, 32610 Seri Iskandar, Perak Darul Ridzuan, Malaysia
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Beaussier M, Vanoli E, Zadegan F, Peray H, Bezian E, Jilesen J, Gandveau G, Gayraud JM. Aerodynamic analysis of hospital ventilation according to seasonal variations. A simulation approach to prevent airborne viral transmission pathway during Covid-19 pandemic. ENVIRONMENT INTERNATIONAL 2022; 158:106872. [PMID: 34547639 PMCID: PMC8443368 DOI: 10.1016/j.envint.2021.106872] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 09/07/2021] [Accepted: 09/07/2021] [Indexed: 06/13/2023]
Abstract
During the Covid-19 pandemic, location of the SARS-CoV-2 infected patients inside the hospital is a major issue to prevent viral cross-transmission. The objective of this study was to evaluate the risk of contamination through aerosol by using a global approach of the multiple environmental parameters to simulate, including seasonal context. A computational fluid dynamic (CFD) simulation based on the Lattice Boltzmann Method approach was used to predict airflow on the entire floor of a private hospital in Paris. The risk of contamination outside the rooms was evaluated by using a water vapor mass fraction tracker. Finally, the air contamination was estimated by a "cough model" producing several punctual emissions of contaminated air from potentially infected patients. In a winter configuration, the simulation showed a well-balanced ventilation on the floor and especially inside the rooms. After cough emissions from COVID-positive rooms, no significant contamination was observed in the circulation area, public waiting space and nurse office. On the contrary, in a summer configuration, the temperature difference due to the impact of the sun radiation between both sides of the building created additional air transport increasing the contamination risk in neighboring rooms and public spaces. Airborne spread was limited to rooms during winter conditions. On the contrary, during summer conditions, market airflow with potentially contaminated air coming from rooms located on the side of the building exposed to solar radiation was evidenced. These observations have implications to locate infected patients inside the building and for the conception of future health care structures.
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Affiliation(s)
- Marc Beaussier
- Institut Mutualiste Montsouris, 42 Bd Jourdan, 75014 Paris, France.
| | - Emmanuel Vanoli
- Institut Mutualiste Montsouris, 42 Bd Jourdan, 75014 Paris, France
| | - Frédéric Zadegan
- Institut Mutualiste Montsouris, 42 Bd Jourdan, 75014 Paris, France
| | - Herve Peray
- Institut Mutualiste Montsouris, 42 Bd Jourdan, 75014 Paris, France
| | - Elodie Bezian
- Institut Mutualiste Montsouris, 42 Bd Jourdan, 75014 Paris, France
| | - Jonathan Jilesen
- Institut Mutualiste Montsouris, 42 Bd Jourdan, 75014 Paris, France
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Ho CD, Lin GG, Chew TL, Lin LP. Conjugated heat transfer of power-law fluids in double-pass concentric circular heat exchangers with sinusoidal wall fluxes. MATHEMATICAL BIOSCIENCES AND ENGINEERING : MBE 2021; 18:5592-5613. [PMID: 34517502 DOI: 10.3934/mbe.2021282] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
An analytical formulation, referred to as conjugated Graetz problems, is developed to predict the temperature distribution and Nusselt numbers for the power-law fluid flowing in a double-pass concentric circular heat exchanger under sinusoidal wall fluxes. A new design of inserting an impermeable sheet into a concentric tube, in parallel, to conduct recycling double-pass operations has been studied theoretically in the fully developed region, resulting in substantial improvements in the performance of heat exchanger device. The analytical solution was derived using the complex functions by transforming the boundary value problem into ordinary differential equations with the aid of the Frobenius method. The influences of power-law index and impermeable-sheet position on average Nusselt numbers with various designs and operating parameters are also delineated. The theoretical predictions show that the heat transfer efficiency is considerably improved through operating the double-pass device compared to via a single-pass circular heat exchanger (where an impermeable sheet is not inserted). The economic feasibility of operating double-pass concentric circular heat exchanger for power-law fluids is exemplified by the ratio of the heat-transfer efficiency enhancement and the increment in power consumption. The double-pass effect from increasing the convective heat-transfer coefficient can compensate for the rise in power consumption, which serves as important economic advantage of this design.
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Affiliation(s)
- Chii-Dong Ho
- Department of Chemical and Materials Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui, New Taipei, Taiwan 251
| | - Gwo-Geng Lin
- Department of Chemical and Materials Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui, New Taipei, Taiwan 251
| | - Thiam Leng Chew
- Department of Chemical Engineering, Faculty of Engineering, Universiti Teknologi Petronas, 32610 Seri Iskandar, Perak Darul Ridzuan, Malaysia
- CO2 Research Center (CO2RES), Institute of Contaminant Management, Universiti Teknologi Petronas, 32610 Seri Iskandar, Perak Darul Ridzuan, Malaysia
| | - Li-Pang Lin
- Department of Chemical and Materials Engineering, Tamkang University, 151 Yingzhuan Road, Tamsui, New Taipei, Taiwan 251
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A Graphics Process Unit-Based Multiple-Relaxation-Time Lattice Boltzmann Simulation of Non-Newtonian Fluid Flows in a Backward Facing Step. COMPUTATION 2020. [DOI: 10.3390/computation8030083] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
A modified power-law (MPL) viscosity model of non-Newtonian fluid flow has been used for the multiple-relaxation-time (MRT) lattice Boltzmann methods (LBM) and then validated with the benchmark problems using the graphics process unit (GPU) parallel computing via Compute Unified Device Architecture (CUDA) C platform. The MPL model for characterizing the non-Newtonian behavior is an empirical correlation that considers the Newtonian behavior of a non-Newtonian fluid at a very low and high shear rate. A new time unit parameter (λ) governing the flow has been identified, and this parameter is the consequence of the induced length scale introduced by the power law. The MPL model is free from any singularities due to the very low or even zero shear-rate. The proposed MPL model was first validated for the benchmark study of the lid-driven cavity and channel flows. The model was then applied for shear-thinning and shear-thickening fluid flows through a backward-facing step with relatively low Reynolds numbers, Re = 100–400. In the case of shear-thinning fluids (n=0.5), laminar to transitional flow arises while Re≥300, and the large vortex breaks into several small vortices. The numerical results are presented regarding the velocity distribution, streamlines, and the lengths of the reattachment points.
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Afra B, Nazari M, Kayhani MH, Ahmadi G. Direct numerical simulation of freely falling particles by hybrid immersed boundary – Lattice Boltzmann – discrete element method. PARTICULATE SCIENCE AND TECHNOLOGY 2019. [DOI: 10.1080/02726351.2018.1536092] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Affiliation(s)
- Behrooz Afra
- Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran
| | - Mohsen Nazari
- Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran
| | - Mohammad H. Kayhani
- Faculty of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran
| | - Goodarz Ahmadi
- Department of Mechanical and Aeronautical Engineering, Clarkson University, Potsdam, NY, USA
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Wei Y, Wang Z, Qian Y, Guo W. Study on Bifurcation and Dual Solutions in Natural Convection in a Horizontal Annulus with Rotating Inner Cylinder Using Thermal Immersed Boundary-Lattice Boltzmann Method. ENTROPY 2018; 20:e20100733. [PMID: 33265822 PMCID: PMC7512296 DOI: 10.3390/e20100733] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/22/2018] [Revised: 09/13/2018] [Accepted: 09/17/2018] [Indexed: 11/16/2022]
Abstract
A numerical investigation has been carried out to understand the mechanism of the rotation effect on bifurcation and dual solutions in natural convection within a horizontal annulus. A thermal immersed boundary-lattice Boltzmann method was used to resolve the annular flow domain covered by a Cartesian mesh. The Rayleigh number based on the gap width is fixed at 104. The rotation effect on the natural convection is analyzed by streamlines, isotherms, phase portrait and bifurcation diagram. Our results manifest the existence of three convection patterns in a horizontal annulus with rotating inner cylinder which affect the heat transfer in different ways, and the linear speed ( U i * ) determines the proportion of each convection. Comparison of average Nusselt number versus linear speed for the inner cylinder indicates the existence of the three different mechanisms which drive the convection in a rotation system. The convection pattern caused by rotation reduces the heat transfer efficiency. Our results in phase portraits also reveal the differences among different convection patterns.
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Affiliation(s)
- Yikun Wei
- Faculty of Mechanical Engineering & Automation, Zhejiang Sci-Tech University, Hangzhou 310018, China
- State-Province Joint Engineering Lab of Fluid Transmission System Technology, Hangzhou 310018, China
| | - Zhengdao Wang
- Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072, China
- Correspondence: (Z.W.); (Y.Q.)
| | - Yuehong Qian
- School of Mathematical Sciences, Soochow University, Suzhou 215006, China
- Correspondence: (Z.W.); (Y.Q.)
| | - Wenjing Guo
- Basic Courses Department, Shandong University of Science and Technology, Taian 271019, China
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Ren Q. Investigation of pumping mechanism for non-Newtonian blood flow with AC electrothermal forces in a microchannel by hybrid boundary element method and immersed boundary-lattice Boltzmann method. Electrophoresis 2018; 39:1329-1338. [DOI: 10.1002/elps.201700494] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2017] [Revised: 02/05/2018] [Accepted: 02/05/2018] [Indexed: 01/02/2023]
Affiliation(s)
- Qinlong Ren
- Key Laboratory of Thermo-Fluid Science and Engineering of MOE, School of Energy and Power Engineering; Xi'an Jiaotong University; Xi'an Shaanxi P. R. China
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