scholarly journals Exhaust Gases Cleaning Technology for Vessels

2020 ◽  
Vol 9 (6) ◽  
pp. 1085-1091
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Rational Design ◽  
Solid Particles ◽  
Cfd Modeling ◽  
Sulfur Oxides ◽  
The Heat Transfer Coefficient

The present investigation aims to propose results of development of an effective system for the purification of exhaust gases that are emitted to the environment by ship power plant from sulfur oxides (SOx ) and solid particles. Numerical simulation of a combined scrubber with vortex plate based on the developed theoretical approach was performed. Mathematical model of aerohydrodynamic and heat-mass transfer processes contains five interconnected modeling blocks. There was investigated the influence of the scrubber’s geometric characteristics onto the quality of its work. As a result, for the elements of vortex plate the rational design parameters were determined (the angle of blades installation for the swirls =60-90, the ratio between internal and outer radius of the swirls R1 /R2=0,6-0,7). The interaction of gas aerosol with water foam was studied during numerical simulation. It was done with consideration of hydrodynamic regime on the surface of a vortex plate. As a result, for the scrubber rational design and operating parameters were formulated (inlet flow velocity V=18-25 m/s, the height of foam layer H=70-150 mm, inlet dust concentration 40-50 g/cub.m of the gas to be cleaned, cross-sectional area of the purification unit up to 2 sq.m). Computer-based solid-body scrubber model was created during numerical simulation. CFD modeling of the main hydrodynamic processes based on this model was carried out. It was done for all developed structural solutions for scrubber elements. The main results obtained during CFD modeling of the scrubber operation make it possible to analyze the technology of its use and to achieve a reduction in energy costs while maintaining the quality of gas cleaning. The developed theoretical model of a scrubber gives an ability to simulate the flow of a gas-dust stream considering all changes that were done in the geometry of the scrubber. The very model can also be used to optimize the scrubber’s design depending on the type of production and parameters of the gas to be contaminated. During research works there was formulated a conclusion about the necessity to take into consideration the uneven distribution of the field of velocity when modeling the process of gas purification and cooling inside a scrubber. In order to determine the efficiency of heat transfer process inside the scrubber, heat transfer coefficients were found out. They were compared with characteristics of a traditional scrubber’s model based on a perforated plate. Calculation data have shown an excess of the heat transfer coefficient of the vortex plate by 5-7%. It was stated also that the value of the heat transfer coefficient depends on average velocity and moisture content of the gas to be supplied. The rational design and operational parameters of the scrubber obtained on the models made it possible to develop a pilot industrial model of the scrubber and method of engineering calculation. During experimental studies of the scrubber, new scientific results were obtained. They allow one to establish the technological range of irrigation density values, at which the maximum efficiency of trapping solid particles and sulfur oxides (SOx ) is ensured. Experiments were carried out that reveal the relationship between the angle of blades installation of the swirl and the height of the installation of the baffle plate onto the efficiency of foaming and total resistance of the vortex plate.

Effect of nanoparticle diameter on the forced convective heat transfer of nanofluid (water + Al2O3) in the fully developed laminar region

2014 ◽  
Vol 05 (03) ◽  
pp. 1450008 ◽  
Author(s):  
Seyyed Shahabeddin Azimi ◽  
Mansour Kalbasi ◽  
Mohammad Hosain Namazi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Quantitative Characteristic ◽  
Solid Particles ◽  
Nanoparticle Size ◽  
Forced Convective Heat Transfer ◽  
The Heat Transfer Coefficient

Nanofluid is a suspension of nanoparticles (solid particles with diameters below 100 nm) in a conventional base fluid with significantly improved heat transfer characteristics compared to the original fluid. The heat transfer coefficient is a quantitative characteristic of the convective heat transfer. The purpose of this paper is to study the effect of the nanoparticle size (diameter) on the heat transfer coefficient of forced convective heat transfer of nanofluid in the fully developed laminar region of a horizontal tube. Using thermal conductivity model which is a function of the nanoparticle size, flow of a nanofluid (water + Al 2 O 3) in a circular tube submitted to a constant wall temperature is numerically investigated with two particle sizes of 11 nm and 47 nm. The calculated results show that the nanoparticle size does not significantly affect the heat transfer coefficient, however, the heat transfer coefficient decreases as the particle size increases.

scholarly journals Numerical Simulation on Heat Transfer Characteristics of Water Flowing through the Fracture of High-Temperature Rock

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-14 ◽  
Author(s):  
Xiaohu Zhang ◽  
Zhaolun Wang ◽  
Yanhua Sun ◽  
Chun Zhu ◽  
Feng Xiong ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Water Velocity ◽  
Aperture Size ◽  
Heat Transfer Characteristics ◽  
Fracture Roughness ◽  
Rock Temperature ◽  
The Heat Transfer Coefficient

Deep geothermal resources are becoming an increasingly important energy source worldwide. To achieve the optimal efficiency of this resource, the heat transfer characteristics between flowing water and rock need to be further studied. Using the stereotopometric scanning system 3D CaMega, the fracture geometry data of five cuboid granite rocks were obtained to determine the effects of fracture roughness on the heat transferability of rock. A 3-D model was built based upon the scanned geometry data to assess the effects of rock temperature, water velocity, and roughness, and aperture size of fracture surface on the heat transfer coefficient. The simulation tests show that water velocity has the most noticeable effect, followed by aperture size and rock roughness. On the other hand, the initial rock temperature has the least influence. A new heat transfer coefficient was proposed considering aperture size, water flow velocity, and rock fracture roughness. The calculated values of Reynolds, Prandtl, and Nusselt numbers obtained using this coefficient are in good agreement with the numerical simulation results. This study provides a reference for enhancing the heat transfer coefficient to benefit the exploitation of heat energy of hot dry rock.

scholarly journals Analysis of the Thermal Characteristics of a Composite Ceramic Product Filled with Phase Change Material

Buildings ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 217 ◽  
Author(s):  
Joanna Krasoń ◽  
Przemysław Miąsik ◽  
Lech Lichołai ◽  
Bernardeta Dębska ◽  
Aleksander Starakiewicz
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Phase Change Material ◽  
Thermal Characteristics ◽  
Ceramic Product ◽  
Change Material ◽  
The Heat Transfer Coefficient

The article presents a comparative analysis carried out using three methods, determining the heat transfer coefficient U for a ceramic product modified with a phase change material (PCM). The purpose of the article is to determine the convergence of the resulting thermal characteristics, obtained using the experimental method, numerical simulation, and standard calculation method according to the requirements of PN-EN ISO 6946. The heat transfer coefficient is one of the basic parameters characterizing the thermal insulation of a building partition. Most often, for the thermal characteristics of the partition, we obtain from the manufacturer the value of the thermal conductivity coefficient λ for individual homogeneous materials or the heat transfer coefficient U for the finished (prefabricated) partition. In the case of a designed composite element modified with a phase change material or other material, it is not possible to obtain direct information on the above parameter. In such a case, one of the methods presented in this article should be used to determine the U factor. The U factor in all analyses was determined in stationary conditions. Research has shown a significant convergence of the resulting value of the heat transfer coefficient obtained by the assumed methods. Thanks to obtaining similar values, it is possible to continue tests of thermal characteristics of partitions by means of numerical simulation, limiting the number of experimental tests (due to the longer test time required) in assumed different partition configurations, in stationary and dynamic conditions.

scholarly journals Transient behavior of a plate-fin-and-tube heat exchanger taking into account different heat transfer coefficients on the individual tube rows

2019 ◽  
Vol 128 ◽  
pp. 04001
Author(s):  
Dawid Taler ◽  
Jan Taler ◽  
Katarzyna Wrona
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Analytical Formula ◽  
Cfd Modeling ◽  
Tube Heat Exchanger ◽  
Individual Tube ◽  
The Heat Transfer Coefficient

Experimental studies of multi-row plate-fin heat exchangers show that the highest average heat transfer coefficient on the air side occurs in the first row of tubes when the air velocity in front ofthe exchanger is less thanapproximately 3.5 m/s. In the subsequent rows of tubes up to about the fourth row the heat transfer coefficient decreases. In the fifth and further rows, it can be assumed that the heat transfer coefficient is equal in each tube row. It is necessary to find the relationships fortheair–side Nusselt number on each tube row to design a plate–fin and tube heat exchanger(PFTHE) with the appropriate number of tube rows. The air–side Nusselt number correlations canbe determined experimentally or by CFD modeling (Computational and Fluid Dynamics). The paper presents a newmathematical model of the transient operation of PFTHE, considering that the Nusselt numbers on the air side of individual tube rows are different. The heat transfer coefficient on an analyzed tube row was determined from the equality condition of mass– average air temperature differences on agiven tube row determined using the analytical formula and CFD modeling. The results of numerical modelingwere compared with the results of the experiments.

Numerical Simulation of Heat Losses between a Partition Plate and the Wall of the Head of a Plastic Heat Exchanger

2010 ◽  
Vol 297-301 ◽  
pp. 650-655
Author(s):  
Rita Aguilar Osorio ◽  
Keith Cliffe
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Polyvinylidene Fluoride ◽  
Plastic Shell ◽  
Tube Heat Exchanger ◽  
Heat Exchanger Design ◽  
The Heat Transfer Coefficient

For this research it was considered that the heat exchanger was affected by leakage in the head across the partition plate and the wall between the tube passes. Leakage was a problem in the plastic shell and tube heat exchanger, because it was difficult to seal the partition plate to the head of the exchanger. The material used for manufacturing the heat exchanger was polyvinylidene fluoride, PVDF. In order to predict the amount of flow leaking through the clearances of the tube passes, a numerical simulation was carried out using the computational Fluid Dynamics CFD Fluent Software. To obtain the percentage of the heat loss across the 4 tube passes, different clearance sizes between the partition plate and the wall of the head of the exchanger were analysed. For the smaller clearance size of 0.2 mm the heat transfer coefficient was reduced up to 15%. These results suggest that the flow mass bypassing the head between tube passes affect the results of the heat transfer coefficient and confirm the experimental observation, that its performance was affected by leakage between tube passes. This research served as an extension of the preliminary plastic heat exchanger design.

scholarly journals Physical and numerical simulation of the thermal and mechanical characteristics of stationary flows in the gasair paths of piston engines

2019 ◽  
Vol 21 (5) ◽  
pp. 22-28
Author(s):  
L. V. Plotnikov ◽  
Yu. M. Brodov ◽  
B. P. Zhilkin ◽  
A. M. Nevolin ◽  
M. O. Misnik
Keyword(s):  
Heat Transfer ◽  
Numerical Simulation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Cross Sections ◽  
Experimental Studies ◽  
Hydraulic Systems ◽  
Reciprocating Engines ◽  
The Heat Transfer Coefficient ◽  
Exhaust Systems

Thermomechanical perfection of intake and exhaust systems largely determine the efficiency of the working process of reciprocating engines (ICE). The article presents the results of numerical simulation and experimental study of the heat transfer of gas flows in profiled gas- air systems of ICEs. A description of the numerical simulation technique, experimental setup, configurations of the studied hydraulic systems, measuring base and features of the experiments are given. On the basis of numerical modeling, it has been established that the use of profiled sections with cross sections in the shape of a square or a triangle in exhaust systems of an ICEs leads to a decrease in the heat transfer coefficient by 5-11%. It is shown that the use of similar profiled sections in the intake system of reciprocating engines also leads to a decrease in the heat transfer coefficient to 10 % at low air flow rates (up to 40 m/s) and an increase in the heat transfer coefficient to 7% at high speeds. Experimental studies qualitatively confirm the simulation results.

A General Correlation for Condensation Heat Transfer in Micro-Fin for Herringbone and Dimple-Texture Tubes

2015 ◽  
Author(s):  
Wei Li ◽  
Si-pu Guo ◽  
Xiao-peng Zhou ◽  
David J. Kukulka ◽  
Jin-liang Xu
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Smooth Tube ◽  
Outer Diameter ◽  
Coefficient Multiplier ◽  
The Heat Transfer Coefficient

An experimental investigation was performed to evaluate the condensation characteristics inside smooth, herringbone and dimple-textured (Vipertex 1EHT) tubes; with the same outer diameter (12.7 mm); using R22 and R410a refrigerants; for a mass flux that ranges from 81 to 178.5 kg/m 2 s. The condensation saturation temperature is 47°C; with an inlet quality of 0.8 and an outlet vapor quality of 0.2. Results indicate that the condensation heat transfer coefficient of the herringbone tube was approximately 3 times that of the smooth tube for R22; and has an enhancement heat transfer factor of 2.3 for R410a. The enhancement heat transfer coefficient multiplier for the textured dimple tube is approximately 2 times that of a smooth tube for R22; and 1.8 for R410a. Severalpreviously reported correlations are used to compare the heat transfer coefficient measurements in the plain tube; while a new equation is proposed to predict the heat transfer coefficient in the herringbone tube.

scholarly journals ЧИСЛЕННОЕ ИССЛЕДОВАНИЕ ТЕПЛООТДАЧИ В КАМЕРЕ ПОДШИПНИКА ГТД

2018 ◽  
pp. 92-103
Author(s):  
Дуаиссиа Омар Хадж Аисса
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Numerical Study ◽  
Cfd Modeling ◽  
Accurate Calculation ◽  
Film Distribution ◽  
Multiphase Mixture ◽  
Rotor Support ◽  
The Heat Transfer Coefficient

To determine the required oil pumping through the GTE rotor support, an accurate calculation of the heat flow from the engine to the GTE bearing chamber is necessary. The complexity of the mathematical description of thermo-hydraulic processes is associated with the presence of a multiphase mixture in the bearing chamber, consisting of oil, going for lubrication and cooling of the support elements, and air, used for seals pressurization. The work is devoted to the issues of numerical study of the effect of regime parameters on the heat transfer coefficient in the bearing chamber of the GTE. For these purposes, the methodology based on conservation laws and CFD modeling methods is applied. The change in the heat transfer coefficient in the characteristic sections of the chamber is considered. The influence of the oil film distribution around the circumference of the chamber is shown.

scholarly journals Enhanced Phase-Change Condensation Using Inverse Opals

2021 ◽  
Author(s):  
Solomon Adera ◽  
Nikolaj K. Mandsberg ◽  
Lauren Naworski ◽  
Anna V. Shneidman ◽  
Jack Alvarenga ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Rational Design ◽  
High Surface ◽  
Material Design ◽  
Copper Tube ◽  
Inverse Opals ◽  
The Heat Transfer Coefficient

Abstract Phase-change condensation is commonplace in power and process engineering. Due to high surface energy, most condenser surfaces exhibit filmwise mode wherein the condensate is removed due to gravity when the weight overcomes pinning forces. Here, we use cracks (fabrication defects), which form when a copper tube is coated with inverse opals, to transport the condensate away from the condensing surface. Our visualization and experiments show that the cracks have high hydraulic conductivity that preferentially transports the condensate towards the ends of the copper tube. This improves the heat transfer coefficient to ~ 80 kW/m2·K from ~ 12 kW/m2·K for filmwise condensation on smooth copper tubes. Additionally, when the porous inverse opals are impregnated with a lubrication film, the heat transfer coefficient increases by an additional 30% to 103 kW/m2·K. Repeated experiments show that our material design is durable. The insights gained from this work informs the rational design of condenser surfaces.

scholarly journals Transient behavior of a plate-fin-and-tube heat exchanger taking into account different heat transfer coefficients on the individual tube rows

2019 ◽  
Vol 137 ◽  
pp. 01036
Author(s):  
Dawid Taler ◽  
Jan Taler ◽  
Katarzyna Wrona
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Exchangers ◽  
Experimental Studies ◽  
Analytical Formula ◽  
Cfd Modeling ◽  
Individual Tube ◽  
The Heat Transfer Coefficient

Plate-fin and tube heat exchangers (PFTHE) are made of round, elliptical, oval or flat tubes to which continuous fins ( lamellas) are attached. Liquid flows inside the tubes and gas flows outside the tubes perpendicularly to their axes and parallel to the surface of continuous fins. Experimental studies of multi-row plate-fin and tube heat exchangers show that the highest average heat transfer coefficient on the air side occurs in the first row of tubes when the air velocity in front of the exchanger is less than approximately 3.5 m/s when a Reynolds number based on an equivalent hydraulic diameter equal to the distance between tube rows in the direction of air flow is less than 10,000. In the subsequent rows of tubes up to about the fourth row the heat transfer coefficient decreases. In the fifth and further rows, it can, that the heat transfer coefficient is equal in each tube row. It is necessary to find the relationships for the air-side Nusselt number on each tube row to design a PFTHE with the appropriate number of tube rows. The air-side Nusselt number correlations can be determined experimentally or by CFD modeling (Computational and Fluid Dynamics). The paper presents a new mathematical model of the transient operation of PFTHE, considering that the Nusselt numbers on the air side of individual tube rows are different. The heat transfer coefficient on an analyzed tube row was determined from the equality condition of mass- average air temperature differences on a given tube row determined using the analytical formula and CFD modeling. The results of numerical modeling were compared with the results of the experiments.

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