The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Kwan-soo Lee - One of the best experts on this subject based on the ideXlab platform.
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Frosting behaviors and thermal performance of Louvered fins with unequal Louver pitch
International Journal of Heat and Mass Transfer, 2016Co-Authors: Jin-seong Park, Dong Rip Kim, Kwan-soo LeeAbstract:We created heat exchanger Louvered fin designs in which the Louver pitch successively increased or decreased by 20% from the air inlet region to the redirection region. The frost behavior and thermal performance of the unequal Louver pitch design were compared with those of an equal Louver pitch design, under both dry and frost conditions. When unequal Louver pitch design was used, frost blocking of the spaces between Louvers at the front side was delayed and the thermal performance was improved by 21%, compared with the equal Louver pitch design. The frost blocking ratios of the two unequal Louver pitch designs were compared; the design in which the Louver pitch successively decreased from the air inlet region to the redirection region provided more uniform frost growth and improved thermal performance, compared to the design in which the Louver pitch successively increased.
Jurandir Itizo Yanagihara - One of the best experts on this subject based on the ideXlab platform.
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interaction effects between parameters in a flat tube Louvered fin compact heat exchanger with delta winglets vortex generators
Applied Thermal Engineering, 2015Co-Authors: Daniel Jonas Dezan, Leandro Oliveira Salviano, Jurandir Itizo YanagiharaAbstract:Abstract The combination of multi-Louvered fins and delta-winglet vortex generators is a promising strategy to enhance heat transfer in flat-tube compact heat exchangers. This paper focuses on screening analysis and, pressure drop and heat transfer characteristics of some parameters of multi-Louvered heat exchangers combined with delta-winglets. Two rows of delta-winglets were considered for this research. The thermal-hydraulic performance of two distinct geometries, GEO1 and GEO2, were evaluated. The main differences between those two geometries are the Louver height and delta-winglet frontal area. The contribution of the input parameters such as Louver angle, angle of attack of the delta-winglet and streamwise position of the delta-winglet are also investigated in order to understand which of these parameters strongly influences heat transfer and pressure drop. Reynolds numbers of 120 and 240, based on hydraulic diameter, were investigated. The Smoothing Spline ANOVA model was used to investigate main and interaction effects among the input parameters. The randomly sample generation is performed by the Latin Hypercubes Sampling (LHS) method. The results indicate that the Louver angle is the main contributor to increase the Friction factor for GEO1 and GEO2 for both Reynolds numbers. At the lower Reynolds number, the most important heat transfer parameter was the Louver angle for both geometries, while at the higher Reynolds number, the angles of attack of the first row of delta-winglets mostly contributed to GEO1, and the angle of attack of the first row of delta-winglets was as important as the Louver angle for GEO2. Although those specific geometries can be considered a kind of compound enhancement technique, relevant interactions were not verified between Louvers and delta-winglet vortex generators parameters, i.e., the main effects were predominant in heat transfer and pressure drop.
Hossein Shokuhmand - One of the best experts on this subject based on the ideXlab platform.
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Experimental and numerical investigation of heat transfer, temperature distribution, and Louver efficiency on the dimpled Louvers fin banks
Advances in Mechanical Engineering, 2015Co-Authors: F. Sangtarash, Hossein ShokuhmandAbstract:Numerical models have been developed by commercial package Fluent 6.3 to simulate the air flow through single dimple, simple, and dimpled Louvers in low and medium Reynolds numbers. Experiments have also been conducted to measure the temperature and heat transfer in these geometries. Heat transfer augmentation of 8% has been observed by implying dimples on Louver at the same mass flow rate. For accurate investigation of the effect of dimple, a single dimpled surface has been modeled numerically and experimentally. The simulation revealed that these heat transfer and temperature augmentations occur due to existence of a circulation region created by dimple. Additionally, the effects of Louver’s thermal resistance on temperature distribution over the Louver surface have been considered to gain the actual contours. Continuous temperature gradients have been observed over the Louver surface with the highest temperature at the base of the Louver and the lowest temperature at the middle of the Louver. Louver ef...
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Experimental and numerical investigation of the heat transfer augmentation and pressure drop in simple, dimpled and perforated dimpled Louver fin banks with an in-line or staggered arrangement
Applied Thermal Engineering, 2015Co-Authors: F. Sangtarash, Hossein ShokuhmandAbstract:Numerical and experimental models have been developed to investigate the effect of adding an in-line and staggered arrangement of dimples and perforated dimples to multiLouvered fins on the heat transfer augmentation and the pressure drop of the air flow through a multiLouvered fin bank. Three-dimensional simulations of single row of Louvers were conducted for the given geometries. Simulations were performed for different Reynolds numbers. The simulations revealed that the heat transfer and temperature augmentations occur due to the existence of a circulation region that is created by the dimple. Additionally, continuous temperature gradients have been observed over the Louver surface with the highest temperature at the base of the Louver and the lowest temperature at the middle of the Louver. Additionally, the difference between these two points is more obvious with greater Reynolds numbers. Fin efficiency and fin effectiveness were calculated to assess Louver performance. The air-side performance of the heat exchanger is evaluated by calculating the Colburn j factor and the Fanning friction f factor. The results demonstrate that adding dimples on the Louver surface increases the j factor and the f factor. Likewise, adding perforation to the dimples results in the same increase. The present results indicate that compared with the in-line arrangement, the staggered arrangement could effectively enhance the heat transfer performance.
F. Wang - One of the best experts on this subject based on the ideXlab platform.
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Design and performance analysis of the novel shell-and-tube heat exchangers with Louver baffles
Applied Thermal Engineering, 2017Co-Authors: Yonggang Lei, Yazi Li, Shenglan Jing, Chongfang Song, Yongkang Lyu, F. WangAbstract:Two novel shell-and-tube heat exchangers with Louver baffles are invented and designed for energy conservation. A certain amount Louver baffles at the inclination angle between shell side flow direction and Louver baffle are equipped in shell side to support tube bundles. Numerical simulations are carried out to investigate the thermo-hydraulic performance of the two reformed shell-and-tube heat exchangers with Louver baffles. For comparison, a shell-and-tube heat exchanger with conventional segmental baffles also studied in the paper. Fluid flow structures and temperature distributions are presented for the analysis of the physical behavior of fluid flow and heat transfer. Oblique flow is produced in the shell side of the shell-and-tube heat exchangers with Louver baffles that decrease and eliminate the dead spaces and augment the local heat transfer. Compared with the shell-and-tube heat exchanger with segmental baffles, abrupt change of fluid flow is avoided that decrease the pressure drop in the shell side. The numerical results indicated that the heat transfer coefficient per pressure drop of both the shell-and-tube heat exchangers with Louver baffles are higher than that of the shell-and-tube heat exchanger with segmental baffles. This implies that at the same heat transfer quantity, the pumping power of the shell-and-tube heat exchangers with Louver baffles is lower than that of the shell-and-tube heat exchanger with conventional segmental baffles.
Karen A. Thole - One of the best experts on this subject based on the ideXlab platform.
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Scaling of heat transfer coefficients along Louvered fins
Experimental Thermal and Fluid Science, 2002Co-Authors: A.c Lyman, R.a Stephan, Karen A. Thole, L.w Zhang, S.b MemoryAbstract:Louvered fins provide a method for improving the heat transfer performance of compact heat exchangers without a prohibitive increase in the pressure drop. Spatially resolved heat transfer coefficients along the Louvers protruding from the fins are needed to understand the details of compact heat exchanger performance. Experiments were conducted in a number of large-scale Louver models with varied fin pitch and Louver angle over a range of Reynolds numbers. This paper presents a method for evaluating the spatially resolved Louver heat transfer coefficients using various reference temperatures, such as the bulk flow temperature and adiabatic wall temperature, to define the convective heat transfer coefficients. The results from this study indicate that the thermal field surrounding a particular Louver is the overriding influence on the heat transfer from that Louver.
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Entry region of Louvered fin heat exchangers
Experimental Thermal and Fluid Science, 1999Co-Authors: Marlow E Springer, Karen A. TholeAbstract:The dominant thermal resistance for most compact heat exchangers occurs on the gas side and as such an understanding of the gas side flowfield is needed before improving current designs. Louvered fins are commonly used in many compact heat exchangers to increase the surface area and initiate new boundary layer growth. For this study, detailed flowfield measurements were made in the entry region of several Louvered fin geometries whereby the Louver angle, ratio of fin pitch to Louver pitch, and Reynolds number were all varied. In addition to mean velocity measurements, time-resolved velocity measurements were made to quantify unsteady effects. The results indicated larger fin pitches resulted in lower average flow angles in the Louver passages and longer development lengths. Larger Louver angles with a constant ratio of fin pitch to Louver pitch resulted in higher average flow angles and shorter development lengths. As the Reynolds number increased, longer development lengths were required and higher average flow angles occurred as compared with a lower Reynolds number case. Time-resolved velocity measurements indicated some flow periodicity behind the fully developed Louver for a range of Reynolds numbers. The Strouhal number of these fluctuations was constant for a given Louver geometry, but the value increased with increasing fin pitch.
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Experimental design for flowfield studies of Louvered fins
Experimental Thermal and Fluid Science, 1998Co-Authors: Marlow E Springer, Karen A. TholeAbstract:Abstract The dominant thermal resistance for most compact heat exchangers occurs on the gas side and as such an understanding of the gas side flowfield is needed before improving current designs. Louvered fins are commonly used in many compact heat exchangers to increase the surface area and initiate new boundary layer growth. Detailed measurements can be accomplished with large-scale models of these Louvered fins to gain a better understanding of the flowfield. This paper describes a methodology used for designing an experimental model of a two-dimensional Louvered fin geometry, scaled up by a factor of 20, that allows for flowfield measurements. The particular Louver geometry studied for these experiments had a Louver angle of 27° and a ratio of fin pitch to Louver pitch of 0.76. Simulations using computational fluid dynamics (CFD) both aided in designing the large-scale Louver model, resulting in a total number of 19 Louver rows, and identified the region where the flowfield could be considered as periodic. This paper also presents two component velocity measurements taken in the scaled up model at Reynolds numbers of Re=230, 450, and 1016. For all three Reynolds numbers the flow was Louver directed rather than duct directed. The results indicated that significant differences between the three Reynolds numbers occurred. While the flow entering the Louver passage at Re=1016 still had remnants of the Louver wake convected from two Louvers upstream, the Re=230 case did not. Time-resolved velocity measurements were also made in the wake region of a fully developed Louver for a range of Reynolds numbers. For 1000
