Design Considerations and Heat Transfer Enhancement of CFB Heat Exchangers for Flue Gas Heat Recovery

2005 ◽  
Author(s):  
Yong-Du Jun ◽  
Kum-Bae Lee ◽  
Seok-Bo Ko ◽  
Sheikh Zahidul Islam
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Flue Gas ◽  
Heat Exchangers ◽  
Heat Recovery ◽  
Heat Transfer Performance ◽  
Fluid Composition ◽  
Generation Model ◽  
Transfer Performance

Now-a-day’s energy recovery process in the industry is a common practice for improving the production process while major concern goes to environment. The performance of the heat exchangers, used for the purpose of recovering energy, decreases continuously with time due to fouling depending on surface temperature, surface condition, construction material, fluid velocity, flow geometry and fluid composition. To overcome the fouling of fly ash on the heat transfer surface and erosion and periodical cleaning which are the major drawbacks in conventional heat exchangers for flue gas heat recovery, a no-distributor-circulating-fluidized-bed (NDCFB) heat exchanger with automatic particle controlling is devised. One of the main advantages of this model is the reduced pressure drop through the entire heat exchanger system, while increasing heat transfer performance. The research started with a single riser system with multiple down comers and multi-riser system is also studied. The heat transfer performance and pressure drop have been evaluated through experiments for these gas-to-water lab scale heat exchanger systems. However, due to the operational complexity, these two models are not readily applicable to real applications. As a derivation of the previous studies regarding the no-distributor CFB heat exchangers, third generation model of the heat exchanger is now under investigation.

Heat Transfer Performance of Different Nanofluids Flows in a Helically Coiled Heat Exchanger

2013 ◽  
Vol 832 ◽  
pp. 160-165 ◽  
Author(s):  
Mohammad Alam Khairul ◽  
Rahman Saidur ◽  
Altab Hossain ◽  
Mohammad Abdul Alim ◽  
Islam Mohammed Mahbubul
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Friction Factor ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Volume Concentration ◽  
Transfer Performance

Helically coiled heat exchangers are globally used in various industrial applications for their high heat transfer performance and compact size. Nanofluids can provide excellent thermal performance of this type of heat exchangers. In the present study, the effect of different nanofluids on the heat transfer performance in a helically coiled heat exchanger is examined. Four different types of nanofluids CuO/water, Al2O3/water, SiO2/water, and ZnO/water with volume fractions 1 vol.% to 4 vol.% was used throughout this analysis and volume flow rate was remained constant at 3 LPM. Results show that the heat transfer coefficient is high for higher particle volume concentration of CuO/water, Al2O3/water and ZnO/water nanofluids, while the values of the friction factor and pressure drop significantly increase with the increase of nanoparticle volume concentration. On the contrary, low heat transfer coefficient was found in higher concentration of SiO2/water nanofluids. The highest enhancement of heat transfer coefficient and lowest friction factor occurred for CuO/water nanofluids among the four nanofluids. However, highest friction factor and lowest heat transfer coefficient were found for SiO2/water nanofluids. The results reveal that, CuO/water nanofluids indicate significant heat transfer performance for helically coiled heat exchanger systems though this nanofluids exhibits higher pressure drop.

Air-Side Heat Transfer Performance of Louver Fin and Multitube Heat Exchanger for Direct Methanol Fuel Cell Cooling Application

2014 ◽  
Vol 11 (4) ◽  
Author(s):  
Hie Chan Kang ◽  
Hyejung Cho ◽  
Jin Ho Kim ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Direct Methanol Fuel Cell ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Side Pressure ◽  
Direct Methanol ◽  
Methanol Fuel Cell

The present work is performed to evaluate the heat transfer performance of a heat exchanger used in a direct methanol fuel cell. Because of material constraints and performance requirements, a louver fin heat exchanger is modified for use with conventional microchannel tubes and also with multiple small-diameter tubes (called multitubes). Prototype heat exchangers are tested, and the air-side heat transfer, pressure drop, and fan power are measured in a wind tunnel and simulated using a commercial code. The air-side pressure drop and heat transfer coefficient of the multitubes show similar trends to those of the flat-tube heat exchanger if the contact resistance is negligible. The tube spacing of the prototype multitube heat exchangers has a small effect on the pressure drop and heat transfer, but it has a profound effect on the air-side heat transfer performance because of the contact resistance between the tubes and louver fins. The air-side pressure drop agrees well with an empirical correlation for flat tubes.

Numerical simulation of the fluid flow and heat transfer characteristics of microchannel heat exchangers with different reentrant cavities

2019 ◽  
Vol 29 (11) ◽  
pp. 4334-4348
Author(s):  
Minqiang Pan ◽  
Hongqing Wang ◽  
Yujian Zhong ◽  
Tianyu Fang ◽  
Xineng Zhong
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Content Type ◽  
Microchannel Heat Exchanger ◽  
Flow And Heat Transfer

Purpose With the increasing heat dissipation of electronic devices, the cooling demand of electronic products is increasing gradually. A water-cooled microchannel heat exchanger is an effective cooling technology for electronic equipment. The structure of a microchannel has great impact on the heat transfer performance of a microchannel heat exchanger. The purpose of this paper is to analyze and compare the fluid flow and heat transfer characteristic of a microchannel heat exchanger with different reentrant cavities. Design/methodology/approach The three-dimensional steady, laminar developing flow and conjugate heat transfer governing equations of a plate microchannel heat exchanger are solved using the finite volume method. Findings At the flow rate range studied in this paper, the microchannel heat exchangers with reentrant cavities present better heat transfer performance and smaller pressure drop. A microchannel heat exchanger with trapezoidal-shaped cavities has best heat transfer performance, and a microchannel heat exchanger with fan-shaped cavities has the smallest pressure drop. Research limitations/implications The fluid is incompressible and the inlet temperature is constant. Practical implications It is an effective way to enhance heat transfer and reduce pressure drop by adding cavities in microchannels and the data will be helpful as guidelines in the selection of reentrant cavities. Originality/value This paper provides the pressure drop and heat transfer performance analysis of microchannel heat exchangers with various reentrant cavities, which can provide reference for heat transfer augmentation of an existing microchannel heat exchanger in a thermal design.

Numerical Study on Forced Convective Heat Transfer in Porous Pin Fin Channels

2008 ◽  
Author(s):  
Jian Yang ◽  
Min Zeng ◽  
Qiuwang Wang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Transfer Performance ◽  
Numerical Study ◽  
Porous Metal ◽  
Transfer Model ◽  
Transfer Performance ◽  
Pin Fin ◽  
Heat Exchanges

Pin fin heat exchanges are often used in cooling of high thermal loaded electronic components due to their excellent heat transfer performance. However, the pressure drop in such heat exchanges is usually much higher than that in others, so their overall heat transfer performance is seriously reduced. In order to reduce the pressure drop and improve the overall heat transfer performance for pin fin heat exchangers, porous metal pin arrays are used and the performance of fluid flow and heat transfer in heat exchanger unit cells are numerically studied. The Forchheimer-Brinkman extended Darcy model and two-equation heat transfer model for porous media are employed and the effects of Reynolds number (Re), permeability (K) and pin fin cross-section forms are studied in detail. The results show that, with proper selection of governing parameters, the overall heat transfer performance of porous pin fin heat exchanger is much better than that of traditional solid pin fin heat exchanger; the overall heat transfer performance of long elliptic porous pin fin heat exchanger is the best, that is, the heat transfer per unit pressure drop of such heat exchanger is the highest and the maximum value of the heat transfer over pressure drop is obtained at K = 2×10−7 m2.

Incorporating Moldability Considerations During the Design of Polymer Heat Exchangers

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Juan Cevallos ◽  
S. K. Gupta ◽  
Avram Bar-Cohen
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Polymer Composites ◽  
Heat Exchangers ◽  
Life Cycle Cost ◽  
Heat Transfer Performance ◽  
Integrated Design ◽  
Parametric Models ◽  
Transfer Performance ◽  
Molding Process

Recently, available formulations of thermally enhanced polymer composites are attractive in heat exchanger applications due to their low cost and improved corrosion resistance compared to the conventional metal options. This paper presents a systematic approach to the design of plate-fin heat exchangers made out of thermally enhanced polymer composites. We have formulated the design problem as the life cycle cost minimization problem. The integrated design model introduced here accounts for heat transfer performance, molding cost, and assembly costs. We have adopted well-known models to develop individual parametric models that describe how heat transfer performance, molding cost, and assembly cost varies as a function of the geometric parameters of the heat exchanger. Thermally enhanced polymer composites behave differently from the conventional polymers during the molding process. The desired thin walled large structures are expected to pose challenges during the filling phase of the molding process. Hence, we have utilized experimentally validated simulations to develop a metamodel to identify difficult and impossible to mold design configurations. This metamodel has been integrated within the overall formulation to address the manufacturability considerations. This paper also presents several case studies that show how the material and labor cost strongly influence the final design.

Simulation Investigation on Multi-Unit Parallel-Flow Type Condenser with Flat Tubes Distribution

2013 ◽  
Vol 423-426 ◽  
pp. 1910-1913
Author(s):  
Jian Rong Du ◽  
Zu Yi Zheng ◽  
Jun Hua Wan ◽  
Yi De Wang ◽  
Zhong Min Wan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Transfer Performance ◽  
Air Velocity ◽  
Flat Tube ◽  
Tube Arrangement ◽  
First Pass ◽  
Flat Tubes

Three heat exchangers, all of which have 38 tubes in total and 6 passes, with different tube arrangements were simulation investigated in laboratory. The effect of flat tube distribution on heat transfer performance and pressure drop characteristic was simulation investigated. The effect of different air velocity and flow on heat transfer performance and pressure drop characteristic was simulation investigated too. The results show that similar tube distribution has little effect on heat transfer but has great effect on pressure drop. It was found the tube arrangement from first pass to sixth pass is 10,9,6,5,4,4 has the best heat transfer performance and its pressure drop is small. The heat transfer and pressure drop increase with the air velocity and refrigerant flow.

scholarly journals Experimental Study on the Heat Transfer Characteristics of the Enhanced Fin-Tube Heat Exchanger Applied a Coiled Turbulator

2017 ◽  
Author(s):  
Sun-Joon Byun ◽  
Sang-Jae Lee ◽  
Jae-Min Cha ◽  
Zhen-Huan Wang ◽  
Young-Chul Kwon
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Water Flow ◽  
Flow Rate ◽  
Heat Transfer Performance ◽  
Water Flow Rate ◽  
Transfer Performance ◽  
Tube Heat Exchanger ◽  
Fin Tube

This study presents the comparison of heat transfer capacity and pressure drop characteristics between a basic fin-tube heat exchanger and a modified heat exchanger with the structural change of branch tubes and coiled turbulators. All experiments were carried out using an air-enthalpy type calorimeter based on the method described in ASHRAE standards, under heat exchanger experimental conditions. 14 different kinds of heat exchangers were used for the experiment. Cooling and heating capacities of the turbulator heat exchanger were excellent, compared to the basic one. As the insertion ratio of the coiled turbulator and the number of row increased, the heat transfer performance increased. However, the capacity per unit area was more effective in 4 rows than 6 rows, and the cooling performance of the 6 row turbulator heat exchanger (100% turbulator insert ratio) was down to about 6% than that of 4 row one. As the water flow rate and the turbulator insertion ratio increased, the pressure drop of the water side increased. This trend was more pronounced in 6 rows. In the cooling condition, the pressure drop on the air side was slightly increased due to the generation of condensed water, but was insignificant under the heating condition. The power consumption of the pump was more affected by the water flow rate than the coiled turbulator. The equivalent hydraulic diameter of a tube by the turbulator was reduced and then the heat transfer performance was improved. Thus, the tube diameter was smaller, the heat flux was better.

The Technical Derivation of Heat Transfer Performance of the Airside of a Novel Pin Design Heat Exchanger Using Computational Fluid Dynamics

2012 ◽  
Author(s):  
Tosha Churitter
Keyword(s):  
Heat Transfer ◽  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchanger ◽  
Mass Flow ◽  
Heat Exchangers ◽  
Heat Transfer Performance ◽  
Diameter Ratio ◽  
Transfer Performance ◽  
Extended Surface

Pins are a common type of extended surface used in the field of heat transfer; their main application being in the electronics field. Historically, pins used in heat exchangers have diameters that are considered negligible in comparison to their lengths and are therefore termed as tubes. In this report, the use of pins as an extended surface is investigated for the heat transfer on the airside (cold) of the Compact Advanced Pin Surface Heat Exchanger. The pins are circular in cross section and follow a staggered arrangement. The uniqueness of the pin design is such that they cannot be treated as tubes. Key Pin Design features are as follows: • Pins have a maximum Length: Diameter ratio of 3. • Pin Spacing to Pin Diameter ratio is greater than in traditional arrangements. • Pins function as a primary as well as secondary surface. The heat transfer performance of extended surfaces possessing the above features has not been characterized, using commercially available Computational Fluid Dynamics (CFD) software, in any research specifically focused on applications for the aerospace industry. Based on actual test results, this study specially develops a unique approach that can predict the outlet temperature of the heat exchanger to within 1% accuracy. This ‘developed’ approach is applied over cold-side mass flow rates ranging from 0.05 kg/s to 0.23 kg/s, while keeping the hot side mass flow rate constant at 0.05 kg/s. At worst, the simulation results lie within 5% accuracy and at best the simulation accuracy is 1%, a significant improvement on traditional derivations. This article specifically discusses the methodology developed to analyse the heat transfer performance of the novel pin design using Fluent 6.2. It highlights the current limitations of existing equations as well as the theoretical knowledge gap that currently exists in the analysis of pins as extended heat transfer surfaces in heat exchangers.

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