Best Strategies for the Development of a Holistic Porosity Model of a Heat Exchanger for Aero Engine Applications

2015 ◽  
Author(s):  
K. Yakinthos ◽  
D. Misirlis ◽  
Z. Vlahostergios ◽  
M. Flouros ◽  
S. Donnerhack ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Engine Performance ◽  
Operational Parameters ◽  
Tubular Heat Exchanger ◽  
Tube Heat Exchanger ◽  
Aero Engine ◽  
Porosity Model

In an attempt to manage CFD computations in aero engine heat exchanger design, this work presents the best strategies and the methodology used to develop a holistic porosity model, describing the heat transfer and pressure drop behavior of a complex profiled tubular heat exchanger for aero engine applications. Due to the complexity of the profile tube heat exchanger geometry and the very large number of tubes, detailed CFD computations require very high CPU and memory resources. For this reason the complex heat exchanger geometry is replaced in the CFD computations by a simpler porous medium geometry with predefined pressure loss and heat transfer. The present work presents a strategy for developing a holistic porosity model adapted for heat exchangers, which is capable to describe their macroscopic heat transfer and pressure loss average performance. For the derivation of the appropriate pressure loss and heat transfer correlations, CFD computations and experimental measurements are combined. The developed porosity model is taking into consideration both streams of the heat exchanger (hot and cold side) in order to accurately calculate the inner and outer pressure losses, in relation to the achieved heat transfer and in conjunction with the selected heat exchanger geometry, weight and operational parameters. For the same heat exchanger, RAM and CPU requirement reductions were demonstrated for a characteristic flow passage of the heat exchanger, as the porosity model required more than 80 times less computational points than the detailed CFD model. The proposed porosity model can be adapted for recuperation systems with varying heat exchanger designs having different core arrangements and tubes sizes and configurations, providing an efficient tool for the optimization of the heat exchangers design and leading to an increase of the overall aero engine performance.

Derivation of an Anisotropic Model for the Pressure Loss Through a Heat Exchanger for Aero Engine Applications

2009 ◽  
Author(s):  
Kyros Yakinthos ◽  
Stefan Donnerhack ◽  
Dimitrios Missirlis ◽  
Olivier Seite ◽  
Paul Storm
Keyword(s):  
Heat Transfer ◽  
Porous Medium ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Pressure Loss ◽  
Pollutant Emissions ◽  
Experimental Measurements ◽  
Loss Model ◽  
Aero Engine ◽  
Porosity Model

We present an effort to model the pressure loss together with the heat transfer mechanism, in a heat exchanger designed for an integrated recuperative aero engine. The operation of the heat exchanger is focusing on the exploitation of the thermal energy of the turbine exhaust gas to pre-heat the compressor outlet air before combustion and to decrease fuel consumption and pollutant emissions. Two basic parameters characterize the operation of the heat exchanger, the pressure loss and the heat transfer. The derivation of the pressure loss model is based on experimental measurements that have been carried-out on a heat exchanger model. The presence of the heat exchanger is modeled using the concept of a porous medium, in order to facilitate the computational modeling by means of CFD. As a result, inside the integrated aero engine, the operation of the heat exchanger can be sufficiently modeled as long as a generalized and accurate pressure drop and heat transfer model is developed. Hence, the porosity model formulation should be capable of properly describing the overall macroscopic hydraulic and thermal behavior of the heat exchanger. The effect of the presence of the heat exchanger on the flow field is estimated from experimental measurements. For the derivation of the porous medium pressure loss model, an anisotropic formulation of a modified Darcy-Forchheimer pressure drop law is proposed in order to take into account the effects of the three-dimensional flow development through the heat exchanger. The heat transfer effects are taken also into account with the use of a heat transfer coefficient correlation. The porosity model is adopted by the CFD solver as an additional source term. The validation of the proposed model is performed through CFD computations, by comparing the predicted pressure drop and heat transfer with available experimental measurements carried-out on the heat exchanger model.

scholarly journals Performance analyses of helical coil heat exchangers. The effect of external coil surface modification on heat exchanger effectiveness

2016 ◽  
Vol 37 (4) ◽  
pp. 137-159 ◽  
Author(s):  
Rafał Andrzejczyk ◽  
Tomasz Muszyński
Keyword(s):  
Heat Transfer ◽  
Surface Modification ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Helical Structure ◽  
Nuclear Industry ◽  
Helical Coil ◽  
Tube Heat Exchanger ◽  
High Heat Transfer ◽  
Coil Heat

Abstract The shell and coil heat exchangers are commonly used in heating, ventilation, nuclear industry, process plant, heat recovery and air conditioning systems. This type of recuperators benefits from simple construction, the low value of pressure drops and high heat transfer. In helical coil, centrifugal force is acting on the moving fluid due to the curvature of the tube results in the development. It has been long recognized that the heat transfer in the helical tube is much better than in the straight ones because of the occurrence of secondary flow in planes normal to the main flow inside the helical structure. Helical tubes show good performance in heat transfer enhancement, while the uniform curvature of spiral structure is inconvenient in pipe installation in heat exchangers. Authors have presented their own construction of shell and tube heat exchanger with intensified heat transfer. The purpose of this article is to assess the influence of the surface modification over the performance coefficient and effectiveness. The experiments have been performed for the steady-state heat transfer. Experimental data points were gathered for both laminar and turbulent flow, both for co current- and countercurrent flow arrangement. To find optimal heat transfer intensification on the shell-side authors applied the number of transfer units analysis.

scholarly journals Performance Analysis and Design Optimization of Shell and Tube Heat Exchangers

2021 ◽  
Author(s):  
praveen math
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Pressure Loss ◽  
Fluid Flows ◽  
Hot Water ◽  
Flow Conditions ◽  
Shell Side ◽  
Shell And Tube ◽  
Side Flow

Abstract Shell and Tube heat exchangers are having special importance in boilers, oil coolers, condensers, pre-heaters. They are also widely used in process applications as well as the refrigeration and air conditioning industry. The robustness and medium weighted shape of Shell and Tube heat exchangers make them well suited for high pressure operations. The aim of this study is to experiment, validate and to provide design suggestion to optimize the shell and tube heat exchanger (STHE). The heat exchanger is made of acrylic material with 2 baffles and 7 tubes made of stainless steel. Hot fluid flows inside the tube and cold fluid flows over the tube in the shell. 4 K-type thermocouples were used to read the hot and cold fluids inlet and outlet temperatures. Experiments were carried out for various combinations of hot and cold water flow rates with different hot water inlet temperatures. The flow conditions are limited to the lab size model of the experimental setup. A commercial CFD code was used to study the thermal and hydraulic flow field inside the shell and tubes. CFD methodology is developed to appropriately represent the flow physics and the procedure is validated with the experimental results. Turbulent flow in tube side is observed for all flow conditions, while the shell side has laminar flow except for extreme hot water temperatures. Hence transition k-kl-omega model was used to predict the flow better for transition cases. Realizable k- epsilon model with non-equilibrium wall function was used for turbulent cases. Temperature and velocity profiles are examined in detail and observed that the flow remains almost uniform to the tubes thus limiting heat transfer. Approximately 2/3 rd of the shell side flow does not surround the tubes due to biased flow contributing to reduced overall heat transfer and increased pressure loss. On the basis of these findings an attempt has been made to enhance the heat transfer by inducing turbulence in the shel l side flow. The two baffles were rotated in opposite direction to each other to achieve more circulation in the shell side flow and provide more contact with tube surface. Various positions of the baffles were simulated and studied using CFD analysis and th e results are summarized with respect to heat transfer and pressure loss.

Failure Analysis of Heat Exchangers

2021 ◽  
pp. 3-19
Author(s):  
Dusan P. Sekulic
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Failure Analysis ◽  
Thermal Energy ◽  
Solid Surface ◽  
Heat Exchangers ◽  
Heat Transfer Surface ◽  
Tubular Heat Exchanger ◽  
Erosion Corrosion ◽  
Different Temperatures

Abstract Heat exchangers are devices used to transfer thermal energy between two or more fluids, between a solid surface and a fluid, or between a solid particulate and a fluid at different temperatures. This article first addresses the causes of failures in heat exchangers. It then provides a description of heat-transfer surface area, discussing the design of the tubular heat exchanger. Next, the article discusses the processes involved in the examination of failed parts. Finally, it describes the most important types of corrosion, including uniform, galvanic, pitting, stress, and erosion corrosion.

scholarly journals Performance and Exergy Transfer Analysis of Heat Exchangers with Graphene Nanofluids in Seawater Source Marine Heat Pump System

Energies ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1762 ◽  
Author(s):  
Zhe Wang ◽  
Fenghui Han ◽  
Yulong Ji ◽  
Wenhua Li
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Transfer Model ◽  
Enhanced Heat Transfer ◽  
Pump System ◽  
Heat Pump System ◽  
Tube Heat Exchanger ◽  
Exergy Transfer

A marine seawater source heat pump is based on the relatively stable temperature of seawater, and uses it as the system’s cold and heat source to provide the ship with the necessary cold and heat energy. This technology is one of the important solutions to reduce ship energy consumption. Therefore, in this paper, the heat exchanger in the CO2 heat pump system with graphene nano-fluid refrigerant is experimentally studied, and the influence of related factors on its heat transfer enhancement performance is analyzed. First, the paper describes the transformation of the heat pump system experimental bench, the preparation of six different mass concentrations (0~1 wt.%) of graphene nanofluid and its thermophysical properties. Secondly, this paper defines graphene nanofluids as beneficiary fluids, the heat exchanger gains cold fluid heat exergy increase, and the consumption of hot fluid heat is heat exergy decrease. Based on the heat transfer efficiency and exergy efficiency of the heat exchanger, an exergy transfer model was established for a seawater source of tube heat exchanger. Finally, the article carried out a test of enhanced heat transfer of heat exchangers with different concentrations of graphene nanofluid refrigerants under simulated seawater constant temperature conditions and analyzed the test results using energy and an exergy transfer model. The results show that the enhanced heat transfer effect brought by the low concentration (0~0.1 wt.%) of graphene nanofluid is greater than the effect of its viscosity on the performance and has a good exergy transfer effectiveness. When the concentration of graphene nanofluid is too high, the resistance caused by the increase in viscosity will exceed the enhanced heat transfer gain brought by the nanofluid, which results in a significant decrease in the exergy transfer effectiveness.

The Effect of Geometrical Features on Air-Side Heat Transfer and Friction Characteristics, and Optimization of a Large-Size Plain Fin-and-Tube Heat Exchanger by 3-D Numerical Simulation

2009 ◽  
Author(s):  
M. Izadi ◽  
D. K. Aidun ◽  
P. Marzocca ◽  
H. Lee
Keyword(s):  
Heat Transfer ◽  
Numerical Modeling ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Simple Algorithm ◽  
Operating Conditions ◽  
Friction Characteristics ◽  
Tube Heat Exchanger ◽  
Large Size ◽  
Geometrical Features

The effect of geometrical features on the air-side heat transfer and friction characteristics of an industrial plain fin-and-tube heat exchanger is investigated by 3-D numerical modeling and simulations. The heat exchanger has been designed and employed as an intercooler in a gas power plant and is a large-size compact heat exchanger. Most of the available design correlations developed so far for plain fin–and–tube heat exchangers have been prepared for small-size exchangers and none of them fits completely to the current heat exchanger regarding the geometrical limitations of correlations. It is shown that neglecting these limitations and applying improper correlations may generate considerable amount of error in the design of such a large-size heat exchanger. The geometry required for numerical modeling is produced by Gambit® software and the boundary conditions are defined regarding the real operating conditions. Then, three-dimensional simulations based on the SIMPLE algorithm in laminar flow regime are performed by FLUENT™ code. The effect of fin pitch, tube pitch, and tube diameter on the thermo-hydraulic behavior of the heat exchanger is studied. Some variations in the design of the heat exchanger are suggested for optimization purposes. It is finally concluded that the current numerical model is a powerful tool to design and optimize of large-size plain fin-and-tube heat exchangers with acceptable accuracy.

Finned Elliptical Tubes and Their Application in Air-Cooled Heat Exchangers

1966 ◽  
Vol 88 (2) ◽  
pp. 179-186 ◽  
Author(s):  
Franz J. Schulenberg
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Heat Transfer Surface ◽  
Great Success ◽  
Sufficient Criterion ◽  
Tube Heat Exchanger ◽  
Circular Tubes ◽  
Fin Tube

Finned circular tubes have been used exclusively in air-cooled heat exchangers built for the American petroleum and chemical industries. In Europe, however, other tube geometries, in particular, finned elliptical tubes, have been used with great success. In this paper, the theory of the finned elliptical tube and its application in air-cooled heat exchangers are discussed. Finned circular and elliptical tubes are compared; it is shown that the developed heat transfer surface alone is not a sufficient criterion for predicting the performance of an air-cooled fin-tube heat exchanger.

Impact of an Anisotropic Fin Surface Design on the Thermal-Hydraulic Performance of a Plain-Fin-and-Tube Heat Exchanger

2011 ◽  
Author(s):  
Rong Yu ◽  
Andrew D. Sommers ◽  
Nicole C. Okamoto ◽  
Koushik Upadhyayula
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Hydraulic Performance ◽  
Normal Operation ◽  
Surface Design ◽  
Tube Heat Exchanger ◽  
Silane Coating ◽  
Side Pressure

In this study, we have explored the effectiveness of heat exchangers constructed using anisotropic, micro-patterned aluminum fins to more completely drain the condensate that forms on the heat transfer surface during normal operation with the aim of improving the thermal-hydraulic performance of the heat exchanger. This study presents and critically evaluates the efficacy of full-scale heat exchangers constructed from these micro-grooved surfaces by measuring dry/wet air-side pressure drop and dry/wet air-side heat transfer data. The new fin surface design was shown to decrease the core pressure drop of the heat exchanger during wet operation from 9.3% to 52.7%. Furthermore, these prototype fin surfaces were shown to have a negligible effect on the heat transfer coefficient under both dry and wet conditions while at the same time reducing the wet airside pressure drop thereby decreasing fan power consumption. That is to say, this novel fin surface design has shown the ability, through improved condensate management, to enhance the thermal-hydraulic performance of plain-fin-and-tube heat exchangers used in air-conditioning applications. This paper also presents data pertaining to the durability of the alkyl silane coating.

A Fully Wet and Fully Dry Tiny Circular Fin Method for Heat and Mass Transfer Characteristics for Plain Fin-and-Tube Heat Exchangers Under Dehumidifying Conditions

2006 ◽  
Vol 129 (9) ◽  
pp. 1256-1267 ◽  
Author(s):  
Worachest Pirompugd ◽  
Chi-Chuan Wang ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Mass Transfer ◽  
Heat Exchanger ◽  
Heat And Mass Transfer ◽  
Heat Exchangers ◽  
Heat Transfer Characteristic ◽  
Transfer Characteristic ◽  
Tube Heat Exchanger ◽  
Mass Transfer Characteristic ◽  
Transfer Characteristics

This study proposes a new method, namely the “fully wet and fully dry tiny circular fin method,” for analyzing the heat and mass transfer characteristics of plain fin-and-tube heat exchangers under dehumidifying conditions. The present method is developed from the tube-by-tube method proposed in the previous study by the same authors. The analysis of the fin-and-tube heat exchangers is carried out by dividing the heat exchanger into many tiny segments. A tiny segment will be assumed with fully wet or fully dry conditions. This method is capable of handling the plain fin-and-tube heat exchanger under fully wet and partially wet conditions. The heat and mass transfer characteristics are presented in dimensionless terms. The ratio of the heat transfer characteristic to mass transfer characteristic is also studied. Based on the reduced results, it is found that the heat transfer and mass transfer characteristics are insensitive to changes in fin spacing. The influence of the inlet relative humidity on the heat transfer characteristic is rather small. For one and two row configurations, a considerable increase of the mass transfer characteristic is encountered when partially wet conditions take place. The heat transfer characteristic is about the same in fully wet and partially wet conditions provided that the number of tube rows is equal to or greater than four. Correlations are proposed to describe the heat and mass characteristics for the present plain fin configuration.

Comparative Experimental Study on Performance of Corrugated Tube and Straight Tube Heat Exchanger

2012 ◽  
Vol 560-561 ◽  
pp. 156-160
Author(s):  
Lin Ping Lu ◽  
Liang Ying
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Heat Exchangers ◽  
Straight Tube ◽  
Lower Stress ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Corrugated Tube

The experiments on heat transfer coefficient, pressure drop and thermal stress were done to heat exchangers with corrugated tubes and staight tubes. By analyising and comparing the heat transfer coeffient, pressure drop in tube side and shell side and axial force and stress, some conclusions can be conducted that the corrugated tube heat exchanger has better heat transfer coeffient, higher pressure drop and much lower stress caused by temperatur difference, also, it has obvious advantages under the circumstance of low Reynolds number and high temperature difference.

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