Mathematical heat transfer equations for finned double pipe heat exchangers based on experimental work carried out in the 1970s can be programmed in a spreadsheet for repetitive use. Thus avoiding CFD analysis which can be time consuming and costly. However, it is important that such mathematical equations be evaluated for their accuracy. This paper uses CFD methods in evaluating the accuracy of mathematical equations. Several models were created with varying; geometry, flue gas entry temperature,
and flow rates. The analysis should provide designers and manufacturers a judgment on the expected level
of accuracy when using mathematical modelling methodology. This paper simultaneously identifies best
practices in carrying out such CFD analysis
Abstract The requirement of energy in any processing industry is not only a need but it is indeed a most wanted utility. In a typical processing or manufacturing industry the most common utility are steam and cooling water. However the cost of these utility are no longer cheap, in fact they are expensive. Therefore saving these utility or minimizing the usage of these utilities is one of the most needed practice in a processing industry. Pinch technology is the most common method, which is aimed at minimizing the requirement of utilities by maximizing the process to process heat transfer. In the present study temperature interval diagram or TID is used to identify the targets for minimum utility requirement and maximum process to process heat transfer in a processing facility. The targets for heat exchanger network are presented and minimization of number of heat exchangers are provided using stream splitting technique. Keywords: Pinch design, stream splitting, HEN synthesis, Utilities, TID
Comparative Study of ECONOMISER Using the CFD Analysis IJMER
This paper presents a simulation of the economizer zone, which allowsstudying the flow
patterns developed in the fluid, while it flows along the length of the economizer. The past failure
details revelsthat erosion is more in U-bend areas of Economizer Unit because of increase in flue gas
velocity near these bends. But it isobserved that the velocity of flue gases surprisingly increases near
the lower bends as compared to upper ones. The model issolved using conventional CFD techniques by
FLUENT software. In which the individual tubes are treated as sub-gridfeatures. A geometrical model
is used to describe the multiplicity of heat-exchanging structures and the interconnectionsamong them.
The Computational Fluid Dynamics (CFD) approach is utilised for the creation of a three-dimensional
modelof the economizer coil of single column tube. With equilibrium assumption applied for
description of the system chemistry. The flue gastemperature, pressure and velocity field of fluid flow
within an economizer tube using the actual bounda
Abstract The requirement of energy in any processing industry is not only a need but it is indeed a most wanted utility. In a typical processing or manufacturing industry the most common utility are steam and cooling water. However the cost of these utility are no longer cheap, in fact they are expensive. Therefore saving these utility or minimizing the usage of these utilities is one of the most needed practice in a processing industry. Pinch technology is the most common method, which is aimed at minimizing the requirement of utilities by maximizing the process to process heat transfer. In the present study temperature interval diagram or TID is used to identify the targets for minimum utility requirement and maximum process to process heat transfer in a processing facility. The targets for heat exchanger network are presented and minimization of number of heat exchangers are provided using stream splitting technique. Keywords: Pinch design, stream splitting, HEN synthesis, Utilities, TID
Comparative Study of ECONOMISER Using the CFD Analysis IJMER
This paper presents a simulation of the economizer zone, which allowsstudying the flow
patterns developed in the fluid, while it flows along the length of the economizer. The past failure
details revelsthat erosion is more in U-bend areas of Economizer Unit because of increase in flue gas
velocity near these bends. But it isobserved that the velocity of flue gases surprisingly increases near
the lower bends as compared to upper ones. The model issolved using conventional CFD techniques by
FLUENT software. In which the individual tubes are treated as sub-gridfeatures. A geometrical model
is used to describe the multiplicity of heat-exchanging structures and the interconnectionsamong them.
The Computational Fluid Dynamics (CFD) approach is utilised for the creation of a three-dimensional
modelof the economizer coil of single column tube. With equilibrium assumption applied for
description of the system chemistry. The flue gastemperature, pressure and velocity field of fluid flow
within an economizer tube using the actual bounda
Episode 60 : Pinch Diagram and Heat Integration
The optimal allocation of mass and energy within a unit operation, process and/or site.
Optimal allocation can be based on economic, environmental or other important objectives.
SAJJAD KHUDHUR ABBAS
Ceo , Founder & Head of SHacademy
Chemical Engineering , Al-Muthanna University, Iraq
Oil & Gas Safety and Health Professional – OSHACADEMY
Trainer of Trainers (TOT) - Canadian Center of Human
Development
Heat exchangers are used widely in industrial application such as chemical,
food processing, power production, refrigeration and air-conditioning
industries. Helical coiled heat exchangers are used in order to obtain a large
heat transfer per unit volume and to enhance the heat transfer rate on the inside
surface. In the present study, CFD simulations are carried out for a counter
flow tube in tube helical heat exchanger where hot water flows through the
inner tube and cold water flows through the outer tube. From the simulation
results heat transfer coefficient, pressure drop and nusselt number are
calculated. The heat transfer characteristics of the same are compared with that
of a counter flow tube in tube straight tube heat exchanger of same length
under same temperature and flow conditions. CFD simulation results showed
that the helical tube in tube heat exchanger is more effective than the straight
tube in tube heat exchanger.
Abstract:This paper deals with the thermal and CFD analysis of automobile radiator. The theoretical calculation has been done in MAT Lab by varying the mass flow rate of coolant. Modeling has been done in Solidworks and exported to Ansys for CFD analysis. The temperature distribution, heat transfer rate for different velocities of coolant to has been done for different tube materials such as copper, aluminium and stainless steel. The numerical results were compared and found that copper has best heat transfer rate and has better efficiency than the others.
1 ijebm jan-2018-1-combustion adjustment in a naturalAI Publications
Shortage of detailed and accurate experimental data on fuel-air mixing in furnaces is due to the difficulty and complexity of measurements in flames. Although it may be possible with infra-Red camera to obtain an indication of what happens in the furnace by graphical image resolution this is not expected to be sufficiently detailed because it contains only the temperature gradient. More detailed information, however, may be obtained from the simulated resolution using Computational Fluid Dynamics (CFD) technique where the total number of elements/points defines the detailed level that can be displayed or captured in graphical image. Simulation resolution studies two aspects of the momentum effects on flame which are the forward momentum normally associated with the average outlet velocity of the combustion products and the lateral momentum caused by swirl. Following the American Petroleum Institute guidelines (API 560) for combustion adjustment in furnaces, it may be possible to have less emission and a maximum efficiency, but the potential interaction between the several operation and design factors are not thereby considered as in a mathematical model of CFD.
A study on the edm of al7075+3 wt%sic+3wt% b4c hybrid mmceSAT Journals
Abstract The objective of the project is to investigate the effect of current, pulse on time and pulse off time. For the proposed work Material removal rate (MRR) and Tool wear rate (TWR) were chosen as responses and Current, Pulse on time and pulse off time were chosen as process parameters. Hybrid Aluminium Silicon Carbide (Al 7075 + 3wt. % of SiCp+ 3wt. % of B4C) is used as work material and copper is used as tool material. Design of experiment technique is employed for the experimentation. The mathematical models are prepared by Response Surface Methodology (RSM) technique and Box Behnken Design (BBD) is selected to design the matrix for different combination of process parameters. After completion of the experiments analysis was done using analysis of variance (ANOVA) for 90% confidence level. Keywords: Current, Pulse on time, Pulse off time, Material removal rate (MRR), Tool wear rate (TWR), Design of experiments (DOE), Response surface methodology (RSM), Box-Behken design (BBD), Analysis of variance (ANOVA).
Experimental investigation of double pipe heat exchanger with helical fins on...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Heat transfer equipment is defined by the function it fulfills in a process. On the similar path, Heat exchangers are
the equipment used in industrial processes to recover heat between two process fluids. They are widely used in space
heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, and
natural gas processing. The operating efficiency of these exchangers plays a very key role in the overall running cost
of a plant. So the designers are on a trend of developing heat exchangers which are highly efficient, compact, and cost
effective.
Episode 60 : Pinch Diagram and Heat Integration
The optimal allocation of mass and energy within a unit operation, process and/or site.
Optimal allocation can be based on economic, environmental or other important objectives.
SAJJAD KHUDHUR ABBAS
Ceo , Founder & Head of SHacademy
Chemical Engineering , Al-Muthanna University, Iraq
Oil & Gas Safety and Health Professional – OSHACADEMY
Trainer of Trainers (TOT) - Canadian Center of Human
Development
Heat exchangers are used widely in industrial application such as chemical,
food processing, power production, refrigeration and air-conditioning
industries. Helical coiled heat exchangers are used in order to obtain a large
heat transfer per unit volume and to enhance the heat transfer rate on the inside
surface. In the present study, CFD simulations are carried out for a counter
flow tube in tube helical heat exchanger where hot water flows through the
inner tube and cold water flows through the outer tube. From the simulation
results heat transfer coefficient, pressure drop and nusselt number are
calculated. The heat transfer characteristics of the same are compared with that
of a counter flow tube in tube straight tube heat exchanger of same length
under same temperature and flow conditions. CFD simulation results showed
that the helical tube in tube heat exchanger is more effective than the straight
tube in tube heat exchanger.
Abstract:This paper deals with the thermal and CFD analysis of automobile radiator. The theoretical calculation has been done in MAT Lab by varying the mass flow rate of coolant. Modeling has been done in Solidworks and exported to Ansys for CFD analysis. The temperature distribution, heat transfer rate for different velocities of coolant to has been done for different tube materials such as copper, aluminium and stainless steel. The numerical results were compared and found that copper has best heat transfer rate and has better efficiency than the others.
1 ijebm jan-2018-1-combustion adjustment in a naturalAI Publications
Shortage of detailed and accurate experimental data on fuel-air mixing in furnaces is due to the difficulty and complexity of measurements in flames. Although it may be possible with infra-Red camera to obtain an indication of what happens in the furnace by graphical image resolution this is not expected to be sufficiently detailed because it contains only the temperature gradient. More detailed information, however, may be obtained from the simulated resolution using Computational Fluid Dynamics (CFD) technique where the total number of elements/points defines the detailed level that can be displayed or captured in graphical image. Simulation resolution studies two aspects of the momentum effects on flame which are the forward momentum normally associated with the average outlet velocity of the combustion products and the lateral momentum caused by swirl. Following the American Petroleum Institute guidelines (API 560) for combustion adjustment in furnaces, it may be possible to have less emission and a maximum efficiency, but the potential interaction between the several operation and design factors are not thereby considered as in a mathematical model of CFD.
A study on the edm of al7075+3 wt%sic+3wt% b4c hybrid mmceSAT Journals
Abstract The objective of the project is to investigate the effect of current, pulse on time and pulse off time. For the proposed work Material removal rate (MRR) and Tool wear rate (TWR) were chosen as responses and Current, Pulse on time and pulse off time were chosen as process parameters. Hybrid Aluminium Silicon Carbide (Al 7075 + 3wt. % of SiCp+ 3wt. % of B4C) is used as work material and copper is used as tool material. Design of experiment technique is employed for the experimentation. The mathematical models are prepared by Response Surface Methodology (RSM) technique and Box Behnken Design (BBD) is selected to design the matrix for different combination of process parameters. After completion of the experiments analysis was done using analysis of variance (ANOVA) for 90% confidence level. Keywords: Current, Pulse on time, Pulse off time, Material removal rate (MRR), Tool wear rate (TWR), Design of experiments (DOE), Response surface methodology (RSM), Box-Behken design (BBD), Analysis of variance (ANOVA).
Experimental investigation of double pipe heat exchanger with helical fins on...eSAT Publishing House
IJRET : International Journal of Research in Engineering and Technology is an international peer reviewed, online journal published by eSAT Publishing House for the enhancement of research in various disciplines of Engineering and Technology. The aim and scope of the journal is to provide an academic medium and an important reference for the advancement and dissemination of research results that support high-level learning, teaching and research in the fields of Engineering and Technology. We bring together Scientists, Academician, Field Engineers, Scholars and Students of related fields of Engineering and Technology
Heat transfer equipment is defined by the function it fulfills in a process. On the similar path, Heat exchangers are
the equipment used in industrial processes to recover heat between two process fluids. They are widely used in space
heating, refrigeration, air conditioning, power plants, chemical plants, petrochemical plants, petroleum refineries, and
natural gas processing. The operating efficiency of these exchangers plays a very key role in the overall running cost
of a plant. So the designers are on a trend of developing heat exchangers which are highly efficient, compact, and cost
effective.
Effect of nanofluid on heat transfer characteristics of double pipe heat exch...eSAT Journals
Abstract A nanofluid is a suspension of nano sized particles made up of metal, oxides or carbides of size up to 100 nm in a base fluid of water, ethylene glycol or oil. Recently large numbers of experiments have been are carried out to evaluate the effect of nanofluid in enhancement of the heat transfer rate in various heat exchangers. The heat transfer enhancement using nanofluid mainly depends on type of nanoparticles, size of nanoparticles, shape of nanoparticles, type of base fluid and concentration of nanoparticles in the base fluid. In the present paper, an experimental evaluation has been carried out to determine the effect of various concentration of CuO nanoparticles mixed in water on heat transfer characteristics of double pipe heat exchanger for parallel flow and counter flow arrangement. The volume concentrations of CuO nanofluid prepared by two step method are 0.002 %, 0.003% and 0.004 %. The conclusion derived for the study is that overall heat transfer coefficient increases with increase in volume concentration of CuO nanoparticle compared to water which have been validated by theoretical prediction also. Keywords: Nanofluid, Heat Transfer Characteristics, Double Pipe Heat Exchanger, CuO Nanoparticles
Design and experimental analysis of pipe in pipe heat exchangerIJMER
Pipe in pipe heat exchanger are used in industrial process to recover heat between two
process fluids. The project carried out design of pipe in pipe heat exchanger having tube with fin and
without fin. The fins were taken in the form of semi-circular type arranged in altenating way with
spacing of 50mm.The fins were only provided on the inner tube for creating turbulence of cold water.
The number of fin were 18 and its height and thickness 10 and 1.6mm respectively. Experiment were
performed for heat exchanger with fins and without fins. The experiment were performed for different
flow rates of hot and cold fluid Different parameters like Overall heat transfer,Nusselt
number,Convective heat transfer coefficient,Pressure drop,friction factor were obtained and compared
for simple inner tube and finned tube.
The Effect of insertion of different geometries on heat transfer performance ...IJMER
Abstract: Under turbulent flow conditions, the increase in heat transfer rate is more significant than that under laminar flow conditions. The turbulent effects become a dominant factor over secondary flow at higher Reynolds number. The turbulent flow can be produced by inserting different geometries in the circular pipe. This study focuses on the various methods or geometries used to produce turbulent geometries and its effect on the heat transfer. The turbulent generators with different geometrical
configurations have been used as one of the passive heat transfer enhancement techniques and are the most widely used in tubes in several heat transfer applications. Insertion of such geometries may lead to increase the friction factor and pressure drop which directly enhances the heat transfer characteristics.
Optimization of Air Preheater for compactness of shell by evaluating performa...Nemish Kanwar
Designing of an Air Preheater with increased performance from an existing design through alteration in baffle placement. Analysis of 4 Baffle designs for segmented Baffle case was done using Ansys Fluent. The net heat recovery rate was computed by subtracting pump work from heat recovered. Based on the result, Air Preheater design was recommended.
International Journal of Computational Engineering Research(IJCER)ijceronline
International Journal of Computational Engineering Research(IJCER) is an intentional online Journal in English monthly publishing journal. This Journal publish original research work that contributes significantly to further the scientific knowledge in engineering and Technology.
Numerical Modeling and Simulation of a Double Tube Heat Exchanger Adopting a ...IJERA Editor
The double tube heat exchangers are commonly used in industry due to their simplicity in design and also their
operation at high temperatures and pressures. As the inlet parameters like temperatures and mass flow rates
change during operation, the outlet temperatures will also change. In the present paper, a simple approximate
linear model has been proposed to predict the outlet temperatures of a double tube heat exchanger, considering it
as a black box. The simulation of the heat exchanger has been carried out first using the commercial CFD
software FLUENT. Next the linear model of the double tube heat exchanger based on lumped parameters has
been developed using the basic governing equations, considering it as a black box. Results have been generated
for outlet temperatures for different inlet temperatures and mass flow rates of the cold and hot fluids. The results
obtained using the above two methods have then been discussed and compared with the numerical results
available in the literature to justify the basis for the assumption of a linear approximation. Comparisons of the
predicted results from the present model show a good agreement with the experimental results published in the
literature. The assumptions of linear variation of outlet temperatures with the inlet temperature of one fluid
(keeping other inlet parameters fixed) is very well justified and hence the model can be employed for the
analysis of double tube heat exchangers.
Application of Pinch Technology in Refrigerator Condenser Optimization by Usi...ijtsrd
Refrigeration is the major application area of thermodynamics, in which the heat is transferred to higher temperature region from a lower temperature region. Refrigerators are the devices which produce refrigeration and the refrigerators which operate on the cycles are called refrigeration cycles. Pinch technology and computational fluid dynamics CFD is key for study the condenser and enhance the better option for new design. Pinch Analysis also known as process integration, heat integration, energy integration, or pinch technology is method for minimizing the energy costs of a process by reusing the heat energy in the process streams rather than outside utilities. Mr. Mayur B. Ramteke | Prof. S. K. Bawne "Application of Pinch Technology in Refrigerator Condenser Optimization by Using CFD" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-5 | Issue-6 , October 2021, URL: https://www.ijtsrd.com/papers/ijtsrd46440.pdf Paper URL : https://www.ijtsrd.com/engineering/mechanical-engineering/46440/application-of-pinch-technology-in-refrigerator-condenser-optimization-by-using-cfd/mr-mayur-b-ramteke
Heat Transfer Characteristics of a Plate Fin Heat Sink with Pin Fins of Vario...ijtsrd
In recent decades, attempts have been made to create more advanced effective cooling technology for electronic and microelectronic devices, but heat dissipation is still a major challenge for increasing the cooling performance of heat sinks in a highly competitive electronics market. In the present analysis, the research is designing a new thermal design for plate fin heat sinks with hexagonal pin fin connected to the plate fins. A theoretical analysis focused on publicly usable computational fluid dynamics CFD codes has been performed to test the thermal efficiency of the proposed designs. Modelling done using ANSYS 14.5 and meshing has done using ICEM CFD software, simulations has done by using CFD FLUENT software. In specific, in terms of their thermal performance, hexagonal pin fin connected to the plate fins subject to flow have been contrasted. The plate fin heat sink was made of Aluminium and an electrical heaters provide a heat of 10W constantly to warm up a plate plate fin heat sink with hexagonal pin fin subject to flow of air at variable values i.e. 6.5, 9.5, and 2.5 m s .Based on the results, the analysis has shown that the plate fin heat sinks demonstrate superior thermal performance with hexagonal 3 pin fin subject to flow. The Nusselt number is approximately 1.32 times higher than the conventional plate fin heat sink without pin fin and 1.13 times higher than plate fin heat sink with elliptical 3 pin fin. Prof. Pushparaj Singh | Prashant Kumar Pandey "Heat Transfer Characteristics of a Plate Fin Heat Sink with Pin Fins of Various Profile using CFD" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-6 , October 2020, URL: https://www.ijtsrd.com/papers/ijtsrd33375.pdf Paper Url: https://www.ijtsrd.com/engineering/mechanical-engineering/33375/heat-transfer-characteristics-of-a-plate-fin-heat-sink-with-pin-fins-of-various-profile-using-cfd/prof-pushparaj-singh
ELECTRIC AND THERMAL ENERGY PRODUCTION AND STORAGE SYSTEM BY PINECONE WASTEaeijjournal
Rural ecosystems are the main source of biomass used in the production of renewable energy in Portugal.
However, it is based on pruning residues are most of the raw material for biomass leaving other
opportunities aside. This paper highlights the role of pinecone waste without pinion for the energy sector.
The present paper studies different solutions to enhance the use of the pinecones for energy proposes. The
present paper also presents the different principal technologies.
It is possible to conclude that the use of residual biomass is a way to reduce the national dependence on
energy imports (fossil specialties), decreases transport losses (by allowing local production and
consumption locally) and encourages the management of forest areas (fixing people in rural areas and
lowers the risk of fire).
AN ENGINEERING APPROACH FOR HARVESTING ENERGY FROM WIND, WAVE AND STORMaeijjournal
The world is now facing energy scarcity and climate change. In that context, renewable energy is gradually replacing fossil fuels. However, this source of energy has not been fully exploited. Some natural disasters bring a lot of energy but are not exploited; in particular, storms are among the heavyweights. In this paper, I propose a device for harvesting energy from wind, waves and especially storms. One such device is called a Stormbuoy. If used in practice and deployed on a large scale, the Stormbuoy will harvest significant amounts of energy from wind, waves and storms. This not only solved the problem of energy scarcity but also mitigated the destruction of the storm with humans.
FEASIBILITY STUDY OF ORKNEY’S WINDFARM DEVELOPMENT FOR SELF-SUFFICIENT FOR EN...aeijjournal
In Orkney islands, a number of wind energy projects have been established due to its potential for wind energy development especially as cluster developments on hilltop and moorland. This Self-sufficient Orkney Wind Energy (SOWE) project is trying to follow this pattern of development and has designed as a simple linear development of medium-large scale wind turbines which avoids dominating the landscape, while providing diversification required for the energy security, along with strong economic benefits to the local community. The developer completed preliminary designs and landscape assessment, resulting in the detailed design and the development of 27 wind turbine project for the expectation to generated electricity
of 549.2 GWh annually. The SOWE project has been designed and selected the use of the Enercon E44 - 900 kW and Norex N80 - 2.5 MW wind turbines. These machines represent the maximum scale, respectively, as; • the site layout and all modelling have used a 45m, and 60m turbine tower height;
• a rotor diameter of 44 m, and 80 m; and • The blade length is 22 m and 40 m. It has been found that the SOWE project provides a promising contribution towards the Scottish
Government renewable energy production and carbon reduction targets.
KEYWORDS
feasibility study, windfarm, Orkney, road transport
ENERGY STATUS AND ALTERNATIVE ENERGY PLANS OF MAJOR ENERGY CONSUMERS IN SOUTH...aeijjournal
Southeast Asia comprises an extraordinarily diverse set of countries with vast differences in the scale and
patterns of energy use and energy resources endowments. Indonesia and Thailand have been selected to be
compared because they are the two largest consumers in energy sector in the region and both countries
still similarly rely on energy imports such as oil. They have been facing challenges in energy policy reformation distorting energy markets. The combined energy status of Indonesia and Thailand not only aims at providing policy makers with an understanding of the energy trends and challenges being faced by the countries up to the next two decades, but also at confidently convincing them the future energy pathways to unlocking energy efficiency potential and investment. This work contains data and information on pattern of energy use in the past, present, and future, some economic and political factors that may be affecting energy demand and supply of Indonesia and Thailand. Key energy issues that need to be considered are introduced. The potential future energy pathways are included and compared between the countries. Investment opportunities in each country are also identified.
Advanced Energy: An International Journal (AEIJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Energy Engineering and allied fields. This multi disciplinary journal is devoted to the publication of high quality papers on theoretical and practical aspects of Energy Engineering.
Advanced Energy: An International Journal (AEIJ) is a quarterly open access peer-reviewed journal that publishes articles which contribute new results in all areas of the Energy Engineering and allied fields. This multi disciplinary journal is devoted to the publication of high quality papers on theoretical and practical aspects of Energy Engineering. Authors are solicited to contribute to the journal by submitting articles that illustrate research results, projects, surveying works and industrial experiences that describe significant advances in all areas of Energy Engineering.
A MODIFIED ANT COLONY ALGORITHM FOR SOLVING THE UNIT COMMITMENT PROBLEMaeijjournal
Solving the unit commitment (UC) problem is one of the most complicated issues in power systems that its
exact solving can be calculated by perfect counting of entire possible compounds of generative units. UC is
equated as a nonlinear optimization with huge size. Purpose of solving this problem is to programming the
optimization of the generative units to minimize the full action cost regarding problem constraints. In this
article, a modified version of ant colony optimization (MACO) is introduced for solving the UC problem in
a power system. ACO algorithm is a powerful optimization method which has the capability of fleeing from
local minimums by performing flexible memory system. The efficiency of proposed method in two power
system containing 4 and 10 generative units is indicated. Comparison of obtained results from the proposed
method with results of the past well-known methods is a proof for suitability of performing the introduced
algorithm in economic input and output of generative units.
IMPEDANCE SPECTROSCOPY ANALYSIS OF A LIQUID TIN ANODE FUEL CELL IN VOLTAGE RE...aeijjournal
A concept of a liquid tin anode-indirect carbon air fuel cell (LTA-ICFC) are described. Experimental
setups for analysis of LTA-ICFC polarisations of an operational electrochemical reactor of the LTA-ICFC
are presented. Results from Electrochemical Impedance Spectroscopy (EIS) Analysis of the electrochemical
reactor of the LTA-ICFC are shown and analysed.The rate-determining step of the system is concluded.
The charge-transfer resistance did not show considerable differences at 700-800 °C. This can be implied
that the charge-transfer resistance is not the rate-limiting step of the transport processes of the fuel cell.
The increase of the Warburg impedance concurrently with the resistance to fit mass-transport loss (R3)
suggests that the rate-limiting step for the LTA-ICFC in voltage recovery mode is the diffusion of the oxide
ions through SnO2 layer. The increment of mass transport lost, R3, of the cell causes the slowly increase of
the cell’s voltage over the voltage from 0.7-0.8 V at 700, 750, and 800 °C.
Cointegration relationship betweeCOINTEGRATION RELATIONSHIP BETWEEN ECONOMIC ...aeijjournal
Energy dependent small developing island states are besieged to sustain potential rate of growth. This is
due to increase in energy prices and lack of evidence based policy on long term sustainable energy use.
This paper examines the long run relationship between economic growth, export and electricity
consumption in Fiji over the period 1981-2011. Employing Granger causality test it is found that there is
cointegrating relationship between economic growth, export and electricity consumption. The casual
relationship between the variables was investigated within the error correction model framework. We
found that in the long run causality runs from electricity consumption and export to economic growth.
Based on this empirical analysis some important policy implications are suggested.
Encryption in Microsoft 365 - ExpertsLive Netherlands 2024Albert Hoitingh
In this session I delve into the encryption technology used in Microsoft 365 and Microsoft Purview. Including the concepts of Customer Key and Double Key Encryption.
Epistemic Interaction - tuning interfaces to provide information for AI supportAlan Dix
Paper presented at SYNERGY workshop at AVI 2024, Genoa, Italy. 3rd June 2024
https://alandix.com/academic/papers/synergy2024-epistemic/
As machine learning integrates deeper into human-computer interactions, the concept of epistemic interaction emerges, aiming to refine these interactions to enhance system adaptability. This approach encourages minor, intentional adjustments in user behaviour to enrich the data available for system learning. This paper introduces epistemic interaction within the context of human-system communication, illustrating how deliberate interaction design can improve system understanding and adaptation. Through concrete examples, we demonstrate the potential of epistemic interaction to significantly advance human-computer interaction by leveraging intuitive human communication strategies to inform system design and functionality, offering a novel pathway for enriching user-system engagements.
DevOps and Testing slides at DASA ConnectKari Kakkonen
My and Rik Marselis slides at 30.5.2024 DASA Connect conference. We discuss about what is testing, then what is agile testing and finally what is Testing in DevOps. Finally we had lovely workshop with the participants trying to find out different ways to think about quality and testing in different parts of the DevOps infinity loop.
JMeter webinar - integration with InfluxDB and GrafanaRTTS
Watch this recorded webinar about real-time monitoring of application performance. See how to integrate Apache JMeter, the open-source leader in performance testing, with InfluxDB, the open-source time-series database, and Grafana, the open-source analytics and visualization application.
In this webinar, we will review the benefits of leveraging InfluxDB and Grafana when executing load tests and demonstrate how these tools are used to visualize performance metrics.
Length: 30 minutes
Session Overview
-------------------------------------------
During this webinar, we will cover the following topics while demonstrating the integrations of JMeter, InfluxDB and Grafana:
- What out-of-the-box solutions are available for real-time monitoring JMeter tests?
- What are the benefits of integrating InfluxDB and Grafana into the load testing stack?
- Which features are provided by Grafana?
- Demonstration of InfluxDB and Grafana using a practice web application
To view the webinar recording, go to:
https://www.rttsweb.com/jmeter-integration-webinar
Kubernetes & AI - Beauty and the Beast !?! @KCD Istanbul 2024Tobias Schneck
As AI technology is pushing into IT I was wondering myself, as an “infrastructure container kubernetes guy”, how get this fancy AI technology get managed from an infrastructure operational view? Is it possible to apply our lovely cloud native principals as well? What benefit’s both technologies could bring to each other?
Let me take this questions and provide you a short journey through existing deployment models and use cases for AI software. On practical examples, we discuss what cloud/on-premise strategy we may need for applying it to our own infrastructure to get it to work from an enterprise perspective. I want to give an overview about infrastructure requirements and technologies, what could be beneficial or limiting your AI use cases in an enterprise environment. An interactive Demo will give you some insides, what approaches I got already working for real.
State of ICS and IoT Cyber Threat Landscape Report 2024 previewPrayukth K V
The IoT and OT threat landscape report has been prepared by the Threat Research Team at Sectrio using data from Sectrio, cyber threat intelligence farming facilities spread across over 85 cities around the world. In addition, Sectrio also runs AI-based advanced threat and payload engagement facilities that serve as sinks to attract and engage sophisticated threat actors, and newer malware including new variants and latent threats that are at an earlier stage of development.
The latest edition of the OT/ICS and IoT security Threat Landscape Report 2024 also covers:
State of global ICS asset and network exposure
Sectoral targets and attacks as well as the cost of ransom
Global APT activity, AI usage, actor and tactic profiles, and implications
Rise in volumes of AI-powered cyberattacks
Major cyber events in 2024
Malware and malicious payload trends
Cyberattack types and targets
Vulnerability exploit attempts on CVEs
Attacks on counties – USA
Expansion of bot farms – how, where, and why
In-depth analysis of the cyber threat landscape across North America, South America, Europe, APAC, and the Middle East
Why are attacks on smart factories rising?
Cyber risk predictions
Axis of attacks – Europe
Systemic attacks in the Middle East
Download the full report from here:
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Evaluating mathematical heat transfer effectiveness equations using cfd techniques for a finned double pipe heat exchanger
1. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
1
EVALUATING MATHEMATICAL HEAT TRANSFER
EFFECTIVENESS EQUATIONS USING CFD
TECHNIQUES FOR A FINNED DOUBLE PIPE HEAT
EXCHANGER.
Ali Hasan
Project Management and Construction Management, KEO Consulting Engineers, Doha,
Qatar.
ABSTRACT
Mathematical heat transfer equations for finned double pipe heat exchangers based on experimental work
carried out in the 1970s can be programmed in a spreadsheet for repetitive use. Thus avoiding CFD
analysis which can be time consuming and costly. However, it is important that such mathematical
equations be evaluated for their accuracy. This paper uses CFD methods in evaluating the accuracy of
mathematical equations. Several models were created with varying; geometry, flue gas entry temperature,
and flow rates. The analysis should provide designers and manufacturers a judgment on the expected level
of accuracy when using mathematical modelling methodology. This paper simultaneously identifies best
practices in carrying out such CFD analysis.
Methodology; CFD software was used to simulate different models. Results were tabulated and graphically
presented. The investigated mathematical equations were programmed in a spreadsheet, for data entry.
Results and analysis; data obtained from the two methods were compared and differences were recorded.
Discussions were included explaining the possible reasons for the deviations that surfaced between the two
methodologies.
Conclusions; this analysis has shown that although mathematical equations are effective and simple tools
in producing results, the results may not reflect the actual physical conditions. The analysis showed that the
exhaust gas temperature outlet of a double pipe heat exchanger is actually higher than what were
calculated using mathematical equations, and therefore, more heat energy is available for recapturing.
k-epsilon RNG turbulence model was found to be the most suitable method in analyzing heat transfer in a
finned double pipe heat exchanger.
KEYWORDS
CFD, Heat transfer, Double Pipe Heat Exchanger, Energy recovery.
1. INTRODUCTION
Research in heat transfer and thermo-physical fluid properties in the past three decades have
helped develop heat exchangers designs, by relying on; mathematical, experimental, and
computer numerical analysis. This has allowed designers to better design heat exchangers and
push for better energy recovery systems. Lower energy consumption means lower operating costs
and lower carbon emissions. The importance of heat recovery systems in combined heat and
power systems have created a demand for effective heat recovery systems capable of recapturing
heat energy out of the engine exhaust gas. A good example of this heat recapturing system is a
2. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
2
double pipe heat exchanger. Such a system can easily be fitted as part of an engine exhaust pipe
system. The examples discussed in this paper, consider the process of heat energy transfer from
the exhaust flue gas to water. This paper focuses on evaluating numerical techniques used to
calculate heat transfer effectiveness. Providing designers and manufacturers, an insight on the
expected level of accuracy when using mathematical equations associated with a double pipe heat
exchanger.
CFD software was used to evaluate the model. Results were tabulated and compared with
mathematically driven results. The analysis showed the difference between the results generated
by the two different methods. Discussions on possible causes of differences were included
supported by graphical CFD images. Best practices in CFD analysis were discussed with the
support of similar recently carried out CFD work.
The CFD analysis highlighted the following facts; Mathematical equations are good for an initial
analysis, but will require CFD or experimental modeling to obtain more accurate results on heat
transfer, the mathematically generated results showed an underestimated temperature output for
the exhaust flue gas. This analysis has shown the possibility of further energy recovery from the
higher flue gas outlet temperature which would otherwise be wasted heat energy.
This document describes, and is written to conform to, author guidelines for the journals of
AIRCC series. It is prepared in Microsoft Word as a .doc document. Although other means of
preparation are acceptable, final, camera-ready versions must conform to this layout. Microsoft
Word terminology is used where appropriate in this document. Although formatting instructions
may often appear daunting, the simplest approach is to use this template and insert headings and
text into it as appropriate.
2. MATHEMATICAL MODEL FOR DOUBLE PIPE HEAT
EXCHANGERS
Equations for calculating heat exchanger effectiveness are covered in details in ASHRAE
Fundamentals (2009) [1], representing various types of heat exchangers.
Reference is made to Appendix 1 for a sample calculations with the conditions involved. Counter
flow conditions were assumed in the two techniques; mathematical and CFD models. In certain
cases and usually at the end of such equations, a check is required for a possible further iteration.
Refer to Appendix 1 for such an example.
The example in Appendix 1 refers to heat transfer across a pipe surface area towards water
flowing in the inner pipe. Tables 1 to 3 indicate results computed using the equations shown in
Appendix 1. The second column from left of table shows the first attempt of calculations.
3. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
3
Table 1.Double Pipe Heat Exchanger with 16 fins.
Item Description
CFD
method
Mathematical
method
Temperature
difference (%)
between
mathematical and
CFD methods (*)
After iterations (**)
1 Heat transfer
effectiveness
- 0.984714 -
2 Temperature of
water – out °C
(°F)
42.00
(116)
47.39 (126.8) 13 % -
3 Temperature of
exhaust – out
°C (°F)
64.03
(160.1)
42.44 (116.9) 51 % -
Fin thickness 1 mm (0.04 inch). Fluids temperatures at entry point; water 40 C (104
F), & flue gas 200 C (392 F).Flue gas mass flow rate 0.12 kg/s (0.264 lb/s).
(*) Results without iterations carried out on the mathematically generated results. (**)
Results after iterations using mathematical methods showing temperature and percentage
difference between the CFD and mathematically generated temperatures.
Table 2. Double Pipe Heat Exchanger with 15 fins.
Item Description
CFD
method
Mathematical
method
Difference (%)
between mathematical
and CFD methods (*)
After iterations (**) –
temperature /
[difference %]
1 Heat transfer
effectiveness
- 0.887249 0.884507
2 Temperature of
water – out °C
(°F)
46.05
(124.1)
66.13 (164.3) 43.6 % 66.33 (164.66) / [6.4
%)]
3 Temperature of
exhaust – out
°C (°F)
83.31
(198.6)
74.95 (181.9) 11 % 75.80 (183.6) / [86
%]
Fin thickness 1 mm. Fluids temperatures at entry point; water 40 C (104 F), & flue gas 350
C (662 F). Flue gas mass flow rate 0.243 kg/s (0.535 lb/s).
(*) Results without iterations carried out on the mathematically generated results. (**) Results
after iterations using mathematical methods showing temperature and percentage difference
between the CFD and mathematically generated temperatures.
4. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
4
Table 3. Double Pipe Heat Exchanger with 13 fins.
Ite
m
Description
CFD
method
Mathematical
method
Difference (%)
between
mathematical and
CFD methods (*)
After iterations (**) –
temperature /
[difference %]
1 Heat transfer
effectiveness
- 0.887249 0.882163
2 Temperature of
water – out °C
(°F)
46.36
(124.72)
66.06 (164.12) 42.5 % 66.26 (164.52) / [13.4
%]
3 Temperature of
exhaust – out
C (°F)
81.03
(194.06)
75.67 (183.34) 7.1 % 76.52 (185.04) / [90
%]
Fin thickness 1 mm. Fluids temperatures at entry point; water 40 C (104 F), & flue gas 350
C (662 F). Flue gas mass flow rate 0.243 kg/s.
(*) Results without iterations carried out on the mathematically generated results. (**) Results
after iterations using mathematical methods showing temperature and percentage difference
between the CFD and mathematically generated temperatures.
Figure 1. 16 fin cross sectional view, from ASHRAE Fundamentals Handbook (2009) [1].
t = fin thickness
L = fin length (radial)
40 mm = 1.6 inch
40
mm
t , L
5. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
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Figure 2. Sectional view example of a segment for a 16 fin double pipe heat exchanger. Graphical results
are as shown in Fig 3. The outer pipe wall assumed to have no heat conductance.
Figure 3.Front view images showing a 22.5 degree segment of pipe. Image to the left shows the water inlet
section of the inner pipe. Image to the right shows how the water section of the inner pipe has increased in
temperature. Copper pipe wall and copper fins are one continuous body. The lower and higher gas
temperatures are clearly visible. Flue gas temperatures along the fin/tube metal surfaces are relatively lower
than the middle flue gas volume. This is due to heat energy being transferred across the metal volume and
towards the lower temperature body of fluid, water.
Temperatures produced for water and exhaust gas were added to entry temperatures to produce
the average temperatures. Using the new average temperature results, the new values for density
of water and specific heat capacity for gas were re-entered in the excel sheet to calculate the final
temperature outputs, shown in the first column from right. In table 1 for an example the density of
water and the specific heat capacity of gas at the new average temperatures were found close to
what was originally assumed for, and therefore no further iteration work is required.
6. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
6
ASHRAE Fundamentals Chapter 4 (2009) [2], section on heat exchangers documents the
development and experimental work associated with heat exchangers, including complex
geometrical shapes. The
Reference is made to tables 1 to 3. Second from left column results were based on initial
assumption of specific heat capacity of 1018 J/(kg.K) (0.2431 Btu/lb.F) at 175 °C (347 °F).
First column from right in tables 1 to 3, the specific heat capacity found in standard
thermodynamic tables to be 1029 J/(kg.K) (0.2457 Btu/lb.F) at 212 °C (413.6 °F). Therefore
iterations were carried out by entering in the mathematical equation 1029 J/(kg.K) (0.2457
Btu/lb.F). Results are as shown in tables 1 to 3.
Equations used in Appendix cater for conditions where temperatures of fluids leaving the heat
exchanger are unknown. To avoid trial-and-error calculations, the NTU- ε method uses three
dimensionless parameters: effectiveness ε, number of transfer units (NTU), and capacity rate ratio
cr. Also, the equations used do not consider the inner pipe wall thickness, but just surface area,
unlike CFD analysis carried below.
Fay C McQuiston (2000) [4] notes that, precise values are difficult to predict, and experience
along with experimental data is often relied on.
In practice, improving heat transfer between two fluids in a heat exchanger usually depends on;
construction materials, velocity of fluids, and size of heat exchanger (heat exchange surfaces).
According to Fay C McQuiston (2000) [4], the trade-off between first cost (primarily size) and
operating cost (primarily due to pressure drop) is a major consideration in heat exchanger analysis
and selection.
3. CFD ANALYSIS
Models were developed for a cross sectional segment. AutoCAD 2013 was used for modeling,
and exported to ANSYS Fluent version 13, using IGES files. The AutoCAD file drawing in 2D
first and then extruded into a 5000 mm (200 inch) length segment creating a 3D model. Walls,
boundary conditions were defined, materials, and fluids data were entered. Analysis was run, and
data was produces as shown in Figures 3 to 10. Fluids temperature properties were entered in
tables 1 to 3 for comparison with the mathematically derived results.
Unlike the equations referred to in section 1, CFD modeling considers the inner pipe wall
thickness, the material responsible for transferring heat energy from flue gas to the water body,
and the fluid boundary conditions. Thus, CFD tools provide an effective heat transfer simulation
between the fluid body and the solid body.
7. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
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Figure 4. 3D image (104ºF) temperature contours for a 22.5 degree segment of the double pipe heat
exchanger. Entry point for flue gas shown in red to the left of picture. Water temperate contours are shown
as the water exits inner pipe, left of picture.
Figure 5.Flue temperature line for 22.5 degree segment.
(392ºF)
(190.4ºF)
(305.6ºF)
8. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
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Figure 6.Water temperature line for 22.5 degree segment.
(16.4 ft)
9. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
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Figure 7.Flue temperature line for 24 degree segment.
Figure 8.Water temperature line for 24 degree segment.
10. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
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Figure 9.Flue temperature line for 27 degree segment.
11. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
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Figure 10.Water temperature line for 27 degree segment.
Figure 11. Shows meshing layout for the water inlet and gas outlet heat exchanger section. Geometry
details shown in Fig 2. The solid tube and fin sections were switched off to give a clearer view on fluid
elements layout. Fluid meshing layers at boundary conditions were inflated to give a more accurate
prediction of heat transfer along the copper tube/fin walls. The right hand side image is a zoomed image
of the encircled area shown on the left hand side image.
Tube wall
mesh
switched off
Fin mesh
switched off
Gas
Water
12. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
12
Fay C McQuiston (2000) [4] states, that manual design or simulation of a heat exchanger is an
arduous task and seldom done. Computer programs are available to simulate or select heat
exchangers for various applications.
Assumptions made:
- Flue gas as an ideal gas.
Note: According to E Rathakrishnan (2004) [3], many of the familiar gases such as air,
nitrogen, oxygen, hydrogen, helium, argon, neon, krypton, and even heavier gases such as
carbon dioxide can be treated as ideal gas with negligible error, often less than 1%.
Therefor, air, or gas where referred to in this paper, was assumed as an ideal gas in this
CFD analysis.
- Materials, flue gas, copper fins and pipe wall, and water, as per the software standard
database.
- K- Epsilon RNG, a common turbulence model selected from the software database. Wall
roughness factor constant, 0.5. Refer to Appendix 2 for specific settings. Settings not
specified in this paper were kept a software default settings.
- Inflated layers created along the fluid boundary layers in contact with the tube wall, and
fin surfaces. This will improve boundary conditions simulations.
4. RESULTS AND ANALYSIS
4.1 Results and Analysis discussed separately.
a. Results
Results obtained using the mathematical modelling and the CFD analysis were tabulated as
shown in tables 1 to 3.The results cover three different scenarios addressing different flow rates,
temperatures, fin thickness, and flue gas entering temperatures. The object is to investigate how
the mathematical equations perform under different conditions.
b. Analysis
Impact of fin thickness.
Tables 1 to 3 show that higher heat transfer effectiveness can be achieved with the thinner 1mm
thick 16 fins, when compared to the thicker but lower number of fins.
Impact of flue gas entry temperature.
A high entry flue gas temperature of 350 ºC (732 ºF) produced higher water exiting temperatures,
but lower effectiveness value. In accordance with mathematical and CFD derived exiting
temperatures.
CFD - flue gas temperature line graphs.
Flue gas line graphs showed a positive slope with curvature (nonlinear) in relation to increasing
temperature. Refer to graph Figs 5+.
CFD - water temperature line graphs.
13. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
13
Similar to the flue line graphs, positive slope as temperature increases. Percentage deviations
showed better accuracy or lower percentage deviations using thinner fins. Table 1 indicated a
deviation of 4.5% for a 1mm (0.04 inch) thick fin. Higher percentage deviations were observed
against mathematically generated figures for thicker fins, as shown in tables 2 & 3.
The reasons for the significant differences between the out temperatures calculated using the two
different methods, CFD and mathematical equations, are;
a. The mathematical equation does not take into consideration heat transfer at boundary
conditions. Heat transfer in the mathematical equations assumes that the transfer of
heat energy between the two fluid bodies is a uniform process, with both fluid
volume bodies having a uniform temperature across the body of fluid. In reality and
as demonstrated in Figs 3 and 4. The temperature in the flue gas varies from locations
along the fin surface and the pipe wall surface. The temperature in the middle of the
flue gas volume remains higher than along the pipe wall, and fin surfaces, where heat
energy is being conducted through the copper metal and passed towards the water
fluid body of relatively lower heat temperature.
b. The mathematical equations refer to pipe wall surface area, whereas in reality and in
this CFD model the pipe wall has a thickness.
c. Turbulences in the flue gas contribute to the mixing of the cooled gas boundary
layers, with the inner middle flue gas volume. The higher the fluid turbulences are the
better the heat transfer is between the two different fluid volumes.
d. K-epsilon RNG turbulence models was found to be the most suitable model. Other
models did not converge. This confirms the published work by M Hatami [5].
Stating that the RNG turbulence model converged easily during the processing stage,
whereas SST or Shear Stress Transport theory did not easily converge.
e. B.S. Massey1983 [6] describes flow near the boundary layer may be either laminar or
turbulent. Turbulent flow past a solid surface having a random movement of particles
perpendicular to the surface. Yet fluid particles cannot pass through an impermeable
solid surface, and so, as the surface is approached, these movements perpendicular to
it must die out. It follows then that turbulent flow cannot exist immediately in contact
with the solid boundary. Thus even when main flow possess considerable turbulence,
and even when the greater part of the boundary layer us also turbulent, there is still an
extremely thin layer, adjacent to the solid surface, in which the flow has negligible
fluctuations of velocity. This region, which may be less than a micrometer in
thickness, has frequently been called the laminar sub-layer, but the term viscous sub-
layer is now preferred. The viscous sub-layer plays a significant role in heat transfer
between a fluid body and a solid surface.
It is this low-Reynolds-number extension for near-wall turbulence catered for by the k-epsilon
RNG Near Wall Treatment function which makes the difference. The RNG Near Wall Treatment
was designed to work for coarse and fine mesh, however, for better accuracy, mesh layers were
inflated as shown in Fig 11.
4.2 Advantages & disadvantages between the two techniques.
i) Spread sheets are relatively easier to program and do not require specialist trained
personnel to operate, unlike CFD tools.
ii) CFD techniques as in the example shown above show graphical results, not possible with
excel sheets.
14. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
14
iii) Both numerical techniques can be used to evaluate heat exchanger designs. Minimizing
physical experimental techniques, which can be time consuming and costly.
iv) Experimental techniques used to evaluate established designs, are prone to the
introduction of errors due to non-accurate or non-calibrated instruments.
v) CFD analysis is also cable of calculating pressure drops simultaneously through analysis.
Though, pressure drop calculations can easily be programmed in a spread sheet.
vi) Established CFD tools can be considered as more accurate, when compared with
mathematical techniques, where thicker fins are used.
5. CONCLUSIONS
Analyses showed that the water line exit temperature results produced better accuracy for thinner
fins. Mathematically derived results differed when compared with CFD results by up to 13 % for
a 1mm (0.04 inch) thick fin. Higher deviation between CFD and mathematical equations were
observed for thicker fins.
Larger deviations existed between CFD and mathematical modelling on the flue line exit
temperature results, as in the case of 1 mm fin thickness. Which is greater than 70 % in deviations
on temperature flue gas exits. Therefore, it is important to establish the level of accuracy of
mathematical equations under specific conditions; geometrical, and operational.
The CFD analysis has shown that the exhaust heat temperature is actually higher than what have
been calculated using mathematical equations.
While for water outlet temperature figures, the mathematically derived figures were found to be
higher than the CFD derived results.
In this investigation, it was observed that although the mathematical methods are simpler and
easy to use once programmed in a spread sheet, the level of accuracy and how much energy can
actually be recovered is a concern. Where justified and accuracy is important CFD and/or
experimental investigations are recommended.
This CFD analysis confirms recently published work stating that the k-epsilon RNG turbulence
model is the most suitable method in analyzing heat transfer in double pipe heat exchangers.
6. RECOMMENDATIONS
Further research work using; mathematical, experimental and CFD techniques for different fin
geometry and flow rates.
ACKNOWLEDGEMENTS
The author would like to thank; Dr.Lik F. Sim for setting up and providing access to the FLUENT
software, and MrAbdelkaderBenzamia of Flowpak, Flowpak, Doha, Qatar, www.flowpak.net, for
the guidance and input on best practices in CFD mes.
REFERENCES
15. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
15
[1] ASHRAE Fundamental. F4.22-2009.
[2] ASHRAE Fundamentals. F4.21: 2009.
[3] Author E Rathakrishnan, Title; Gas Dynamics. Fifth edition. Publisher PHI. Year 2004.
[4] Author, Fay C McQuiston. Title, Heating Ventilating and Air Conditioning – Analysis and Design.
Fifth edition. Published by John Wiley and sons, Inc USA. Pages 484 and 485. Year 2000.
[5] Paper by; M. Hatami, M. Jafaryar, D.D. Ganji and M. Gorji-Bandpy. Optimization of finned-tube
heat exchangers for diesel exhaust waste heat recovery using CFD and CCD techniques. International
Communications in Heat and Mass Transfer, Volume 57, October 2014, Pages 254–263.
[6] B.S. Massey, Title; Mechanics of Fluids. Fifth edition. Publisher Van Nostrand Reinhold (UK). Year
1982.
APPENDIX 1
Spreadsheet excel version 2010 was used in programming the equations shown below given in ASHRAE
Fundamentals (2009) [2].
Assumptions:
a. Not heat losses on the outside pipe wall, insulated.
b. Starting with assumed properties of water and specific heat capacity of flue gas. At mean
temperatures. Requirement for iterations can be checked as discussed in section 1 above.
c. Counter flow conditions equation. C ≠ 1, ASHRAE Fundamentals.
Table 3. Shows data entered in a spreadsheet programmed with the equations mentioned in steps 1
to 4.
Description Abbreviation Input Units
Water in pipe tci 40
ºC
Water Velocity vc 0.5 m/s
Gas enters thi 200 ºC
Mass flow rate h 0.12 kg/s
Length of heat exchanger Ltube 5
m
diameter of inner tube d 0.04 m
Fin radial height L 0.06 m
Fin thickness t 0.001 m
Number of fins N 16
Convective heat transfer
coefficient on water side hi
Gas side heat transfer coefficient ho 115 W/(m2
K)
Surface effectiveness øs 0.641964
Fin efficiency ø
Surface are of non-finned surface Auf 0.5484 m2
Fin surface area Af 9.6 m2
Auf +
Af Ao 10.1484 m2
πdLtube Ai 0.6284 m2
(104 ºF)
(1.64 ft/s)
(392 ºF)
(0.264 lb/s)
(16.4 ft)
(0.1312 ft)
(0.1968 ft)
(0.00328 ft)
16. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
16
Density of water ρ 990.4 kg/m3
Specific heat capacity of water cpc 4183 J/(kg.K)
Dynamic viscosity µ 5.96E-04 (N.s)/ m2
Thermal conductivity water side k 0.6376 W/(m.K)
Prandtl Number Pr 3.91
Gas specific heat - assumed
figures for air cph 1018 J/(kg.K)
ε= 0.984714
the= 42.44 C
tce= 47.39 C
the = temperature of gas leaving system, &tce = temperature of water leaving system.
Step 1
Re= ρ vcd / µ
fs/2 =[ [1.58ln(Re)-3.28]^-2
]/2 = 0.00288
Nud= [0.00288×(33213-1000) ×3.91] ÷ [1+12.7×(0.00288)^0.5
×(3.91^2/3
-1) = 180.4
hf= (180.4×0.6376)/0.04 = 2876 W/(m2
K)
Step 2
Calculating fin efficiency ø and surface effectiveness øs. For a rectangular fin with the end of the fin not
exposed.
Ø = [tanh (mL)] / mL
For copper k = 401W/(mK)
mL= (2ho/kt)1/2L = [(2 115)/(401 0.001)]1/2(0.06) = 1.44
Ø = 0.62
Øs= (Auf +ØAf)/A0 = (0.548 + 0.62 × 9.6)/10.15 = 0.64
Step 3
Find heat exchanger effectiveness. For air at an assumed mean temperature
of 175°C, cph= 1018 J/(kg·K).
Ch= cph= 0.12 1018 = 122.2 W/K
c = ρvcπd2/4 = (990.4 × 0.5 × π × 0.042
)/4 = 0.6223 kg/s
Cc = cpc= 0.6223 × 4181 = 2602 W/K
cr= Cmin/Cmax= 122.2/2602 = 0.04696
UA = [1/(0.64 × 115 × 10.15) + 1/(2876 × 0.628)]–1 = 528.5 W/K
NTU = UA/Cmin= 528.5/122.2 = 4.32
ε = 1-exp[-N(1-cr)] ÷ [1-crexp[-N(1-cr)]
ε = 0.983
Step 4
qmax= Cmin× (thi– tci) = 122.2 × (200 – 40) = 19 552 W
q = εqmax= 0.985 × 19 552 = 19 255 W
Step 5
the = thi – q/Ch = 200 – (19255/122.2) = 42.2 C (107.9 F)
tce = tci + q/Cc = 40 + (19255/2602) 47.4 C (117.32 F)
(108.4 °F)
(117.3 °F)
17. Advanced Energy: An International Journal (AEIJ), Vol. 2, No. 1, January 2015
17
APPENDIX 2
This section provides a description of the turbulence model equations used in this CFD analysis, boundary
inlet & outlet conditions, and details of specific settings used in this CFD analysis. A graphical presentation
showing the quality of mesh used can be seen in Fig 11.
k-epsilon RNG
Unlike other turbulence models, the k-epsilon RNG also known as k-ε RNG model focuses on the
mechanisms that affect the turbulent kinetic energy. This model is a development on the standard k-ε
model. A description of this model given in a paper by M Hatami (2014) [5];
RNG k–ε model thermal effect is considered in the enhanced wall treatment panel. Transport equations for
RNG k–ε model in general form are
and
where Gk represents the generation of turbulence kinetic energy due to the mean velocity gradients and Gb
is the generation of turbulence kinetic energy due to buoyancy and C1e=1.42, C2e=1.68 in RNG k–ε model.
In m Hatami’s [2014) [5] paper states that the k-ω SST also known k-omega SST, and k–ε RNG were
found most suitable in analyzing a double pipe heat exchanger, in comparison with experimentally derived
results. Also, quoted that the RNG model was found easier to converge. These statements were found
applicable in this CFD analysis.
The RNG model settings used in this paper were set at default with the exception of the following
selections; Select Enhanced Wall treatment, and then from the Enhanced Wall Treatment Effects, select
Pressure Gradient Effects and Thermal Effects items from the k–ε RNG model menu. These selections
allow the model to address heat transfer and viscous layers at boundary conditions, which are important in
this analysis.
For inlets and outlets boundary conditions, Intensity and Viscosity ratio model was used, with the following
Specification Methods settings;
• Water inlet, 1% turbulence intensity, and 10 for viscosity ratio.
• Water outlet, 10% turbulence intensity, and 10 for viscosity ratio.
• Gas inlet, 1% turbulence intensity, and 10 for viscosity ratio.
• Gas outlet, 10% turbulence intensity, and 10 for viscosity ratio.
AUTHORS
Ali Hasan, MSc Engineering 1993 from Sheffield Hallam University, Sheffield UK. Present employer KEO
Consulting Engineers, Qatar. Working mainly on HVAC, CFD, and Energy efficiency projects. Place of
birth Baghdad, Iraq. Date of birth 03-04-1963.