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Heat transfer to Newtonian and non-Newtonian fluids in cross-corrugated chevron-type plate heat exchangers: numerical approach

Fernandes, Carla S.; Dias, Ricardo P.; Nóbrega, João M.; Maia, João M.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.78%
Food fluids are frequently processed in plate heat exchangers (PHEs) and usually behave as non-Newtonian fluids, this behaviour being scarcely considered for PHEs design purposes. Moreover, many food fluids processed in PHEs have a high viscosity and, therefore, data obtained in laminar flow regime is useful to practical applications. The thermal-hydraulic performance of PHEs is strongly dependent on the physical properties of the fluid and on the geometrical properties of the plates namely, on the corrugation angle and on the channel aspect ratio. The mostly widely used PHEs have corrugations of the chevron type with an area enlargement factor defined as the ratio between the effective plate area and projected plate area close to 1.17. In the present work non-isothermal laminar flows of Newtonian and power-law fluids through cross-corrugated chevron-type plate heat exchangers are studied numerically in terms of the geometry of the channels. The plates area enlargement factor was a typical one (1.17), the corrugation angle varied between 30º and 60º and the flow index behaviour, n, between 0.25 and 1. The numerical calculations were performed using the commercial finite element software package POLYFLOW®. The equations solved were the conservation of mass...

Effect of corrugation angle on the hydrodynamic behaviour of power-law fluids during a flow in plate heat exchangers

Fernandes, Carla S.; Dias, Ricardo P.; Nóbrega, João M.; Maia, João M.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
66.6%
In this study, CFD calculations were made in order to analyze the hydrodynamic behaviour of a power-law fluid in the channels of plate heat exchangers with corrugation angles of 30º and 60º during a non-isothermal flow. For the observed laminar flow, the numerical results show that a typical velocity profile in the 3D channel of the plate heat exchanger with corrugation angle 30º assumes an approximate parabolic shape and that for a corrugation angle of 60º the profile have a irregular core. Simulations considering and discarding the influence of temperature on the non-Newtonian fluid viscosity were performed for the two geometries and the impact of these variations on the relations between fanning friction factors and Reynolds number was analyzed as well as on the ratio between wall and bulk shear rate.

Effect of corrugation angle on the thermal behaviour of power-law fluids during a flow in plate heat exchangers

Fernandes, Carla S.; Dias, Ricardo P.; Nóbrega, João M.; Maia, João M.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
66.68%
In this study, CFD calculations were made in order to analyze the thermal behaviour of a power-law fluid in the channels of plate heat exchangers with corrugation angles of 30º and 60º. For the observed laminar flow, the numerical results show the absence of a typical local temperature profile in the 3D channel. Local Nusselt numbers and transversal variations of viscosity along the plate heat exchangers were studied and simulations considering and discarding the influence of temperature on the non-Newtonian fluid viscosity were performed for the two geometries and the impact of these variations on the thermal correlations was analyzed

Influence of corrugation angle in the stirred yoghurt processing in plate heat exchangers

Fernandes, Carla S.; Afonso, Isabel M.; Melo, Luis F.; Maia, João M.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
66.67%
Research on heat transfer of non-Newtonian fluids during thermal processing is very useful for optimise heat exchanger design, as well as to define quality levels of the final product. In the present study non-isothermal, non-Newtonian flow in plate heat exchangers were simulated numerically, in order to evaluate the influence of corrugation angles on the thermal and hydrodynamics characteristics of yoghurt cooling in a plate heat exchanger. Simulations were carried out using the commercial finite element method package POLYFLOW, being the geometrical domain the representation of a single 3D channel of the plate heat exchanger. Two corrugation angles were considered, 30º and 60º, being the obtained numerical results for the first one compared with experimental data. A laminar flow was observed for the two cases and the decrease of the angle conducted to a decrease of pressure drop and maximum shear rate.

A comparison between heat transfer correlations obtained from experimental data and numerical simulation of flow of stirred yoghurt during cooling in plate heat exchangers

Afonso, Isabel M.; Fernandes, Carla S.; Maia, João M.; Melo, Luis F.
Fonte: Instituto Politécnico de Bragança Publicador: Instituto Politécnico de Bragança
Tipo: Conferência ou Objeto de Conferência
ENG
Relevância na Pesquisa
66.71%
Thermal processing is widely used in the food industry mainly to improve quality and safety of food products. The investigation of heat transfer problems of non-Newtonian fluids during heating and cooling in heat exchangers is of major interest since the main factor limiting heat transfer is the viscous behaviour of these fluids. Therefore, the knowledge of the interface heat transfer coefficients is important in the design of food processes and processing equipment. In the present work, simulations of stirred yoghurt cooling in a plate heat exchanger were performed using computational fluid dynamics (CFD) calculations and the obtained results were compared with experimental data. Simulations were carried out using the commercial finite element method package POLYFLOW, being the geometrical domain the representation of a single 3D channel of the plate heat exchanger with a 30º corrugation angle. The correlation obtained numerically was compared to the one obtained from previous experimental work and they were found to be very similar to the experimental one. The constitutive model, under the assumptions used, was found to be a very good approximation for predicting the convective coefficients of stirred yoghurt during cooling in a plate heat exchanger.

New plates for different types of plate heat exchangers

Fernandes, Carla S.; Dias, Ricardo P.; Maia, João M.
Fonte: Bentham Science Publicador: Bentham Science
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.99%
The first patent for a plate heat exchanger was granted in 1878 to Albretch Dracke, a German inventor. The commercial embodiment of these equipments has become available in 1923. However, the plate heat exchanger development race began in the 1930’s and these gasketed plate and frame heat exchangers were mainly used as pasteurizers (e.g. for milk and beer). Industrial plate heat exchangers were introduced in the 1950’s and initially they were converted dairy models. Brazed plate heat exchangers were developed in the late 1970’s. However, copper brazed units did not start selling until the early 80’s. Nickel brazing came to market around ten years later, since copper presents compatibility problems with some streams (e.g. ammonia). All-welded and semi-welded (laser weld) plate heat exchangers were developed during the 1980’s and early 90’s. Shell and plate heat exchangers were recently introduced in the market and can withstand relatively high pressures and temperatures, as the shell and tube does. The fusion bonded plate heat exchangers (100% stainless steel) are a technology from the 21st century, these equipments being more durable than brazed plate heat exchangers. The plates are the most important elements from the different plate heat exchangers mentioned above. This paper initially introduces the gasketed plate and frame heat exchanger and common chevron-type plates. Resorting to computer fluid dynamics techniques...

Configurações ótimas para trocadores de calor a placas. ; Optimal configurations for plate heat exchangers.

Gut, Jorge Andrey Wilhelms
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 18/06/2003 PT
Relevância na Pesquisa
66.84%
Este trabalho visa a utilização de técnicas de otimização para a determinação da melhor configuração para trocadores de calor a placas. A configuração de um trocador a placas define a distribuição das correntes quente e fria ao longo dos seus canais e ela é definida pelo seu número de canais, pelos números de passes em cada lado e pelas localizações dos fluidos e das conexões de alimentação. É utilizado um conjunto de seis parâmetros para a caracterização da configuração. A modelagem estacionária do trocador é desenvolvida na forma de um algoritmo, já que não é possível representá-la como uma função explícita dos seis parâmetros de configuração. O sistema resultante é composto por equações diferenciais ordinárias de valor de contorno e por equações algébricas não-lineares, o qual é resolvido numericamente pelo método de diferenças finitas. Através do estudo de exemplos de simulação, verifica-se que a hipótese de constância do coeficiente global de troca térmica não é limitante para a avaliação global do trocador. A validação experimental da modelagem estacionária é realizada através da estimação de parâmetros de troca térmica para um conjunto de ensaios com diferentes configurações. É ainda apresentada a modelagem dinâmica do trocador a placas para configurações genéricas...

Eficiência térmica de trocadores de calor compactos através de simulação numérica; Thermal efficiency of compact heat exchangers by numerical simulation

Godoy, Sérgio Machado de
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 06/06/2008 PT
Relevância na Pesquisa
66.71%
Um novo método numérico, para o cálculo da performance térmica de trocadores de calor com fluxos cruzados é apresentado. Dados referentes a efetividade - número de unidades de transferência ('épsilon' - NUT) para vários arranjos de escoamento, padronizados e complexos, foram obtidos usando esta metodologia. Os resultados foram validados através da comparação dos resultados com soluções analíticas conhecidas, para trocadores de calor de fluxos cruzados com um ou múltiplos passes, possuindo de uma até várias fileiras de tubos, e com soluções aproximadas utilizando séries infinitas, para trocadores com ambos os fluidos não misturados. Todos os resultados obtidos apresentaram erros muito pequenos, em relação às soluções analíticas e aproximadas. Dados para efetividade, para arranjos complexos de escoamento são apresentados.; A new numerical methodology for thermal performance calculation in cross-flow heat exchangers is developed. Data related to effectiveness - number of transfer units ('épsilon' - NTU) for several standard and complex flow arrangements are obtained using this methodology. The results are validated through comparison with analytical solutions for one or more pass cross-flow heat exchangers with one to four rows and with approximate series solution for an unmixed-unmixed heat exchanger...

Thermal performance of multipass parallel and counter-cross-flow heat exchangers

Cabezas-Gomez, Luben; Navarro, Helio Aparecido; Saiz-Jabardo, Jose Maria
Fonte: Asme-amer Soc Mechanical Eng Publicador: Asme-amer Soc Mechanical Eng
Tipo: Artigo de Revista Científica Formato: 282-290
ENG
Relevância na Pesquisa
66.75%
A thorough study of the thermal performance of multipass parallel cross-flow and counter-cross-flow heat exchangers has been carried out by applying a new numerical procedure. According to this procedure, the heat exchanger is discretized into small elements following the tube-side fluid circuits. Each element is itself a one-pass mixed-unmixed cross-flow heat exchanger. Simulated results have been validated through comparisons to results from analytical solutions for one- to four-pass, parallel cross-flow and counter-cross-flow arrangements. Very accurate results have been obtained over wide ranges of NTU (number of transfer units) and C* (heat capacity rate ratio) values. New effectiveness data for the aforementioned configurations and a higher number of tube passes is presented along with data for a complex flow configuration proposed elsewhere. The proposed procedure constitutes a useful research tool both for theoretical and experimental studies of cross-flow heat exchangers thermal performance.

A new approach for thermal performance calculation of cross-flow heat exchangers

Navarro, H. A.; Cabezas-Gomez, L.
Fonte: Elsevier B.V. Publicador: Elsevier B.V.
Tipo: Artigo de Revista Científica Formato: 3880-3888
ENG
Relevância na Pesquisa
66.71%
A new numerical methodology for thermal performance calculation in cross-flow heat exchangers is developed. Effectiveness-number of transfer units (epsilon-NTU) data for several standard and complex flow arrangements are obtained using this methodology. The results are validated through comparison with analytical solutions for one-pass cross-flow heat exchangers with one to four rows and with approximate series solution for an unmixed-unmixed heat exchanger, obtaining in all cases very small errors. New effectiveness data for some complex configurations are provided. (c) 2005 Elsevier Ltd. All rights reserved.

Effectiveness-ntu computation with a mathematical model for cross-flow heat exchangers

Navarro, H. A.; Cabezas-Gómez, L. C.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: 509-521
ENG
Relevância na Pesquisa
66.8%
Due to the wide range of design possibilities, simple manufactured, low maintenance and low cost, cross-flow heat exchangers are extensively used in the petroleum, petrochemical, air conditioning, food storage, and others industries. In this paper a mathematical model for cross-flow heat exchangers with complex flow arrangements for determining epsilon -NTU relations is presented. The model is based on the tube element approach, according to which the heat exchanger outlet temperatures are obtained by discretizing the coil along the tube fluid path. In each cross section of the element, tube-side fluid temperature is assumed to be constant because the heat capacity rate ratio C*=Cmin/Cmax tends toward zero in the element. Thus temperature is controlled by effectiveness of a local element corresponding to an evaporator or a condenser-type element. The model is validated through comparison with theoretical algebraic relations for single-pass cross-flow arrangements with one or more rows. Very small relative errors are obtained showing the accuracy of the present model. epsilon -NTU curves for several complex circuit arrangements are presented. The model developed represents a useful research tool for theoretical and experimental studies on heat exchangers performance.

Heat exchangers for cardioplegia systems: In vitro study of four different concepts

Drummond, M.; Novello, W. P.; de Arruda, ACF; Braile, D. M.
Fonte: Blackwell Publishing Publicador: Blackwell Publishing
Tipo: Artigo de Revista Científica Formato: 465-468
ENG
Relevância na Pesquisa
66.75%
The aim of this work is the evaluation of four different heat exchangers used for myocardium during cardioplegic system in cardiac surgeries. Four types of shell and tube heat exchangers made of different exchange elements were constructed, as follows: stainless steel tubes, aluminium tubes, polypropylene hollow fiber, and bellows type. The evaluation was performed by in vitro tests of parameters such as heat transfer, pressure drop, and hemolysis tendency. The result has shown that all four systems tested were able to achieve the heat performance, and to offer low resistance to flow, and safety, as well as have low tendency to hemolysis. However, we can emphasize that the bellows type heat exchanger has a significant difference with regard to the other three types.

Analise numerica do desempenho termico de trocadores de calor de correntes cruzadas; Numerical analysis of thermal performance of crossflow heat exchangers

Cristina Autuori Tomazeti
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 25/07/2006 PT
Relevância na Pesquisa
66.88%
Uma análise foi desenvolvida para avaliar o desempenho de trocadores de calor compactos de correntes cruzadas de placas aletadas com canais de seção transversal arbitrária. Os coeficientes convectivo e de atrito foram obtidos através de simulação numérica, tanto no regime de escoamento laminar quanto no turbulento, utilizando o pacote computacional PHOENICS. Estes resultados foram então usados junto com o método da efetividade para avaliar as características térmicas e de escoamento do trocador de calor. As simulações foram efetuadas inicialmente para o escoamento e a transferência de calor entre duas placas placa paralelas isotérmicas e bastante próximas, porque os resultados podiam ser comparados com aqueles disponíveis na literatura. Resultados numéricos adicionais foram obtidos, em seguida, para seis dutos de paredes isotérmicas com seções transversais distintas. Um deles era um duto retangular, e os outros cinco eram passagens típicas de placas aletadas utilizadas em trocadores de calor compactos. O fluido de trabalho era o ar e as simulações foram tridimensionais devido à presença das paredes das aletas. Perfis uniformes de velocidade e de temperatura sempre foram utilizados na entrada dos dutos, de forma que os resultados refletem os efeitos combinados de entrada hidrodinâmica e térmica. Os resultados para o duto retangular e o método da efetividade foram utilizados para prever o desempenho térmico de um trocador de calor de correntes cruzadas composto por um empilhamento de dutos retangulares idênticos. O desempenho deste trocador de calor foi avaliado também por uma simulação direta do escoamento cruzado e da transferência de calor através da parede de separação de dois dutos retangulares adjacentes do empilhamento. Os resultados obtidos foram bastante semelhantes...

Optimization of baffle configurations to prevent aeroacoustic instabilities in heat exchangers - preliminary experiments

Moreira, Miguel; Antunes, J.; Debut, V.; Pina, H.
Fonte: Repositório Comum de Portugal Publicador: Repositório Comum de Portugal
Tipo: Conferência ou Objeto de Conferência
Publicado em //2008 ENG
Relevância na Pesquisa
66.6%
It is well known that gas heat exchangers are prone to aeroacoustic instabilities, which often lead to severe noise levels, structural vibrations and fatigue. These are unacceptable, as they threaten the component integrity and expose the plant workers to excessive noise levels. Such phenomenon is due to a cooperative interplay between the Karman vortices generated by the cross-flow and the heat exchanger acoustical modes (mainly those transverse to the tube banks). Energy exchanges are then such that, for certain operating velocities, self-excitation of one or more acoustical modes arises. Actually, this problem is solved by placing rigid baffles inside the container, which modify the acoustic modal fields and eventually inhibit the instability. However, an effective location of such baffles is more or less difficult depending on the system complexity and on the range of flow velocities of interest. For realistic industrial components - using a restricted number of acoustical baffles - their optimal location is a challenging problem, as trial and error experimentation is often a costly and frustrating procedure. In this paper we improve a recently proposed strategy for the optimal location of a given number of baffles, in order to inhibit instability of the acoustical modes in a given frequency range. Our approach is based on a stochastic global optimization technique. Some preliminary experiments are also performed and compared with the simulation results.

Effectiveness-ntu computation with a mathematical model for cross-flow heat exchangers

Navarro,H. A.; Cabezas-Gómez,L. C.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2007 EN
Relevância na Pesquisa
66.8%
Due to the wide range of design possibilities, simple manufactured, low maintenance and low cost, cross-flow heat exchangers are extensively used in the petroleum, petrochemical, air conditioning, food storage, and others industries. In this paper a mathematical model for cross-flow heat exchangers with complex flow arrangements for determining epsilon -NTU relations is presented. The model is based on the tube element approach, according to which the heat exchanger outlet temperatures are obtained by discretizing the coil along the tube fluid path. In each cross section of the element, tube-side fluid temperature is assumed to be constant because the heat capacity rate ratio C*=Cmin/Cmax tends toward zero in the element. Thus temperature is controlled by effectiveness of a local element corresponding to an evaporator or a condenser-type element. The model is validated through comparison with theoretical algebraic relations for single-pass cross-flow arrangements with one or more rows. Very small relative errors are obtained showing the accuracy of the present model. epsilon -NTU curves for several complex circuit arrangements are presented. The model developed represents a useful research tool for theoretical and experimental studies on heat exchangers performance.

The effects of turbulence structures on the air-side performance of compact tube-fin heat exchangers.

Allison, Colin Bidden
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2006
Relevância na Pesquisa
66.88%
Energy is an essential and critical commodity and our reliance on it has fuelled much of the debate and interest in society and academia alike. Environmental concerns, depleted energy resources and higher energy prices are the main factors that drive this interest. Energy efficiency is one of the main avenues to preserve and better utilize this valuable commodity. The energy exchange by employment of heat exchangers is extensive and tube-fin heat exchangers are widely used in industrial and commercial applications. Smarter designs could not only improve energy efficiency but may also save on material costs. Although mass production and improved manufacturing techniques have reduced manufacturing costs, tube fin heat exchangers have not evolved greatly to take advantage of these improvements. There has been a large range of fin surface enhancements proposed, such as waffled fins or louvres and while limited improvements in capacity have been achieved, this is generally accomplished at a much larger pressure drop penalty. Numerous studies have been performed in order to examine the potential of various surface enhancement geometries on an ad hoc basis. These presumably operate on the basis of enhanced convection due to increased turbulence levels. However very few of these studies examine the actual nature of turbulence that is responsible for convection enhancement. A series of experiments and numerical studies have been conducted to quantify the effect of the turbulence vortex characteristics on the air side heat convection of a tube-fin heat exchanger. Homogeneous...

On the pressure drop in plate heat exchangers used as desorbers in absorption chillers

García-Hernando, Néstor; Almendros-Ibáñez, José Antonio; Ruiz, G.; Vega, Mercedes de
Fonte: Elsevier Publicador: Elsevier
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article Formato: application/pdf
Publicado em /02/2011 ENG
Relevância na Pesquisa
66.71%
The influence of the pressure drop in Plate Heat Exchangers (PHE) in the boiling temperature of LiBr H₂O and NH₃ H₂O solutions is studied. For the NH₃H₂O solution, the pressure drop-temperature saturation relationship estates that high pressure drops can be allowed in the solution with negligible changes in the saturation temperature, and in the PHE performance. Besides, in the case of the LiBr H₂O solution, as the working pressure is usually very low, the analysis of the pressure drop must be taken as a main limiting parameter for the use of Plate Heat Exchangers as vapour generators. In this case, the pressure drop may considerably change the boiling temperature of the solution entering the heat exchanger and therefore a higher heating fluid temperature may be required. A guideline to design these systems is proposed; This work has been partly supported by the ‘‘Ayuda a grupos” of CAM under the project numbers CCG07 UC3M/AMB 3412 and CCG08 UC3M/AMB 4227

Transient performance of parallel-flow and cross-flow direct transfer type heat exchangers with a step temperature change on the minimum capacity rate fluid stream

Cole, Brian D.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
66.82%
Parallel and cross-flow with both fluids unmixed, direct transfer type heat exchangers are modeled utilizing a thermal network consisting of nodes and resistors. A commercially available software package, Thermonet, calculates the transient outlet temperatures for a steadystate model introduced to a sudden change (step input) in inlet temperature of the Cmin fluid stream. Both models are validated against analytical solutions provided in literature. Solutions are verified to within a maximum percent mean difference of 4 % of analytical solutions for parallel-flow, and 8 % of analytical solutions for cross-flow heat exchangers. Tables are generated which provide new dimensionless transient outlet temperature effectiveness values for parallel and cross-flow with both fluids unmixed, heat exchangers. The parallel-flow temperature responses are presented in graphical form for the specific parameters: NTU equal to 0.5, 1.0, and 3.0; C* equal to 0.2, 0.6, and 1.0; R* equal to 0.5, 1.0, and 2.0; Cw* equal to 1.0, 10.0, and 1000.0; and td equal to 0.25, 1.0, and 4.0. The cross-flow temperature responses are presented in graphical form for the same parameters listed above except NTU is equal to 1.0. Discussion regarding the dimensionless parameters' effects on the transient response of the heat exchanger is provided. The transient performance tables provide a quick reference for transient outlet temperature solutions required for practical industrial heat exchanger analysis.

An Investigation of air side heat transfer enhancement in multi-louver fins within automotive compact heat exchangers

Fix, Patrick
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
66.7%
The multi-louver fin is the primary geometric configuration used to enhance the air-side heat transfer characteristics of automotive heat exchangers today. This work presents an investigation into the effects of multi-louver fins on the air-side Stanton number (St) and Fanning friction factor (f) characteristics of a heat exchanger. Experimental St data ranging between 0.0095 and 0.065 and/ data ranging between 0.04 and 0.55 are reported for louver pitch based Reynolds numbers ranging between 30 and 4000. Brazed core test samples with multi-louver fins are utilized to complete this study. Previous investigators have correlated the air-side St and/ to geometric parameters such as fin height, fin pitch, louver pitch, louver angle and louver length along with flow efficiency and Reynolds number. An example of the range of parameters tested by previous investigators is fin pitch to louver pitch ratio which ranged between 1.65 and 4.1 compared to the range of 2.1 to 5.3 in this work. In general, wider ranges of each parameter than those tested by previous investigators were chosen to produce a more robust correlation. Three new forms of St correlations are derived which can predict heat transfer more accurately than the forms previously derived in the literature. The average percent deviation was improved from -24.37% and +2.10% to +0.59% with the standard deviation of the deviations improved from 1 1.43% and 15.04% to 8.95%. This provided a St correlation which would predict the heat transfer of a heat exchanger to within 3% for 60% of the data or to within 9% for 99% of the data. The correlations of Cowell and Achaichia were modified by the author predict/more accurately than any form examined in this work. The average percent deviation was improved from +12.19% and -23.59% to +0.75% and -0.19% with the standard deviation of the deviations improved from 53.89% to 12.72% for one correlation and maintained around 11 % for the other.

A PROCEDURE FOR TUBE COUNT DETERMINATION IN SINGLE AND MULTIPLE PASS TUBULAR HEAT EXCHANGERS

Medeiros, M. S.; Leiroz, A. J. K.
Fonte: UFPR Publicador: UFPR
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; Peer-reviewed Article Formato: application/pdf
Publicado em 05/07/2006 ENG
Relevância na Pesquisa
66.78%
The development of a simple computational procedure that allows the precise determination of important parameters for the thermal and mechanical design of tubular heat exchangers is discussed in the present work. The design of tubular heat exchangers for a wide variety of applications can involve the use of empirical expressions and data tables for the determination of the tube bundle parameters, such as the tube count and the tube bundle outside diameter. The motivation for developing the discussed procedure resides in addressing cases for which empirical expressions are inapplicable or data table are unavailable. Initially, the shell positions in which tubes can be placed are determined based on specified tube pitch, angle of arrangement, inlet and outlet nozzle diameters and tube bundle-to-shell clearance. The maximum number of tubes for the given configuration is obtained from the tube position searching procedure. A sorting algorithm, based on the tube distance to the shell center, is used to appropriately place a specified number of tubes within the heat exchanger cross section. Results for a single- and multiple-pass fixed-tubesheet heat exchangers are presented and compared with available tube count tables.