A Transient Model for Parallel Flow and Counter Flow Heat Exchangers

2013 ◽  
Author(s):  
K. Abbasi ◽  
M. Del Valle ◽  
A. P. Wemhoff ◽  
A. Ortega
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Transient Behavior ◽  
Parallel Flow ◽  
Thermal Mass ◽  
Dimensionless Time ◽  
Internal Wall ◽  
Counter Flow ◽  
Thermal Capacitance ◽  
Flow Heat

The transient and steady-state response of single pass constant-flow (concentric parallel flow, concentric counter flow) heat exchangers was investigated using a finite volume method. Heat exchanger transients initiated by both step-change and sinusoidally varying hot stream inlet temperatures were investigated. The wall separating the fluid streams was modeled by conduction with thermal mass; hence the heat exchanger transient behavior is dependent on the thermal mass of the fluid streams as well as the internal wall. The outer wall is approximated as fully insulating. The time dependent temperature profiles were investigated as a function of heat exchanger dimensionless length and dimensionless time for both fluids. It was found that the transient response of the heat exchanger is controlled by a combination of the residence time and thermal capacitance of the fluid streams, the overall heat transfer coefficient between the fluid streams, and the thermal capacitance of the internal wall.

Effectiveness-NTU Relations for Heat Exchangers With Streams Having Significant Kinetic Energy Variation

2003 ◽  
Vol 125 (2) ◽  
pp. 377-387 ◽  
Author(s):  
Gregory F. Nellis
Keyword(s):  
Heat Exchanger ◽  
Kinetic Energy ◽  
Differential Equations ◽  
Heat Exchangers ◽  
Parallel Flow ◽  
Temperature Profiles ◽  
Cryogenic Temperatures ◽  
Cold Side ◽  
Counter Flow ◽  
Flow Heat

Effectiveness-NTU equations are derived for counter and parallel-flow heat exchangers with fluids having high velocities. In this case, the change in the kinetic energy occurring within the heat exchanger will significantly affect the temperature profiles. The effectiveness is found to depend on the usual non-dimensional variables that compare the heat exchanger conductance to the hot- and cold-side capacity rates and on four additional nondimensional quantities that reflect the magnitude and distribution of the kinetic energy on the hot and cold-sides of the heat exchanger. The governing differential equations are derived, nondimensionalized, and solved analytically for the case of an exponentially distributed kinetic energy. Graphical solutions are presented and interpreted for several cases. The solutions are applied to a particular case involving high velocities within a counter-flow heat exchanger used to produce cryogenic temperatures.

Analytical Study of Nonstationary Modes in Recuperative Heat Exchangers

2020 ◽  
pp. 60-71
Author(s):  
A.A. Aleksandrov ◽  
V.A. Akatev ◽  
M.P. Tyurin ◽  
E.S. Borodina ◽  
O.I. Sedlyarov
Keyword(s):  
Heat Exchanger ◽  
Stationary State ◽  
Heat Carrier ◽  
Heat Exchangers ◽  
Stationary Mode ◽  
Dimensionless Time ◽  
Counter Flow ◽  
Direct Flow ◽  
Output Section ◽  
Flow Heat

Recuperative heat exchanger transient operation modes during the start-up were considered in order to identify the time for establishing the stationary mode. This is important in carrying out technological processes that require constancy in values of certain parameters ensuring both product quality and process safety. The research was carried out using the analytical method for direct-flow and counter-flow heat exchangers. It was demonstrated that stationary state establishment in the direct-flow heat exchangers occurs immediately after the heat carrier gets into the apparatus. It should be noted that the entire apparatus reaches the stationary mode, when the slower heat carrier arrives at the apparatus output section. In case of a heat exchanger with the heat carrier counter-flow, it was found out that at the moment of the less heated heat carrier appearing at the apparatus output section, it was having the highest temperature. Then the temperature was decreasing, and after passing its minimum was beginning to oscillate along a curve with the damping amplitude. In the case under consideration, the stationary process started, when the dimensionless time value was ϕ ≥ 0.5. The indicated solution was obtained under assumption that thermal and physical characteristics were constant in time and space. It was assumed that total heat capacity of the heat exchanger heat transferring wall was infinitesimal. This assumption is valid with an error of up to 1 % at Fo ≥ 100, which is the case in most practical cases. For apparatuses under study, a formula was also obtained for the time required to reach the stationary state

A Mathematical Confirmation for Higher LMTD Value of Counter Flow Versus Parallel Flow Heat Exchangers

2003 ◽  
Vol 125 (1) ◽  
pp. 182-184 ◽  
Author(s):  
Farshad Kowsary ◽  
Mohammad Biglarbegian
Keyword(s):  
Heat Exchangers ◽  
Parallel Flow ◽  
Counter Flow ◽  
Flow Heat ◽  
Increasing Function

A rigorous argument based on the characteristic of a monotonously increasing function is presented to establish the well-known fact of higher LMTD value of counter flow heat exchangers as compared to parallel flow ones.

Modeling of Recuperative Heat Exchanger in a Joule-Thomson Cooler

2001 ◽  
Author(s):  
Kim Choon Ng ◽  
Jinbao Wang ◽  
Hong Xue
Keyword(s):  
Heat Conduction ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cooling System ◽  
Experimental Measurements ◽  
Temperature Dependent ◽  
Counter Flow ◽  
Flow Heat ◽  
Temperature Dependent Properties ◽  
Recuperative Heat Exchanger

Abstract To develop effective heat exchangers for miniature and micro Joule-Thomson (J-T) cooling system, the performance of a recuperative heat exchanger is analyzed and evaluated. The evaluation is based on a theoretical model of the Hampson-type counter-flow heat exchanger. The effect of the pressure and temperature-dependent properties and longitudinal heat conduction are considered. The results of the numerical simulation are validated with the corresponding experimental measurements. The performance of the heat exchanger on effectiveness, flow and various heat conduction losses as well as liquefied yield fraction are analyzed and discussed. The simulation model provides a useful tool for miniature J-T cooler design.

scholarly journals Kaji efisiensi temperatur penukar panas dengan variasi aliran untuk aplikasi pengering

2018 ◽  
Vol 16 (2) ◽  
pp. 39
Author(s):  
Syukran Syukran
Keyword(s):  
Fluid Flow ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Cross Flow ◽  
Fluid Phase ◽  
Parallel Flow ◽  
Small Scale ◽  
Counter Flow ◽  
Flow Type ◽  
Temperature Efficiency

Abstrak Heat exchanger atau alat penukar panas adalah alat-alat yang digunakan untuk mengubah temperatur fluida atau mengubah fasa fluida dengan cara mempertukarkan panasnya dengan fluida lain. Pada sebuah penukar panas kemampuan mempertukarkan panas sangat ditentukan oleh tipe dan jenis aliran fluida yang melewati penukar panas. Secara garis besar penukar panas dibagi berdasarkan arah aliran fluidanya. Berdasarkan arah aliran fluida penukar panas  dibedakan menjadi 3 (tiga) jenis aliran, yaitu aliran searah (parallel flow), aliran berlawanan (counter flow) dan aliran silang (cross flow). Saat ini penukar panas banyak dipakai dalam  industri pengeringan produk-produk pertanian, perkebunan dan perikanan skala kecil dan menengah. Penggunaan penukar panas dalam bidang pengeringan saat ini sudah menjadi kebutuhan untuk mengatasi permasalahan produktifitas pengeringan. Umumnya penukar panas yang digunakan adalah tipe aliran berlawanan. Beberapa penelitian telah dilakukan untuk mengetahui efektifitas penukar panas tersebut yang umumnya berfokus pada jenis aliran berlawanan. Penelitian penelitian spesifik yang mengkaji perbandingan efisiensi penukar panas  untuk ketiga jenis aliran belum ditemukan. Penelitian ini dilakukan untuk mengetahui efisiensi temperatur penukar panas untuk jenis aliran jenis aliran melintang, sejajar, dan  berlawanan. Metode penelitian dilakukan fabrikasi 3 unit exchanger tipe gas-gas dengan dimensi 50 (P) x 10 (L) x 30 (T) dengan jumlah tube 17 susunan. Hasil  penelitian menunjukkan bahwa efisiensi temperatur untuk ketiga jenis penukar panas tersebut adalah 21,3% aliran melintang, 17,3% aliran berlawanan dan 15,9%  aliran sejajar. Hasil penelitian menyimpulkan bahwa efisiensi temperatur tertinggi diperoleh jenis penukar panas aliran melintang. Kata kunci : Penukar panas, aliran sejajar, aliran berlawanan, aliran silang, temperatur.  Abstrack Heat exchangers or heat exchangers are the means used to change the temperature of the fluid or to change the fluid phase by exchanging heat with other fluids. In a heat exchanger the heat exchange ability is greatly determined by the type and type of fluid flow passing through the heat exchanger. Broadly speaking the exchanger is divided based on the direction of fluid flow. Based on the direction of fluid flow exchanger is divided into 3 (three) types of flow, namely parallel flow, counter flow and cross flow. Currently, heat exchangers are widely used in the drying industry of small and medium-sized agricultural and small-scale plantation and fishery products. The use of exchangers in the field of drying is now a need to overcome the problems of drying productivity. Generally the exchanger used is the opposite flow type (counter flow). Several studies have been conducted to determine the effectiveness of these exchangers which generally focus on the opposite type of flow. Specific research studies that reviewed the efficiency of exchangers for the three types of flow have not been found. This research was conducted to find out the efficiency of heat exchanger temperature for flow type of cross flow, parallel flow and counter flow type. The research method was fabricated 3 units of gas-gas exchanger type with dimension 50 (P) x 10 (L) x 30 (T) with the number of tubes 17 staggered arrangement. The results show that the temperature efficiency for the three types of heat exchanger is 21.3% cross flow flow, 17.3% flow counter flow and 15.9% parallel flow flow. The results concluded that the highest temperature efficiency obtained by cross flow flow type exchanger. Keywords: Heat exchanger, parallel flow, counter flow, cross flow, temperature

scholarly journals Optimization procedure of a new type counter–flow heat exchanger

2021 ◽  
Vol 2116 (1) ◽  
pp. 012093
Author(s):  
R Karvinen
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Optimization Procedure ◽  
Multi Objective Optimization ◽  
Counter Flow ◽  
Overall Heat Transfer Coefficient ◽  
Different Types ◽  
New Type ◽  
Flow Heat

Abstract Plenty of studies exist in books and archival journals dealing with different types of heat exchangers. In the paper an analytical approach to evaluate the overall heat transfer coefficient of a new type heat exchanger is presented. Derived equations are applied to multi-objective optimization of a very large economizer of a recovery boiler, when the exchanger mass and size should be small but simultaneously heat transfer rate high.

A Constant-Wall-Temperature Model for Prediction of Thermal Performance of Gas-to-Gas Counter-Flow and Parallel-Flow Microchannel Heat Exchangers

2011 ◽  
Author(s):  
Kohei Koyama
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Difference Method ◽  
Heat Exchangers ◽  
Parallel Flow ◽  
Counter Flow ◽  
Partition Wall ◽  
Transfer Rates ◽  
Flow Configuration ◽  
Microchannel Heat Exchanger

Thermal performances of gas-to-gas counter-flow and parallel-flow microchannel heat exchanger have been investigated. Working fluid used is air. Heat transfer rates of both heat exchangers are compared with those calculated by a conventional log-mean temperature difference method. The results show that the log-mean temperature difference method can be employed to a parallel-flow configuration whereas that cannot be employed to a counter-flow configuration. This study focuses on the partition wall which separates hot and cold passages of the microchannel heat exchanger. The partition wall is negligibly thin for a conventional-sized heat exchanger. In contrast, the partition wall is thick compared with channel dimensions for a microchannel heat exchanger. A model which includes the effect of the thick partition wall is proposed to predict thermal performances of the microchannel heat exchangers. The heat transfer rates obtained by the model agree well with those obtained by the experiments. Thermal performances of the counter-flow and parallel-flow microchannel heat exchangers are compared with respect to one another based on temperature of the partition wall. The comparison results show that thermal performances of the counter-flow and parallel-flow microchannel heat exchangers are identical. This is due to performance degradation induced by the thick partition wall of the counter-flow microchannel heat exchanger. This study reveals that the thick partition wall dominates thermal performance of a gas-to-gas microchannel heat exchanger.

Differential Methods for the Performance Prediction of Multistream Plate-Fin Heat Exchangers

1992 ◽  
Vol 114 (1) ◽  
pp. 41-49 ◽  
Author(s):  
B. S. V. Prasad ◽  
S. M. K. A. Gurukul
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Performance Prediction ◽  
Heat Exchangers ◽  
Loss Functions ◽  
Computer Algorithms ◽  
Counter Flow ◽  
Flow Heat ◽  
Differential Methods ◽  
Section Level

Use of traditional methods of rating can prove inaccurate or inadequate for many plate-fin heat exchanger applications. The superiority in practical situations of differential methods, based on dividing the heat exchanger into several sections and a step-wise integration of the heat transfer and pressure loss functions, is discussed. Differential methods are developed for counterflow, crossflow, and cross-counter-flow heat exchangers. The methods developed also avoid iterations at the section level calculations. Design of computer algorithms based on these methods is outlined. Two computer programs developed using the methods are presented and the results for a few typical cases are discussed.

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