Evaluation of a Tapered Header Configuration to Reduce Flow Maldistribution in Minichannels and Microchannels

2009 ◽  
Author(s):  
V. V. Dharaiya ◽  
A. Radhakrishnan ◽  
S. G. Kandlikar
Keyword(s):  
Heat Exchanger ◽  
Pressure Difference ◽  
Flow Distribution ◽  
Cross Sectional ◽  
Pressure Distributions ◽  
Actual Flow Rate ◽  
Actual Flow ◽  
Velocity Changes ◽  
Parallel Microchannels ◽  
Flow Maldistribution

In designing a heat exchanger, it is generally assumed that the fluid is uniformly distributed through the heat exchanger core. In reality, the flow distribution is rarely uniform due to inlet and outlet header designs and flow velocity changes in the headers. The flow distribution through a plate-fin heat exchanger (straight Z-type flow) with parallel microchannels and minichannels is studied by using a Computational Fluid Dynamics (CFD) code FLUENT. It was found that the flow maldistribution is quite severe with constant cross-sectional area headers. A modified header design with tapered cross-section was employed and the flow and pressure distributions were investigated using the CFD model. Further, a mathematical model was used to study the effect of the tapered headers on the pressure difference available for each channel across its inlet and outlet ends. The pressure difference across each channel is responsible for the actual flow rate through the channel. Results from the CFD were compared with the model predictions.

Numerical simulation of flow distribution in the header of plate-fin heat exchanger

2020 ◽  
Vol 34 (14n16) ◽  
pp. 2040111
Author(s):  
Shu-Ling Tian ◽  
Ying-Ying Shen ◽  
Yao Li ◽  
Hai-Bo Wang ◽  
Sheryar Muhammad ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Heat Exchangers ◽  
Optimization Design ◽  
High Efficiency ◽  
Flow Distribution ◽  
Optimal Number ◽  
Compact Structure ◽  
Flow Maldistribution

Plate-fin heat exchangers are widely used in industry at present due to their compact structure and high efficiency. However, there is a problem of flow maldistribution, resulting in poor performance of heat exchangers. The influence of the header configuration on fluid flow distribution is studied by using CFD software FLUENT. The numerical results show that the fluid flow inside the header is seriously uneven. The reliability of the numerical simulation is validated against the published results. They are found to be basically consistent within considerable error. The optimal number of the punch baffle is investigated. Various header configuration with different opening ratios have been studied under the same boundary conditions. The gross flow maldistribution parameter (S) is used to evaluate flow nonuniformity, and the flow maldistribution parameters of different schemes under different Reynolds numbers are listed and compared. The optimal header with minimum flow maldistribution parameter is obtained through the performance analysis of headers. It is found that the flow maldistribution of the improved header is significantly smaller compared with the conventional header. Hence, the efficiency of the heat exchanger is effectively enhanced. The conclusion provides a reference for the optimization design of plate-fin heat exchanger.

Minimising Loss in a Heat Exchanger Installation for an Intercooled Turbofan Engine

2011 ◽  
Author(s):  
Pok-Wang Kwan ◽  
David R. H. Gillespie ◽  
Rory D. Stieger ◽  
Andrew M. Rolt
Keyword(s):  
Heat Exchanger ◽  
Cfd Simulation ◽  
Flow Distribution ◽  
Design Guidelines ◽  
Turbofan Engine ◽  
Aerodynamic Loss ◽  
Pressure Distributions ◽  
Cold Fluid ◽  
Core Concepts ◽  
Computational Fluid Dynamics Cfd

An intercooled turbofan engine has been proposed within NEWAC (New Aero Engine Core Concepts, an European Sixth Framework Programme) using lightweight heat exchangers. The requirement for compactness has led to the need for zigzag heat exchanger arrangement where the heat exchanger matrices are inclined to the cooling flows approaching them, but such an arrangement creates non-uniform mass flows through the cold fluid side intercooler ducting and the intercooler heat exchanger matrices. Design guidelines aimed at minimizing aerodynamic losses caused by the flow mal-distribution in such ducting is reported. Minimising the loss has the effect of optimising the heat transfer performance. Flow velocities and pressure distributions were measured experimentally in a simplified model of a heat exchanger and simulated in Computational Fluid Dynamics (CFD). Good agreement was found between measurement and predictions of the flow distribution in the cold fluid side intercooler ducting downstream of the heat exchanger matrices. A dominant jetting flow in the centre of each exit passage was identified as a source of aerodynamic loss. The CFD simulation has also shown that the main source of aerodynamic loss arises from the severe flow mal-distribution within the heat exchanger matrices. From these results, design guidelines are presented in this paper for the ducting, based on CFD studies on a series of simplified heat exchanger arrangement geometries.

Effect of Non Uniform Flow Distribution on Single Phase Heat Transfer in Parallel Microchannels

2007 ◽  
Author(s):  
Akhilesh V. Bapat ◽  
Satish G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Single Phase ◽  
Flow Distribution ◽  
Uniform Flow ◽  
Hydrodynamic Performance ◽  
Flow Area ◽  
Cross Sectional ◽  
Uniform Flow Distribution ◽  
Parallel Microchannels

The continuum assumption has been widely accepted for single phase liquid flows in microchannels. There are however a number of publications which indicate considerable deviation in thermal and hydrodynamic performance during laminar flow in microchannels. In the present work, experiments have been performed on six parallel microchannels with varying cross-sectional dimensions. A careful assessment of friction factor and heat transfer in is carried out by properly accounting for flow area variations and the accompanying non-uniform flow distribution in individual channels. These factors seem to be responsible for the discrepancy in predicting friction factor and heat transfer using conventional theory.

A Numerical Study of Flow and Temperature Maldistribution in a Parallel Microchannel System for Heat Removal in Microelectronic Devices

2012 ◽  
Author(s):  
Manoj Siva ◽  
Arvind Pattamatta ◽  
Sarit Kumar Das
Keyword(s):  
Heat Exchanger ◽  
Cross Section ◽  
Design Theory ◽  
Cooling System ◽  
Search Algorithm ◽  
Numerical Study ◽  
Heat Removal ◽  
Flow Distribution ◽  
Microchannel Cooling ◽  
Flow Maldistribution

A common assumption in basic heat exchanger design theory is that fluid is distributed uniformly at the inlet of the exchanger on each fluid side and throughout the core. However in reality, uniform flow distribution is never achieved in a heat exchanger and is referred to as flow maldistribution. Flow maldistribution is generally well understood for the macrochannel system. But it is still unclear whether the assumptions underlying the flow distribution in conventional macrochannel heat exchangers hold good for microchannel system. In this regard, extensive numerical simulations are carried out in a ‘U’ type parallel micro-channel system in order to study flow and heat transfer maldistribution and validated with in-house experimental data. A detailed parametric analysis is carried out to characterize flow maldistribution in a microchannel system and to study the effect of geometrical factors such as number of channels, n, Area of cross section of the channel Ac, manifold cross section area Ap, and flow parameter such as Reynolds number, Re, on the pressure and temperature distribution. In order to minimize the variation in pressure and to reduce temperature hot spots in the microchannel, a Response surface based surrogate approximation (RSA) and a gradient based search algorithm are used to arrive at the best configuration of microchannel cooling system. A three level factorial design involving three parameters namely Ac/Ap, Re, n are considered. The results from the optimization indicate that the case of n = 5, Ac/Ap = 0.12, and Re = 100 is the best possible configuration to alleviate flow maldistribution and hotspot formation in microchannel cooling system.

Steam Condensation in Parallel Channels of Plate Heat Exchangers

2010 ◽  
Author(s):  
Prabhakara Rao Bobbili ◽  
Bengt Sunden
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Flow Distribution ◽  
Small Degree ◽  
Flow Conditions ◽  
Steam Condensation ◽  
Cooling Fluid ◽  
Plate Heat ◽  
Parallel Channels ◽  
Flow Maldistribution

An experimental investigation has been carried out to find the nature of temperature profiles of the process and cooling fluids during steam condensation across the port to channel in plate heat exchangers (PHEs). In the present study, low corrugation angle (30°) plates have been used for different plate package of PHEs with 41 and 81 plates. The process steam entered at 1 bar with a small degree of superheat. Water has been used as the cold fluid. A traverse temperature probe is inserted into both inlet and outlet ports of the plate heat exchanger. The temperature of the process steam and cooling fluid have been measured and recorded at the location of first, middle and last channels for different inlet and exit flow conditions for each plate package of the heat exchanger. Also, the overall pressure drop has been measured at different conditions at the outlet of the process steam, i.e., full and partial condensation. The traverse temperature measurements have indicated that there is a considerable variation in temperature along inlets and outlets of process steam and cooling fluid, due to flow maldistribution. The experimental data has been analyzed to show how the flow distribution on the cooling side affects the condensation of steam in plate heat exchangers. The present results will help to study further the nature of steam condensation in parallel channels of heat exchangers.

A Numerical Study of Flow and Temperature Maldistribution in a Parallel Microchannel System for Heat Removal in Microelectronic Devices

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
V. Manoj Siva ◽  
Arvind Pattamatta ◽  
Sarit Kumar Das
Keyword(s):  
Heat Exchanger ◽  
Cross Section ◽  
Design Theory ◽  
Cooling System ◽  
Search Algorithm ◽  
Numerical Study ◽  
Heat Removal ◽  
Flow Distribution ◽  
Microchannel Cooling ◽  
Flow Maldistribution

A common assumption in basic heat exchanger design theory is that fluid is distributed uniformly at the inlet of the exchanger on each fluid side and throughout the core. However, in reality, uniform flow distribution is never achieved in a heat exchanger and is referred to as flow maldistribution. Flow maldistribution is generally well understood for the macrochannel system. But it is still unclear whether the assumptions underlying the flow distribution in conventional macrochannel heat exchangers hold good for microchannel system. In this regard, extensive numerical simulations are carried out in a “U” type parallel microchannel system in order to study flow and heat transfer maldistribution and validated with in-house experimental data. A detailed parametric analysis is carried out to characterize flow maldistribution in a microchannel system and to study the effect of geometrical factors such as number of channels, n, Area of cross section of the channel Ac, manifold cross section area Ap, and flow parameter such as Reynolds number, Re, on the pressure and temperature distribution. In order to minimize the variation in pressure and to reduce temperature hot spots in the microchannel, a response surface based surrogate approximation and a gradient based search algorithm are used to arrive at the best configuration of microchannel cooling system. A three level factorial design involving three parameters namely Ac/Ap, Re, n are considered. The results from the optimization indicate that the case of n = 7, Ac/Ap = 0.69, and Re = 100 is the best possible configuration to alleviate flow maldistribution and hotspot formation in microchannel cooling system.

Flow Maldistribution in a Simplified Plate Heat Exchanger Model - A Numerical Study

2011 ◽  
Vol 110-116 ◽  
pp. 2529-2536 ◽  
Author(s):  
Nityanand Pawar ◽  
R.S. Maurya
Keyword(s):  
Heat Exchanger ◽  
Uniform Distribution ◽  
Numerical Study ◽  
Flow Distribution ◽  
Plate Heat Exchanger ◽  
Design Parameters ◽  
Process Equipment ◽  
Numerical Work ◽  
Plate Heat ◽  
Flow Maldistribution

The performance of a plate heat exchanger (PHE) is severely influenced by non-uniform distribution of flow among its channels. Not only the PHEs, but many other process equipment needs uniform flow distribution for their optimum performance. Flow maldistribution (non-uniform distribution) is a common design problem which always puzzles process equipment designers. Being important design parameters, it has been investigated by several researchers and case based solution has been proposed and documented. Present numerical work is intended to target this aspect of the problem of PHEs but starts with a general investigation with simple multichannel geometry. The numerical setup consists of two headers having multiple channels for U-and Z-turn flow configuration under multichannel geometry and a simplified PHE for plate heat exchanger simulation. The problem has been investigated from hydrodynamic and thermodynamic view point. For hydrodynamic study, flow has been varied for Reynolds number 120 to 17600. It has been found that channel flow goes on reducing along downstream side. In thermal study the effect of wall temperature on air flow mal distribution has been investigated. Numerical results have been validated with the experimental results. Investigation reveals new features of flow mal-distribution which is helpful in better understanding of associated mal-distribution physics.

CFD Simulation on Flow Distribution in Plate-Fin Heat Exchangers

2013 ◽  
Vol 655-657 ◽  
pp. 445-448
Author(s):  
Zhe Zhang ◽  
Jin Jin Tian ◽  
Yong Gang Guo
Keyword(s):  
Fluid Flow ◽  
Heat Exchanger ◽  
Cfd Simulation ◽  
Perforated Plate ◽  
Flow Distribution ◽  
Numerical Results ◽  
Flow Maldistribution ◽  
The Mathematical Model ◽  
First Time ◽  
Flow Nonuniformity

The influences of the conventional header configuration used in industry at present on the fluid flow distribution in plate-fin heat exchanger were numerically investigated. The numerical results showed that the fluid flow maldistribution is very serious in the heat exchanger. The header configuration with perforated plate was brought forward for the first time. The computational results indicated that the improved header configuration can effectively improve the performance of fluid flow distribution in the heat exchanger. The fluid flow distribution for the header configuration with curving perforated plate is more uniform than for the header configuration with plane perforated plate. The absolute degree of fluid flow nonuniformity in plate-fin heat exchanger has reduced from 3.47 to 0.32 by changing the header configuration. The numerical results are compared with the experimental results. They are basically consistent which indicates that the mathematical model and the calculating method are reliable.

Flow Distribution on the Tube Side of a High Temperature Heat Exchanger and Chemical Decomposer

2007 ◽  
Author(s):  
Gayatri Kuchi ◽  
Valery Ponyavin ◽  
Yitung Chen ◽  
Steven Sherman ◽  
Anthony E. Hechanova
Keyword(s):  
High Temperature ◽  
Heat Exchanger ◽  
Flow Distribution ◽  
Straight Tube ◽  
Baffle Plate ◽  
Pumping Power ◽  
Tube Heat Exchanger ◽  
Temperature Heat ◽  
Shell And Tube ◽  
Flow Maldistribution

Numerical simulations of a high temperature shell and tube heat exchanger and chemical decomposer (thereafter — heat exchanger) with straight tube configuration have been performed using Fluent 6.2.16 code to examine flow distribution on the tube side. The heat exchanger can be a part of sulfur iodine thermochemical water splitting cycle which is one of the most studied cycles for hydrogen production. Uniformity of the flow distribution in the heat exchanger is very critical because the flow maldistribution among the tube or shell sides can result in decreasing of chemical decomposition and increasing of pumping power. In the current study the flow rate uniformity in the heat exchanger tubes has been investigated. Simulations of the straight tube configuration, tube configuration with baffle plate arrangement and with pebble bed region inside the tubes were performed to examine flow distribution on the tube side. It was found the flow maldistribution along the tube direction is very serious with the simple tube configuration. An improvement of the header configuration has been done by introducing a baffle plate in to the header section. With the introduction of the baffle plate, there was a noticeable decrease in the flow maldistribution in the tubes. Uniformity of flow was also investigated with catalytic bed inside the tubes. A significant decrease in flow maldistribution was observed with this arrangement. But if the catalytic bed zone is created on the shell side, then the improved header configuration with a baffle plate is best suitable to avoid flow maldistribution.

Comparative CFD Analysis of Maldistribution in a Shell and Tube Heat Exchanger With Conical and Cylindrical Headers

2010 ◽  
Author(s):  
Rohitha Paruchuri ◽  
T. S. Ravigururajan ◽  
Arun Muley
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Heat Transfer Performance ◽  
Static Pressure ◽  
Flow Distribution ◽  
Transfer Performance ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Improved Performance ◽  
Flow Maldistribution

The analysis of flow maldistribution in a shell and tube heat exchanger is presented. The flow field within the headers was obtained through numerical solution of conservation equations of mass and momentum in addition to the equations of the turbulence model. The flow maldistribution inside the header was a 3-D numerical simulation with the help of commercial software To increase the performance of the heat exchanger, flow maldistribution among the tubes should be minimized.. Flow maldistribution in the header affects the heat transfer performance. The effects of the pressure drop and velocity distribution in the headers were analyzed, as it effects the heat transfer performance. The study showed that by changing the header geometry, the maldistribution can be reduced leading to improved performance. Two types of headers were considered with varying header length and inlet flow velocities from 0.8373mm/sec to 2.344mm/sec are considered. The uniformity of flow distribution improved with increasing header length, whereas it decreased with increasing flow rate. As the header length increased to 1500mm the flow maldistribution decreased and the static pressure was almost equal for all the tubes in case of a conical header. The results show that conical header minimizes flow maldistribution compared to a cylindrical header.

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