CFD Investigation Into the Flow Field in a Four Row Staggered Plate Fin-and-Tube Heat Exchanger Experiencing Gross Fin-Side Flow Maldistribution Using the K-ω Turbulence Model

2009 ◽  
Author(s):  
J. Hoffmann-Vocke ◽  
J. Neale ◽  
M. Walmsley
Keyword(s):  
Heat Exchanger ◽  
Flow Field ◽  
Flow Regime ◽  
Turbulence Model ◽  
Uniform Flow ◽  
Flow Conditions ◽  
Cfd Modelling ◽  
Tube Heat Exchanger ◽  
Flow Maldistribution ◽  
Side Flow

The flow field in a section of a four-row staggered plate fin-and-tube heat exchanger with gross inlet flow maldistribution has been investigated using CFD modelling. The commercial CFD code Fluent 6.3 has been used to carry out 3D unsteady flow modelling using the low Reynolds number variation of the standard k-ω turbulence model. A significant amount of flow dispersion is shown to occur upstream of the heat exchanger inlet resulting in a 37% reduction in inlet velocity before the flow enters the heat exchanger. Flow dispersion as the fluid passes through the heat exchanger results in a further 28% reduction in the average flow velocity. Significant sections of the heat exchanger experience angled flow resulting in a flow pattern commonly seen in inline tube arrangements. The lower friction factor of the inline flow regime results in a higher mass flux when compared to areas exhibiting the staggered flow regime. This variation results in off-centre velocity peaks entering and leaving the heat exchanger. On average the non-uniform flow cases resulted in a 29.4% increase in pressure drop across the heat exchanger system when compared to uniform flow conditions. Average heat transfer coefficients for the non-uniform flow conditions showed a 20.3% increase over uniform flow conditions of equal mass flow.

scholarly journals Optimization and CFD analysis of a shell-and-tube heat exchanger with a multi segmental baffle

2020 ◽  
pp. 293-293
Author(s):  
Ahmet Aydin ◽  
Halit Yaşar ◽  
Tahsin Engin ◽  
Ekrem Büyükkaya
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Heat Exchanger ◽  
Flow Field ◽  
Heat Exchangers ◽  
Operating Cost ◽  
Shell Side ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Side Flow

The Shell-and-tube type heat exchangers have long been widely used in many fields of industry. These types of heat exchangers are generally easy to design, manufacturing and maintenance, but require relatively large spaces to install. Therefore the optimization of such heat exchangers from thermal and economical points of view is of particular interest. In this article, an optimization procedure based on the minimum total cost (initial investment plus operational costs) has been applied. Then the flow analysis of the optimized heat exchanger has been carried out to reveal possible flow field and temperature distribution inside the equipment using computational fluid dynamics. The experimental results were compared with computational fluid dynamics analyses results. It has been concluded that the baffles play an important role in the development of the shell side flow field. This prompted us to investigate new baffle geometries without compromising from the overall thermal performance. It has been found that the heat exchanger with the new baffle design gives rise to considerably lower pressure drops in the shell side, which in turn reducing operating cost. The new baffle design is particularly well suited for shell-and-tube heat exchangers, where a viscous fluid flows through shell side with/out phase change.

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

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

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

Effect of Flow Maldistribution and Viscosity Variations on Transient Response of Plate Heat Exchangers: A Comparison With Uniform Flow and Constant Viscosity Model

Volume 1 ◽  
2004 ◽  
Author(s):  
H. Shokouhmand ◽  
N. Khareghani
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Transient Response ◽  
Heat Exchangers ◽  
Uniform Flow ◽  
Viscosity Model ◽  
Step Response ◽  
Plate Heat ◽  
Constant Viscosity ◽  
Flow Maldistribution

In this paper, transient response of plate heat exchangers under flow maldistribution and viscosity variations is discussed. This transient response is compared with the response achieved from uniform flow and constant viscosity through the exchanger. Flow maldistribution (unequal flow in channels) is calculated for U and Z types of plate heat exchangers. This flow maldistribution along with viscosity variations, during the growth of the temperature profile in each channel, affect the convective heat transfer coefficient in the transient period of heat transfer, and make it to be different from that of the other channels. These conditions make the transient response of a plate heat exchanger to have some deviations from the uniform flow and constant viscosity model response, which is discussed in this paper. The governing equations of heat transfer are solved using finite difference methods. Frequency response as well as step response of the heat exchanger is implemented as a time dependent initial conditions.

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.

CFD Modeling and Analysis of a Shell-and-Tube Heat Exchanger

2008 ◽  
Author(s):  
Ender Ozden ◽  
I˙lker Tarı
Keyword(s):  
Heat Exchanger ◽  
Turbulence Modeling ◽  
Turbulence Models ◽  
Temperature Fields ◽  
Cfd Modeling ◽  
Shell Side ◽  
Cfd Simulations ◽  
Tube Heat Exchanger ◽  
Shell And Tube ◽  
Side Flow

A shell-and-tube heat exchanger is modeled and numerically analyzed using a commercial finite volume CFD package. The heat exchanger is small, has a single shell and a single tube pass, and its shell side is baffled. The baffles are 25% or 36% cut single-segmental baffles. Tube layout is the staggered layout with a triangular pitch. There is no leakage from baffle orifices and no gap between the baffles and the shell. It is observed that the shell side flow and the temperature distributions are very sensitive to modeling choices such as mesh, order of discretization and turbulence modeling. Various turbulence models are tried for the first and second order discretizations using two different mesh densities. CFD predictions of shell side pressure drop and overall heat transfer coefficient are obtained and compared with Kern and Bell-Delaware method results. After selecting the best modeling approach, the sensitivity of the results to flow rates and the baffle spacing is investigated. It is observed that the flow and temperature fields obtained from CFD simulations can provide valuable information about the parts of the heat exchanger design that need improvement. Correlation based approaches may indicate the existence of the weakness but CFD simulations can also pin point the source and the location of it. Using CFD together with experiments may speed up the design process and may improve the final design.

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