Optimizing Thermal Behavior of Flat Plate Heat Exchanger Tube by Varying Geometrical Configuration

A plate fin heat exchanger is a type of heat exchanger design that uses plates and finned chambers to transfer heat between liquids. It is often classified as a compact heat exchanger to emphasize the relatively high ratio between the heat transfer surface and the volume. The main objective of the present work is to investigation of optimum design of plate fin tube heat exchanger using Computational fluid dynamic approach and maximizing thermal performance. There are total five designs of plate fin and tube heat exchanger are used in present work and CFD analysis have been performed in it to get maximum heat transfer. It has been observed from CFD analysis that the maximum heat transfer can be achieved from plate fin and tube heat exchanger with elliptical tube arrangement inclined at 30o with 23.22% more heat transfer capacity as compared to circular tube plate pin heat exchanger. So that it is recommended that if the plate fins and tube heat exchanger with inclined elliptical tube used in place of circular tube arrangement, batter heat transfer can be achieved.


I. INTRODUCTION
A plate fin heat exchanger is a type of heat exchanger design that uses plates and finned chambers to transfer heat between liquids. It is often classified as a compact heat exchanger to emphasize the relatively high ratio between the heat transfer surface and the volume. The plate fin heat exchanger is widely used in many sectors, including the aerospace one, due to its compact size and light properties, as well as cryotechnics, where its ability to facilitate the transfer of heat is used with small differences in temperature [1]. Plate heat exchangers in finned aluminum alloy, often called welded aluminum heat exchangers, have been used in the aviation industry for over 60 years and have been adopted in the cryogenic separation sector. Air in chemical plants such as the processing of natural gas during the Second World War and immediately afterwards. They are also used in railway engines and motor vehicles. The stainless steel fins have been used in aircraft for 30 years and are currently being established in chemical plants. Plate fin-and-tube heat exchangers are used extensively in heating, ventilating, and air conditioning (HVAC), process engineering, and refrigeration applications such as compressor intercoolers, fan coils, and air-coolers. The governing thermal resistance for heat exchangers is typically located on the air side, accounting for 85% or more of the total resistance in practical applications.

II. LITERATURE REVIEW
BasimFreegah et al. [1] The study showed that finned heat sinks with corrugated vertical semicircular pins exposed to parallel flow and finned heat sinks with symmetrical hollow semicircular pins in a vertical arrangement that are exposed to vertical flow the impact has superior thermal performance compared to other configurations. The old design offers a base temperature and thermal resistance reduction of approximately 25.1% and 29%, respectively, and an increase in the Nusselt number of approximately 34.48% instead of the ribs of the conventional profile plate threaded. For the latter project, the base temperature and thermal resistance were reduced by approximately 22.6% and 25.7% respectively, while the Nusselt number shows values increasing by approximately 31.6%. hang-Hyo Son et al. [2] the single-phase convection heat transfer coefficients were calculated in this work using the modified Wilson diagram method and the pressure drop relative to other correlations. The main results are summarized as follows. The pressure drop corresponds well to the previous correlation, but the convection heat transfer coefficients differ from the others. Based on the experimental results, a new correlation of the single-phase heat transfer for the plate fin heat exchanger is presented. Máté PETRIK et al. [3] the aim of this work is to perform parametric analysis of the thermal power of a compact car cooler using computer-assisted fluid dynamics. The results show that the relationship between the pitch of the slats, the thickness of the walls of the slats, the number of slats, the depth of flow and the geometry of the tube are the main factors of heat transfer. The main goal is to find a reliable correlation of the Nu number for this type of heat exchanger. Also, when using this feature, the goal is to find the optimal shape of the chiller, which can lower the coolant temperature to the required value and have the lightest weight.
Abhishek Tiwari et al. [4] In the field of cryogenics, heat exchangers with a maximum efficiency of the order of 0.96 or more are used to maintain the low temperature effect generated. The compact heat exchanger (CHE) is modified by cross-flow channels between a small volume and a high rate of energy exchange between two liquids. The thermo-hydraulic performance of the compact heat exchangers (CHE) strongly depends on the Colburn fins 'j' and Fanning factor 'f', the triangular and rectangular perforated fins.

III. OBJECTIVES
Where x is the axial coordinate, r is the radial coordinate, is the axial velocity, and is the radial velocity.

Momentum Conservation Equations
Conservation of momentum in an inertial reference frame is described by Where p= static pressure ̿ = stress tensor, ⃗ = gravitational body force and ⃗ = external body forces The stress tensor ̿ is given by where = molecular viscosity I = unit tensor, For 2D axisymmetric geometries, the axial and radial momentum conservation equations are given by

Where
= ℎ for an incompressible phase and ℎ = sensible enthalpy for phase k −∈ : The turbulence kinetic energy, k, and its rate of dissipation, ∈, are obtained from the following transport equations: In these equations, represents the generation of turbulence kinetic energy due to the mean velocity gradients, is the generation of turbulence kinetic energy due to buoyancy, represents the contribution of the fluctuating dilatation in compressible turbulence to the overall dissipation rate,

G. CFD Analysis of plate fin with elliptical tube inclined at 30 o heat exchanger 1. CAD geometry
In this work, a two-dimensional CAD model of a sheet metal fin with an elliptical tube inclined by 30 ° is created using a modular design of the ANSYS workbench. According to that of the table above and the figshows a two-dimensional view of the plate fin with an elliptical tube inclined by a 30 ° heat exchanger.

Meshing
After completing the CAD geometry of the plate fin with an elliptical tube inclined by 30°, the heat exchanger is imported into the ANSYS workbench for a further calculation of the fluid dynamics. The next step is meshing. CAD geometry is divided into a large number of small parts called meshes. in this book it is 16650 and the total number of elements is 16300. The types of elements used are rectangular, which is a rectangular shape with four knots on each element.

Quality of meshing:
The quality of the net plays an important role in the accuracy and stability of the calculation. In this work, square elements were created during discretization. The quality of the cell, including its orthogonal quality, its proportions and its asymmetry, has a significant impact on the accuracy of the solution.

Orthogonal mesh quality
Orthogonal quality is computed for cells using the vector from the cell centroid to each of its faces, corresponding face area vector, and the vector from the cell centroid to centroids of each of the adjacent cells. The worst cells will have an orthogonal quality closer to 0, with the best cells closer to 1. In the present case the minimum value is 0.73761 and maximum value is 1 and average value is 0.99273, which means the mesh quality is acceptable and very good.    H. CFD Analysis of plate fin with circular tube heat exchanger 1. CAD geometry In the present work a two dimensional CAD model of plate fin with circular tube heat exchanger is created with the help of design modular of ANSYS workbench. According to dimensional parameters given in above table no. and a two dimensional view of the plate fin with circular tube heat exchanger is shown in figure.

Meshing
After completing the CAD geometry of plate fin with circular tube heat exchanger is imported in ANSYS workbench for further computational fluid dynamics analysis and the next step is meshing. CAD geometry is divided into large numbers of small pieces called mesh. in the present work is 15417 and total No. of Elements is 15107. Types of elements used are rectangular which is a rectangular in shape with four nodes on each element.

Quality of meshing
The quality of the mesh plays an important role in the accuracy and stability of the calculation. In the present work the Quadrilateral elements have been generated during discretization. The quality of the cell including its orthogonal quality, aspect ratio, and skewers has an important effect on the accuracy of the solution. 4. Factor that affect the mesh quality  Rate of convergence: if the mesh quality is good the rate of convergence will be grater which means the correct solution can be achieved faster.  Solution precision: A better mesh quality provides a more precise solution.  Computational processing time required: for the highly refined mesh the computational time will be relatively large.  Grid Independence result: Once the computations are done and the desired property of fluid does not vary with respect to different mesh elements then it represents that further change in elements doesn't vary the results this term known as Independent Grid.

Orthogonal mesh quality
Orthogonal quality is computed for cells using the vector from the cell centroid to each of its faces, corresponding face area vector, and the vector from the cell centroid to centroids of each of the adjacent cells. The worst cells will have an orthogonal quality closer to 0, with the best cells closer to 1. In the present case the minimum value is 0.73761 and maximum value is 1 and average value is 0.99273, which means the mesh quality is acceptable and very good.  After performing computational fluid dynamic analysis on plate fin with circular tube heat exchanger the temperature distribution over the plate fin with circular tube has been observed. The temperature distribution at Plate fin and tube heat exchangers has been from 353K to 289K which shows the temperature drop of 64 degree. After performing computational fluid dynamic analysis on plate fin with circular tube heat exchanger the velocity distribution over the plate fin with circular tube has been observed. The maximum velocity at plate fin with circular tube heat exchangers has been recorded is 14.8 m/sec. After performing computational fluid dynamic analysis on plate fin with circular tube heat exchanger the pressure distribution over the plate fin with circular tube has been observed. The maximum pressure at over the plate fin with circular tube heat exchangers has been recorded is 50.86Pa.

Meshing
After completing the CAD geometry of plate fin with elliptical tube inclined at 45 o heat exchanger is imported in ANSYS workbench for further computational fluid dynamics analysis and the next step is meshing. CAD geometry is divided into large numbers of small pieces called mesh in the present work is 16601 and total No. of Elements is 16247. Types of elements used are rectangular which is a rectangular in shape with four nodes on each element.

Quality of meshing
The quality of the mesh plays an important role in the accuracy and stability of the calculation. In the present work the Quadrilateral elements have been generated during discretization. The quality of the cell including its orthogonal quality, aspect ratio, and skewness has an important effect on the accuracy of the solution. 4. Orthogonal mesh quality VOLUME 6, ISSUE 8, AUGUST 2020 www.ijoscience.com 20 Orthogonal quality is computed for cells using the vector from the cell centroid to each of its faces, corresponding face area vector, and the vector from the cell centroid to centroids of each of the adjacent cells. The worst cells will have an orthogonal quality closer to 0, with the best cells closer to 1. In the present case the minimum value is 0.75936 and maximum value is 1 and average value is 0.99502, which means the mesh quality is acceptable and very good.

Meshing
After completing the CAD geometry of plate fin with elliptical tube inclined at 60 o heat exchanger is imported in ANSYS workbench for further computational fluid dynamics analysis and the next step is meshing. CAD geometry is divided into large numbers of small pieces called mesh in the present work is 16698 and total No. of Elements is 16339. Types of elements used are rectangular which is a rectangular in shape with four nodes on each element.

Quality of meshing
The quality of the mesh plays an important role in the accuracy and stability of the calculation. In the present work the Quadrilateral elements have been generated during discretization. The quality of the cell including its orthogonal quality, aspect ratio, and skewness has an important effect on the accuracy of the solution.

Orthogonal mesh quality
Orthogonal quality is computed for cells using the vector from the cell centroid to each of its faces, corresponding face area vector, and the vector from the cell centroid to centroids of each of the adjacent cells. The worst cells will have an orthogonal quality closer to 0, with the best cells closer to 1. In the present case the minimum value is 0.75135 and maximum value is 1 and average value is 0.99477, which means the mesh quality is acceptable and very good.

. CAD geometry
In the present work a two dimensional CAD model of plate fin with Vertical elliptical tube heat exchanger is created with the help of design modular of ANSYS workbench. According to dimensional parameters given in above table no. and a two dimensional view of the plate fin with Vertical elliptical tube heat exchanger is shown in figure.

Meshing
After completing the CAD geometry of plate fin with Vertical elliptical tube heat exchanger is imported in ANSYS workbench for further computational fluid dynamics analysis and the next step is meshing. CAD geometry is divided into large numbers of small pieces called mesh. in the present work is 16663 and total No. of Elements is 16303. Types of elements used are rectangular which is a rectangular in shape with four nodes on each element.

Quality of meshing
The quality of the mesh plays an important role in the accuracy and stability of the calculation. In the present work the Quadrilateral elements have been generated during discretization. The quality of the cell including its orthogonal quality, aspect ratio, and skewness has an important effect on the accuracy of the solution.

Orthogonal mesh quality
Orthogonal quality is computed for cells using the vector from the cell centroid to each of its faces, corresponding face area vector, and the vector from the cell centroid to centroids of each of the adjacent cells. The worst cells will have an orthogonal quality closer to 0, with the best cells closer to 1. In the present case the minimum value is 0.70991 and maximum value is 1 and average value is 0.9948, which means the mesh quality is acceptable and very good.   It has also been observed that the heat transfer capacity for plate fins and tube heat exchangers with an arrangement of elliptical tubes inclined by 30° with respect to the basic design of the paper is 23.022%, for plate fins and tube heat exchangers with an elliptical arrangement of the tube inclined by 45° with respect to the basic design of the paper, the value is 21.026% for plate fins and tube heat exchangers with an arrangement of the inclined elliptical tubes of 60° compared to the basic design of the paper is 17.067% and for the plate fins and tube heat exchangers with an elliptical tube arrangement inclined by 90° (vertical ellipse) the basic design of the paper is 14.078%.

VI. CONCLUSION
The main objective of the study of the optimal design of plate and fin heat exchangers through a computer-assisted fluid-dynamic approach and the maximization of thermal power. After performing a computerized analysis of fluid dynamics on various plate and fin heat exchanger designs, the following conclusions were drawn.
 The maximum and minimum temperature for the base paper design (flat tube heat exchanger and circular tube heat exchanger) was observed at 351.38 K and 289.2626 K, therefore the temperature difference is 62.12 degrees.  The maximum and minimum temperature for heat exchangers with plate fins and tubes with an arrangement of the elliptical tube inclined by 30 ° was observed at 349.68 K and 268.77 K, so the temperature difference is 80, 91 degrees and better heat transfer performance than the base card design 23, 22%.  The maximum and minimum temperature for heat exchangers with plate fins and tubes with a 45 ° inclined arrangement of the elliptical tube was observed at 349.02 K and 270.03 K, so the temperature difference is 78 , 9 degrees and improved heat transfer performance compared to the base card design 21, 26%.  The maximum and minimum temperature for heat exchangers with plate fins and tubes with an arrangement of the elliptical tube inclined by 60 ° was observed at 349.04 K and 273.58 K, therefore the temperature difference is 75, 46 degrees and better heat transfer performance than the base card design 17, 67%.  The maximum and minimum temperature for heat exchangers with plate fins and tubes with an arrangement of the elliptical tube inclined by 90° (vertical ellipse) was observed at 347.29 K and 274.39 K, therefore the difference of temperature is 72.9 degrees and the heat transfer performance compared to base paper the improved design is 14.78%.
From the above conclusions, it has been observed that the maximum heat transfer can be obtained from a plate and tube fin heat exchanger with an elliptical tube arrangement inclined by 30 ° with a heat transfer capacity of 23.22% more than a circular plate heat exchanger. Therefore, it is recommended to obtain the heat transfer of the mix if using the plate fins and the tube heat exchanger with an inclined elliptical tube instead of the circular tube arrangement.

VII. FUTURE WORK
This work focuses on improving the heat transfer capacity of finned heat exchangers by changing their design. Although the study is conducted with great care, there is still room for improvement. Some suggestions for future studies may also be possible, such as:  Finned tube heat exchangers with a circular tube and an elliptical arrangement are used in this worktop, but a different section can also be used.  The thickness of the slats does not vary in the current job, so the thickness can also be the criterion in which it is possible to work in the future.  The division of the tube bundle is constant in this work, a variable division can also be used.  In this work elliptical tube angles of 30°, 45°, 60° and 90 ° are used, other angles can be used.