Objective of this project work is the investigation of the geometry of a heat exchanger. The main purpose of a heat exchanger is the exchange of heat between two fluids. Therefore, the final flow and temperature field shall be analyzed.
Heat exchangers are widely used in all sorts of engineering purposes. One of the most known examples for the use of a heat exchanger is found in an engine. Engines run optimal at a certain temperature. This is where the heat exchanger comes into play. Engine coolant is pumped through canals in the engine and transports the built-up heat away. This liquid is warmer now and must be cooled down again. It therefore goes through the heat exchanger, where the relatively cold air from the environment flows past the coils with the liquid and cools the engine coolant. The cycle repeats itself as long as the engine is running.
The procedure is as follows. First, the creation of the geometry will be explained. Then the meshes shall be analyzed based on a description of the quality, grid convergence study and the energy balances between the heat fluxes. After an optimal mesh for further investigation has been chosen, different turbulence models are going to be investigated on the basis of turbulence values, pressure loss and heat transfer coefficients, which will be compared to the flow filament theory. Then a final investigation will be done with the turbulence model with the best results. Thereby the most important flow values for inner as well as outer flow, radial temperature distribution and the specific cooling power of the heat exchanger will be discussed.
Table of Contents
1 Introduction
2 Creation of the Geometry and Mesh
2.1 Geometry
2.2 Mesh
3 Grid study
3.1 Grid convergence study
3.2 Energy Balances
4 Investigation of Turbulence Models
4.1 Comparison of different Turbulence Models
4.2 Flow Filament Theory
5 Final Simulation
5.1 Most important Flow Values
5.2 Comparison to Flow Filament Theory
5.3 Radial Temperature Distribution
5.4 Specific Cooling Power
6 Summary
7 Source Directory
8 Annex
Objectives and Topics
The primary objective of this project is the investigation of a heat exchanger's geometry through Computational Fluid Dynamics (CFD). The study aims to analyze the flow and temperature fields, evaluate different mesh qualities, determine the most suitable turbulence model, and calculate the specific cooling power of the heat exchanger.
- Geometric creation and meshing strategies for heat exchangers.
- Grid convergence studies to ensure numerical stability and accuracy.
- Comparative analysis of turbulence models (SST, k-omega, EVT).
- Validation of simulation results against theoretical flow filament calculations.
- Thermal performance evaluation, including radial temperature distribution and specific cooling power.
Excerpt from the Book
2.1 Geometry
In order to do any fluid mechanical simulation, a proper geometry is needed. This geometry can either be created with a program like Catia, but for this module work the heat exchanger has been created with the tool SpaceClaim inside of Ansys.
Even though in the description of the module work it is described that the number of pipes is 21, possible use of symmetries is made. This means, that only a half-pipe was created, because on the one hand it reduces computational time significantly and on the other hand the results of the simulations can be transferred to 21 pipes without any problem.
The inside diameter of the pipe is 12mm. The wall thickness of the pipe is 1mm, this adds up to an outside diameter of 12mm. The space from the inlet of the air to the pipe is three times the outside diameter, so 42mm. From the pipe to the outlet of the air the length is 98mm, seven times the outside diameter of the pipe. The space above the pipe is only 3.5mm because the distance between two pipes is only 7mm, as given in the description. The pipe and the space around it are 900mm long. The volume of the water and air as well as the pipe have been put together to one component to share the topology of the mesh. This means, that the transition between the different meshes is smooth, as shown in Figure 8-1.
Summary of Chapters
1 Introduction: This chapter outlines the main objectives, focusing on the thermal and flow analysis of a heat exchanger used in engine cooling applications.
2 Creation of the Geometry and Mesh: This section details the construction of the CAD model using SpaceClaim and describes the systematic creation of three different hexahedral-dominant meshes.
3 Grid study: This chapter covers the setup of steady-state simulations and performs a grid convergence study to identify the mesh that provides the best balance between computational efficiency and accuracy.
4 Investigation of Turbulence Models: Here, the performance of various turbulence models (SST, k-omega, EVT) is compared based on their convergence behavior and accuracy against flow filament theory.
5 Final Simulation: This chapter presents the detailed analysis of the flow field, pressure distribution, radial temperature profiles, and the final assessment of the cooling power using the selected SST turbulence model.
6 Summary: The final chapter provides a concise review of the methodology, the rationale for model selection, and the overall conclusions regarding the heat exchanger's performance.
7 Source Directory: This section lists all literature, software documentation, and online resources cited throughout the study.
8 Annex: The appendix contains supplementary figures, mesh statistics, and validation charts supporting the main analysis.
Keywords
Computational Fluid Dynamics, CFD, Heat Exchanger, Turbulence Models, SST Model, Grid Convergence, Mesh Quality, Thermal Energy, Flow Filament Theory, Specific Cooling Power, Boundary Layer, Nusselt Number, Fluid Mechanics, Heat Flux, Ansys
Frequently Asked Questions
What is the core focus of this study?
The study focuses on the numerical investigation and validation of a heat exchanger's thermal and fluid-mechanical performance using CFD software.
What are the primary fields explored in this work?
The document explores geometry modeling, meshing criteria, turbulence modeling, and comparative heat transfer analysis.
What is the ultimate goal of the simulation?
The goal is to determine the cooling efficiency of the heat exchanger and analyze whether the geometry design is optimal for heat dissipation.
Which scientific methods are utilized?
The author employs CFD simulation techniques, including Richardson-Extrapolation for grid convergence and the flow filament theory for theoretical comparison.
What does the main part of the report cover?
The main part encompasses the creation of geometry, the selection of an optimal mesh, the investigation of turbulence models, and a final simulation analysis.
Which keywords best characterize this project?
Key terms include Computational Fluid Dynamics (CFD), Heat Exchanger, SST Turbulence Model, Grid Convergence Study, and Specific Cooling Power.
Why was the SST turbulence model chosen for the final simulation?
The SST model was selected because it combined the advantages of the k-omega and k-epsilon models, showed the best convergence stability, and provided the most accurate results for heat transfer coefficients.
How does the calculated cooling power compare to industry standards?
The simulated specific cooling power was found to be relatively weak compared to the technical specifications of standard industrial heat exchangers documented in the provided literature.
- Arbeit zitieren
- Benno Schönstein (Autor:in), 2021, The Geometry of a Heat Exchanger (CFD/Flow Simulation), München, GRIN Verlag, https://www.grin.com/document/1156507
