L12
Computational Fluid Dynamics 2

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13:20
conference time (CEST, Berlin)
Pressure Drop and Thermal Field Prediction of Car Heat Exchangers Using CFD Submodeling Techniques
27/10/2021 13:20 conference time (CEST, Berlin)
Room: L
T. Płusa, N-Y.Francois (Valeo Thermal Systems, FRA)
T. Płusa, N-Y.Francois (Valeo Thermal Systems, FRA)
In recent years, R&D has undergone a real transformation and is being rationalized in order to increase its efficiency, reduce its development cycles and costs, and improve its capacity to innovate. Turned towards digitalization, Valeo Thermal Systems relies in particular on digital simulation such as CFD (Computational Fluid Dynamics) to optimize concepts, orient its technical choices, make decisions and engage with customers. Its use is becoming a major asset to offer innovative and competitive automotive heat exchangers. Cost of computational power decreases from year to year and it causes resources to be more accessible for different entities like: corporations, research institutes, universities, smaller companies etc... Despite this fact, car heat exchangers like radiators or intercoolers cooled by water or air, are still very challenging in terms of simulation. These heat exchangers have hundreds or even thousands of very small tiny parts called turbulators or fins increasing the area of heat exchange in a unit of volume. It causes that it is nearly impossible in reasonable time to mesh and simulate detailed geometry. As a simplification, special replacement models are used. Pressure drop is calculated using the so-called porous medium while heat transfer is carried out by the 3D heat exchanger interface model. Both models need input like porous medium pressure drop coefficients or local heat transfer coefficients. This article presents a new numerical method based on a CFD submodeling technique to characterize the pressure losses and the heat transfer coefficients from a small periodic pattern of the heat exchanger. Then, based on CFD submodeling results, special laws are built using dimensionless numbers such as Reynolds number, Nusselt number, Prandtl and Bejan number. Finally, these laws of pressure drop and heat transfer are applied to a full CFD model of the heat exchanger to predict its fields of temperature and flow with its performances.
heat exchangers, heat transfer, pressure drop, cfd, submodeling
13:40
conference time (CEST, Berlin)
A Streamlined Approach to Couple In-cylinder and Conjugate Heat Transfer Engine Models
27/10/2021 13:40 conference time (CEST, Berlin)
Room: L
J. Fernandes, W. Seeley (Siemens Digital Industries Software, GBR)
J. Fernandes, W. Seeley (Siemens Digital Industries Software, GBR)
Increasing regulatory and commercial requirements have led to widespread adoption of digital analysis in the IC engine design process. This has helped to improve fuel efficiency, reduce emissions, as well as reduce reliance on physical testing and the development of costly prototypes. CFD is one of the key types of analysis employed in generating a digital twin of the IC engine. It is it able to model a wide range of physical processes that include gas and coolant flow, combustion, emissions and conjugate heat transfer (CHT). When using CFD to evaluate the thermal field of engine components, the most common approach is to generate separate models for the gas flow and combustion (the in-cylinder model), and the coolant flow and metal temperatures (the CHT model). The in-cylinder model is used to estimate spatially varying heat flux which are averaged over a cycle and then applied as thermal boundary conditions to the CHT model. Spatially varying temperatures on the combustion boundaries from the CHT simulation can be then passed back to the in-cylinder simulation and data exchanged between the two simulations until convergence is achieved. Traditionally the in-cylinder and CHT models have been generated using separate software packages. Within the digital environment, this has created a few challenges relating to efficient and accurate data exchange between the two models as well as overall process automation. This paper presents a coupled in-cylinder/CHT approach carried out using a single software package that employs state of the art physics models for both the in-cylinder and CHT analysis. It highlights how integrating both analyses into a single user environment can help to make the process more streamlined, efficient and automated. The approach is applied on a 4-stroke gasoline engine and comparison of the predicted in-cylinder combustion performance and component temperatures are made with experimental measurements.
CFD, ICE, In-cylinder, Conjugate Heat Transfer
14:00
conference time (CEST, Berlin)
Simulation Studies for Condensation in Domestic Refrigerators
27/10/2021 14:00 conference time (CEST, Berlin)
Room: L
P. Goel, V. Marathe, S. Sahoo, A. Shukla (Whirlpool India, IND)
P. Goel, V. Marathe, S. Sahoo, A. Shukla (Whirlpool India, IND)
Condensation in refrigerators can be a major challenge and is not acceptable even at minimum level. Generally, refrigerators experience two types of condensation: 1) Internal condensation and 2) External condensation. It experiences large temperature differences between internal compartments and the ambient and thus, there is a possibility that the external surface temperature may drop below ambient air temperature. If the temperature of the surface drops below the Dew Point Temperature (DPT), the ambient air coming in contact with the surface will result in condensation of water vapor on the refrigerator surface - external condensation. Improper door closing can result in high humidity inside the compartment leading to internal condensation, specifically near the door and in the gasket region. For predicting the external condensation risk 3D steady state thermal simulations using ANSYS WB 19.2 is used. For calculation inside air is considered at a temperature of 4 ℃ and the ambient air is considered at 32 ℃. In this study, 3D steady state Computational Fluid Dynamics (CFD) simulations using Ansys Fluent 19.2 are used to predict the zones, which are prone to internal condensation risk in the refrigerator compartment. Moisture calculations at surfaces are performed using 1D simulation in Dymola. The study demonstrates the procedure to ensure no moisture at the internal or external surface of the refrigerator, and the refrigerator performance is calculated. The increase in condensation in the refrigerator is directly proportional to the heat load. Hence, it hampers the overall performance main score of the refrigerator which also impacts the energy rating. The present study is promising in terms of qualitative understanding of internal and external condensation that occurs in the refrigerator. This study helps to make early decisions and avoid a number of prototype testing. This helps to reduce overall project cost and time consumption.
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