C. Oliet

Thermal and Fluid Dynamic Simulation of Automotive Fin-and-Tube Heat Exchangers, Part 1: Mathematical Model

The aim of this paper is to present a developed detailed model for the simulation of automotive fin-and-tube heat exchangers (Compact Heat Exchanger Simulation Software, CHESS). The simulation strategy and the mathematical methodology are described in detail. The model is based on a 3D discretization around the tubes as small heat exchangers, where the appropriate governing equations (mass, momentum and energy) are applied for each control volume on the air-side, the solid elements, and the coolant side. Some verification and illustrative results are also provided to show the features of the model. A comparison between numerical simulation results and experimental data is presented in a companion paper (Part 2).

Thermal and Fluid Dynamic Simulation of Automotive Fin-and-Tube Heat Exchangers, Part 2: Experimental Comparison

A detailed model for the simulation of automotive fin-and-tube heat exchangers previously developed by the authors (Part 1) has been experimentally validated for a wide range of geometries and boundary conditions. Some of this experimental information was collected in an academic testing unit, while a second group of experiments was conducted in the experimental set-up of an industrial partner. The data cover a wide range of operational conditions and analyze the effect of most influential geometric parameters. The paper presents the experimental units and shows the comparison between numerical predictions and experimental values. The numerical calculations have been carried out using the most suitable available air-side heat transfer and friction correlations. Although the comparison is reasonably accurate, the deviations appearing among the predictions using different correlations indicate that further research work is still necessary to describe in a more accurate way the fundamental behavior of the louver fin geometry.

Analysis of the Dynamic Behavior of Refrigerated Spaces Using Air Curtains

This article is devoted to the study of air curtains applied to reduce the refrigerated chambers heat gains. The proposed strategy is based on the numerical simulation of air curtains by means of computational fluid dynamics (CFD) using RANS modeling and their corresponding experimental validation. Further work on the reduction of the detailed numerical results into overall energetic parameters is also presented. Unsteady three-dimensional numerical parametric studies are carried out, simulating the process of refrigerated chamber sudden door opening. The numerical solutions are verified and the influence of the turbulence model used is also investigated. The studies are centered on the influence of air curtain location, the air suction combination, and both the air discharge velocity and the discharge angle.

Multidimensional and Unsteady Simulation of Fin-and-Tube Heat Exchangers

This article presents a model for the analysis of fin-and-tube heat exchangers, focusing on the heat conduction processes within the finned tube bundle. A cutting cell discretization has been proposed for the fins to adapt to the tubes shape, while the tubes have been discretized in axial and angular directions to consider complex heat transfer coefficient variations. A set of results is given on fin efficiency and transient response comparing with well-established methods. A full-scale condenser is also analyzed as an illustrative result, detecting important thermal bridges through the fins.

Large Eddy Simulations (LES) on the Flow and Heat Transfer in a Wall-Bounded Pin Matrix

In this article, the three-dimensional turbulent forced convection in a matrix of wall-bounded 8 × 8 cylindrical pins is studied. Large eddy simulations (LES) are performed for Reynolds numbers 3,000, 10,000 and 30,000. Three different subgrid-scale (SGS) models (WALE, QR, and VMS) are compared on a row-by-row study. Local values of velocity and pressure coefficient are depicted. Turbulence characteristics of the flow are well illustrated. The thermal field is analyzed and validated with the time-averaged Nusselt number at the end walls of the pin matrix. The capabilities of the methodology for predicting the turbulent flow features is also shown.

Experimental Facility for the Study of Liquid Overfeed Fin-and-Tube Evaporators: Validation of Numerical Models

An experimental facility specially designed for the study of liquid overfeed fin-and-tube evaporators was developed. It is intended for the experimental validation of a detailed liquid overfeed evaporator model, permitting testing as either a part of the refrigeration system or in a loop without a compressor. The facility can also be used for the experimental evaluation of refrigeration system performance-prediction models. A detailed description of the facility and its instrumentation, emphasizing the data uncertainty analysis and the verification techniques, is provided. A method for experimentally estimating the systematic uncertainties in the measurement of the temperature sensors after calibration, accounting for the whole signal path, is also presented. Results from a detailed numerical model of liquid overfeed evaporators, developed for design optimization, were compared with the experimental data. Six well-known correlations for the two-phase flow heat transfer coefficients were studied in order to assess their influence in the overall evaporator performance prediction.