A literature review of building energy simulation and computational fluid dynamics co-simulation strategies and its implications on the accuracy of energy predictions

Author(s):  
Manan Singh ◽  
Ryan Sharston

The paper presents a review of existing literature in the field of coupling Computational Fluid Dynamics (CFD) with Building Energy Simulations (BES) to better predict indoor environmental conditions and building energy implications. CFD is capable of providing a detailed analysis of airflow profile and temperature gradients in the space as well as better prediction of heat transfer involving convection and radiation. Whereas BES can provide dynamically changing boundary conditions to CFD to facilitate a precise transient analysis. Combining the two simulations provides a powerful framework to accurately predict building performance parameters. The review examines the variables exchanged between the two simulations and establishes that the Convective Heat Transfer Coefficient (CHTC) as the most important exchanged variable that can significantly improve the accuracy of energy simulations. Issues regarding the application of co-simulation mechanism are then discussed in terms of simulation discontinuities, along with strategies adopted by researchers to overcome the same. In the later sections, the review evaluates the applicability of co-simulation from the perspective of year-long building energy simulations and presents an overview of methods used in research to implement the same. Finally, the conclusions are discussed and the scope for future research in the field is presented. Practical implication: The review presents a critical analysis of essentially all major coupling strategies that can be used to perform a BES-CFD coupled analysis along with their strengths, limitations and possible application scenarios. Additionally, the problems associated with establishing the co-simulation are examined and various adopted solutions are presented along with methods implemented towards extending the practical applicability of such an analysis to encapsulate year-long simulations.

2020 ◽  
Vol 44 (2) ◽  
pp. 137-180 ◽  
Author(s):  
Martin Rodríguez-Vázquez ◽  
Iván Hernández-Pérez ◽  
Jesus Xamán ◽  
Yvonne Chávez ◽  
Miguel Gijón-Rivera ◽  
...  

Building energy simulations coupled with computational fluid dynamics tools have emerged, recently, as an accurate and effective tool to improve the estimation of energy requirements and thermal comfort in buildings. Building modelers and researchers usually implement this coupling in the boundary conditions of both tools (e.g. surface temperature, ambient temperature, and conductive and convective fluxes). This work reviews how the building energy simulation–computational fluid dynamics coupling has evolved since its first implementation to the present day. Moreover, this article also summarizes and discusses the research studies in which the building energy simulation–computational fluid dynamics coupling has been used to analyze building systems, building components, and building urban configurations. Implementing a building energy simulation–computational fluid dynamics coupling brings a series of benefits when compared with the conventional building energy simulation methodology, a building energy simulation–computational fluid dynamics coupling provides an improvement that ranges between 10% and 50% for estimating the building energy requirements. Moreover, the computation time to implement computational fluid dynamics with information obtained from the building energy simulation could be reduced by as well.


Author(s):  
J. Bryce Taylor ◽  
Savas Yavuzkurt ◽  
Anthony J. Baratta

The Pebble Bed Modular Reactor (PBMR), a promising Generation IV nuclear reactor design, raises many novel technological issues for which new experience and techniques must be developed. This brief study explores a few of these issues, utilizes a computational fluid dynamics code to model some simple phenomena, and points out deficiencies in current knowledge that should be addressed by future research and experimentation. A highly simplified representation of the PBMR core is analyzed with FLUENT, a commercial computational fluid dynamics code. The applied models examine laminar and turbulent flow in the vicinity of a single spherical fuel pebble near the center of the core, accounting for the effects of the immediately adjacent fuel pebbles. Several important fluid flow and heat transfer parameters are examined, including heat transfer coefficient, Nusselt number, and pressure drop, as well as the temperature, pressure, and velocity profiles near the fuel pebble. The results of these “unit cell” calculations are also compared to empirical correlations available in the literature. As FLUENT is especially sensitive to geometry during the generation of a computational mesh, the sensitivity of code results to pebble spacing is also examined. The results of this study show that while a PBMR presents a novel and complex geometry, a code such as FLUENT is suitable for calculation of both local and global flow characteristics, and can be a valuable tool for the thermal-hydraulic study of this new reactor design. FLUENT results for pressure drop deviate from the Darcy correlation by several orders of magnitude in all cases. When determining the heat transfer coefficient, FLUENT is again much lower than Robinson’s correlation. Results for Nusselt number show better agreement, with FLUENT predicting results that are 10 or 20 times as large as those from the Robinson and Lancashire correlations. These differences may arise because the empirical correlations concern mainly integral parameters, while the FLUENT model focuses on local flow behaviors. Local phenomena are significant in the case of local heat transfer characteristics, fine temperature distribution calculations to identify hot spots, and fission product transport phenomena. All of these are important to a safety analysis of the PBMR reactor during normal operation, as well as during transient circumstances, and should be the focus of future research efforts.


Author(s):  
Riccardo Da Soghe ◽  
Cosimo Bianchini ◽  
Antonio Andreini ◽  
Lorenzo Mazzei ◽  
Giovanni Riccio ◽  
...  

Combustor liner of present gas turbine engines is subjected to high thermal loads as it surrounds high temperature combustion reactants and is hence facing the related radiative load. This generally produces high thermal stress levels on the liner, strongly limiting its life expectations and making it one of the most critical components of the entire engine. The reliable prediction of such thermal loads is hence a crucial aspect to increase the flame tube life span and to ensure safe operations. The present study aims at investigating the aerothermal behavior of a GE Dry Low NOx (DLN1) class flame tube and in particular at evaluating working metal temperatures of the liner in relation to the flow and heat transfer state inside and outside the combustion chamber. Three different operating conditions have been accounted for (i.e., lean–lean partial load, premixed full load, and primary load) to determine the amount of heat transfer from the gas to the liner by means of computational fluid dynamics (CFD). The numerical predictions have been compared to experimental measurements of metal temperature showing a good agreement between CFD and experiments.


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