A zero-equation turbulence model for indoor airflow simulation

Chen, Qingyan; Xu, W.

doi:10.1016/s0378-7788(98)00020-6

Cited by 275 publications

(151 citation statements)

References 12 publications

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“…This is made on the basis of Prandtl's mixing-length hypothesis, which gives that the viscosity is proportional to the local shear rate. Results calculated by Chen et al, 1998 shows that the accuracy of the zero-equation model is acceptable for indoor airflow design purpose. More experiments have been done to validate the zero-equation model ability to predict indoor airflow (Srebric et al, 1999).…”

Section: Zero-equation Turbulence Modelmentioning

confidence: 90%

Comfort climate evaluation with thermal manikin methods and computer simulation models

Nilsson¹,

Holmér²

2003

Indoor Air

133

103

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Increasing concern about energy consumption and the simultaneous need for an acceptable thermal environment makes it necessary to estimate in advance what effect different thermal factors will have on the occupants. Temperature measurements alone do not account for all climate effects on the human body and especially not for local effects of convection and radiation. People as well as thermal manikins can detect heat loss changes on local body parts. This fact makes it appropriate to develop measurement methods and computer models with the corresponding working principles and levels of resolution. One purpose of this thesis is to link together results from these various investigation techniques with the aim of assessing different effects of the thermal climate on people. The results can be used to facilitate detailed evaluations of thermal influences both in indoor environments in buildings and in different types of vehicles. This thesis presents a comprehensive and detailed description of the theories and methods behind full-scale measurements with thermal manikins. This is done with new, extended definitions of the concept of equivalent temperature, and new theories describing equivalent temperature as a vector-valued function. One specific advantage is that the locally measured or simulated results are presented with newly developed "comfort zone diagrams". These diagrams provide new ways of taking into consideration both seat zone qualities as well as the influence of different clothing types on the climate assessment with "clothing-independent" comfort zone diagrams.Today, different types of computer programs such as CAD (Computer Aided Design) and CFD (Computational Fluid Dynamics) are used for product development, simulation and testing of, for instance, HVAC (Heating, Ventilation and Air Conditioning) systems, particularly in the building and vehicle industry. Three different climate evaluation methods are used and compared in this thesis: human subjective measurements, manikin measurements and computer modelling. A detailed description is presented of how developed simulation methods can be used to evaluate the influence of thermal climate in existing and planned environments. In different climate situations subjective human experiences are compared to heat loss measurements and simulations with thermal manikins. The calculation relationships developed in this research agree well with full-scale measurements and subject experiments in different thermal environments. The use of temperature and flow field data from CFD calculations as input produces acceptable results, especially in relatively homogeneous environments. In more heterogeneous environments the deviations are slightly larger. Possible reasons for this are presented along with suggestions for continued research, new relationships and computer codes.Key-words: equivalent temperature, subject, thermal manikin, mannequin, thermal climate assessment, heat loss, office environment, cabin climate, ventilated seat, computer model, CFD, clothi...

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Section: Zero-equation Turbulence Modelmentioning

confidence: 90%

Comfort climate evaluation with thermal manikin methods and computer simulation models

Nilsson¹,

Holmér²

2003

Indoor Air

133

103

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“…The time step size for the former two mass flow rates is 0.1 s and for others is 0.05 s. To simulate the turbulence introduced by the high-velocity jet, we employed the zero equation model proposed by Chen and Xu (1998). Figure 6 shows the mass flow rates ratio at opening 1 and opening 2 in Zone 1.…”

Section: Isothermal With Non-uniform Momentum Distributionmentioning

confidence: 99%

Coupled Simulation between CFD and Multizone Models Based on Modelica Buildings Library to Study Indoor Environment Control

Tian

Sevilla

Sohn

2017

Linköping Electronic Conference Proceedings

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Multizone models are widely used in building airflow and energy performance simulations because they are often suitable for the analysis needed, and due to their fast computation speed. However, the results provided by the multizone models are sometimes limited due to the underlying well-mixed assumption of the air in a zone (e.g., a room). For zones where this assumption is not suitable, a Computational Fluid Dynamics (CFD) models may be needed. This paper proposes a coupled simulation model between the multizone and CFD model, which in the paper is fast fluid dynamics, a freely available and publicly released program. The model allows the simulation of a dynamic interaction between airflow and Heating, Ventilation and Air-Conditioning (HVAC) systems for buildings with stratified airflow distribution in some of the zones. The approach is implemented using Modelica and its buildings library. In this presentation, we first discuss the design and implementation of a data synchronization strategy between the two models. We then show a possible validation of the implementation by comparing the simulated results with experimental data from previous research. Finally, we perform a case study by linking a Variable Air Volume (VAV) terminal box to space in order to evaluate the capability of the coupled simulation. Finally, further research needs are discussed at the end of the paper.

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“…The set of equations (1a), (1b) and (2), are spatially discretised with reference to finite volume elements (not necessary uniform) of parallelepiped shape. To deal with said spatial discretisation, a staggered grid of points [15,19] is defined in the spatial domain of interest, as illustrated in figure 1.…”

Section: Balance Equationsmentioning

confidence: 99%

Object-oriented sub-zonal room models for energy-related building simulation

Bonvini

Leva

2011

Linköping Electronic Conference Proceedings

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Simulation is important to evaluate the energy-related performance of a building, and for reliable results, reproducing the behaviour of the contained air volumes is particularly relevant. For such a purpose, fully mixed models (i.e., for instance, a single temperature per room) easily prove inadequate, while Computational Fluid Dynamics (CFD) ones are too complex, and difficult to formulate in a modular manner, to the detriment of their usefulness if the simulator has to be used throughout the project, and not only to assess its final result. This manuscript presents an intermediate solution based on the Modelica language.

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A zero-equation turbulence model for indoor airflow simulation

Cited by 275 publications

References 12 publications

Comfort climate evaluation with thermal manikin methods and computer simulation models

Comfort climate evaluation with thermal manikin methods and computer simulation models

Coupled Simulation between CFD and Multizone Models Based on Modelica Buildings Library to Study Indoor Environment Control

Object-oriented sub-zonal room models for energy-related building simulation

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