Study of Influence of Boundary Condition of Diffuser with Non-Uniform Velocity on the Jet Characteristics and Indoor Flow Field

Li, Kaijun; Song, Linye; Zhang, Xinghui; Wang, Qi; Hua, Jing

doi:10.3390/en16031079

Cited by 5 publications

(4 citation statements)

References 20 publications

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“…This method can be well adapted to the boundary condition settings of different sub-tuyere opening states and simplify the modelling process. 41 The air outlet has little effect on the indoor airflow distribution, which provided a pressure outlet for exhausting air.…”

Section: Methodsmentioning

confidence: 99%

An active diffuser control method based on the constant jet throw for improving airflow distribution in variable air volume systems

Song

Zhang

et al. 2023

Indoor and Built Environment

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The air supply of the variable air volume (VAV) system could decrease with indoor load, resulting in reduced indoor comfort. An active diffuser is a good solution, but its adjustment process is often neglected. In most cases, the diffuser maintains the air supply velocity constant by controlling the air supply area. This traditional control method based on constant velocity (CMV) often fails to reach jet throw expectation due to the continuous change of airflow diffusion performance during the adjustment process. In this study, a new control method based on constant jet throw length (CMT) is proposed and applied in two typical rooms (office and conference). The results show that the CMT could increase the throw length in the spreading zone and enhances the airflow at the wall zone and ground zone, providing a more uniform temperature and more comfortable indoor environment. In 40% air volume condition, the air diffusion performance index (ADPI) in the office using CMT has improved from 89.66% to 95.69% compared to CMV, while ADPI in the conference improved from 92.11% to 97.37%. This study can help designers determine the optimal adjustment scheme to improve the adaptability of the active diffuser to the VAV system.

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Section: Methodsmentioning

confidence: 99%

An active diffuser control method based on the constant jet throw for improving airflow distribution in variable air volume systems

Song

Zhang

et al. 2023

Indoor and Built Environment

Self Cite

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“…Each zone is equipped with an independently controlled MCD (Figure 3a), and its simplified model and geometric dimensions are shown in Figure 3b. The magnitude and direction of velocity can be defined by the horizontal and vertical components, and the feasibility of this method has been shown in [40]. The geometric dimensions of the vents involved can be seen in Table 1.…”

Section: Airflow Modelingmentioning

confidence: 99%

Differentiated Control of Large Spatial Environments: Air Curtain Grid System

Song

Zhang

et al. 2023

Sustainability

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Large public buildings (LPBs) are the main energy consumers in cities, and the air conditioning system contributes a large part. Supply air allocation by partition can avoid excessive regulation of the system. In spatially interconnected LPBs, thermal coupling relationships exist between different subzones. The convective heat transfer to the non-occupied zone increases the actual cooling/heating capacity of the air conditioning area. This paper applies the air curtain as an airflow barrier indoors, and the air curtain grid system (ACGS) is created by the combined operation of multiple air curtains, which aims to reduce the convective heat exchange between adjacent subzones. The computational fluid dynamics (CFD) model is established and simulated. The main conclusions are as follows: (1) For the scenarios addressed in this paper, the combination of a 60° diffuser air supply angle and 2 m/s air curtain velocity can reduce the convective load from the adjacent space by more than 50%. (2) It is recommended to install incomplete air curtains indoors, and a 50% air curtain coverage ratio can reduce 52% of the heat exchange. (3) The mathematical model of air infiltration/exfiltration under the combined operation of multiple air curtains is established and verified in ACGS. This paper provides a new approach to the air conditioning partition control of LPBs.

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“…Nocente et al [17] conducted a numerical simulation to characterize the impact of diffuse ceiling ventilation on the internal comfort of a typical office room and compared the performance between continuous and non-continuous diffuser designs. Li et al [18] studied the uniform and non-uniform velocity inlet boundary conditions for simulating diffusers, as well as the effects of different boundary conditions on the jet characteristics and airflow distribution.…”

Section: Introductionmentioning

confidence: 99%

Simplified Simulation Method of Diffusers for Indoor Non-Uniform Temperature Distribution: A Case Study in Shanghai

Li,

Pan,

Huang

et al. 2024

Buildings

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The specific air jet of a diffuser is formed by the complex internal structure, which affects the outlet airflow distribution of the diffuser directly and the indoor environment distribution indirectly. If the diffusers are developed based on their actual geometry structure and their boundary conditions are set as their inlet flowrate, the simulated indoor temperature distribution will be more accurate. However, it is noted that many problems may arise, such as model complexity, many grid cells, and slow convergence of calculations. Therefore, this paper focuses on a simplified method for four-way square diffusers in a computational fluid dynamics (CFD) simulation of indoor non-uniform temperature distribution. Firstly, the airflow distribution is simulated on the outlet air supply cross-section of the diffuser. Then, according to the outflow characteristics of the diffuser, the diffuser model is simplified and simulated in an experimental room. Finally, the temperature distribution at the 1.2 m height plane is obtained from CFD simulation and compared with the experimental results. The results show that the 68-point air supply opening model can well simulate the effects of the outlet airflow distribution of the diffuser, and the simulated indoor temperature distribution meets the experiment results well. The deviations for three scenarios are between −7.4~1.7% and the average deviation is −3.0%, while the root mean square error of temperature for three scenarios is 0.7 °C, 0.7 °C, and 1.0 °C, respectively. The results also demonstrate the mutual influence of the airflow from different diffusers and the indoor non-uniform temperature distribution under the action of multiple diffusers. The proposed method can contribute to balancing the model complexity and the accuracy in CFD simulation, especially for multiple diffusers in the room.

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Study of Influence of Boundary Condition of Diffuser with Non-Uniform Velocity on the Jet Characteristics and Indoor Flow Field

Cited by 5 publications

References 20 publications

An active diffuser control method based on the constant jet throw for improving airflow distribution in variable air volume systems

An active diffuser control method based on the constant jet throw for improving airflow distribution in variable air volume systems

Differentiated Control of Large Spatial Environments: Air Curtain Grid System

Simplified Simulation Method of Diffusers for Indoor Non-Uniform Temperature Distribution: A Case Study in Shanghai

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