Study on Self-Cleaning Time and Suspended Particle Distribution in Medical Clean Room

Abstract CFD numerical simulation of clean room in Class D medical factory was carried out and compared with the actual measurement to verify the feasibility of the simulation method. On this basis, four typical air flow organizations were simulated and compared by changing air change rate from two directions of self-cleaning time and suspended particle concentration field. According to the simulation results, in order to meet the self-cleaning time within 20 min, the best air change rate should be between 15/h and 25/h. Different air flow organizations have different self-cleaning capacity, and the value of air change rate can be relatively small in the form of single-side supply same-side down return. Different airflow organizations have different suspended particle distribution characteristics, and there are differences in the applicable scenarios, and the applicability of the top supply down return is the best.

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Aircraft Cabin Ventilation Theory

10.31224/osf.io/ac6p8 ◽

2021 ◽

Author(s):

Dieter Scholz

Keyword(s):

Steady State ◽

Flow Rate ◽

Air Flow ◽

Source Strength ◽

Air Flow Rate ◽

Change Rate ◽

Aircraft Cabin ◽

Air Change Rate ◽

Ventilation Efficiency ◽

State Case

Ventilation on board of an aircraft is governed by the ventilation equation. In the steady state case, a concentration of any substance depends only on the source strength and the effective air flow rate for ventilation. Not all air for ventilation is effective and helps to lower concentration. Some air leaves the cabin without mixing and rinsing. This is expressed by the ventilation efficiency. The dynamics follows an exponential function and is expressed by a time constant that depends on the air change rate and the ventilation efficiency. The (theoretical) air change rate is the air flow rate divided by the volume of the room. With full mixing (i.e. ventilation efficiency of 1), the concentration is reduced to 36.8% after one air change.

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Influence of Ceiling Height on Airflow and Particle Distribution in an Operating Room

E3S Web of Conferences ◽

10.1051/e3sconf/201911101032 ◽

2019 ◽

Vol 111 ◽

pp. 01032

Author(s):

Aleyna Agirman ◽

Yunus Emre Cetin ◽

Mete Avci ◽

Orhan Aydin

Keyword(s):

Operating Room ◽

Particle Distribution ◽

Numerical Study ◽

Surgical Site Infections ◽

Particle Dispersion ◽

Ansys Fluent ◽

Change Rate ◽

Numerical Predictions ◽

Air Change Rate ◽

Ceiling Height

Bacteria-carrying particles released by surgical staff are the main factors leading to surgical site infections (SSI). Operating rooms must be designed to reduce risks of such infections. In this numerical study, the effect of different ceiling heights on particle dispersion and deposition are studied for an operating room with laminar airflow (LAF) system. Two different particle diameters (12 and 20 ìm) are tested under three different ceiling heights (2.43–2.8–3.0 m) at a constant air change rate (ACH=20). Numerical predictions are performed by using the commercial software ANSYS Fluent 16.0. The results reveal that decreasing of the ceiling height reduces the amount of particle deposited on the surgical table.

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Comparison of Downdraught and Up Draft Passive Air Conduction Systems (PACS) in a Winery Building

Buildings ◽

10.3390/buildings11060259 ◽

2021 ◽

Vol 11 (6) ◽

pp. 259

Author(s):

Ádám László Katona ◽

István Ervin Háber ◽

István Kistelegdi

Keyword(s):

Air Conditioning ◽

Natural Ventilation ◽

Dynamics Simulation ◽

Computational Fluid Dynamics Simulation ◽

General Applicability ◽

Change Rate ◽

Air Change Rate ◽

Simulation Based ◽

Ventilation Performance ◽

Air Conduction

A huge portion of energy consumption in buildings comes from heating, ventilation, and air conditioning. Numerous previous works assessed the potential of natural ventilation compared to mechanical ventilation and proved their justification on the field. Nevertheless, it is a major difficulty to collect enough information from the literature to make decisions between different natural ventilation solutions with a given situation and boundary conditions. The current study tests the passive air conduction system (PACS) variations in the design phase of a medium-sized new winery’s cellar and production hall in Villány, Hungary. A computational fluid dynamics simulation based comparative analysis enabled to determine the differences in updraft (UD) and downdraught (DD) PACS, whereby the latter was found to be more efficient. While the DD PACS performed an air change range of 1.02 h−1 to 5.98 h−1, the UD PACS delivered −0.25 h−1 to 12.82 h−1 air change rate. The ventilation performance of the DD version possessed lower amplitudes, but the distribution was more balanced under different wind incident angles, thus this version was chosen for construction. It could be concluded that the DD PACS provides a more general applicability for natural ventilation in moderate climates and in small to medium scale industry hall domains with one in- and one outlet.

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Determination of Optimal Air Change Rate for Cooling the Bedrooms of Residential Buildings in Guangzhou

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/719/2/022048 ◽

2021 ◽

Vol 719 (2) ◽

pp. 022048

Author(s):

Cuicui Qin ◽

Yufeng Zhang ◽

Lihua Zhao

Keyword(s):

Residential Buildings ◽

Change Rate ◽

Air Change Rate

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Air change rate vs airflow pathway: bioaerosol containment and removal in patient rooms

Antimicrobial Resistance and Infection Control ◽

10.1186/2047-2994-4-s1-p94 ◽

2015 ◽

Vol 4 (S1) ◽

Author(s):

K Grosskopf

Keyword(s):

Change Rate ◽

Air Change Rate

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Numerical and Experimental Investigations of the Siemens SGT-800 Burner Fitted to a Water Rig

Volume 4A: Combustion, Fuels and Emissions ◽

10.1115/gt2017-64129 ◽

2017 ◽

Cited By ~ 1

Author(s):

Daniel Moëll ◽

Daniel Lörstad ◽

Annika Lindholm ◽

David Christensen ◽

Xue-Song Bai

Keyword(s):

Gas Turbine ◽

Gas Turbines ◽

Flame Temperature ◽

Concentration Field ◽

Simulation Method ◽

Experimental Investigations ◽

High Concentration ◽

Air Mixing ◽

Les Model ◽

Gas Turbine Burner

DLE (Dry Low Emission) technology is widely used in land based gas turbines due to the increasing demands on low NOx levels. One of the key aspects in DLE combustion is achieving a good fuel and air mixing where the desired flame temperature is achieved without too high levels of combustion instabilities. To experimentally study fuel and air mixing it is convenient to use water along with a tracer instead of air and fuel. In this study fuel and air mixing and flow field inside an industrial gas turbine burner fitted to a water rig has been studied experimentally and numerically. The Reynolds number is approximately 75000 and the amount of fuel tracer is scaled to represent real engine conditions. The fuel concentration in the rig is experimentally visualized using a fluorescing dye in the water passing through the fuel system of the burner and recorded using a laser along with a CCD (Charge Couple Device) camera. The flow and concentration field in the burner is numerically studied using both the scale resolving SAS (Scale Adaptive Simulation) method and the LES (Large Eddy Simulation) method as well as using a traditional two equation URANS (Unsteady Reynolds Average Navier Stokes) approach. The aim of this study is to explore the differences and similarities between the URANS, SAS and LES models when applied to industrial geometries as well as their capabilities to accurately predict relevant features of an industrial burner such as concentration and velocity profiles. Both steady and unsteady RANS along with a standard two equation turbulence model fail to accurately predict the concentration field within the burner, instead they predict a concentration field with too sharp gradients, regions with almost no fuel tracer as well as regions with far too high concentration of the fuel tracer. The SAS and LES approach both predict a more smooth time averaged concentration field with the main difference that the tracer profile predicted by the LES has smoother gradients as compared to the tracer profile predicted by the SAS. The concentration predictions by the SAS model is in reasonable agreement with the measured concentration fields while the agreement for the LES model is excellent. The LES shows stronger fluctuations in velocity over time as compared to both URANS and SAS which is due to the reduced amounts of eddy viscosity in the LES model as compared to both URANS and SAS. This study shows that numerical methods are capable of predicting both velocity and concentration in a gas turbine burner. It is clear that both time and scale resolved methods are required to accurately capture the flow features of this and probably most industrial DLE gas turbine burners.

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Air Change Rate Measurements using Tracer Gas Carbon Dioxide from Dry Ice

International Journal of Ventilation ◽

10.1080/14733315.2014.11684051 ◽

2014 ◽

Vol 13 (3) ◽

pp. 235-246 ◽

Cited By ~ 6

Author(s):

Pok Lun Cheng ◽

Xiaofeng Li

Keyword(s):

Carbon Dioxide ◽

Tracer Gas ◽

Change Rate ◽

Dry Ice ◽

Air Change Rate

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Estimation of a room ventilation air change rate using a stochastic grey-box modelling approach

Measurement ◽

10.1016/j.measurement.2018.04.029 ◽

2018 ◽

Vol 124 ◽

pp. 539-548 ◽

Cited By ~ 8

Author(s):

Marcel Macarulla ◽

Miquel Casals ◽

Núria Forcada ◽

Marta Gangolells ◽

Alberto Giretti

Keyword(s):

Change Rate ◽

Room Ventilation ◽

Air Change Rate ◽

Modelling Approach

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Quality of life control by selected methods of air exchange in a typical apartment building

10.20944/preprints202103.0362.v1 ◽

2021 ◽

Author(s):

Iveta Bullová ◽

Peter Kapalo ◽

Dušan Katunský

Keyword(s):

Air Quality ◽

Indoor Air Quality ◽

Indoor Air ◽

Allergic Diseases ◽

Well Being ◽

Indoor Climate ◽

Apartment Building ◽

Change Rate ◽

Air Change Rate ◽

Negative Effect

Air change rate is an important parameter for quantification of ventilation heat losses and also affects the indoor climate of buildings. Indoor air quality is significantly associated with ventilation. If air change isn't sufficient, trapped allergens, pollutants and irritants can degrade the indoor air quality and affect the well-being of a building's occupants. Many studies on ventilation and health have concluded that lower air change rates can have a negative effect on people’s health and low ventilation may result in an increase in allergic diseases. Quantification of air change rate is complicated, since it is affected by a number of parameters, of which the one of the most variable is the air-wind flow. This study aims to determination and comparison of values of the air change rate in two methods - by quantifying of aerodynamic coefficient Cp = Cpe - Cpi – so called aerodynamic quantification of the building and the methodology based on experimental measurements of carbon dioxide in the selected reference room in apartment building.

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