Ventilation scheme for electronic industrial cleanrooms based on numerical simulations of airflow patterns

WANG Can; WANG Haitao; GUO Erbao; JIANG Chengxin; ZHANG Zelong; ZHU Xingxin; CHEN Zhuo

doi:10.13732/j.issn.1008-5548.2025.06.016

Abstract：Objective To build electronic industrial cleanrooms that comply with the ISO Class 6 cleanliness standards while reducing energy consumption,this study focuses on optimizing non-unidirectional airflow ventilation schemes in electronic industrial cleanrooms. Methods For the non-unidirectional airflow organization in a cleanroom utilizing a make-up air unit-fan filter unit-dry cooling coil(MAU-FFU-DCC)ventilation system,computational fluid dynamics(CFD)simulations were conducted to evaluate four ventilation schemes.These schemes varied in air supply velocities and return air configurations,such as single-side or double-side returns,all operating under an upper-supply and side-return airflow pattern.A three-dimensional geometric model and a mathematical model of the cleanroom were established,and their reliability was verified.A systematic evaluation was conducted on the distribution characteristics of temperature and pressure fields of non-unidirectional airflow organization and the potential occurrence of upward airflow recirculation across different ventilation schemes.Three performance indices,temperature inhomo-geneity coefficient,thermal ventilation efficiency,and air age,were used to identify the optimal ventilation scheme that meets the ISO Class 6 cleanliness standards. Results and Discussion In the four ventilation schemes(S1,S2,S3,and S4),the average temperatures in the cleanroom were recorded as 22.04 ℃,21.95 ℃,21.98 ℃,and 21.80 ℃,respectively,all of which met the regulatory requirements for tem-perature.All four ventilation systems maintained a positive pressure environment.Compared to schemes S2 and S4 with an air supply velocity of 0.35 m/s,S,and S3with an air supply velocity of 0.30 m/s had lower air supply volumes and lower airflow pressure in the airflow patterns.Under the same supply velocities,no significant difference in pressure distribution was observed between the single-side return and double-side return configurations within the cleanroom.In single-side return schemes,eddies formed due to airflow collisions with walls on the non-outlet side,whereas in double-side return systems,the air was smoothly exhausted from both sides,reducing eddy phenomena.The average airflow deflection angles measured for S1,S2,S3,and S4 were 82.4°,83.5°,82.1°,and 83.2° respectively,all of which were below 90°.This indicated there was no upward return airflow in any of these schemes,thus meeting the cleanroom standards.The temperature non-uniformity coefficients for S1,S2,S3,and S4were calculated as 0.012,0.013,0.026,and 0.023,respectively,suggesting relatively uniform temperature distributions within the cleanroom.The thermal ventilation efficiency for these schemes reached 0.95,0.96,1.09,and 1.13,respectively.For the single-side return schemes,the efficiency was below 1,showing that the outlet temperatures were lower than those in the working zone.This resulted in insufficient heat exchange and energy waste.Conversely,in the double-side return schemes,the efficiency exceeded 1.0,with outlet temperatures higher than those in the working zone.This suggested more waste heat was absorbed before exhaust,leading to higher energy utilization efficiency and better economic viability.When the air supply velocities were 0.30 m/s and 0.35 m/s,the mean air ages for the single-side return schemes(S,and S2)were 75 s and 60 s,respectively,while those for the double-side return schemes(S3 and S4)were 60 s and 35 s,respectively.The mean air ages in S2,S3,and S4 met the regulatory standards and decreased with increasing air supply velocity.Notably,S3 required less air supply than S4,offering greater energy savings.Overall,the double-side return scheme with an air supply velocity of 0.3 m/s was found to be optimal.It delivered a cost-effective production environment that satisfied national cleanliness standards. Conclusion All four ventilation schemes demonstrate no upward airflow phenomena and meet the temperature and positive pres-sure requirements of the cleanroom.Among them,the double-side return scheme with an air supply velocity of 0.3 m/s is the most optimal one.It has a smaller air supply volume,conserves energy,and provides a cost-effective production environment that adheres to national cleanliness standards.