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• The heat pipe heat recovery technology has the highest EER when used in different climate regions. • A two-stage heat pipe heat recovery device is proposed. • The device has significantly improved the heat recovery efficiency, shortened the investment recovery period. To investigate the efficient waste heat recovery (WHR) technology suitable for cleanrooms, the energy-saving effectiveness of three WHR technologies of heat pipe, liquid circulation, and solution absorption was compared and the comparison was conducted across four different climate regions: severe cold, cold, hot summer cold winter, and hot summer warm winter. The findings reveal that the energy efficiency ratio (EER) of the heat pipe WHR surpasses that of the other two technologies. Specifically, the EER values for the heat pipe WHR in the four climate regions are 21.0, 15.4, 14.1, and 7.3, respectively. Furthermore, a two-stage heat pipe WHR technology is proposed to enhance the heat recovery efficiency of the heat pipe WHR technology, and experimental research has been conducted. The results show that the average heat recovery efficiency reaches 61.64 % when the wind speed is 2 m/s and the new exhaust air temperature difference is 6–11 °C. Compared to the single-stage HPHE, the use of two-stage heat pipe WHR technology in the four climates regions resulted in 6.9 %, 12.8 %, 21.5 %, and 13.6 % higher net heat recovery, 7.1 %, 13.5 %, 16.6 %, and 40.2 % higher energy-efficiency ratios, and 8.2 %, 13.5 %, 12.2 %, and 37.3 % shorter static payback periods, respectively. The heat recovery solution shows a good application prospect in cleanroom WHR. [ABSTRACT FROM AUTHOR]

In this research, the airflow pattern and particle dispersion in a contaminated full-scale cleanroom are investigated numerically using both Eulerian and Lagrangian approaches. Three different supply diffuser configurations namely (1) central, (2) horizontal and (3) vertical and three different exhaust grille configurations namely (4) vertical symmetric, (5) asymmetric and (6) horizontal symmetric are selected for the analysis. The presented results reveal that the supply/exhaust openings arrangement has a significant influence on the particulate contaminant dispersion in the cleanrooms. The comparison of the above different supply diffuser configurations shows that the vertical and horizontal supply diffuser configurations lead to a more escaped particles and less deposited particles on the room walls and installed working table in the room than the central one. It is also found that for different exhaust grille arrangements, the performance of the ventilation system in the horizontal symmetric case is higher than asymmetric and vertical symmetric ones. At the same time, it is observed that the variations of contaminant concentration in both Eulerian and Lagrangian approaches are almost the same. The results of the velocity and particle concentration show good agreement with the available experimental data in the literature. [ABSTRACT FROM AUTHOR]

Traditional wall-return re-circulation air systems with ceiling-supply and wall-return air grilles are fairly common in non-unidirectional airflow industrial cleanrooms. Such re-circulation systems normally have longer airflow circulation pathways, which inherently induced higher airflow resistance, resulting in higher fan power demand per unit of airflow rate delivered. To overcome the airflow resistance, Fan Filter Units (FFUs) used in the traditional wall-returned re-circulation system are designed to operate with high external pressures, which also induce high negative pressures in supply air plenums (SAP). The negative pressures within SAP can increase the risks of infiltration of outdoor air and contaminants. A longer airflow pathway corresponds to a higher level of negativity of the air pressure inside the supply air plenum, thus inducing higher risks of cross-contamination. To overcome the above-mentioned drawbacks, a new re-circulation system using fan dry coil unit (FDCU) was proposed. This new system exhibits shorter air re-circulation paths while providing effective environmental controls (e.g., removal rate of 0.1 μm particle and temperature control) for a cleanroom. In this study, experiments were conducted in a full-scale cleanroom to investigate the energy performance of applying the innovative FDCU-return system, compared to a traditional wall-return system. Results showed that the FDCU-return system can increase energy efficiency and reduce the electric energy consumption by more than 4% compared to the wall-return system. [ABSTRACT FROM AUTHOR]

Abstract: The substantial energy demands of today''s cleanroom environmental-maintenance systems provide large opportunities for energy conservation. However, cleanroom environments are subject to much more stringent standards and operate with much smaller tolerances, and therefore simple application of industrial/commercial controls is not sufficient. We conducted a set of measurements in a Class 1000 cleanroom to confirm that humans are the predominant source of particles in a cleanroom, supporting that occupancy can be used as an effective surrogate for particle concentrations. Our data suggest that people release approximately 1.7×104 particles per minute into the cleanroom and raise the local concentration of particles by 1742±481 particles m−3 person−1. Furthermore, our timescale analysis on control system and ventilation unit responses indicates that a predictive-occupancy system is required for implementing demand-controlled ventilation. [Copyright &y& Elsevier]

Abstract: In the recent decades, cleanrooms have found growing applications in broad range of industries such as pharmacy and microelectronics. Concerns about negative effects of the contaminant exposure on the human health and product quality motivate many researchers towards understanding of the airflow and contaminant distribution though these environments. With an improvement in computational capacity of the computers, computational fluid dynamics (CFD) technique has become a powerful tool to study the engineering problems including indoor air quality (IAQ). In this research, indoor airflow in a full-scale cleanroom is investigated numerically using Eulerian–Eulerian approach. To evaluate the ventilation system effectiveness, a new index, called final efficiency, is introduced which takes all aspects of the problem into account. The results show that the contaminant source motion and its path have a great influence on the contaminant dispersion through the room. Based on the results, the contaminant distribution indexes, e.g. final efficiency and spreading radius, are improved when the source motion path is in the dominant direction of the ventilation airflow. Consequently, the efficiency of an air distribution system which provides a directional airflow pattern shows the least source path dependency. This study and its results may be useful to gain better understanding of the source motion effects on the indoor air quality (IAQ) and to design more effective ventilation systems. [Copyright &y& Elsevier]

Abstract: Operation of make-up air units (MAUs) for cleanrooms of high-technology fabrication plant in subtropical climates is very energy intensive, in that it is expected to deliver conditioned air at elevated airflow rates, compared to conventional commercial applications. Optimizing the design of MAU via reducing or displacing mechanical cooling or electrical heating processes can improve energy efficiency in cleanrooms since cleanroom air-conditioning systems typically use 30–65% of the total energy consumption in a high-tech fabrication plant . This paper investigates the difference in energy efficiency performance of MAU systems with different pre-cooling and preheating/humidification schemes. Additionally, a comparative study was carried out for humidification schemes including wet media, directly atomized water, steam, and two-phase flow. The results show that energy recovery by DCC water return method exhibits the best energy efficiency among a total of eight schemes evaluated in this study. In addition, wet media scheme is the best humidification scheme in winter time, compared with the other three types of humidification schemes. [ABSTRACT FROM AUTHOR]

• An improved system is proposed based on multi-fans with frequency conversion. • The improved system meets pressure control requirement in non-working modes. • The energy saving and cleanliness can be achieved by switching operation modes. Pressure control for cleanrooms in the pharmaceutical industry is a necessary means to avoid the cross-contamination. The pressure control of traditional air conditioning can only handle the working stage. In the non-working stage, the system cannot reduce the air change rate per hour (ACH) in order to alleviate the problem of high energy consumption. This paper proposes an improved air conditioning system, which focuses on the ability to control pressure gradient of the system in working and non-working mode. By theoretical derivation of the combined fan frequency conversion, when the impedance and volume of the infiltration air satisfy S i G Z , i = S j G Z , j = S k G Z , k = c o n s t a n t , the pressure gradient in multi-zone cleanrooms can remain stable. A mathematical model of the system has been established, which includes five modules: air pipe network, fan characteristic curve, fan operating point solution, variable volume damper characteristic curve and multi-zone network pressure gradient solution. The correctness of the model is verified by field measurements. Taking a clean workshop as case study, the room pressure can be stabilized in the range of ± 3 Pa by switching the working and non-working mode, which can save 39.8% of the energy consumption in non-working mode, while ensuring cleanliness. This paper demonstrates the process of the air pipe network's influence on cleanrooms pressure and proves the effectiveness of improved purification air conditioning system in pressure gradient control and energy saving potential. [ABSTRACT FROM AUTHOR]

[Display omitted] The artificial earth satellites with different numbers and sizes are stored in a large clean space in the satellite factory before they are launched. The cleanliness of the satellite factory is maintained by an air-conditioning system consisting of three rows of nozzles installed on the side walls of the factory. Traditionally, all the nozzles are operated at a rated air volume regardless of the arrangement of the satellites, which results in a high energy consumption by the air circulating fans. In this study, we proposed a control method for the nozzles, based on the number and size of satellites. A CFD model was developed to simulate the cleanliness in the satellite factory and the cleanliness for different scenarios with different sizes and numbers of satellites was simulated. The control strategy and rate of reduction of the circulating air volume was obtained for different arrangements of satellites. The results show that the less circulating air volume is required when the number of satellites is small or the size is short. The total air volume can be reduced by 49.1% for a year and the energy consumption of the fan can be reduced 57.8%. This study provides a feasible method to reduce the circulating air volume, which can be used to guide the design and operation of actual projects. [ABSTRACT FROM AUTHOR]

Abstract: Benchmarking is an important step in implementing energy conservation in a semiconductor fabrication plant (hereafter referred to as “fab”). A semiconductor cleanroom facility system is complicated, usually comprised of several sub-systems, such as a chilled water system, a make-up system, an exhaust air system, a compressed air system, a process cooling water (PCW) system, a nitrogen system, a vacuum system, and an ultra-pure water (UPW) system. It is a daunting task to allocate energy consumption and determine an optimum benchmark. This study aims to establish the energy benchmark of a typical 8-in. DRAM semiconductor fab through field measurement data. Results of the measured energy consumption index were: chilled water system (including chiller, chilled water pump and cooling tower): 0.257kW/kW (=0.9kW/RT) in summer and 0.245kW/kW (=0.86kW/RT) in winter air recirculation air system: 0.00018kWh/m3 make-up air system: 0.0042kWh/m3 general exhaust air system: 0.0007kWh/m3 solvent exhaust air system: 0.0021kWh/m3 acid exhaust air system: 0.0009kWh/m3 alkaline exhaust air system: 0.0025kWh/m3 nitrogen system: 0.2209kWh/m3 compressed dry air system: 0.2250kWh/m3 process cooling water system: 1.3535kWh/m3 and ultra-pure water system: 9.5502kWh/m3. These data can be used to assess the efficiency of different energy-saving schemes and as a good reference for factory authorities. The PCW system''s status before and after implementing energy conservation is discussed. [Copyright &y& Elsevier]

• On-site performances of the LDAC system and conventional system are compared. • The LDAC system can avoid reheating and recover cooling from the exhaust air. • The LDAC system shows a competitive COP sys ranging 3.5–4.5 in summer conditions. • An electric power saving rate of 37.3% can be achieved by the LDAC system. Considerable ventilation rates in laboratory animal rooms indicate huge energy consumption of air-conditioning systems. The liquid-desiccant air-conditioning (LDAC) system is regarded as an energy-efficient system, which can help to save energy in laboratory animal rooms. However, limited studies have applied LDAC systems to this kind of rooms for energy conservation. In this study, a demonstration project is focused on, wherein both the LDAC system and conventional vapor-compression system are used in the laboratory rodent center. On-site measurements were conducted to reveal the energy performance difference between the two systems. The test results reveal that the considerable cooling loads of two rodent rooms air-conditioned by the conventional system and LDAC system are 482.1 W/m2 and 576.8 W/m2, respectively, under the summer conditions in Beijing. The LDAC system can avoid reheating and recover cooling from the exhaust air from indoors. Thus, the coefficient of performance (COP sys) of the LDAC system ranges 3.5–4.5, whereas the COP sys of the conventional system only ranges 1.8–2.3 during the test period. During the entire cooling season, an electric power saving rate of 37.3% can be achieved by the LDAC system. Moreover, although both systems can satisfy all the environment control requirements, the LDAC system is beneficial for particulate matter filtration, yet slightly unfavorable for reducing indoor ammonia concentration, compared to the conventional system. [ABSTRACT FROM AUTHOR]