Yew Khoy Chuah

Power consumption of semiconductor fabs in Taiwan

This paper reports and analyzes power consumption for nine representative semiconductor fabs in Taiwan. The power consumption data were obtained by surveys and site visits. Analysis results indicate that the average power consumption for the fabs is 2.18 kW/m2 and the average cooling load is 0.434 RT/m2. The average power consumption per unit product (wafer) area is 1.432 kWh/cm2, which is consistent with the data (3.1 kWh/cm2 in 1983 to 1.41 kWh/cm2 in 1995) reported by the US Department of Commerce and Dataquest. The facility system consumes the most of the power consumption (about 56.6%) of the semiconductor fabs. Process tools are the next largest power consuming item, accounting for 40.4% of the power consumed in the fabs. A facility system includes the chiller plant, makeup air, recirculation air, exhaust air, gases, compressed dry air, process cooling water, vacuum and ultra-pure water systems. The power consumption of the different facility components is analyzed and compared.

Design and evaluation of a minienvironment for semiconductor manufacture processes

A new minienvironment for controlling the process area from ambient air contamination was designed and evaluated. The new design has a buffer zone between the ambient and the process zones. A parametric study of this design using a Computational Fluid Dynamics (CFD) method was conducted for various cases. A full-scale experimental model was fabricated. The evaluation was completed by measurements of airflow patterns, zone pressure differentials and particle concentration levels for the fabricated minienvironment. It is concluded that this new minienvironment is capable of maintaining a cleanliness of less than one particle per cubic meter, and the buffer zone is effective in preventing cross contamination between the process and the ambient zones.

Deterministic simulation and assessment of air-recirculation performance of unidirectional-flow cleanrooms that incorporate age of air concept

Abstract The airflow characteristics of a unidirectional cleanroom are largely determined by the airflow in the supply air plenum, the return air plenum and the return air shaft. A deterministic computational fluid dynamic model that incorporates fan-performance characteristics was applied to investigate and compare the air-recirculation performance of the two general designs of unidirectional-flow cleanrooms. Typical flow-resistance models of the various components in the air path were used in the simulation. Non-uniformity (NU) of supply air velocity (at the filter face), airflow parallelism (deflection angle, α), and the distribution of the mean age of air were computed for the two types of unidirectional-flow cleanrooms. The results show that the performance of the fan filter unit system is generally superior to that of an axial fan system in terms of NU, deflection angle of airflow in the working zone, and the air-change efficiency derived from the age of air distribution. It was also found that the three performance indices provide a good assessment of the air-recirculation performance of unidirectional-flow cleanrooms.

Simultaneous control of particle contamination and VOC pollution under different operating conditions of a mini-environment that contains a coating process

Abstract Improvement in contamination control for a LCD color filter coater was studied by using a mini-environment design. Different operating conditions of the door and the exhaust of the mini-environment were studied. Measurements of particle concentration, flow field, and VOC concentration were performed. Both the particle contamination to the coating process and the VOC contamination to the outside cleanroom environment were considered in this study. It was found that a mini-environment could be designed to significantly reduce the particle concentration. Also, the exhaust of the mini-environment was found to affect the flow field in the mini-environment and result in an increase of particle contamination at a level close to the coating process. The design of the mini-environment requires optimal operating conditions.

Effects of Window Position on the Air Flow Distribution in a Cross-Ventilated Residential Bedroom

Results of an investigation of the effects of window position on the airflow characteristics for a typical bedroom setting in Taiwan are presented. Four different window positions were examined in the experiment which used a full-scale laboratory bedroom model with a single bed. A three-dimensional ultrasonic anemometer was used to measure airflow distribution and the results of flow measurements at two height levels are presented. Computer simulation of the airflow distribution was performed using the standard k-ε turbulence model. The measurements and the computer calculations resulted in similar airflow distributions for all positions of window openings. Close congruence between the results of calculations and those of the measurements shows the validity of using such a computer simulation in the airflow design of a residential bedroom. The results also show that the positions of window openings have appreciable effects on the airflow distribution. Proper window position is therefore an important factor in the design of ventilation for a cross-ventilated bedroom.

Energy Saving and Payback Period for Retrofitting Air Conditioning Systems in Taiwan

In Taiwan, AC systems in buildings with central air conditioning account for over 45% of the total electricity consumed. Inefficient and poorly designed AC systems in existing buildings waste considerable amounts of money and energy. Therefore, retrofitting AC systems has become a widely adopted strategy to save energy while maintaining a comfortable indoor thermal environment. This study analyzes the potential energy savings and payback period of retrofitting AC systems in public buildings. In addition to the required Building Energy Management System (BEMS), several measures are introduced to reduce energy consumption during retrofitting. The main measures include testing, adjusting, and balancing (TAB) of existing AC systems; replacing over-designed chillers with chillers with smaller capacity; installing frequency conversion in original systems, such that they become variable water volume (VWV) and variable air volume (VAV) systems; and utilizing CO2 concentration control and pre-cooling air systems. Based on analytical results, we conclude that AC system retrofitting can reduce total energy usage by 11.75%, while the average payback period for a retrofit project is 4.71 years, demonstrating that AC system retrofitting in Taiwan is economically sound.

Regenerative heat recovery - its industrial applications

Regenerative heat recovery has many industrial applications such in VOC treatment of automobile painting booth. A generalized thermal regeneration process coupled with a process and a pre-process was reviewed. Heat transfer and energy balance of the processes were analyzed and heat gain in the cycles is presented with relation to the efficiency of the regenerator. Applications in regenerative thermal oxidizer are discussed. It was found that in applications when the recovery efficiency is increased to 90%, the system in operation can save tremendous amount of burner heat and can have excess amount of heat recovery that could be used in other applications.

Analytical model for transient and stabilized conditions of RTO operation

Heat recovery efficiency is critical in the applications of regenerative thermal oxidizer (RTO). This study attempts to present a generalized mathematical model comprising all the parameters necessary to evaluate RTO performance for transient and stabilized conditions. The model includes governing equations for heat generation, heat degeneration and intermediate temperatures of the heat media in cyclic operation. The model derived expressions for all the necessary temperature parameters. The temperature parametric expressions presented are of useful in the design and evaluation of RTO performances. In addition, an expression for the evaluation of heat recovery efficiency is presented.

A Study of the Effects of the External Environment and Driving Modes on Electric Automotive Air-Conditioning Load

After driving power, the air-conditioning system is the main item of power load for electric vehicles. The air-conditioning load is not only affected by the external environment, but also by the driving modes. Moreover, the cooling load calculation is very different to that for buildings. This study develops an Excel-VBA-based air conditioning load calculation tool. Air-conditioning load calculation is based on inputs of ambient air temperature, wind speed, solar radiation, driving mode, and other parameters. The calculation also considers the vehicle’s shell structure and materials, glass radiation angle, low-e glass, occupancy, outdoor air, etc. Heat conduction, convection, and radiation are all considered in the calculation of the surface temperature of the vehicle’s shell structure. The calculated results agree well with the measured data and thus verify the developed calculation tool. In addition, the dynamic cooling load can be calculated when incorporating driving speed, GPS location, etc. An energy control strategy for different driving modes can be applied for dynamic cooling load. A variable speed compressor was studied for regulating the energy need of electric automotive air conditioning. It was found that occupant comfort can still be satisfied while reducing air-conditioning energy consumption, and hence prolong the driving range and battery life. It was found that when a five-passenger car has only a driver in the car, the control strategy can reduce the air-conditioning load by 11.2%. With further optimization of the compressor operation matching the cooling capacity, the compressor power consumption can save up to 52.8%.

A Study on the Control of Surface Condensation on a Multi-Cone Diffuser in Cold Air Distribution Applications

Multi-cone diffusers have good air distribution characteristics in cooling applications. However, surface condensation has been a problem impeding the use of multi-cone diffusers in cold air applications. An experimental study and a computer analysis are presented to show the causes of surface condensation on a multi-cone diffuser when distributing cold air. This study also attempts to alter the flow field characteristics near the diffuser cone surfaces by using an open inner cone with an insert that has a porous structure. Computer analysis has shown that the resultant airflow from the inner cone will repel the entrained room air away from the diffuser, thus preventing contact of the more humid air with the cold cone surfaces. The analysis has also shown that the altered flow field will cause the air dew point temperature in the vicinity of the diffuser to be lower than the temperature of the cone surfaces. Inserts with different porosities that were effective in preventing surface condensation were tested and the results are presented. These results indicate that the proposed airflow control method is effective in preventing surface condensation.