Feasibility analysis of canceling reheating after condensation dehumidification in semiconductor cleanrooms

Abstract

Cold-heat offset problem occurs due to reheating after condensation dehumidification in the make-up air unit (MAU) of semiconductor cleanrooms . This study conducted on-site measurement and analyzed the indoor thermal balance in five tested factories A-E. Based on the measured results, this study focuses on the feasibility analysis of canceling reheating to avoid cold-heat offset. It is indicated indoor condensation will not be caused in the cleanrooms. Indoor subcooling is determined by air change rates of outdoor air ( A a ) and supplied indoor air ( A s ), and heat dissipation of indoor equipment ( Q in ). The larger A a , the less A s and the less Q in , the more likely indoor subcooling will be caused. When Q in is 0–100 W/m 2 , 100–200 W/m 2 and larger than 200 W/m 2 , the requirement range of A a to avoid indoor subcooling is 7–21/h, 12–26/h and 20–26/h respectively. It is concluded that canceling reheating is possible when factories A-D is within the operating parameters. In factory E, canceling reheating is impossible since indoor subcooling is unavoidable. The performance and energy saving potential of the proposed system which cancels reheating are then analyzed. Compared with the conventional system, the required cooling capacity and heating capacity are both decreased, and the energy saving ratio of the proposed system is 10.4%–38.3%. • Cold-heat offset is prominent in both make-up unit and entire system. • Canceling reheating will not cause indoor condensation, but may indoor subcooling. • Low outdoor air change rate and high sensible load do good to canceling reheating. • Energy saving ratio of the canceling reheating system is 10.4%–38.3%.