Flow Features to Control Thermally Induced Convection in a Vertical Laminar Flow Cleanroom

Abstract

This paper presents results of a flow simulation study of convection heat currents above a heat source in a vertical laminar flow (VLF) cleanroom as determined both experimentally and computationally. Typical clcanroom operations have numerous pieces of equipment that generate heat— thus the importanec of this study. The experiment was carried out in a full-scale mockup of a cleanroom. Temperature distributions above an electrical hot plate were measured for 12 airflow velocities and four heat source levels. The results showed that when the mean downward airflow velocity was 0.20 m/s or greater, the plume of heated air was completely suppressed and rose only 30 cm above the heat source. The relation between the convection current zone and the Richardson number was determined. Computer models simulating the turbulent incompressible fluid flow in a Cartesian coordinate system were applid to analyze the three-dimensional heat currents inside the VLF cleanroom and to prediet the temperature and velocity distributions. The velocity distributions clearly indicated the magnitude of the area within which the heat current disturbed the vertical flow. Comparisons between the experimental findings and the calculated results provided significant information on how to apply the computer simulation to a practical design.