Experimental and Numerical Investigation of Temperature and Flow Distribution Inside a Glove Box Enclosure for a High-Accuracy Coordinate Measurement Machine

Experiments and simulations were performed to assess the performance of an HVAC system for the cooling of a Leitz Infinity coordinate measurement machine (CMM) enclosed within a glove box (GB). Manufacturer specifications require maintaining very uniform temperatures with spatial and temporal variations not to exceed 0.3 °C/hr, 0.4 °C/day, and 0.1°C/m. Data were collected at 0.17 Hz by 2 thermocouples located outside the glovebox, 10 static thermocouples located inside the glovebox, and up to 28 thermocouples attached to the moving granite table of the CMM. The latter thermocouples are arrayed in a grid in the volume of interest (VOI) which envelopes the motion of the CMM measuring head above the granite table. Data were collected for periods ranging from 1 to 5 days to observe the effects of temperature variations within the enclosing facility. Simulations were then performed on the enclosed volume of the GB using ANSYS-CFX to better understand the heat loads, and test temperature variation mitigation strategies. These simulations consisted of 18 runs which varied heat input from the CMM motors, inflow gas temperature from the HVAC system into the GB, and non-uniform GB wall temperature boundary conditions. Heat loads from the motors were found to be insignificant influences on the temperature distribution, while fluid entrainment inside the diffuser was discovered to lead to an adverse temperature distribution, and insufficient cooling in the VOI. Velocity distributions were examined by using a TSI VelociCalc 8345 to verify the presence of stagnant regions in the GB. Finally, modifications to the diffuser design were proposed to eliminate entrainment, improve the flow distribution, and enhance temperature uniformity.