Squeeze-film damping on microresonators is a significant damping source even when the surrounding gas is highly rarefied. This article presents a general modeling approach based on Monte Carlo (MC) simulations for the prediction of squeeze-film damping on resonators in the freemolecule regime. The generality of the approach is demonstrated in its capability of simulating resonators of any shape and with any accommodation coefficient. The approach is validated using both the analytical results of the free-space damping and the experimental data of the squeeze-film damping on a clamped-clamped plate resonator oscillating at its first flexure mode. The effect of oscillation modes on the quality factor of the resonator has also been studied and semi-analytical approximate models for the squeeze-film damping with diffuse collisions have been developed.
This report describes models of building faults that were created for OpenStudio to support the ongoing development of fault detection and diagnostic (FDD) algorithms at the National Renewable Energy Laboratory. Building faults are operating abnormalities that degrade building performance, which include using more energy than normal operation or failing to maintain building temperatures according to the thermostat set points. Models of building faults in OpenStudio can be used to estimate fault impacts on building performance and to develop and evaluate FDD algorithms. The aim of the project was to develop fault models for typical heating, ventilating, and airconditioning (HVAC) equipment in the United States. The fault models in this report are grouped as follows: Control fault models, which simulate the impacts of inappropriate thermostat control schemes such as an incorrect thermostat set point in unoccupied hours and manual changes of thermostat set point due to extreme outside temperatures Sensor fault models, which focus on the modeling of sensor biases including economizer relative humidity sensor bias, supply air temperature sensor bias, and water circuit temperature sensor bias Packaged and split air conditioner fault models, which simulate refrigerant undercharging, condenser fouling, condenser fan motor efficiency degradation, noncondensable entrainment in the refrigerant, and liquid line restriction Water-cooled chiller fault models, which simulate refrigerant overcharging, excessive oil, noncondensable entrainment in the refrigerant, and condenser fouling Other uncategorized fault models, which include duct fouling, excessive infiltration into the building, and blower and pump motor degradation.
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