Validating insertion loss predictions for HVAC silencers

Ventilation systems normally contain large dissipative splitter silencers that are used to attenuate fan noise. Recently, numerical models have been developed that seek to predict the insertion loss of these silencers; however, there is very little experimental data available in the literature that is suitable for validating these insertion loss predictions and so questions marks still remain regarding the accuracy of the models. This issue is investigated here by comparing theory with experiment for a range of splitter silencers. Here, the insertion loss predictions are compared against experimental measurements obtained on a test rig that conforms to ISO 7235. Measurements are presented for silencers of differing geometry, although each silencer is restricted to one central splitter with two baffles lining the opposite walls of the duct. Furthermore, validation of the numerical models is based on measurements taken both with and without flow. Comparison between prediction and experiment is reported in one-third octave frequency bands up to a frequency of 8 kHz. Results indicate that the theoretical model is capable of providing accurate predictions for silencers of high percentage open area, but when the percentage open area is low significant discrepancies appear between prediction and experiment at higher frequencies

Pore Scale Observations of Trapped CO2 in Mixed-Wet Carbonate Rock: Applications to Storage in Oil Fields

Geologic CO2 storage has been identified as a key to avoiding dangerous climate change. Storage in oil reservoirs dominates the portfolio of existing projects due to favorable economics. However, in an earlier related work (Al-Menhali and Krevor Environ. Sci. Technol. 2016, 50, 2727−2734), it was identified that an important trapping mechanism, residual trapping, is weakened in rocks with a mixed wetting state typical of oil reservoirs. We investigated the physical basis of this weakened trapping using pore scale observations of supercritical CO2 in mixed-wet carbonates. The wetting alteration induced by oil provided CO2-wet surfaces that served as conduits to flow. In situ measurements of contact angles showed that CO2 varied from nonwetting to wetting throughout the pore space, with contact angles ranging 25° < θ < 127°; in contrast, an inert gas, N2, was nonwetting with a smaller range of contact angle 24° < θ < 68°. Observations of trapped ganglia morphology showed that this wettability allowed CO2 to create large, connected, ganglia by inhabiting small pores in mixed-wet rocks. The connected ganglia persisted after three pore volumes of brine injection, facilitating the desaturation that leads to decreased trapping relative to water-wet systems

Comparison of simultaneous shock temperature measurements from three different pyrometry systems

Pyrometry is one of the most prevalent techniques for measuring temperature in shock physics experiments. However, the challenges of applying pyrometry in such highly dynamic environments produces multiple sources of uncertainty that require investigation. An outstanding question is the degree of agreement between different pyrometers and different experiments. Here we report a series of novel plate impact experiments with simultaneous thermal radiance measurements using three different multi-wavelength optical pyrometry systems, each with different spatial and temporal resolutions, on samples shocked to identical states. We compare the temperatures measured by each system and their associated uncertainties using a number of emissivity assumptions. The results shown that the measurements from all three systems agree within uncertainty. Some non-thermal light contamination was observed despite a number of prevention measures