Date of Graduation
Statler College of Engineering and Mineral Resources
Industrial and Managements Systems Engineering
The primary indicator of capturing hood effectiveness is widely assumed to be the "capture velocity" measured normal to the center of the hood face, at the furthest location of the contaminant source. The velocity required at this distance (Vx) is thought to correspond to the appropriate flow (Q) required to capture the contaminant. The adequacy of Vx as a surrogate for hood effectiveness has long been poorly understood and has been little studied. Few considerations of potentially disruptive parameters, such as draft velocity, hood orientation, and operator presence are made during the design phase.;In this study, an anatomically correct heated, breathing, and moving manikin was used as a surrogate for a human hood operator. Velocity profiles of the capture envelope were obtained by particle image velocimetry (PIV) at three orientations (0°, 90°, 180°), with respect to the cross drafts (30, 60, and 120 fpm) generated inside a large wind tunnel. The capturing hood fan speed was set to maintain the Q of nominal Vx values of 50, 100, and 200 fpm, as measured 11 inches away from the hood face, in a controlled environment.;A condensation particle counter (CPC) was used to compare the capture efficiency and protection efficiency of the rectangular hood with the traditional, expensive, and time-consuming tracer gas method. Salt aerosols and Freon 134-A were released, at separate occasions, 11 inches away from the hood face. Measurements were taken within the duct (Cduct) and between the mouth and nose (CBreathingZone) of the manikin. Duct measurements (Cduct100 ) were also collected when the contaminant was directly fed into the duct, and breathing zone measurements were also conducted with the hood turned off (CBreathingZone100). The capture efficiency results of each method were compared, and no significant difference between the methods was found.;With the CPC method established as a viable method, studies were conducted to test the effects of operator presence, movement, hood orientation, and cross drafts under the same conditions as the PIV study. All effects, except for manikin movement, were found to have a significant effect on hood performance. Manikin movement did, however, have a significant effect on contaminant concentrations within the breathing zone of the operator.
Geissler, Brian Scott, "Effects of a Manikin on the Capture Efficiency and Protection Efficiency of a Small Rectangular Hood" (2017). Graduate Theses, Dissertations, and Problem Reports. 5658.