Engineering Analysis And Design
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Engineering Analysis And Design
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Thermal Design Support For Explosive Detection System
As part of their constant drive to improve the performance of the CTX 9000 DSi scanner system, InVision contracted Q-Metrics to assist in thermal testing of a prototypic system and to analyze the cooling system using a 3-D computation fluid dynamics (CFD) code. To ensure high performance and reliability even in hot, dusty and humid airport environments, InVision has equipped each system with a self-contained, compact air-conditioning unit. The air-conditioning unit forces cool, filtered air through the entire system in a closed circuit. Cooling of the unit is complicated by the fact that X-ray source, its power supply, and the detection electronics are mounted on a gantry that rotates at 120 RPM. While the gantry rotation allows a “slice” image to be generated within half a second, it also creates a constantly changing flow regime around the critical electronic components. The intent of the Q-Metrics’ analysis was to create a numerical simulation of this complex flow regime and to recommend changes in the system design to improve the thermal performance of the current system and for future design variations. Q-Metrics employed the IcepakÔ software to create a 3-D model of the center module of the CTX 9000 DSi scanner system. This module houses the rotating gantry and system’s electronics. The in-feed and out-feed conveyor modules were not modeled since these components contain no significant heat sources and they are not directly cooled. The results of the thermal testing and analysis (example figures shown below) were used to provide design direction for improving the performance of the air-conditioning unit and to reduce the flow leakage that was occurring at the junction between the inlet plenum and the rotating gantry.
Analytical Model of Center Module Interior Equipment Model
Flow Vectors At Center Of Gantry Particle Trace Of Flow Lines |
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The
CTX 9000 DSi system is a FAA-certified Explosives Detection System (EDS). The
system, designed by InVision Technologies, uses a 1-meter wide conveyor to move
each bag through the machine. Once the bag enters the system, a scan projection
X-ray image is created and used by the onboard computer to determine which areas
need additional "slice" images. If required, these “slice” images are taken by
a rotating X-ray source. Using sophisticated computer algorithms, the CTX 9000
DSi analyzes these images and compares their properties with those of known
explosives. If a match is found, the system alarms and displays the object on
the screen. 
