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Technical Briefs

Autonomous Thermal Control System for Highly Variable Environments

[+] Author and Article Information
G. A. Richardson

Department of Mechanical and Aerospace Engineering, University of Alabama in Huntsville, Huntsville, AL 35899georgia.richardson@uah.edu

J. Heat Transfer 131(6), 064505 (Apr 13, 2009) (3 pages) doi:10.1115/1.3085826 History: Received March 12, 2008; Revised November 13, 2008; Published April 13, 2009

An autonomous thermal control system has been developed for instruments with steady temperature requirements that are exposed to widely varying environmental conditions. The active thermal control system uses thermo-electric (Peltier) coolers with a programmable power supply, digital temperature sensors, and on-board proportional differential logic to track and predict temperature variations. This system is designed for instruments with large thermal mass and thermally sensitive electronic components that would be effected by variabilities in the local outdoor environment including weather, sunrise, and sunset. Presented are the test results of the design showing the temperature stayed within ±0.125°C during smooth ambient temperature changes (27°C ambient change over 80 min), remained within +0.375/0.6875°C under a sharp ambient temperature drop (27°C sudden drop), and remained within +0.25/0.875°C when random variabilities in the ambient were introduced (210°Cdegree variabilities over the time frame of minutes). For the thermal control system and test results presented, it is shown that several calibration and design points must be considered for a large thermal mass system in order to achieve steady thermal control. The system presented is capable of maintaining steady thermal control within the given constraints.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

Grahic Jump Location
Figure 1

System configuration: An aluminum plate is actively cooled using TECs. Thermally sensitive components are mounted directly to the cooled plate (0.305×0.203×0.00635 m3) and temperature sensors are attached to the components.

Grahic Jump Location
Figure 2

Thermal test with 27°C sudden ambient temperature drop after a gradual increase. The maximum temperature change in the measurement is +0.375/−0.6875 deg.

Grahic Jump Location
Figure 3

Thermal test with a variable ambient temperature and 12°C sudden ambient temperature rise. The maximum temperature change in the control plate is +0.25/−0.875 deg.

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