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Case Study: Convection For Heat Cure In Medical Appliances Bring Healthy Solutions

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Stovall Life Science makes a hybridization oven for research and development by molecular biologists on DNA (deoxy-ribonucleic acid) and RNA (ribonucleic acid).

The early oven concepts included a coiled-resistance wire heating system. One major problem: the tightly wound spirals of heat-concentrated wire kept failing. Compounding this reliability issue was the fact that the wire coil acted like a spring. When the element broke, it would touch an electrically conductive component within the oven. Not only would the heater short out, but the reliability failure became a hazard to the oven’s operator.

The first order of business at Thermal Circuits was to do a root cause analysis as to why the reliability problem. Thermal Circuits determined the open-wire element was running in excess of its thermal limitation. To rectify the situation, an etched-foil-element was designed. The same energy (watts) of the wire element was spread over the flat-foil conductor’s larger surface area. By not confining the wattage to tightly spiraled coils, the new etched-foil-element heating system runs cooler and lasts longer, still with the same power.

Second, the application required that the new and improved element be packaged as a forced convection assembly. This requirement was fulfilled by retrofitting two concentric cylinders to the hybridization oven’s existing muffin fan. Specifically, the smaller inner cylinder is constructed by forming the heating element, itself, into a tube. The outer larger cylinder has a dual nature. It directs the flow of air, similar to ductwork, and provides a dielectric shell for safety.

Finally, thermal fuses are incorporated as a fail-safe measure to enable U.L. recognition of the hybridization oven. This added feature protects the entire hybridization oven should any other component, such as the fan or temperature-controlling system, fail or the airflow be restricted.

By solving a reliability problem with a more thermally responsive and safer design, Thermal Circuits total solution yielded the hybridization industry a revolutionary improvement and its customer a sustainable competitive advantage.

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