摘要 |
<p>A fluid flow control device includes a thermally conductive conduit section having both interior and exterior heat exchange surfaces, with the interior surface being adapted to contact fluid flowing thereover. A controllable heat transfer means coupled to the conduit section has a first operative state for removing heat from the exterior heat exchange surface to reduce the temperature of the conduit section sufficiently to freeze liquid adjacent the interior heat exchange surface and thereby at least partially restrict the flow of fluid thereover. In a second operative state, the heat transfer means supplies heat to the interior heat exchange surface to melt at least a portion of any frozen liquid adjacent the interior heat exchange surface and thereby permit the flow of fluid thereover. In one exemplary embodiment of the invention, the heat transfer means includes a heat sink for receiving and dissipating heat removed from the conduit section, and a thermal electric heat pump controls the flow of heat to and from the conduit section. In another exemplary embodiment of the invention, the heat transfer means includes a heat sink and one or more electrical resistance heaters for heating the liquid adjacent the interior heat exchange surface.</p> |