Abstract: 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.

Abstract: 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.

Abstract: Method and apparatus for the processing of fluid materials, particularly in the preparation of samples for radioactive isotope tracer studies by combustion of starting materials containing such isotope tracers. The sample is burned in a combustion chamber which tapers upwardly and inwardly above the sample receptacle so as to approximate the shape of the flame of a burning sample, and the combustion products are continuously exhausted from the combustion chamber and passed through a heat exchanger which condenses the condensable vapors in the combustion products. The condensed vapors are then separated from the gases, and the gases are passed into a reaction column if there is a radioactive isotope tracer remaining in gas form.

Abstract: Method and apparatus for the processing of fluid materials, particularly in the preparation of samples for radioactive isotope tracer studies by combustion of starting materials containing such isotope tracers. The sample is burned in a combustion chamber which tapers upwardly and inwardly above the sample receptacle so as to approximate the shape of the flame of a burning sample, and the combustion products are continuously exhausted from the combustion chamber and passed through a heat exchanger which condenses the condensable vapors in the combustion products. The condensed vapors are then separated from the gases, and the gases are passed into a reaction column if there is a radioactive isotope tracer remaining in gas form.

Abstract: A system for combusting materials containing radioactive nuclides to permit recovery of the radioactive nuclides includes a combustion zone for combusting a sample material containing at least one radioactive nuclide. The combustion products are continuously exhausted from one end of the combustion zone, and a continuous pressurized stream of oxygen-containing gas is introduced into the combustion zone between the exhaust end of the zone and the sample during the combustion thereof. At least a portion of the pressurized oxygen-containing gas stream is directed through the combustion zone in a spiral path toward the sample to circulate at least a portion of the combustion products around the combustion zone as they flow toward the exhaust end of the zone counter to the flow of the spiraling stream of oxygen-containing gas, thereby intimately mixing the combustion products with the oxygen-containing gas in the combustion zone.

Abstract: Method and apparatus for the processing of fluid materials, particularly in the preparation of samples for radioactive isotope tracer studies by combustion of starting materials containing such isotope tracers. The sample is burned in a combustion chamber which tapers upwardly and inwardly above the sample receptacle so as to approximate the shape of the flame of a burning sample, and the combustion products are continuously exhausted from the combustion chamber and passed through a heat exchanger which condenses the condensable vapors in the combustion products. The condensed vapors are then separated from the gases, and the gases are passed into a reaction column if there is a radioactive isotope tracer remaining in gas form.

Abstract: A combustion system for combusting materials containing radioactive nuclides to permit recovery of the radioactive nuclides. The system comprises a primary combustion zone in which the sample material is initially combusted and from which the combustion products are continuously exhausted. The exhaust products from this primary combustion zone are passed through a secondary combustion zone in which uncombusted materials in the exhaust products are combusted. In the secondary combustion zone, the exhaust products from the primary zone are directed in a helical path so that centrifugal forces drive the gases and any particulate matter entrained therein toward the walls of the secondary zone while intimately mixing the materials with each other to achieve rapid and complete combustion. The secondary combustion zone preferably comprises a helical tube which is heated by passing an electric current through the walls thereof. The helical path preferably has a radius of curvature of less than about 1.