Abstract: A freeze and thaw system using knowledge-based hardware and methodology is provided for repair of oil-filled pipes. Liquid nitrogen is boiled off inside freeze jackets installed over the pipe, exiting in a superheated vapor state. Liquid nitrogen flow rates, controlled by the temperature controllers, are based on the requirements of the freeze process to maintain a desired level of superheat. The freeze operation is divided into distinct phases each with a different nitrogen superheated exhaust temperature. At the end of the repair, electric heaters wrapped over the pipe proceed to thaw the frozen oil. The heater controller thaws the frozen plugs based on an embedded time versus temperature protocol. The freeze prevention heaters are wrapped over the freeze jackets to prevent ice formation over the cold freeze jackets while the freeze plug is formed and maintained. This technology results in less thaw and freeze time at reduced liquid nitrogen usage.

Abstract: The performance of a compact heat exchanger in which a flow of air is employed to cool a flow of water can be enhanced by spraying water as a fine mist into the stream of coolant air. The water droplets, preferably less than 100 microns in diameter, coat the heat exchanger surface on the air side of the heat exchanger and provide evaporative cooling. The preferred form of heat exchange surface has strip fins.

Abstract: A system for cooling water from a spent fuel pool of a nuclear power generating plant. The system includes a heat exchanger in which a flow of air is employed to cool a flow of pool water. The performance of the heat exchanger is enhanced by spraying water as a fine mist into the flow of coolant air. The water droplets, preferably less than 100 microns in diameter, coat the heat exchange surface on the air side of the heat exchanger and provide evaporative cooling. The preferred form of heat exchange surface has strip fins.