Abstract: An integral combination of expansion valve and evaporator in a cryostat using a single support member. The valve includes two flow orifices, one orifice being used primarily for steady-state operation and the other orifice being used only during cool-down. An actuator having a high coefficient of thermal expansion moves a needle positioned in the cool-down orifice such that a large orifice flow area at the start of cool-down is automatically and continuously reduced as the actuator temperature decreases as refrigerant is throttled through the orifice. Within a range of approximately 30 K from the desired steady-state evaporator temperature, the needle completely blocks the cool-down orifice. Then, refrigerant flows through the steady-state orifice which has a remotely adjustable needle. In the final stage of cool-down, the refrigerant system is entirely controlled by the steady-state orifice and its associated needle.

Abstract: A counter flow heat exchanger comprising a plurality of tubes disposed in a bundle array or tube within tube configuration to enhance heat transfer between high and low pressure tubes in the array or tube in tube configuration. Also disclosed are a method of increasing the heat transfer capacity of a tube bundle heat exchanger and a liquid helium temperature refrigerator or a reliquefier utilizing the heat exchanger.

Abstract: A heat exchanger for a fast cooldown cryostat having high pressure and low pressure flow paths wherein a low pressure flow path is defined by a finely divided matrix which in turn defines a plurality of flow paths and said high pressure flow path is disposed in heat exchange relationshp to said matrix.