Abstract: A heat exchanger for vaporizing a cryogenic fluid comprises a conduit through which the fluid is passed and a heat transfer sleeve surrounding the conduit. The sleeve is comprised of two heat transfer sections, each having a central arcuate portion in close partial circumferential contact with the conduit, a plurality of radially extending heat transfer fins, and a pair of interlocking members located on the fins at a predetermined distance from the central portion for assembling the two sections together around the conduit. In the assembled state, the resiliency of the fins on which the interlocking members are located provides a continuous clamping for which permits the two central portions to maintain intimate contact with the conduit as it undergoes thermal contraction, while also facilitating assembly and disassembly of the two sections. Each heat transfer fins is also provided with a corrugated or rippled surface near its tip to increase its surface area and the rate of heat transfer and vaporization.

Abstract: A multi-cylinder pump for a cryogenic liquid is provided with an unloading system in which the inlet valve of each cylinder can be selectively held open or permitted to close. In the closed position, the operation of the cylinder is normal; while, in the open position, the liquid fails to attain sufficient pressure to exit through the outlet valve, thereby deactivating the cylinder. Preferably, the unloading system comprises several plunger assemblies which may be extended in order to engage the inlet valve and hold it in the open position. Each plunger assembly may be activated by means of a manual thumb screw or in accordance with the change in a pressure differential acting on the plunger. Alternatively, the plunger assembly may be activated electronically by means of a solenoid.