Abstract: A linear spool valve device is employed in a work exchanger system for directing flow of fluid therein. The device comprises a cylinder in which first and second pistons are movably disposed, a high pressure inlet located at substantially a central point along the length of the cylinder, and work exchanger ports located between respective ends of the cylinder and the high pressure inlet. Low pressure outlets can be provided at each end of the cylinder, or alternatively a single low pressure outlet can be provided. The design of the piston/cylinder arrangement is such that each of the work exchangers is alternately completely pressurized, partially pressurized, or completely depressurized, but only one work exchanger at a time is completely pressurized or completely depressurized.