Showing Thar Processes in Closed and Open Systems Are Different A mass M of gas is to be compressed from a temperature T, and a pressure P, to T, and P. in (a) a one-step process in a frictionless piston and cylinder,' and (b) a continuous process in which the mass M of gas is part of the feed stream to the compressor of the previous illustration. Compute the sum Q + W for each process. Reservoir Water turbine Water ow Dam Hydroelectric power generating station Figure 3.1-2 A hydroelectric power generating station: a device for obtaining work from a Auid Aowing across a large pressure drop