Fig. 2. Dual heat-exchanger thermodynamic cycle for closed-cycle EDL operation. gas heating. Now in this simplified cycle, we consider the particular case where enough power is added to the gas so that the Mach number at the laser channel exit is unity, i.e., the flow is choked. This gives the minimum mass flow and compressor power for any given laser power output and, as such, represents an idealized situation which permits ease of calculation without the complication of additional gasdynamic parameters. These conditions will not be realized in any practical device, in which the power added must be consistent with the discharge stability limits and with the maximum temperature increase allowable by lasing kinetics. Thus, the simplifications and restrictions of the present model yield an upper limit to the predicted performance and, as such, represent an optimistic situation which may only be approached with realistic devices. After flowing through a subsonic diffuser and encountering various frictional and turning losses, adiabatic compression restores the gas to the original stagnation pressure P01 and an elevated stagnation temperature Tm. The power added to the gas is r)cPc, where t)c is the compressor adiabatic efficiency. Finally, the gas flows through a waste heat exchanger which reduces the stagnation temperature back to the original value, T„i. Qw is the quantity of heat removed from the gas which must be radiated away into space. The second thermodynamic cycle, shown in Figure 2, uses two waste heat exchangers. Monson (5) found that this second configuration reduces the compressor power but increases the
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