No single working fluids may have desirable requirements of working fluid. Different working fluids may have different attractive feature in them, but not all. In such cases two vapour cycles operating on two different working fluids are put together, one is high temperature region and the other in low temperature region and the arrangement is called binary vapour cycle.

Mercury has high critical temperature (898°C) and low critical pressure (180 bar) which makes a suitable working fluid will act as high temperature cycle (toppling cycle) and steam cycle will act as low temperature cycle. Mercury vapours are generated in mercury boiler and sent for expansion in mercury turbine and expanded fluid leaves turbine to condenser. In condenser, the water is used for extracting heat from the mercury so as to condensate it. The amount water entering mercury condenser.

The mercury condenser also act as steam boiler for super heating of heat liberated during condensation of mercury is too large to evaporate the water entering of seam an auxiliary boiler may be employed or superheating may be realized in the mercury boiler itself.

From the cycle,

Since pump works are very small, it may be neglected.

Work from Mercury Turbine, WHg = mg (ha -hb)

Work from Steam Turbine, Wsteam = msteam (h1 -h2)

Pump work, Wpump = mHg (hd -hc) + msteam (h4 -h3)

Heat supplied to the cycle, Qin = mHg (ha -hd) + msteam éë (h1 -h6) + (h5 -h4)

Heat rejected, Qout = msteam (h2 –h3)