5-31 Saturated water vapor at 8 bar is generated in a natural gas boiler at a rate of 0.25 kg/s. This steam is used for process heating in an industrial facility and returns to the boiler at the same pressure as a saturated liquid. If the natural gas (HHV = 50,000 kJ/kg) is consumed at a rate of 0.72 kg/min, determine the boiler efficiency. 5-32 Reconsider Prob. 5-31. Determine the evaporation ratio. If the evaporation ratio in this boiler is increased by 3 percent for the same rate of steam output, what is the new value of boiler efficiency?