a. A process heater uses Dowtherm A heat transfer fluid to provide 850 kW of heat. Estimate the annual operating cost of the heater if the Dowtherm evaporator is 80% efficient and the price of natural gas is $4.60/MMBtu. Assume 8000 operating hours per year.
b. A site steam system consists of HP steam at 40 bar, MP steam at 18 bar, and LP steam at 3 bar. If natural gas costs $3.50/MMBtu and electricity is worth $0.07/kWh, estimate the cost of steam at each level in $/metric ton.