Here is the energy analysis of the hydronic heating system depicted in the diagram.
The boiler plant consists of two identical boilers, each having the following characteristics:
• Fuel: natural gas
• Burner Type: on/off
• Rated Output = 85 kW
• Rated Efficiency, nFL = 80%
The boilers operate in a “Lead/Lag” arrangement, i.e., Boiler 1 operates first to meet the load (up to its capacity), and Boiler 2 operates as necessary to meet any remaining load.
The pump and motor have the following characteristics:
• Flow Rate = 15 L/s
• Pressure Rise = 160 kPa
• Pump Efficiency = 60%
• Motor Efficiency = 88%
a) Estimate the shaft power (W) required by the pump
b) Estimate the fuel consumption rate of the boiler plant (m3 /hr) during a moment when both boilers are cycled on. Assume the heat content of natural gas is 10.33 kWh/m3 .
c) Consider a period when the heat extraction rates from the loop are as follows: Zone 1 = 30 kW, Zone 2 = 12 kW, Zone 3 = 22 kW. Estimate the heat load to be met by each boiler (kW) during this period.