A fuel oil-fired condensing boiler consumes 0.006 kg/s of fuel with an LHV of 42.5 MJ/kg, the boiler efficiency is 97%. Calculate the thermal capacity of the boiler and the mass flow rate of water heated from tc = 23°C in return line to th = 45°C in supply line. Specific heat of water is

Question

A fuel oil-fired condensing boiler consumes 0.006 kg/s of fuel with an LHV of 42.5 MJ/kg, the boiler efficiency is 97%. Calculate the thermal capacity of the boiler and the mass flow rate of water heated from [latex]t_{c}[/latex] = 23°C in return line to [latex]t_{h}[/latex] = 45°C in supply line. Specific heat of water is 4.19 kJ/kgK.

Accepted Answer

1. Thermal capacity of the boiler ([latex]m_{f}[/latex] = 0.006 kg/s, LHV = 42,500 kJ/kg, [latex]\eta_{b}[/latex] = 0.97)

[latex]Q_{\mathrm{b}}=m_{f}{\mathrm{LHV}}~\eta_{\mathrm{b}}=0.006~{\mathrm{kg/s}}~{*}~42,500~{\mathrm{kJ/kg}}~{*}~0.97=247.35\,{\mathrm{kJ/s}}[/latex]

2. Mass flow rate of heating water

[latex]m_{w}=Q_{\mathrm{b}}/[c_{\mathrm{pw}}(t_{\mathrm{h}}-t_{\mathrm{c}})]=247.35/[4.19*(45-23)]=2.68~\mathrm{kg/s}=9660~\mathrm{kg/h}.[/latex]

Question 14.4: A fuel oil-fired condensing boiler consumes 0.006 kg/s of fu......

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