Please calculate the current for the circuit below
1 answer:
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Answer:
1) q=18414.93 W
2) C=12920$
Explanation:
Given data:
pipe length L=25m
pipe diameter D=100mm =0.1 m
air temperature =
=25
°C.....= 298.15k
pipe surface temp =150
°C.....=423.15k
surface emissivity e= 0.8
boiler efficiency η=0.90
natural gas price Cg=$0.02 per MJ
1) Total heat loss and radiation heat loss combined
q=
q=б(
^4-
^4)]....... (1)
б=5.67×10^-8 W/m^2K^4 (boltzmann constant)
area A =L.Dπ=25×0.1π=7.85 m^2
putting all these values in eq (1)
q=18414.93 W
2) suppose boiler is operating non stop annual energy loss will be
E=q.t
=18414.93.3600.24.365
=5.81×10^11 J
to find furnace energy consumption
Ef =E/η
=6.46×10^5 MJ
annual cost
C=Cg. Ef
=12920$
Answer:
net boiler heat = 301.94 kW
Explanation:
given data
saturated steam = 6.0 bars
temperature = 18°C
flow rate = 115 m³/h = 0.03194 m³/s
heat use by boiler = 90 %
to find out
rate of heat does the boiler output
solution
we can say saturated steam is produce at 6 bar from liquid water 18°C
we know at 6 bar from steam table
hg = 2756 kJ/kg
and
enthalpy of water at 18°C
hf = 75.64 kJ/kg
so heat required for 1 kg is
=hg - hf
= 2680.36 kJ/kg
and
from steam table specific volume of saturated steam at 6 bar is 0.315 m³/kg
so here mass flow rate is
mass flow rate =
mass flow rate m = 0.10139 kg/s
so heat required is
H = h × m
here h is heat required and m is mass flow rate
H = 2680.36 × 0.10139
H = 271.75 kJ/s = 271.75 kW
now 90 % of boiler heat is used for generate saturated stream
so net boiler heat =
net boiler heat =
net boiler heat = 301.94 kW