# Given data: T1=500+273.0 #source temp in kelvin T2=100+273.0 #sink temperature in kelvin W=1 # output power in kW nth=1-(T2/T1) # thermal efficiency Q1=1/nth # heat supplied in kW Q2=Q1-W # heat rejected in kW print " The heat rejected is ",Q2,"kW" # the answer in book is wrong due to incorrect value of T1
The heat rejected is 0.9325 kW
# Given data: T1=40+273.0 # ambient temp in kelvin T2=-10+273.0 # freezer temp in kelvin Q2=2 # heat loss rate for freezer in kJ/s Q1=T1*(Q2/T2) # heat transfer rate in kJ/s W=Q1-Q2 # work in kW print "The least power required is ",round(W,2),"kW"
The least power required is 0.38 kW
# Given data: Q1=3e4 # heat required in kJ/h W=2e3 # work required in kJ/h Q2=Q1-W # heat abstracted from outside in kJ/h COP=Q1/(Q1-Q2) # COP of heat pump print "Heat abstracted from outside air is ",Q2,"kJ/h" print "COP heat pump is ",COP
Heat abstracted from outside air is 28000.0 kJ/h COP het pump is 15.0
# Given data: T11=320+273.0 # temp at source 1 in kelvin Q1=10000.0 # heat transfer rate at source 1 in kJ/min T12=65+273.0 # temp at source 2 in kelvin Q2=120000.0 # heat transfer rate at source 2 in kJ/min T2=35+273.0 # temp of surrounding in kelvin n1=1-(T2/T11) # efficiency by source 1 n2=1-(T2/T12) # efficiency by source 2 W1=Q1*n1 # work at source 1 in kJ/min W2=Q2*n2 # work at source 2 in kJ/min print "The work done at two sources is W1=",W1," kJ/min W2=",W2,"kJ/min" print "The larger power is provided by source 2"
The work done at two sources is W1= 4806.07082631 kJ/min W2= 10650.887574 kJ/min The larger power is provided by source 2