A house in Finland has 280 m2 of walls constructed of panels of the type shown...

 

Transcribed Image Text:

A house in Finland has 280 m2 of walls constructed of panels of the type shown in Figure 1. The wood is pine and the insulation has thermal conductivity kins = 0.07 W/m.K. A central heating system driven by a furnace maintains the inside conditions of the house at Too,i = 20ºC and hi = 20 W/m².K while on the outside, Too,o= -18°C and ho= 68 W/m².K. The thermal conductivities of pine and plaster can be taken as 0.12 W/m-K and 0.50 W/m-K, respectively. hi, Too,i Р 1 a S t e r 2.5 x wood insulation 15 * All dimensions in cm W 0 0 d 32.5 ho, Too,o (a) Assuming isothermal conditions at each location of x, draw a fully labelled thermal circuit and determine the rate of heat transfer through the composite wall. State your assumptions clearly. (b) Assuming surfaces parallel to the x-axis to be adiabatic, repeat the heat transfer analysis as in Part (a). Comment on your answer in relation to that obtained in Part (a). (c) If the furnace delivers 30,700 kJ of heat per litre of fuel, how many litres of fuel are burned per day for these conditions based on the methods used in Part (a) and Part (b)? (d) If 46 m2 of single-pane window glass (kg = 0.85 W/m.K) of 0.48 cm thickness were to be added, how many additional litres of fuel would have be burned per day under the same conditions using the method of Part (a)? What do you conclude? A house in Finland has 280 m2 of walls constructed of panels of the type shown in Figure 1. The wood is pine and the insulation has thermal conductivity kins = 0.07 W/m.K. A central heating system driven by a furnace maintains the inside conditions of the house at Too,i = 20ºC and hi = 20 W/m².K while on the outside, Too,o= -18°C and ho= 68 W/m².K. The thermal conductivities of pine and plaster can be taken as 0.12 W/m-K and 0.50 W/m-K, respectively. hi, Too,i Р 1 a S t e r 2.5 x wood insulation 15 * All dimensions in cm W 0 0 d 32.5 ho, Too,o (a) Assuming isothermal conditions at each location of x, draw a fully labelled thermal circuit and determine the rate of heat transfer through the composite wall. State your assumptions clearly. (b) Assuming surfaces parallel to the x-axis to be adiabatic, repeat the heat transfer analysis as in Part (a). Comment on your answer in relation to that obtained in Part (a). (c) If the furnace delivers 30,700 kJ of heat per litre of fuel, how many litres of fuel are burned per day for these conditions based on the methods used in Part (a) and Part (b)? (d) If 46 m2 of single-pane window glass (kg = 0.85 W/m.K) of 0.48 cm thickness were to be added, how many additional litres of fuel would have be burned per day under the same conditions using the method of Part (a)? What do you conclude?

Answer rating: 100% (QA)

SOLUTION a Fully labelled thermal circuit and rate of heat transfer Assuming isothermal conditions a... View the full answer