A house in Scotland has a back (kitchen) door that is 1 m wide and 2 m high. The lower half of the door (which is 1 m high) is made of uPVC of thickness 10 mm and thermal conductivity 0.2 W m¹ K-¹, and the upper half is made of a single pane of glass of thickness 5 mm and thermal conductivity 1.2 W m¹ K¹. In the middle of January, the air temperature outside is -10°C and is maintained on the inside of the kitchen at 20°C. The convection heat transfer coefficients on the inside and outside of the door are 25 W m2 K-¹ and 15 W m² K-¹, respectively. Assume that all heat loss will occur only through the door from the inside to the outside, and no heat transfer will take place between the two parts of the door. i) ii) Calculate the rate of heat loss through the door. What percentage of this rate is lost through the uPVC part and what is lost through the glass part?

A house in Scotland has a back (kitchen) door that is 1 m wide and 2 m high. The lower half of the door (which is 1 m high) is made of uPVC of thickness 10 mm and thermal conductivity 0.2 W m¹ K-¹, and the upper half is made of a single pane of glass of thickness 5 mm and thermal conductivity 1.2 W m¹ K¹. In the middle of January, the air temperature outside is -10°C and is maintained on the inside of the kitchen at 20°C. The convection heat transfer coefficients on the inside and outside of the door are 25 W m2 K-¹ and 15 W m² K-¹, respectively. Assume that all heat loss will occur only through the door from the inside to the outside, and no heat transfer will take place between the two parts of the door. i) ii) Calculate the rate of heat loss through the door. What percentage of this rate is lost through the uPVC part and what is lost through the glass part?

Elements Of Electromagnetics

7th Edition

ISBN:9780190698614

Author:Sadiku, Matthew N. O.

Publisher:Sadiku, Matthew N. O.

ChapterMA: Math Assessment

Section: Chapter Questions

Problem 1.1MA

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Question

A house in Scotland has a back (kitchen) door that is 1 m wide and 2 m high. The
lower half of the door (which is 1 m high) is made of uPVC of thickness 10 mm
and thermal conductivity 0.2 W m¹ K¹, and the upper half is made of a single
pane of glass of thickness 5 mm and thermal conductivity 1.2 W m¹ K-¹.
In the middle of January, the air temperature outside is -10°C and is maintained
on the inside of the kitchen at 20°C. The convection heat transfer coefficients on
the inside and outside of the door are 25 W m2 K-¹ and 15 W m² K-¹,
respectively. Assume that all heat loss will occur only through the door from the
inside to the outside, and no heat transfer will take place between the two parts of
the door.
i)
ii)
Calculate the rate of heat loss through the door.
What percentage of this rate is lost through the uPVC part and what is lost
through the glass part?

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