Question

A pipe 10 cm in diameter contains steam at 100 o C . It is covered with an insulating material that is 5 cm thick. This insulating material has a constant of thermal conductivity K = 0.0006 .The outside surface of the system is 30
o
C.

Find the heat loss per hour from a meter length of the pipe.

Answer 1

Answer:

14000 cal/hr. it is right

Answer 2

Given

• 10 cm in diameter
• T1 = 100 o C
• T2 = 30℃
• K = 0.0006
• insulating material that is 5 cm thick

To find

• heat loss per hour from a meter length of the pipe.

Solution

heat loss per second is given by the equation,

note: here d is thickness of insulating material.

$q = \dfrac{ka(t2 - t1)}{d}$

here area, a = 2πrh

or, a = 2π(0.05)1 【since d of pipe is 10cm and length is 1m】

or, a = 0.31 sq m

Thus, substituting the values in the above equation.

$Q = \dfrac{0.0006×0.31(100-30)}{5 \times {10}^{ - 2} }$

Q = 0.01302/0.05

or, Q = 0.2604 J/s

Therefore, heat lost in 1 hour

Q = 0.2604×60×60

or, Q = 937.44 J/hr

Heat loss per hour from a meter length of the pipe is 937.44 J/hr.