Question

A furnace wall is made of composite wall of total thickness 550 mm. The inside
layer of wall is made of refractory material (k = 1.5 W/m°C) and outside layer of
wall is made of an insulating material (k = 0.2 W/m°C). The mean temperature of
the gases inside the furnace is 900°C and interface temperature is 520°C. The
average heat transfer coefficient between the gases and inner surface is 230
W/m2-°C and between the outside surface and atmosphere is 46 W/m2-°C. Taking
air temperature = 30°C, calculate: (a) Thickness of each layer of wall, (b) Rate of
heat loss per unit area, (c) Temperatures of surfaces exposed to gases and
atmosphere.​

Answer 1

Answer:

Step-by-step explanation:

Let h be the height.

Rate of covering the floor with mat = Rs 25 per square metre

Total cost for floor = RS 2700

Area of the floor = (total cost)/ (cost per meter)  

Area of the floor =  

25

2700

​  

=108m  

2

 

Breadth = (area of the floor) / Length =  

12

108

​  

 = 9m

Length of a wall = 12 m

Rate  of painting the four walls of a room = Rs 30 per square metre

Total cost = RS 7560

Again,

Area of walls = (total cost)/ (cost per meter) =7560/30=252m  

2

 

Now,

Area of 4 walls = 2(Length of walls × Height of walls) + 2(Breadth of walls × Height of walls)

252=2(12×h)+2(9×h)

252=24h+18h

252=42h

h=6

⇒ Height is 6 m

Therefore dimensions of the room are :12m×9m×6m