Question

The brick wall (of thermal conductivity

1.16 W/m ° C) of a building has dimensions

of 5 m by 7 m and is 18 cm thick.

How much heat flows through the wall in

a 17.2 h period when the average inside and

outside temperatures are, respectively, 24°C

and 8°C?

Answer in units of MJ.

Answer 1

Answer:223.46 MJ

Step-by-step explanation:

Given

The thermal conductivity of brick wall is
`k=1.16\ W/m.^(\circ)C`

Cross-section of Wall
`A=5\m * 7\ m`

time period
`t=17.2\ h=17.2* 60* 60=61,920\ s`

Inside temperature
`T_i=24^(\circ)C`

Outside temperature
`T_o=8^(\circ)C`

Heat transfer through the bricks

`\dot{Q}=kA(dT)/(dx)`

`\dot{Q}=1.16* 35* (16)/(0.18)\\\\\dot{Q}=3608.88\ W`

Heat flow for 17.2 h

`Q=3608.88* 61,920=223.46\ MJ`