Question

A 20cm-thick cement mortar wall for a warehouse has a temperature on the inside-21°C and outside 26°C. a) What is the temperature difference between the inside and outside in: a. Kelvin (convert inside and outside temperatures to Kelvin and then subtract) b. Celsius b) What is the heat loss through a 4m x 4m section of this wall

Answer 1

a).a. 5K

b. 5°C

b). 480 W

Step-by-step explanation:

Given:

Thickness of mortar, L = 20 cm = 0.2 m

Inside temperature,
`T_(in)` = 21°C

=21+273 = 294 K

Outside temperature,
`T_(out)` = 26°C

=26+273 = 299 K

a). Temperature difference in --

a) Kelvin

ΔT =
`T_(out)` -
`T_(in)`

= 299 - 294

= 5 K

b). Celcius

ΔT =
`T_(out)` -
`T_(in)`

= 26 -21

= 5°C

b). We know thermal conductivity for cement mortar is k = 1.2 W / m-K

For steady state we know

`Q = (\Delta T)/((L)/(K.A))`

`Q = (5)/((0.2)/(1.2* 2* 2))`

`Q = 480` W