A20cm-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

a).a. 5K

   b. 5°C

b). 480 W

Explanation:

Given:

Thickness of mortar, L = 20 cm  = 0.2 m

Inside temperature, = 21°C

                                                           =21+273 = 294 K

Outside temperature, = 26°C

                                                           =26+273 = 299 K

a). Temperature difference in --

  a) Kelvin

      ΔT = -

         = 299 - 294

         = 5 K

  b). Celcius

       ΔT = -

             = 26 -21

             = 5°C

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

For steady state we know

W

the equation above shows how temperature f, measured in degrees fahrenheit, relates to a temperature c, measured in degrees celsius. based on the equation, which of the following must be true?

a temperature increase of 1 degree fahrenheit is equivalent to a temperature increase of

5

9

degree celsius.

a temperature increase of 1 degree celsius is equivalent to a temperature increase of 1.8 degrees fahrenheit.

a temperature increase of

5

9

degree fahrenheit is equivalent to a temperature increase of 1 degree celsius.

a) i only

b) ii only

c) iii only

d) i and ii only