Air-Conditioning/Refrigeration , May/June 2014  
Questions: 1 2 3 4   Main
General Comments

Question 4

(a)       Define an insulator.
                        (b)       State three properties of an insulating materials
                        (c)        A cold room has its walls measuring 10 m by 4 m.  If the conditional
temperature is 5OC and the outer temperature is 28OC, calculate the total heat transmitted through the wall.  (take U – factor to be 0.93W/m2K).

Candidates performed well in parts (a) and (b) of the question.  The required response to part (c) of the question is given below:

Area    =          L x B
            =          10 x 4
            =          40m2



Temperature difference (TD) = 28OC - 5 OC = 23 OC

U = O.93 W/m2K
Q = A x U x TD = 40 m2 x O.93W/ m2K x 23 OC
            =          855.6W.





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