Question $6$

$($a$)$ A mild steel steam pipe has an outside diameter of $20$ cm and a wall thickness of $0\mathrm{.}7$ cm $.$ It is insulated with a $6$ cm $-$thick layer of fibreglass insulation. Hot water is supply at $320$ K flows through the pipe, and the inside heat transfer coefficient is $35\frac{W}{m^2}K.$ Heat is lost by convection and radiation to surroundings at $300$ K $,$ and the sum of outside convection and radiation coefficients is estimated to be $8\frac{W}{m^2}K.$ Find the rate of heat loss for a $40$ m length of pipe. Conductivity with temperature for steel and fibreglass are $54$ and $0\mathrm{.}04\frac{W}{m}K,$ respectively?

$(5$ Marks$)$

$($b$)$ Proposed effective measures to improve residential thermal transfer value $($RTTV$)$ performance.

$(4$ Marks$)$

$($c$)$ By the use of table, illustrate different fan control strategies according to it energy consumption and initial cost.

$(7$ Marks$)$

$($d$)$ Suggest any FOUR $(4)$ disadvantages of all$-$air system.

$(4$ Marks$)$