..A copper pipe carries hot water for domestic central heating. It is proposed to insulate the...

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..A copper pipe carries hot water for domestic central heating. It is proposed to insulate the pipe to prevent heat loss to the surrounding air. (a) Calculate critical radius given that the thermal conductivity of the lagging is 0.2 W m K- and the convection heat transfer coefficient outside the insulation is 3.5 W m K-. (b) If the external diameter of the copper pipe is 5 cm, calculate the heat loss per unit length using the critical radius in (a) if the hot water is at 60 C, the surface temperature of the external pipe wall is 57 C and the surrounding air temperature is 25 C. (c) If the available lagging is 4 mm thick determine whether its use is beneficial by calculating and comparing the total thermal resistance with and without its use. ..A copper pipe carries hot water for domestic central heating. It is proposed to insulate the pipe to prevent heat loss to the surrounding air. (a) Calculate critical radius given that the thermal conductivity of the lagging is 0.2 W m K- and the convection heat transfer coefficient outside the insulation is 3.5 W m K-. (b) If the external diameter of the copper pipe is 5 cm, calculate the heat loss per unit length using the critical radius in (a) if the hot water is at 60 C, the surface temperature of the external pipe wall is 57 C and the surrounding air temperature is 25 C. (c) If the available lagging is 4 mm thick determine whether its use is beneficial by calculating and comparing the total thermal resistance with and without its use.

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a Calculation of Critical Radius The critical radius rcrit represents the radius at which the heat transfer rate through convection and conduction bec... View the full answer