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A disk 40 cm in diameter and 5 cm thick is to be cast of pure aluminum in an open mold casting operation. the melting temperature of aluminum = 660c, and the pouring temperature will be 800c. assume that the amount of aluminum heated will be 5% more than what is needed to fill the mold cavity. compute the amount of heat that must be added to the metal to heat it to the pouring temperature, starting from a room temperature of 25c.

Respuesta :

radius of the disc = 20 cm

thickness = 5 cm

density of aluminium = 2700 kg/m^3

now the mass of the disc = density * volume

[tex]m = \rho* \pi r^2 * t[/tex]

[tex]m = 2700 *\pi * (0.20)^2* 0.05[/tex]

[tex]m = 16.96 kg[/tex]

since it is taken 5% more so mass must be

[tex]m = 17.8 kg[/tex]

now the heat required would be

[tex]Q = mc\Delta T + mL + mc\delta T[/tex]

[tex]Q = 17.8* 900 * (660 - 25) + 17.8*398*10^3 + 17.8*900 * (800 - 660)[/tex]

[tex]Q = 1.95 * 10^7 J[/tex]

so above heat is required for melting the material

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