A 1 kg sample of a new ore was ground for 10 minutes in a laboratory rod mill. The 80 percent passing size of the sample before grinding was 1.48 mm while after grinding it was 115 microns. Using the same mill, another ore sample with a known Work Index of 12.8 KWh/t was also ground for 10 minutes from a feed 80 percent passing size of 0.84 mm to a product 80 percent passing size of 65 microns. Use the Bond Work Index formula to determine the Work Index of the new ore sample.

Acommercial grade cubical freezer, 4 m on a side, has a composite wall consisting of an exterior sheet of 5.0-mm thick plain carbon steel (kst= 60.5 w/m k), an intermediate layer of 100-mm thick polyurethane insulation (kins 0.02 w/m k), and an inner sheet of 5.0- mm thick aluminium alloy (kal polyurethane insulation and both metallic sheets are each characterized by a thermal contact resistance of r 2.5 x 104 m2 k/w. (a) what is the steady-state cooling load that must be maintained by the refrigerator under conditions for which the outer and inner surface temperatures are 25°c and -5°c, respectively? (b) for power saving purpose, which wall material should be increased/reduced in. thickness in order to reduce 50% of the cooling load found in part (a)? redesign the thickness of the proposed material. 177 w/m-k). adhesive interfaces between the q=575.93 w