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Baseplate Insulated (hatched areas) C b = 10 mm Baseplate 0.2 m x 0.1 m x 0.01 m W = 0.1 m To 20°C kp= 45 W/mK B = 0.2 m Part 2 (20 marks) A solid rectangular block of dimensions 2L x W x B, shown as dark grey in cross-section in the top left diagram, has a conductivity of kg = 2 W/mK and uniformly generates heat at a per volume rate of 30,000 W/m². The block is encased on four sides (top, bottom and both short sides) by insulating material (hatched region in top right diagram), whilst b = 10 mm thick baseplates of conductivity ke = 45 W/mK encase the long sides of the block (light grey). The system is symmetric about the vertical dot-dashed centre-line ("CL"). The ambient air temperature is T. = 20°C and a convection coefficient h = 10 W/m²K acts on all the baseplate outer surfaces. Assuming 1-D heat transfer: (a) For one plain baseplate : (i) Sketch/label the thermal resistance network between Ts and To, (ii) calculate the heat flux q (in W) leaving through one 9 baseplate and (iii) the block core temperature Tc. In order to reduce Tc to an acceptable level it is now necessary to add N = 16 flat plate fins (dimensions: 4 x W x t) to the outside of both base plates, as shown in the lower two diagrams, made of the same material as the baseplate and attached to it so there is no contact resistance between them. h = 10 W/m²K L = L = Block 0.05 m 0.05 m kg= 2 W/mK À = 30 kW/m3 N = 16 flat plate fins t = 4 mm attached to Baseplate (Fin length 4 = 0.05m) = b = 10 mm Elevation view of baseplate Plan view of baseplate (b) For one finned baseplate : (i) Sketch/label the new thermal resistance network between Ts and To, (ii) calculate the efficiency (nt) and effectiveness (e) of a single fin, allowing for heat transfer from the fin tip by using the fin effective length (Le), (iii) calculate the overall surface efficiency (n.) and (iv) determine the new block core temperature Tc Activa