Avery thick slab with thermal diffusivity 5.6x10^-6 m^2/s and thermal conductivity 20w/m. k js initially at a uniform temperature of 325 degree c. suddenly, the surface is exposed to a coolant at 15 degree c for which the convection heat transfer coefficient is 100 w/m^2 .k. determine temperatures at the surface and at a depth of 45 mm after 3 min have elapsed. compute and plot temperature histories (0 less than or equal to t less than or equal to 300 s) at x = 0 and x = 45 mm for the following parametric variations: alpha = 5.6 x 10^-7, 5.6 x 10^-6, and 5.6 x 10^-5 m^2/s; and k = 2, 20, and 200 w/m. k.

Determine the time of the day and month of the year at which the peak sensible cooling load occurs for a top floor, north-eastern corner room of an office building in durban for the following conditions: floor area: 8 x 8 x 3 m east and north walls: 115 mm face brick (outside), 20 mm air space, 115 mm ordinary brick (inside) with 15 mm plaster roof construction: suspended plasterboard ceiling, 450 mm air space, 150 mm concrete, 75mm screed, waterproofing no heat transfer across other surfaces window area 3x 1,5 m high in north wall only. ordinary glass with venetian blinds. lights and occupants : from 07: 00 to 18: 00 average light density: 25 w/m2 number of occupants : 5 seated, light office work room temperature 24°c