A 2-shell passes and 4-tube passes heat exchanger is used to heat glycerin from 20\degc to 50\degc by hot water, which enters the thin-walled 2-cm-diameter tubes at 80\degc and leaves at 40\degc . The total length of the tubes in the heat exchanger is 60 m. The convection heat transfer coefficient is 25 W/m2.K on the glycerin (shell) side and 160 W/m2.K on the water (tube) side. Determine the rate of heat transfer in the heat exchanger (a) before any fouling and (b) after fouling with a fouling factor of 0.0006 m2.K/W occurs on the outer surfaces of the tubes.

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