A lamp has a luminous intensity of 1200 candelas and acts as a point source. The lamp is situated 2.5m above the office floor, which is 6m wide.Calculate the illuminance in lux, on the floor surface directly below the lamp.

a) Calculate the total rate of heat lossfor the building described below:

•The building is 15m long by 8m wide by 3.5m high.

•In the walls are two windows, one 1.2m x 0.6m, the other 1.8m x 1.8m and there is one door 1.75m x 0.8m.

•The construction has the following U-values in W/m²K: windows 1.8, door 1.2, walls 1.5, flat roof 0.5, floor 1.5.

•The inside comfort temperature is 21°C while the outside air temperature is minus 1°C.

•The volumetric specific heat capacity of the air is taken to be 1300 J/mK.

•There are 1.0 air changes per hour. Present your fabric heat loss calculations in table form and show the calculation of the ventilation heat loss, showing the correct formulas and units of measurement. (13 marks)

b) A lamp has a luminous intensity of 1200 candelas and acts as a point source. The lamp is situated 2.5m above the office floor, which is 6m wide.

i) Calculate the illuminance in lux, on the floor surface directly below the lamp. (4 marks)

ii) Calculate the illuminance at the opposite edge of the room. (4 marks)

iii)Explain the significance of your results (4 marks) (Total 25 marks)

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