. A disposable coffee cup (including a lid) may be regarded as apolystyrene cylinder, diameter 50mm, height 80mm and thickness2.5mm. The base and lid may be regarded as 2.5mm thick disks. Whenbeing held using finger tips (having a very small area) the heattransfer coefficient from the outside of the cup is 20W/m2K andfrom the coffee to the inner wall is 100W/m2K. Estimate the rate ofheat loss from the cup when the coffee is at 65oC and ambienttemperature is 18oC. The conductivity of the polystyrene is0.04W/mK.
Ans = 6.33W
