An ordinary egg can be approximated as a 5.5- cm diameter sphere whose properties are roughly k = 0.6 W/m·k and α = 0.14 × 10-6 m2 /s. The egg is initially at a uniform temperature of 4°C and is dropped into boiling water at 97°C.

Taking the convection heat transfer coefficient to be h = 1400 W/m2 ·K, determine how long it will take for center of the egg to reach 70°C.

8.29 two streams containing pyridine and acetic acid at 25°c are mixed and fed into a heat exchanger. due to the heat-of-mixing effect, it is desired to reduce the temperature after mixing to 25°c using a stream of chilled ethylene glycol as indicated in the diagram. calculate the mass flow rate of ethylene glycol needed. the heat capacity of ethylene glycol at these conditions is approximately 2.8 kj/(kg k), and the enthalpy change of mixing (δmixh) is given below.