Unit-01
Problem -02
A hollow sphere (thermal conductivity is 65 W/m k)of 120
mm inner diameter and 350 mm outer diameter is covered
with 10 mm layer of insulation (thermal conductivity is 10
W/m k).The inside and outside temperature are 500°C and
50°C respectively. Calculate the rate of heat flow through
this sphere.
A hollow sphere of 1.2 m inner diameter and 1.7 m
outer diameter is having a thermal conductivity of 1
W/m k.The inner surface temperature is 70 K and
outside surface temperature is 300 k. Calculate the
heat transfer rate and temperature at a radius of 650
mm.
A hollow sphere inside surface temperature of 300°C and
outside surface temperature 30°C. If thermal conductivity
is 18 W/m k.Calculate heat lost by conduction for inside
diameter of 5 cm and outside diameter of15 cm.
A wire of 6mm diameter with 2mm thick insulation
(k=0.11W/mk).If convective heat transfer coefficient
between the insulating surface and air is 25 W/m²k.Find
the critical thickness of insulation and also find the
percentage of change in the heat transfer rate if critical
radius is used.
.A electrical wire of 10m length 1 mm diameter dissipates 200 W in
air at 25°C.The heat transfer coefficient between the surface and air is
15W/m²K and thermal conductivity of wire is 0.582W/mK.Calculate
the critical radius of insulation and also determine the temperature
of wire if it is insulated to the critical thickness of insulation