Question

A copper hot water pipe (outer diameter ½”) has an exterior temperature of 49oC. For insulation,it is wrapped in polyethylene foam that is ½” thick. If the pipe is 12 feet long and runs through a utility room whose temperature is 7oC

Find a) the rate at which heat is lost through the insulation. Polyethylene foam has a thermal conductivity of 0.024W/(m·K) (Hint: use the outer surface area of the insulation)

b)the heat lost (in kWh) through the insulation in 30.0 days

Answer #1

Water flows through a pipe at an average temperature of
T =50°C. The inner and outer radii of the pipe are
r1 = 6 cm and r2 = 6.5 cm,
respectively. The outer surface of the pipe is wrapped with a thin
electric heater that consumes 300 W per m length of the pipe. The
exposed surface of the heater is heavily insulated so that the
entire heat generated in the heater is transferred to the pipe.
Heat is transferred...

A steel hot-water tank of cylindrical shape has an inside
diameter of 0.600 m and inside height of 1.40 m. The tank is
enclosed by a 5.00 cm thick insulating layer of glass wool whose
thermal conductivity is 0.0350 W / (m·K). The insulation is covered
by a thin sheet metal skin. The steel tank and the sheet metal skin
have thermal conductivities that are much greater than that of the
glass wool. How much electrical power (W) must be...

hot fluid at 230°C flows through a 1-meter pipe of 0.02m outside
radius and 0.015m inside radius. The thermal conductivity of the
pipe is 0.5 W/m.k, and the heat transfer coefficient (hi) inside is
300 W/m2 K. The pipe is located in a room at 30°C, and the heat
transfer coefficient (ho) at the outer surface is 10 W/m2 k.
Calculate the temperature drop (∆T) across the pipe wall.

Steam at an average temperature of ?∞= 400°C flows through a
steel pipe. The inner and outer radii of the pipe are r1 = 4 cm and
r2 = 4.5 cm, respectively, and the outer surface of the pipe is
insulated with a layer of 50 mm thick-calcium silicate of thermal
conductivity of k = 0.5 W/m.K, and is maintained at 350 °C. If the
convection heat transfer coefficient on the inner surface of the
pipe is h = 65...

Steam at 350°F flows through a 3-in (ID) copper pipe having a
thickness of 0.22 in. The outside surface of the pipe is insulated
with 1-in-thick layer of fiberglass and 0.008-in-thick layer of
aluminum. The outside surface of the insulation is exposed to air
at 130°F. The convection coefficients for steam and air are 25 and
12 Btu/h-ft2 -°F, respectively. The thermal conductivity of
fiberglass is 0.022 Btu/h-ft-°F.
a. Calculate the rate of heat transfer for 30-ft length of the...

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