Along aluminum wire of diameter 3 mm is extruded at a temperature of 280°c. the wire is subjected to cross air flow at 20°c at a velocity of 5.50 m/s. determine the rate of heat transfer from the wire to the air per meter length when it is first exposed to the air. the properties of air at 1 atm and the film temperature of (ts + t[infinity])/2 = (280 + 20)/2 = 150°c are k = 0.03443 w/m·°c, ν = 2.860 × 10−5 m2/s, and pr = 0.70275.

Explanation:

Given:

Diameter of aluminum wire, D = 3mm

Temperature of aluminum wire,

Temperature of air,

Velocity of air flow

The film temperature is determined as:

from the table, properties of air at 1 atm pressure

At

Thermal conductivity, ; kinematic viscosity ; Prandtl number

The reynolds number for the flow is determined as:

sice the obtained reynolds number is less than , the flow is said to be laminar.

The nusselt number is determined from the relation given by:

The covective heat transfer coefficient is given by:

Rewrite and solve for

The rate of heat transfer from the wire to the air per meter length is determined from the equation is given by:

The rate of heat transfer from the wire to the air per meter length is

post office i thinkexplanation:

answer:

is a

explanation: