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Curl Up and Dye produces a line of hair dyes for professional hairdressers.

In 20XX, they had sales revenues of \$500,000, a cost of goods sold of \$300,000, equipment

of \$100,000, amortization expenses of \$50,000, an ending inventory of \$40,000, and

income tax expenses of \$50,000.

In 20XY, they had sales revenues of \$400,000, a cost of goods sold of \$281,250, equipment

of \$100,000, amortization expenses of \$50,000, an ending inventory of \$35,000, and

income tax expenses of \$25,000.

Competitors in the same industry have an inventory turnover of 40 days.

Calculate and interpret the company?s inventor

A common thermal energy generation process involves the conversion from electrical

to thermal energy in a current-carrying medium (Ohmic, or resistance, or Joule heating).

The rate at which energy is generated by passing a current I through a medium of electrical

resistance Re is

(3.42)

If this power generation (W) occurs uniformly throughout the medium of volume V, the

volumetric generation rate (W/m3

) is then

(3.43)

Energy generation may also occur as a result of the deceleration and absorption of neutrons in

the fuel element of a nuclear reactor or exothermic chemical reactions occurring within a

medium. Endothermic reactions would, of course, have the inverse effect (a thermal energy

sink) of converting thermal energy to chemical bonding energy. Finally, a conversion from

electromagnetic to thermal energy may occur due to the absorption of radiation within the

medium. The process occurs, for example, when gamma rays are absorbed in external nuclear

reactor components (cladding, thermal shields, pressure vessels, etc.) or when visible radiation is absorbed in a semitransparent medium. Remember not to confuse energy generation

with energy storage (Section 1.3.1).

3.5.1 The Plane Wall

Consider the plane wall of Figure 3.10a, in which there is uniform energy generation per

unit volume ( is constant) and the surfaces are maintained at Ts,1 and Ts,2. For constant

thermal conductivity k, the appropriate form of the heat equation, Equation 2.22, is

(3.44)

d2

T q?

0

q?

q?

E?g

V

I

2

Re

V

E?gI

2

Re

TABLE 3.3 One-dimensional, steady-state solutions to the heat

equation with no generation

Plane Wall Cylindrical Wall

a

Spherical Wall

a

Heat equation

Heat ?ux ( )

Heat rate (q)

a

The critical radius of insulation is rcr k/h for the cylinder and rcr 2k/h for the sphere.

(1/r1) (1/r2)

4k

ln (r2 /r1)

2Lk

L

kA

4k T

(1/r1) (1/r2)

2Lk T

ln (r2 /r1)

kA

T

L

kT

r

2

[(1/r1) (1/r2)]

kT

r ln (r2

/r1)

k

T

L

q

Ts,1 T

1 (r1/r)

1 (r1/r2

) Ts, 2 T

ln (r/r2)

ln (r1/r2)

Ts,1 T

x

L

1

r

2

d

dr

r

2

dT

dr 0

1

r

d

dr

r

dT

dr 0

d2

T

dx2

0

Temperature

distribution

Thermal

resistance (Rt,cond)v

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This question was answered on: Feb 21, 2020

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