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3 years ago

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Technician A says that crush zones on a vehicle are designed to collapse in a controlled manner. Technician B says that reinforc

ements are designed to transfer collision energy. Who is right?

1 answer:

Ierofanga [76]3 years ago

3 0

Answer:

only A

Explanation:

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A long 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

Musya8 [376]

Answer:

Explanation:

Given:

Diameter of aluminum wire, D = 3mm

Temperature of aluminum wire, $T_{s}=280^{o}C$

Temperature of air, $T_{\infinity}=20^{o}C$

Velocity of air flow $V=5.5m/s$

The film temperature is determined as:

$T_{f}=\frac{T_{s}-T_{\infinity}}{2}\\\\=\frac{280-20}{2}\\\\=150^{o}C$

from the table, properties of air at 1 atm pressure

At $T_{f}=150^{o}C$

Thermal conductivity, $K = 0.03443 W/m^oC$ ; kinematic viscosity $v=2.860 \times 10^{-5} m^2/s$ ; Prandtl number $Pr=0.70275$

The reynolds number for the flow is determined as:

$Re=\frac{VD}{v}\\\\=\frac{5.5 \times(3\times10^{-3})}{2.86\times10^{-5}}\\\\=576.92$

sice the obtained reynolds number is less than $2\times10^5$ , the flow is said to be laminar.

The nusselt number is determined from the relation given by:

$Nu_{cyl}= 0.3 + \frac{0.62Re^{0.5}Pr^{\frac{1}{3}}}{[1+(\frac{0.4}{Pr})^{\frac{2}{3}}]^{\frac{1}{4}}}[1+(\frac{Re}{282000})^{\frac{5}{8}}]^{\frac{4}{5}}$

$Nu_{cyl}= 0.3 + \frac{0.62(576.92)^{0.5}(0.70275)^{\frac{1}{3}}}{[1+(\frac{0.4}{(0.70275)})^{\frac{2}{3}}]^{\frac{1}{4}}}[1+(\frac{576.92}{282000})^{\frac{5}{8}}]^{\frac{4}{5}}\\\\=12.11$

The covective heat transfer coefficient is given by:

$Nu_{cyl}=\frac{hD}{k}$

Rewrite and solve for $h$

$h=\frac{Nu_{cyl}\timesk}{D}\\\\=\frac{12.11\times0.03443}{3\times10^{-3}}\\\\=138.98 W/m^{2}.K$

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

$Q=hA_{s}(T_{s}-T{\infin})\\\\=h\times(\pi\timesDL)\times(T_{s}-T{\infinity})\\\\=138.92\times(\pi\times3\times10^{-3}\times1)\times(280-20)\\\\=340.42W/m$

The rate of heat transfer from the wire to the air per meter length is $Q=340.42W/m$

6 0

3 years ago

The ampere draw of a 5000 watt electric heater used on 120 volts is

Salsk061 [2.6K]

Answer:

41.67amps

Explanation:

v*a=w

120*a=5000

5000/12=41.67

8 0

3 years ago

An ideal fluid flows through a pipe made of two sections with diameters of 1.0 and 3.0 inches, respectively. The speed of the fl

geniusboy [140]

Answer:

$(\frac{r_1}{r_2})^2=\frac{1}{9}$

Explanation:

From the question we are told that:

Diameter 1 $d_1=1.0$

Diameter 2 $d_2=3.0$

Generally the equation for Radius is mathematically given by

At Diameter 1

$r_{1}=\frac{1}{2} inch$

At Diameter 2

$r_{2}=\frac{3}{2} inch$

Generally the equation for continuity is mathematically given by

$A_1V_1=A_2V_2$

Therefore

$(\frac{r_1}{r_2})^2=(\frac{1/2}{3/2})^2$

$(\frac{r_1}{r_2})^2=\frac{1}{9}$

5 0

3 years ago

What are the common approximations made in the analysis of heat exchangers?

Oksanka [162]

Answer: making sure that they are up to date

Explanation:

7 0

3 years ago

Select the correct answer.

irina [24]

The answer is C because the word graphic means picture.

4 0

3 years ago