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3 years ago

7

Air at 25ºC flows in an electric hair drier with a velocity of 6 m/s perpendicular to a Nichrome heating element. The heating el

ement is 1-mm in diameter and 36-cm long with a resistance of 1.52 Ω/m. The wire temperature cannot exceed 420ºC so that the wire will not lose strength and sag. Determine the electric current in the wire.

1 answer:

Hunter-Best [27]3 years ago

3 0

Answer:

Check the explanation

Explanation:

Electrical current can be measured according to the rate of electric charge flow in any electrical circuit:

$i(t) = dQ(t) / dt$

the derivative of the electric charge by time determines the momentary current.

i(t) will be the momentary current I at time t in amps (A).

Q(t) will also be the momentary electric charge in coulombs (C).

t is the time in seconds (s).

so if the current is constant:

I = ΔQ / Δt

I will be the current in amps (A).

ΔQ will be the electric charge in coulombs (C), which is expected to flows at time duration of Δt.

Δt is the time duration in seconds (s).

Kindly check the attached image below to get the step by step explanation to the question above.

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What is EL Niño?

postnew [5]

Answer:

B

Explanation:

This occurs over the Pacific Ocean, so C and D are already wrong. El Nino heats the water and not cools it, so A is incorrect. So commonsense says that the answer is B.

4 0

3 years ago

The Cv factor for a valve is 48. Compute the head loss when 30 GPM of water passes through the valve.

dlinn [17]

Answer:

The head loss in Psi is 0.390625 psi.

Explanation:

Fluid looses energy in the form of head loss. Fluid looses energy in the form of head loss when passes through the valve as well.

Given:

Factor cv is 48.

Flow rate of water is 30 GPM.

GPM means gallon per minute.

Calculation:

Step1

Expression for head loss for the water is given as follows:

$c_{v}=\frac{Q}{\sqrt{h}}$

Here, cv is valve coefficient, Q is flow rate in GPM and h is head loss is psi.

Step2

Substitute 48 for cv and 30 for Q in above equation as follows:

$48=\frac{30}{\sqrt{h}}$

${\sqrt{h}}=0.625$

h = 0.390625 psi.

Thus, the head loss in Psi is 0.390625 psi.

5 0

3 years ago

The y component of velocity in a steady, incompressible flow field in the xy plane is v = -Bxy3, where B = 0.4 m-3 · s-1, and x

love history [14]

Answer:

attached below

Explanation:

3 0

3 years ago

The hot and cold inlet temperatures to a concentric tube heat exchanger are Th,i = 200°C, Tc,i = 100°C, respectively. The outlet

alexgriva [62]

Answer:Counter,

0.799,

1.921

Explanation:

Given data

$T_{h_i}=200^{\circ}C$

$T_{h_o}=120^{\circ}C$

$T_{c_i}=100^{\circ}C$

$T_{c_o}=125^{\circ}C$

Since outlet temperature of cold liquid is greater than hot fluid outlet temperature therefore it is counter flow heat exchanger

Equating Heat exchange

$m_hc_{ph}\left [ T_{h_i}-T_{h_o}\right ]=m_cc_{pc}\left [ T_{c_o}-T_{c_i}\right ]$

$\frac{m_hc_{ph}}{m_cc_{pc}}$ = $\frac{125-100}{200-120}=\frac{25}{80}=C\left ( capacity rate ratio\right )$

we can see that heat capacity of hot fluid is minimum

Also from energy balance

$Q=UA\Delta T_m=\left ( mc_p\right )_{h}\left ( T_{h_i}-T_{h_o}\right )$

$NTU=\frac{UA}{\left ( mc_p\right )_{h}}$ = $\frac{\left ( T_{h_i}-T_{h_o}\right )}{T_m}$

$T_m=\frac{\left ( 200-125\right )-\left ( 120-100\right )}{\ln \frac{75}{20}}$

$T_m=41.63^{\circ}C$

NTU=1.921

$And\ effectiveness \epsilon =\frac{1-exp\left ( -NTU\left ( 1-c\right )\right )}{1-c\left ( -NTU\left ( 1-c\right )\right )}$

$\epsilon =\frac{1-exp\left ( -1.921\left ( 1-0.3125\right )\right )}{1-0.3125exp\left ( -1.921\left ( 1-0.3125\right )\right )}$

$\epsilon =\frac{1-exp\left ( -1.32068\right )}{1-0.3125exp\left ( -1.32068\right )}$

$\epsilon =\frac{1-0.2669}{1-0.0834}$

$\epsilon =0.799$

5 0

3 years ago

A pipeline (NPS = 14 in; schedule = 80) has a length of 200 m. Water (15℃) is flowing at 0.16 m3/s. What is the pipe head loss f

dangina [55]

Answer:

Head loss is 1.64

Explanation:

Given data:

Length (L) = 200 m

Discharge (Q) = 0.16 m3/s

According to table of nominal pipe size , for schedule 80 , NPS 14, pipe has diameter (D)= 12.5 in or 31.8 cm 0.318 m

We know, $head\ loss = \frac{f L V^2}{( 2 g D)}$

where, f = Darcy friction factor

V = flow velocity

g = acceleration due to gravity

We know, flow rate Q = A x V

solving for V

$V = \frac{Q}{A}$

$= \frac{0.16}{\frac{\pi}{4} (0.318)^2} = 2.015 m/s$

obtained Darcy friction factor

calculate Reynold number (Re) ,

$Re = \frac{\rho V D}{\mu}$

where, $\rho$ = density of water

$\mu$ = Dynamic viscosity of water at 15 degree C = 0.001 Ns/m2

so reynold number is

$Re = \frac{1000\times 2.015\times 0.318}{0.001}$

= 6.4 x 10^5

For Schedule 80 PVC pipes , roughness (e) is 0.0015 mm

Relative roughness (e/D) = 0.0015 / 318 = 0.00005

from Moody diagram, for Re = 640000 and e/D = 0.00005 , Darcy friction factor , f = 0.0126

Therefore head loss is

$HL = \frac{0.0126 (200)(2.015)^2}{( 2 \times 9.81 \times 0.318)}$

HL = 1.64 m

7 0

3 years ago