Physics, 08.04.2020 04:39 alexis539

Air at 1 atm and 20 c is flowing over the top surface of a .2x.5 m thin metal foil. the air stream velocity is 100 m/s and the metal foil is heated electrically with a uniform heat fluz of 6100 W/m2. If the friction force on the metal foil surface is 0.3 N, determine the surface temperature of the metal foil. Evaluate the fluid properties at 100°C.

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Answer from: tiannahines810

The surface temperature of the metal foil is 453.645 K

Explanation:

The properties of the air at 100°C and 1 atm are the follows:

ρ = density = 0.9458 kg/m³

Cp = specific heat = 1009 J/kg K

Pr = 0.7111

The surface area of the plate is equal to:

A=WL

Where

W = width of the plate = 0.2 m

L = length of the plate = 0.5 m

$A=0.2*0.5=0.1m^{2}$

The average friction coefficient is equal to:

$C_{f} =\frac{F}{\frac{A\rho V^{2} }{2} }$

Where

F = drag force = 0.3 N

V = velocity of air flow = 100 m/s

$C_{f} =\frac{0.3}{\frac{0.1*0.9458*100^{2} }{2} } =0.000634$

The average heat transfer coefficient is equal to:

$h=\frac{C_{f}\rho VC_{p} }{2Pr^{2/3} } =\frac{0.000634*0.9458*100*1009}{2*(0.7111x^{2/3}) } =37.972W/m^{2} K$

The surface temperature is:

$T_{s} =\frac{q}{h} +T\alpha$

Where

q = heat flux = 6100 W/m²

Tα = temperature of the air = 20°C = 293 K

$T_{s} =\frac{6100}{37.972} +293=453.645K$

Answer from: Quest

1.the balanced chemical equation is as below

cu + 2 ag(no)₃ → cu(no₃)₂ +2 ag

2.the much silver produced is 50.9 g

step 1: find the moles of cu

moles = mass÷ molar mass

from periodic table the molar mass of cu = 63.5 g/mol

moles is therefore = 15.00 g÷ 63.5 g/mol = 0.236 moles

step 2: use the mole ratio to determine the moles of ag

from equation above cu: ag is 1: 2

therefore the moles of ag =0.236 moles x 2/1 =0.472 moles

step 3: find the mass of ag

mass = moles x molar mass

from periodic table the molar mass of ag =107.87 g/mol

mass = 0.472 moles x 107.87 g/mol = 50.9 g

3. the much silver collected worth is 1.797 oz

convert 50.9 g to oz

that is 1 gram = 0.0353 oz

50.9 grams =? oz

by cross multiplication

={(50.9 grams x 0.0353 oz) / 1 gram} =1.797 oz

Answer from: Quest

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