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3 years ago

What is compression ratio of an Otto cycle? How does it affect the thermal efficiency of the cycle?

Engineering

1 answer:

GuDViN [60]3 years ago

6 0

Answer:

$r= \dfrac{V_1}{V_2}$

$\eta =1-\dfrac{1}{r^{\gamma-1}}$

Explanation:

Compression ratio:

Compression ratio is the ratio of volume in the cylinder.Generally it is denoted by r.

The compression ratio for Otto cycle is about 8 to 12.But the compression ratio of diesel engine is about 14 to 25.

So from the Otto cycle compression ratio can be define as

$r= \dfrac{V_1}{V_2}$

As we know that efficiency defines as the ratio of work out to the heat input.In the Otto cycle the efficiency is given as in terms of compression ratio r as

$\eta =1-\dfrac{1}{r^{\gamma-1}}$

Where γ is the heat capacity ratio.

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For unrestrained cube made from linear, isotropic, homogeneous material the temperature increase causes strain in_____ direction

LenKa [72]

Answer: The answer is four; four

Explanation: This is because of the mixture of material used and the number of directions it causes strain I directly proportional to the number of times it causes stress.

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3 years ago

Two units for measuring magnetic flux density are:

romanna [79]

The correct answer is A
Faraday and Weber
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2 years ago

A hair dryer is basically a duct in which a few layers of electric resistors are placed. A small fan pulls the air in and forces

nika2105 [10]

Answer:

a) volume flow rate of air at the inlet is 0.0471 m³/s

b) the velocity of the air at the exit is 8.517 m/s

Explanation:

Given that;

The electrical power Input W_elec = -1400 W = -1.4 kW

Inlet temperature of air T_in = 22°C

Inlet pressure of air p_in = 100 kPa

Exit temperature T_out = 47°C

Exit area of the dyer is A_out = 60 cm²= 0.006 m²

cp = 1.007 kJ/kg·K

R = 0.287 kPa·m3/kg·K

Using mass balance

m_in = m_out = m_air

W _elec = m_air ( h_in - h_out)

we know that h = CpT

W _elec = m_air.Cp ( T_in - T_out)

we substitute

-1.4 = m_air.1.007 ( 22 - 47 )

-1.4 = - m_air.25.175

m_air = -1.4 / - 25.175

m_ air = 0.0556 kg/s

a) volume flow rate of air at the inlet

we know that

m_air = P_in × V_in

now from the ideal gas equation

P_in = p_in / RT_in

we substitute our values

= (100×10³) / ((0.287×10³)(22+273))

= 100000 / 84665

P_in = 1.18 kg/m³

therefore inlet volume flowrate will be;

V_in = m_air / P_in

= 0.0556 / 1.18

= 0.0471 m³/s

the volume flow rate of air at the inlet is 0.0471 m³/s

b) velocity of the air at the exit

the mass flow rate remains unchanged across the duct

m_ air = P_in.A_in.V_in = P_out.A_out.V_out

still from the ideal gas equation

P_out = p_out/ RT_out ( assume p_in = p_out)

P_out = (100×10³) / ((0.287×10³)(47+273))

P_out = 1.088 kg/m³

so the exit velocity will be;

V_out = m_air / P_out.A_out

we substitute our values

V_out = 0.0556 / ( 1.088 × 0.006)

= 0.0556 / 0.006528

= 8.517 m/s

Therefore the velocity of the air at the exit is 8.517 m/s

6 0

2 years ago

Which of the following explains the purpose of a convertible screwdriver?

aliya0001 [1]

Answer:

The correct option is;

To be able to switch between different heads quickly and easily

Explanation:

A screwdriver is a tool or device that has a grip handle which surrounds an extension shaft that has a forged tip that fits into the complementary groove on a screw head such that by turning the handle while the forged head of the screwdriver sits in a screw head, the screw is turned

A convertible screw driver is built with the capability to easily change the tip or other attributes of the screwdriver quickly.

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2 years ago

This graph shows the US unemployment rate from<br> August 2010 to November 2011

MrRissso [65]

The graph could help an economist predict that how many people will be out of work in the next year. The correct option is c.

<h3>What is unemployment?</h3>

Unemployment is the condition where people who have knowledge or eligible for doing job, but they are not getting job. Unemployment is the scarcity of jobs.

The options are attached:

a. how the government will address unemployment.

b. why workers might have a harder time finding jobs.

c. how many people will be out of work in the next year.

d. why producers might hire fewer workers in the future.

Thus, the correct option is c. how many people will be out of work in the next year.

Learn more about unemployment

brainly.com/question/14227610

#SPJ1

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1 year ago