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2 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]2 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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Some of our modern kitchen cookware is made of ceramic materials. (a) List at least three important characteristics required of

Alisiya [41]

Answer:

It should be Non- toxic

It should possess high Thermal conductivity

It should have the Required Thermal diffusivity

stoneware : This material has good thermal diffusivity and it is quite affordable and it is used in making pizza stones
porcelain: mostly used for mugs and it is non-toxic
Pyrex : posses good thermal conductivity used in oven

C) All the materials are suitable because they serve different purposes when making modern kitchen cookware

Explanation:

A) characteristics required of a ceramic material to be used as a kitchen cookware

It should be Non- toxic
It should possess high Thermal conductivity
It should have the Required Thermal diffusivity

B) comparison of three ceramic materials as to their relative properties

stoneware : This material has good thermal diffusivity and it is quite affordable and it is used in making pizza stones
porcelain: mostly used for mugs and it is non-toxic
Pyrex : posses good thermal conductivity used in ovens

C) material most suitable for the cookware.

All the materials are suitable because they serve different purposes when making modern kitchen cookware

8 0

2 years ago

A sum of $500,000 will be invested by a firm two years from now. If money is worth 12%, what will be the worth of this investmen

notka56 [123]

Answer:

investment 10 years from now is $1,238,000 .

Explanation:

given data

sum = $500,000

rate = 12% =0.12

total time = 10 year

solution

as present value After 2 years from now is $500,000

so time period is now = 8 year ( 10 - 2 )

so we apply future value formula that is

Future value = present value × $(1+r)^{t}$ ............1

put here value we get

Future value = $500,000 × $(1+0.12)^{8}$

Future value = $500,000 × 2.476

Future value = $1,238,000

so investment 10 years from now is $1,238,000 .

8 0

3 years ago

Which of following are coding languages used in controlling a robot? *

Bess [88]

Answer:

C/C++

Explanation:

C/C++

7 0

2 years ago

You are evaluating the lifetime of a turbine blade. The blade is 4 cm long and there is a gap of 0.16 cm between the tip of the

Tcecarenko [31]

Answer:

Explanation:

Given conditions

1)The stress on the blade is 100 MPa

2)The yield strength of the blade is 175 MPa

3)The Young’s modulus for the blade is 50 GPa

4)The strain contributed by the primary creep regime (not including the initial elastic strain) was 0.25 % or 0.0025 strain, and this strain was realized in the first 4 hours.

5)The temperature of the blade is 800°C.

6)The formula for the creep rate in the steady-state regime is dε /dt = 1 x 10-5 σ4 exp (-2 eV/kT)

where: dε /dt is in cm/cm-hr σ is in MPa T is in Kelvink = 8.62 x 10-5 eV/K

Young Modulus, E = Stress, $\sigma$ /Strain, ∈

initial Strain, $\epsilon_i = \frac{\sigma}{E}$

$\epsilon_i = \frac{100\times 10^{6} Pa}{50\times 10^{9} Pa}$

$\epsilon_i = 0.002$

creep rate in the steady state

$\frac{\delta \epsilon}{\delta t} = (1 \times {10}^{-5})\sigma^4 exp^(\frac{-2eV}{kT} )$

$\frac{\epsilon_{initial} - \epsilon _{primary}}{t_{initial}-t_{final}} = 1 \times 10^{-5}(100)^{4}exp(\frac{-2eV}{8.62\times10^{-5}(\frac{eV}{K} )(800+273)K} )$

but Tinitial = 0

$\epsilon_{initial} - \epsilon _{primary}} = 0.002 - 0.003 = -0.001$

$\frac{-0.001}{-t_{final}} = 1 \times 10^{-5}(100)^{4}\times 10^{(\frac{-2eV}{8.62\times10^{-5}(\frac{eV}{K} )1073K} )}$

solving the above equation,

we get

Tfinal = 2459.82 hr

3 0

3 years ago

A heat pump operates on a vapor-compression refrigeration cycle with R-134a as the working fluid. The refrigerant enters the com

Rudiy27

Answer:

Hello your question has some missing information below are the missing information

The refrigerant enters the compressor as saturated vapor at 140kPa Determine The coefficient of performance of this heat pump

answer : 2.49

Explanation:

For vapor-compression refrigeration cycle

P1 = P4 ; P1 = 140 kPa

P2( pressure at inlet ) = P3 ( pressure at outlet ) ; P2 = 800 kPa

<u>From pressure table of R 134a refrigerant</u>

h1 ( enthalpy of saturated vapor at 140kPa ) = 239.16 kJ/kg

h2 ( enthalpy of saturated liquid at P2 = 800 kPa and t = 60°C )

= 296.8kJ/kg

h3 ( enthalpy of saturated liquid at P3 = 800 kPa ) = 95.47 kJ/kg

also h4 = 95.47 kJ/kg

To determine the coefficient of performance

Cop = ( h1 - h4 ) / ( h2 - h1 )

∴ Cop = 2.49

3 0

2 years ago