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zmey [24]
3 years ago
14

A petrol engine produces 20 hp using 35 kW of heat transfer from burning fuel. What is its thermal efficiency, and how much powe

r is rejected to the ambient surroundings?
Engineering
1 answer:
hoa [83]3 years ago
5 0

Answer:

efficiency =42.62%

AMOUNT OF POWER REJECTED IS 20.080 kW

Explanation:

given data:

power 20 hp

heat energy = 35kW

power production = 20 hp = 20* 746 W = 14920 Watt   [1 hp =746 watt]

efficiency = \frac{power}{heat\ required}

efficiency = \frac{14920}{35*10^3}

                = 0.4262*10^100

                 =42.62%

b) heat\ rejected = heat\ required - amount\ of\ power\ generated

                           = 35*10^3 - 14920

                           = 20.080 kW

AMOUNT OF POWER REJECTED IS 20.080 kW

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Stells [14]

Answer:

\dfrac{\bar{h}}{h}=\dfrac{5}{4}

Explanation:

Given that

Nu_x=0.035Re_x^{0.8} Pr^{1/3}

We know that

Rex=ρvx/μ

So

Nu_x=0.035Re_x^{0.8} Pr^{1/3}

Nu_x=0.035\times\left(\dfrac{\rho vx}{\mu}\right)^{0.8}Pr^{1/3}

All other quantities are constant only x is a variable in the above equation .so lets take all other quantities as a constant C

Nu_x=C.x^{0.8}=C.x^{4/5}

We also know that

Nux=hx/K

C.x^{4/5}=\dfrac{hx}{k}

m is the constant

h=mx^{-1/5}

This is local heat transfer coefficient

The average value of h given as

\bar{h}=\dfrac{\int_{0}^{L}hdx}{L}

\bar{h}=\dfrac{5m}{4}\times\dfrac{L^{4/5}}{L}

\bar{h}=\dfrac{5m}{4}L^{-1/5}             ---------1

The value of local heat transfer coefficient at x=L

h=mx^{-1/5}

h=mL^{-1/5}            -----------2

From 1 and 2 we can say that

\dfrac{\bar{h}}{h}=\dfrac{5}{4}

8 0
3 years ago
A masonry facade consisting of 3,800 square feet is to be constructed for a building. The total cost per worker hour is estimate
lana66690 [7]

Answer:

Days: 6.9444 days

Production rate: 547.2035 ft²/s

Explanation:

the solution is attached in the Word file

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6 0
2 years ago
After replacing a vacuum booster, the brakes lock up on a road test. Technician A says there is air trapped inside the brake lin
vitfil [10]

Answer:

Technician B

Explanation:

The brakes can lockup due to the following reasons

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2) Use of wrong brake fluid

3) Broken or damaged drum brake backing plates, rotors, or calipers

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5 0
3 years ago
Three groups of students are given study outlines for 6 weeks. One group studies 2 hours a night, a second group studies 1 hour
katrin2010 [14]

Answer:

The constant here is the study outline

Explanation:

In scientific research, the constant variable is that part/variable of the experiment that does not change or is set not to change. Examples include temperature, environment or height.

Assuming the scenery described in this question is an experiment. All the groups presented are bound by a constant during the experiment. The constant here is the study outline. The study outline provided to the students is not going to change.

NOTE: There could be confusion as regards the answer being the final exam grade but that will be the dependent variable as that will be the outcome of the experiment while the time spent to study will be the independent variable.

8 0
2 years ago
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Lorico [155]

Answer: False

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4 0
3 years ago
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