1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
kow [346]
4 years ago
8

On a cold winter day, wind at 55 km/hr is blowing parallel to a 4-m high and 10-m long wall of a house. If the air outside is at

5o C and the surface temperature of the wall is 12o C, find the rate of heat loss from the wall by convection
Engineering
1 answer:
koban [17]4 years ago
3 0

Answer:

16.21 kW

Explanation:

Solution

Given that,

The velocity of wind = 55 km/hr

The length of the wall L = 10m

The height of the wall w = 4m

The surface temperature at wall Ts = 12° C

Temperature of air T∞ = 5°C

Now,

The properties  of the air at atm and average film temperature =( 12 + 5)/2 = 8.5°C, which is taken from the air table properties.

k= 0.02428 W/m°C

v= 1.413 *10 ^⁻5

Pr =0.7340

Now,

Recall Reynolds number when air flow parallel to 10 m side

[ 55 * 1000/3600) m/s (10 m)/1.413 *10^⁻5 m²/s

Rel =1.081 * 10⁷

This value is greater than Reynolds number.

The nusselt number is computed as follows:

Nu =hL/k

(0.037Rel^0.08 - 871)Pr^1/3

Nu =1.336 * 10 ^4

The heat transfer coefficient is

h = k/L Nu

= 0.2428 W/m°C /10 m (1.336 * 10 ^4)

h = 32.43 W/m°C

The heat transfer area of surface,

As = 40 m²

= ( 4 m) (10 m)

As = 40 m²

The rate of heat transfer is determined as follows:

Q = hAs( Ts - T∞)

= (32.43 W/m²°C) (40 m) (12 - 5)°C

=9081 W

Q = 9.08 kW

When the velocity is doubled,

let say V = 110km/hr

The Reynolds number is

Rel = VL/v

= [110 * 100/3600) m/s] (10 m)/ 1.413 *10^⁻5 m²/s

Rel = 2.163 * 10 ^7

This value is greater for critical Reynolds number

The nusselt number is computed as follows:

Nu =hL/k

(0.037Rel^0.08 - 871)Pr^1/3

[0.037 ( 2.163 * 10 ^7)^0.08 - 871] (0.7340)^1/3

Nu =2.344 * 10^4

The heat transfer coefficient is

h = k/L Nu

= 0.2428 W/m°C /10 m (2.384 * 10 ^4)

h= 57.88 W/m²°C

The heat transfer area of surface,

As =  wL

= ( 10 m) (4 m)

As = 40 m²

he rate of heat transfer is determined as follows:

Q = hAs( Ts - T∞)

= (57.88 W/m²°C) (40 m²) (12 - 5)°C

= 16,207 W

= 16.21 kW

You might be interested in
A silicon carbide plate fractured in bending when a blunt load was applied to the plate center. The distance between the fractur
Amanda [17]

Question in order:

A silicon carbide plate fractures in bending when a blunt load was applied to the plate center. The distance between the fracture origin and the mirror/mist boundary on the fracture surface was 0.796 mm. To determine the stress used to break the plate, three samples of the same material were tested and produced the following. What is the estimate of the stress present at the time of fracture for the original plate?

Mirror Radius (mm) Bending Failure Stress (MPa)

0.603                         225

0.203                         368

0.162                         442

Answer:

191 MPa

Explanation:

Failure stress of bending is Inversely proportional to the mirror radius

Bending Stress = \frac{1}{(Mirror Radius)^{n}}

At mirror radius 1 = 0.603 mm   Bending stress 1 = 225 Mpa..............(1)

At mirror radius 2 = 0.203 mm  Bending stress 2 = 368 Mpa...............(2)

At mirror radius 3 = 0.162 mm   Bending stress 3 = 442 Mpa...............(3)

comparing case 1 and 2 using the above equation

\frac{Stress 1}{Stress 2} = ({\frac{Radius 2}{Radius 1}})^{n_1}

\frac{225}{368} = ({\frac{0.203}{0.603}})^{n_1}

0.6114 = (0.3366)^{n_1}

Taking the natural logarithm of both side

ln(0.6114) = n ln(0.3366)

n₁ = ln(0.6114)/ln(0.3366)

n₁ = 0.452

comparing case 2 and 3 using the above equation

\frac{Stress 2}{Stress 3} = ({\frac{Radius 3}{Radius 2}})^{n_2}

\frac{368}{442} = ({\frac{0.162}{0.203}})^{n_2}

0.8326 = (0.7980)^{n_2}

Taking the natural logarithm of both side

ln(0.8326) = n ln(0.7980)

n₂ = ln(0.8326)/ln(0.7980)

n₂ = 0.821

comparing case 1 and 3 using the above equation

\frac{Stress 1}{Stress 3} = ({\frac{Radius 3}{Radius 1}})^{n_3}

\frac{225}{442} = ({\frac{0.162}{0.603}})^{n_3}

0.5090 = (0.2687)^{n_3}

Taking the natural logarithm of both side

ln(0.5090) = n ln(0.2687)

n₃ = ln(0.5090)/ln(0.2687)

n₃ = 0.514

average for n

n = \frac{n_1 + n_2 + n_3}{3}

n = \frac{0.452 +0.821 + 0.514}{3}

n = 0.596

Hence to get bending stress x at mirror radius 0.796

\frac{Stress x}{Stress 3} = ({\frac{Radius 3}{Radius x}})^{0.596}

\frac{Stress x}{225} = ({\frac{0.603}{0.796}})^{0.596}

\frac{Stress x}{225} = 0.8475

stress x = 191 MPa

3 0
4 years ago
A TV USE 75 WATTS WHILE IN USED ASSMING THAT ITIS USED 4 HOURS EVERY DAY HOW MUCH ENERGY IN 4 IN KWH WOULD THE TV CONSUME ANNUAL
prohojiy [21]

Answer:

i don't think i understand the question

Explanation:

7 0
2 years ago
Read 2 more answers
CAD(computer-aided design) software and is used in__________and __________that show how to construct an object. Technical drawin
8_murik_8 [283]

Answer:

Plans; blueprints.

Explanation:

In Engineering, it is a common and standard practice to use drawings and models in the design and development of various tools or systems that are being used for proffering solutions to specific problems in different fields such as engineering, medicine, telecommunications and industries.

Hence, a design engineer make use of drawings such as pictorial drawings, sketches, or technical drawing to communicate ideas about a design to others, to record and retain informations (ideas) so that they're not forgotten and to analyze how different components of a design work together.

Technical drawing is mainly implemented with CAD (computer-aided design) software and is typically used in plans and blueprints that show how to construct an object.

Additionally, technical drawings show in detail how the pieces of something (object) relate to each other, as well as accurately illustrating the actual (true) shape and size of an object in the design and development process.

5 0
3 years ago
Your manager has asked you to research and recommend a writing guide that examiners in your digital forensics company can use fo
vivado [14]

Answer:

Kindly Check the explanation

Explanation:

Report

A Report is a way to present the forensic examination result in front of judge. A report contains warrants, all affidavits issued for arrest, expenses occur during forensic test and lists of evidence. Apart from evidence a report also contains expert opinions.  

Guidelines  

These are the set of rules and written statement which are used to present the important information in a structured and clear format. The main motive behind to define the guidelines is to achieve standardization in the reports. It also improves the readability of the report.  

Guidelines for report  

Abstract:  

Each report must contain an abstract of the report which gives the brief review about the report. It came at the starting of the report. The main motive behind to give abstract is to give brief about report to someone in a very less time. The size of abstract must not be more than one page.  

Index:  

Each report must contain an index which display's which content is available at which page of report. The content of index must be appropriate and clear so that the reader will not get confuse.

Format of report:

The formatting of report is also one of the essential parts of the guidelines. It makes the report attractive and also due to this reader not gets bored while reading the report. The guidelines regarding layout of report are as follow:  

1. Use time roman font and 12 font size as a default font to explain anything in the report.  

2. The explanation must be justified

3. As possible divide the long paragraph. if possible explain in points.

4. The page must have border on all sides

5. Each pages must have numbering and footer

Rules for grammar:

1. The language of the report must be simple and clear. So that everyone can understand it easily.

2. Avoid repeating same sentence or word again and again.

3. Use active instead of passive voice, in order to give importance to doer.

4. Write expressions between commas.

5. Avoid spelling mistakes in report which also make wrong impact.

6. As possible give heading or subheading to material or explanation which must be accurate.

7. Explain, new or difficult words used in the report.

8. What ever written in the report must be through the point and accurate on bases of fact.

Body of report:

The body of the report referred to as a content written inside the report. In order to write an impressive report, it must include all these things:

1. Avoid use of hypothetical question, if still hypothetical question arises it must be bases on factual evidence.  

2. Add all the affidavits and warrants in the report issued for search and arrest.

3. The cost money expenses while solving the case.

4. The expert opinion which must be bases on knowledge or previously declare case results.

5. The list of people and evidence which are collected and interrogative during the investigation.

6. If investigation is further going on than write the area in which the investigation further goes on and also mention when the investigation get complete.  

Forensic software used:  

A short must be given about the software used in the investigation. The result generated by the software must also be pasted in that report. It is more good if attach the snap shot of the result. Add any previous case result in which the same software result is taken as evidence, in order to justify that the result generated by the software is true. Some of forensic softwares are FTK, ProDiscover, Hexworkshop. The result of these softwares must be heighted so that everyone can notice it.  

Conclusion:  

The conclusion must be given at the end of report to tell according him what result came after investigation. In conclusion also write on which basis the result concludes. There must be strong behind the conclusion.  

References:  

In Reference write all the cases, thesis, books which an investigator followed to solve the current case. In addition if they referred any internet article. They can also write the website name where  that article lies. In short can say that write everything where they got an idea which is helpful in solving the case.

 

8 0
3 years ago
Why is tubing sometimes coiled when installed in a car or vechile
andriy [413]

Answer:

Coiled tubing is often used to carry out operations similar to wire lining.

8 0
3 years ago
Other questions:
  • You are given a partial implementation of one header file, GildedRose.hpp. Item is a class that holds the information for each i
    6·1 answer
  • The news media often report an earthquake's magnitude on the Richter scale. Which of the following items are characteristics of
    14·1 answer
  • What is compression ratio of an Otto cycle? How does it affect the thermal efficiency of the cycle?
    14·1 answer
  • Which one of the following activities is not exempt from licensure pursuant to Chapter 471, F.S.? A person practicing engineerin
    5·1 answer
  • Suppose that we have a 1000 pF parallel-plate capacitor with air dielectric charged to 1000 V. The capacitors terminals are open
    13·1 answer
  • Carbon dioxide at a temperature of 0oC and a pressure of 600 kPa (abs) flows through a horizontal 40-mm- diameter pipe with an a
    10·1 answer
  • An Otto cycle with air as the working fluid has a compression ratio of 8.2. Under cold air standard conditions, what is the ther
    14·1 answer
  • Which type of blade is used with a demolition saw?
    11·1 answer
  • Why are there few effective HCI standards?
    6·1 answer
  • Characteristics of 3 types of soil​
    10·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!