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
leonid [27]
3 years ago
8

9.21 A household oven door of 0.5-m height and 0.7-m width reaches an average surface temperature of 32℃ during operation. Estim

ate the heat loss to the room with ambient air at 22℃. If the door has an emissivity of 1.0 and the surroundings are also at 22℃, comment on the heat loss by free convection relative to that by radiation.
Engineering
1 answer:
miss Akunina [59]3 years ago
4 0

Answer:

Q convection = 11.361 W

Q radiation = 21.438 W

Explanation:

Given data:

v = 1.524 \times 10^{-5}m^2/s

Pr = 0.7

Isobaric volume expansion is calculated as

\beta = \frac{1}{v} {\partial v}{\partial T}

\beta = \frac{1}{T_{ambient}} = \frac{1}{22+273} = 3.39\times 10^{-3} K^{-1}

L = 0.5 m Since door is vertical

grasshoff number is

Gr = \frac{g \beta(T_S - T_A)L^3}{v^2}

Gr = \frac{9.81 \times 3.39\times 10^{-3} (32.22) \times 0.5^3}{(1.524\times ^{-5})^2}

Gr = 1.79\times 10^8

Rayleigh number

Ra = GrPr

Ra = 1.253\times 10^8 \times 0.7 = 1.253\times 10^8< 10^8

therefore given flow is laminar

Nusselt number is

Nu = 0.5 (Ra)^{1/4}

Nu= 0.59(1.253\times 10^8)^{1/4})

Nu = 62.4223

Heat transfer coefficient

h = \frac{NuK_{air}}{L}

h = 62.4223 \times 0.026}{0.5}

h = 3.246 W/m^2 K

convection heat transfer

Q = hA(T_S - T_A)

Q = 3.246\times 0.5\times 0.7(32-22)

Q = 11.361 W

Radiation heat transfer

Q_R = \sigma \epsilon A(T_s^4 - T_A^4}

Q_R = 5.67 \times 10^{-8} \times 1\times 0.5\times 0.7(305^4 - 294^4)

Q_R = 21.438 W

You might be interested in
What does it mean when it says technology is A dynamic process
Degger [83]

Answer:

It studies the process of technological change. Under the field of Technology Dynamics the process of technological change is explained by taking into account influences from "internal factors" as well as from "external factors

Explanation:

5 0
3 years ago
What is the following passage saying about the relationship between sustainability and responsibility?
7nadin3 [17]

What the given passage is saying about the relationship between sustainability and responsibility is that;

C: We should only consider products or services to be green if their broad impact can be considered so.

<h3>Sustainability</h3>

From the passage, we see a write up questioning if the things we term to be green are truly green.

Now, from the passage, we see that a biofuel that is considered to be green is not really green if we consider that if it requires massive overproduction, it could wreck the water table.

Also, he says that if the production is local but also wasteful then it is not green.

Thus, we can see clearly that before we term a product or service as green, we should also consider their broad impact on the environment.

Read more about sustainability at; brainly.com/question/14154063

7 0
2 years ago
The function below takes a single parameter, a list of numbers called number_list. Complete the function to return a string of t
makkiz [27]

Answer:

The solution code is written in Python:

  1. def convertCSV(number_list):
  2.    str_list = []
  3.    for num in number_list:
  4.        str_list.append(str(num))
  5.    
  6.    return ",".join(str_list)
  7. result = convertCSV([22,33,44])
  8. print(result)

Explanation:

Firstly, create a function "convertCSV" with one parameter "number_list". (Line 1)

Next, create an empty list and assign it to a new variable <em>str_list</em>. (Line 2)

Use for-loop to iterate through all the number in the <em>number_list</em>.(Line 4). Within the loop, each number is converted to a string using the Python built-in function <em>str() </em>and then use the list append method to add the string version of the number to <em>str_list</em>.

Use Python string<em> join() </em>method to join all the elements in the str_list as a single string. The "," is used as a separator between the elements (Line 7) . At the end return the string as an output.

We can test the function by calling the function and passing [22,33,34] as an argument and we shall see "22,33,44" is printed as an output. (Line 9 - 10)

6 0
3 years ago
Write the following decorators and apply them to a single function (applying multiple decorators to a single function): 1. The f
natita [175]

Answer:

Complete question is:

write the following decorators and apply them to a single function (applying multiple decorators to a single function):

1. The first decorator is called strong and has an inner function called wrapper. The purpose of this decorator is to add the html tags of <strong> and </strong> to the argument of the decorator. The return value of the wrapper should look like: return “<strong>” + func() + “</strong>”

2. The decorator will return the wrapper per usual.

3. The second decorator is called emphasis and has an inner function called wrapper. The purpose of this decorator is to add the html tags of <em> and </em> to the argument of the decorator similar to step 1. The return value of the wrapper should look like: return “<em>” + func() + “</em>.

4. Use the greetings() function in problem 1 as the decorated function that simply prints “Hello”.

5. Apply both decorators (by @ operator to greetings()).

6. Invoke the greetings() function and capture the result.

Code :

def strong_decorator(func):

def func_wrapper(name):

return "<strong>{0}</strong>".format(func(name))

return func_wrapper

def em_decorator(func):

def func_wrapper(name):

return "<em>{0}</em>".format(func(name))

return func_wrapper

@strong_decorator

@em_decorator

def Greetings(name):

return "{0}".format(name)

print(Greetings("Hello"))

Explanation:

5 0
4 years ago
What is the shape of the output signal on a rigexpert analyzer?
Gekata [30.6K]

Answer:

Output signal shape: square, from 0.1 to 230 MHz. Output power: -10 dBm (at a load of 50 Ohms).

Explanation:

8 0
2 years ago
Read 2 more answers
Other questions:
  • The following C program asks the user for two input null-terminated strings, each stored in uninitialized 100-byte buffer, and c
    6·1 answer
  • Members of the student council have been asked by their
    5·1 answer
  • Write down one metal or alloy that is best suited for each of the following applications:
    8·1 answer
  • A rod of length L lies along the x axis with its left end at the origin. It has a nonuniform charge density λ = αx, where α is a
    14·2 answers
  • Global Courier Services will ship your package based on how much it weighs and how far you are sending the package. Packages abo
    14·1 answer
  • There are two questions about SolidWorks.
    9·1 answer
  • The unit weight of a soil is 14.9kN/m3. The moisture content of the soil is17% when the degree of saturation is 60%. Determine:
    15·1 answer
  • Water of dynamic viscosity 1.12E-3 N*s/m2 flows in a pipe of 30 mm diameter. Calculate the largest flowrate for which laminar fl
    13·1 answer
  • Which of the following is not necessary a reason to machine a brake drum?
    8·1 answer
  • What speeds did john j montgomerys gliders reach
    12·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!