The following is a correlation for the average Nusselt number for natural convection over spherical surface. As can be seen in the above, the Nusselt number approaches 2 as Rayleigh number approaches zero. Prove that this situation corresponds to conduction heat transfer and in conduction heat transfer over sphere, the Nusselt number becomes 2. Hint: First step: Write an expression for heat transfer between two spherical shells that share the same center. Second step: Assume the outer spherical shell is infinitely large.

Answers

Answer 1

Answer:

Explanation:

[tex]r_2=[/tex]∞

[tex]q=4\pi kT_1(T_2-T_1)\\[/tex]

[tex]q=2\pi kD.[/tex]ΔT--------(1)

[tex]q=hA[/tex] ΔT[tex]=4\pi r_1^2(T_2_s-T_1_s)\\[/tex]

[tex]N_u=\frac{hD}{k} = 2+\frac{0.589 R_a^\frac{1}{4} }{[1+(\frac{0.046}{p_r}\frac{9}{16} )^\frac{4}{9} } ------(3)[/tex]

By equation (1) and (2)

[tex]2\pi kD.[/tex]ΔT=h.4[tex]\pi r_1^2[/tex]ΔT

[tex]2kD=hD^2\\\frac{hD}{k} =2\\N_u=\frac{hD}{k}=2\\[/tex]-------(4)

From equation (3) and (4)

So for sphere [tex]R_a[/tex]→0


Related Questions

Work to be performed can come from the work package level of the work breakdown structure as well as other sources. Which of these is NOT a source of authorized work to be performed?

a. Scope creep
b. Defect repairs
c. Preventive actions
d. Corrective actions

Answers

A project is meant to achieve clearly defined goals within present constraints

The correct option for the source of work in a project which is NOT a source of authorized work to be performed is option (a)

a. Scope creep

The reason for the selecting the above option is as follows;

In project management, alongside work planned in a work package, authorized work to be performed can come from;

The repairing of defects found in completed work and which is a requirement for the project to be approvePreventive actions, that are meant to mitigate factors that affect the project timeline and costCorrective actions which include actions meant to rectify parts of the project that produce an error outcome

A scope creep, however, is generally is due to the inclusion of the end

users of the project at a time that is behind schedule, insufficient analysis of

the requirements, and project complexity underestimation. and consists of

changes made after a project has commenced

A scope creep therefore, changes the amount of work to be done which

therefore alters the project timeline, and due to project, budgetary, and

end user constraints, CANNOT be a source of authorized work to be

performed

The correct option for the source that is NOT a authorized work to be performed is option a. Scope creep

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Consider the following lines of Python:

>>> x = input()

>? 12

>>> x + “abc”

What is the output?

Answers

Answer:

I don't know

............................

The output will be an error message since the input() function in Python always takes input as a string, even if the entered value is an integer like 12.

Here,

It cannot directly concatenate a string with an integer.

In order to fix this, we need to convert the input string into an integer using the int() function,

```

x = int(input())

x = x + "abc" # this will give an error message

```If we fix the code, the correct output will be:

`>>> x = int(input())`

`12`

`>>> x + "abc"`

`TypeError: unsupported operand type(s) for +: 'int' and 'str'`

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Which tool is used to measure movement automotive

Answers

Answer:

Speedometer

It shows our speed, or how fast we're moving.

What is the following diagram called?

Answers

Answer:

flow chart

Explanation:

it's a flow chart right ? don't know the explanation cause I am not even sure I am right

there are many different values associated with an AC sine wave which one of the following continually changes throughout the cycle?

A. instantaneous value
b. effective value
c. peak value
d. average value​

Answers

A. The instantaneous value (of voltage for sure and also possibly of current) continually changes thought the cycle.

Sine waves are by far the most common type of alternating current waveform employed in electrical engineering. The correct option is A.

What are Sine Waves?

Sine waves are by far the most common type of alternating current waveform employed in electrical engineering. An AC Waveform is the shape formed by charting the instantaneous ordinate values of either voltage or current against time.

There are many different values associated with an AC sine wave but the one that continually changes throughout the cycle is the instantaneous value.

Hence, the correct option is A.

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2 Air enters the compressor of a cold air-standard Brayton cycle at 100 kPa, 300 K, with a mass flow rate of 6 kg/s. The compressor pressure ratio is 10, and the turbine inlet temperature is 1400 K. The turbine and compressor each have isentropic efficiencies of 80%. For k 5 1.4, calculate (a) the thermal efficiency of the cycle. (b) the back work ratio. (c) the net power developed, in kW. (d) the rates of exergy destruction in the compressor and turbine, respectively, each in kW, for T0 5 300 K.

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You can see and download from the link

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which type of clectrical circuit is represented by this diagram?​

Answers

Answer:

  parallel

Explanation:

All components in this circuit are tied in parallel. Each component experiences the same voltage from one terminal to the other. It is a parallel circuit.

A steam turbine generator unit is used to produce electricity, where steam enters the turbine with a velocity of 30 m/s and enthalpy (internal energy) of 3348 kJ/kg. The 1 steam leaves the turbine as a mixture of vapor and liquid having a velocity of 60 m/s and an enthalpy of 2550 kJ/kg. The flow through the turbine is adiabatic, and changes in elevation are negligible. Determine the work output from the turbine, if the mass flow rate is 5kg/s.

Answers

Answer:

3.983 MW

Explanation:

Given that:

At the inlet:

Velocity (v₁) = 30 m/s

Enthalpy (h₁) = 3348 kJ/kg

At the outlet:

Velocity (v₂) = 60 m/s

Enthalpy (h₂) = 2550 kJ/kg

Mass flow rate (m) = m₁ = m₂ = 5kg/s

According to the steady flow energy equation:

[tex]Q+ m_1 (h_1 + \dfrac{v_1^2}{2000}+ \dfrac{gz_1}{1000} )= m_2(h_2+\dfrac{v_2^2}{2000}+\dfrac{gz_2}{1000})+W_{shaft}[/tex]

Since the elevation (z) is negligible and flow via the turbine is adiabatic:

Then,

Q = 0 and z₁ = z₂

[tex]W_{shaft} = (mh_1-mh_2) + (\dfrac{mv_1^2-mv_2^2}{2000})[/tex]

[tex]W_{shaft} = ((5*3348) -(5*2550)) + (\dfrac{(5*(30)^2)-(5*(60)^2)}{2000})[/tex]

[tex]W_{shaft} = (16740-12750) + (\dfrac{4500-18000}{2000})[/tex]

[tex]W_{shaft} = (16740-12750) + (-6.75)[/tex]

[tex]W_{shaft} = 3983.25 \ kW[/tex]

[tex]\mathbf{W_{shaft} = 3.983 \ MW}[/tex]

số bit của pic 16f887

Answers

Answer:

what does it mean

Explanation:

sorry

plz write in English

Why is logging done during drilling?

Answers

Answer:

Logging while drilling (LWD) is a technique of conveying well logging tools into the well borehole downhole as part of the bottom hole assembly (BHA). ... In these situations, the LWD measurement ensures that some measurement of the subsurface is captured in the event that wireline operations are not possible

What is the following diagram called?

Answers

Answer:

business

Explanation:

because shopping has great income

Answer:

is ur question right

Explanation:

is ur question right

is ur question right

Hydraulic fracturing is: Select one: a. a first step in storage of high-level radioactive waste b. a way of extracting natural gas shale formations c. a step in oil refining where oil is separated into different viscosities d. none of the above

Answers

The answer is B - a way of extracting natural gas shale formations.

Hydraulic fracturing is “a way of extracting natural gas shale formations.”

Shale and other types of "tight" rock, or impermeable rock formations that lock in oil and gas and complicate the production of fossil fuels, can be extracted of their natural gas or oil using the modern high-volume hydraulic fracturing process. Thus, option B is correct.

What are the factor involving in Hydraulic fracturing?

Shale gas is extracted through a procedure called hydraulic fracturing, also referred to as “fracking.” Due to the fact that shale reserves are often dispersed horizontally rather than vertically, deep holes are first drilled into the shale rock, then horizontal drilling is used to reach more of the gas.

A mixture of sand, chemicals, and water is pushed at high pressure down a borehole during hydraulic fracturing. The released gas can flow out of the rocks and back up the borehole because the water pressure causes cracks in the rock to widen, and the sand particles settle into the openings to keep them open.

Therefore, a way of extracting natural gas shale formations.

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The base of an aluminum block, which is fixed in place, measures 90 cm by 90 cm, and the height of the block is 60 cm. A force, applied to the upper face and parallel to it, produces a shear strain of 0.0060. The shear modulus of aluminum is . What is the displacement of the upper face in the direction of the applied force

Answers

The question is incomplete. The complete question is :

The base of an aluminum block, which is fixed in place, measures 90 cm by 90 cm, and the height of the block is 60 cm. A force, applied to the upper face and parallel to it, produces a shear strain of 0.0060. The shear modulus of aluminum is [tex]3.0 \times 10^{10} \ Pa[/tex] . What is the displacement of the upper face in the direction of the applied force?

Solution :

The relation between shear modulus, shear stress and strain,

[tex]$\text{Shear modulus, S =} \frac{\text{Shear stress}}{\text{shear strain}}$[/tex]

Shear stress = shear modulus (S) x shear strain

                     [tex]$=3 \times 10^{10} \times 0.0060$[/tex]

                     [tex]$=1.80 \times 10^8$[/tex] Pa

                     [tex]$=180 \times 10^6$[/tex] Pa

                     [tex]$=180 \ MPa$[/tex]

The length represents the distance between the fixed in place portion and where the force is being applied.

Therefore,

[tex]$\text{Displacement} = \text{shear strain} \times \text{length}$[/tex]

                     = 0.006 x 60 cm

                      = 0.360 cm

                      = 3.6 mm

Thus, the displacement of the upper face is 3.6 mm in the direction of the applied force.

You toss two coins. If you get heads with the first coin, you stop. If you get tails, you toss it again. The second coin is tossed regardless. What is the ratio of heads to tails?

Answers

Answer:

1:1

Explanation:

A coin has either a head or tail.

Thus, probability of head = ½

Probability of tail = ½

The first coin is tossed twice and probability of head or tail on both tosses is still ½. Thus, they will have a ratio 1:1.

The second coin is still tossed regardless and thus continuously and so should have same ratio of 1:1.

Therefore, the ratio of the both of them must, also be 1:1.

prove that Sin^6 ϴ-cos^6ϴ=(2Sin^2ϴ-1)(cos^2ϴ+sin^4ϴ) please sove step by step with language it is opt maths question guys i willl give you 100 point and mark as brainlest answer​

Answers

By using basic trigonometric identity.....

biến tần là gì trong công nghiệp

Answers

Nguồn điện là một yêu cầu thiết yếu của các ngành công nghiệp. Biến tần là một thiết bị độc lập có chức năng chuyển đổi điện áp một chiều thành điện áp xoay chiều. Biến tần đảm bảo rằng việc cung cấp điện không bị gián đoạn và liên tục. ... Các ngành công nghiệp yêu cầu sử dụng bộ nghịch lưu công nghiệp để hoạt động liên tục của các hoạt động trong ngành.

A gear component (0.2% C) is carburized with C for increased hardness. By specification, a carbon concentration of 0.75% C is required at an 80 um depth. Calculate the time required (ir hours) at 1100°C with the gas surface concentration of 1.3 % C. D=5x10-13 m2/s. Show relevant steps how you arrived at the answer Comment on whether the suggested carburizing time of 3 hours is sufficient, also mention the calculated time in hours

Answers

Answer:

The carburizing process takes 3.92 hours or 14,123.3 seconds. the suggested time of 3 hrs is not sufficient.

answer this qustion plz

Answers

Answer:

click here and I'm so happy I have been doing this weekend I can see the same way you could come back in a bit and then we are all of you to know you do for a bit of time with me or

You are given a pot of hot tea (350 mL) at a temperature of 85°C and a quantity of ice at -12°C. Determine the absolute minimum amount of ice you can add to the hot tea so that at equilibrium you have iced tea (ie. a very, very small amount of ice and some water). You can assume tea has the same density (1.00 g/mL) and specific heat (4190 J/kgK) as liquid water. The heat of fusion of H2O is 3.33x10^5 J/kg. The specific heat of ice is 2090 J/kgK.

Answers

Answer:

348 g

Explanation:

The heat gained by the ice equals the heat lost by the hot tea.

Also, since we require a very, very small amount of ice and some water, to still have some ice, the temperature of the hot tea has to decrease to the melting point of ice which is 0°C. So, the final temperature of the mixture is 0 °C.

So, mc(T - T') + mL = -MC(T - T") where m = mass of ice, c =  specific heat of ice = 2090 J/kgK., T = final temperature of mixture = 0 °C, T' = initial temperature of ice = -12 °C, L = heat of fusion of H2O = 3.33 × 10⁵ J/kg, M = mass of hot tea = ρV where ρ = density of tea = 1.00 g/mL and V = volume of hot tea = 350 mL. So, M = ρV = 1.00 g/mL × 350 mL = 350 g = 0.350 kg, C = specific heat of tea = 4190 J/kgK and T" = initial temperature of tea = 85 °C.

Making m subject of the formula, we have

mc(T - T') + mL = -MC(T - T")

m[c(T - T') + L] = -MC(T - T")  

m = -MC(T - T")/[c(T - T') + L]

substituting the values of the variables into the equation, we have

m = -MC(T - T")/[c(T - T') + L]

m = -0.350 kg × 4190 J/kgK(0 °C - 85 °C.)/[2090 J/kgK(0 °C. - (-12 °C)) + 3.33 × 10⁵ J/kg]

m = -1466.5 J/kK(- 85 °C)/[2090 J/kgK(0 °C + 12 °C)) + 3.33 × 10⁵ J/kg]

m = 124652.5 J/[2090 J/kgK(12 °C) + 3.33 × 10⁵ J/kg]

m = 124652.5 J/[25080 J/kg + 3.33 × 10⁵ J/kg]

m = 124652.5 J/358080 J/kg

m = 0.3481 kg

m = 348.1 g

m ≅ 348 g

So, the minimum amount of ice to be added is 348 g.

There are some sections of the SDS that are not mandatory

True or false

Answers

Answer:

True

Explanation:

There are 16 in all and 4 are not mandatory

There are some sections of the SDS that are not mandatory. Thus, option A is correct.

What is SDS?

A Safety Data Sheet, previously known as a Material Safety Data Sheet, is a thorough instructional report written by a dangerous product's producer or exporter. It gives a description of something like the product's chemical and physical characteristics.

Sections 1 through 11 and 16 must be used; sections 12 through 15 are optional but could be included. the section which will are not compulsory are:

Section 12: Environmental data

Section 13: Guidelines for Recycling

Section 14: Documentation regarding mobility

Section 15: Relevant data about regulations

In Safety Data Sheet, all the sections are not compulsory or mandatory. this statement is true. Therefore, option A is the correct option.

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Side milling cutter is an example of ______ milling cutter.

Answers

Answer:

special type

Explanation:

As per the classification of milling cutters. This cutter can handle deep and long open slots in a more comfortable manner, which increase the productivity.

A bird is flying in air. It is stretching its wings all along the sky and is flying in a certain direction Flying a bird is an example of: a. Composition of vector b. Collinear vector c. Addition of vector d. Multiplication of vector

Answers

Answer:

a. Composition of Vector.

Explanation:

When a bird flies in the air, it stretches its wings into air and this movement helps it move in a certain direction. This is an example of composition of vector. Air strikes the wings in opposite direction and bird wing movement helps it move against the wind.

The end of the industrial robotic arm extends along the path (r = 2 + 2 cos (5t)) m. At the instant ( 0 = 0.8t ) radians. When the arm is located at (t = 0.85) second Determine the velocity and acceleration of the object A at this instant.​

Answers

Answer:

  v = 8.95 rad / s,    a = 22.3 rad / s²

Explanation:

This is an exercise in kinematics, where we must use the definitions of velocity and acceleration

          v = dr / dt

       

we perform the derivative

          v = 0+ 2 (-sin 5t) 5

          v = -10 sin 5t

we calculate for t = 0.85 t,

remember angles are in radians

           v = -10 sin (5 0.85)

           v = 8.95 rad / s

acceleration is defined by

           a = dv / dt

             

we perform the derivatives

          a = -10 (cos 5t) 5

          a = - 50 cos 5t

we calculate for t = 0.85 s

          a = -50 are (5 0.85)

          a = 22.3 rad / s²

Uses of P-N junction

Answers

Answer:

Explanation:

Two that come to mind:

a semiconductor diode is essentially a PN junctiona transistor is made of two pn junctions.

Suppose we have 999 records of employees Emp1, Emp2, Emp5, Emp6 and so on up to Emp998 and Emp999 stored in a sequence. Hence, records are nothing but a row in the table. In the employee table, we want to insert new records Emp3 and Emp4 in the sequence, and once we have done insertion we need to update and retrieve the record efficiently to optimize the performance of a database by minimizing the access time when query is being executed.

Answers

The records in the table represents the employee ID of each employee. Assume the table name is EMPLOYEES and the field name of employee IDs is ID, the following SQL query inserts Emp3 and Emp4 into the employees table.

INSERT INTO EMPLOYEES (ID) values (Emp3), (Emp4)

The complete question requires that we list the pros and cons of solving the problem using Index sequential access method (ISAM).

The advantage of using ISAM is that priorities are given to the indices of the records being inserted. So, Emp3 and Emp4 will be inserted immediately after Emp2.

However, a major disadvantage of using ISAM is that it is very expensive to keep the indices in a sequential order;

See attachment for the illustration of Index sequential access method (ISAM).

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Troy must keep track of the amount of refrigerant he uses from a 50-pound cylinder to ensure that accurate
records are kept. He used 13 pounds on a systein for Ms. Jones and 9 pounds on a system for a commercial
client. How many pounds should he have left in the cylinder?
tof
Troy should have
pounds of refrigerant left in the cylinder.
baon naid Thamar basic
محمود احمد مجد
12
اهداء ما در

Answers

Answer:

Amount of gas still in cylinder = 28 pound

Explanation:

Given:

Amount of gas in cylinder = 50 pound

Amount of gas used in Ms. Jones system = 13 pound

Amount of gas used in client system = 9 pound

Find:

Amount of gas still in cylinder

Computation:

Amount of gas still in cylinder = Amount of gas in cylinder - Amount of gas used in Ms. Jones system - Amount of gas used in client system

Amount of gas still in cylinder = 50 - 13 - 9

Amount of gas still in cylinder = 28 pound

Why do we use radians in numerical methods? What is the problem of using degrees?

Answers

Radians make it possible to relate a linear measure and an angle measure. ... The length of the arc subtended by the central angle becomes the radian measure of the angle. This keeps all the important numbers like the sine and cosine of the central angle, on the same scale.

Explanation:

radians make it possible to relate to Linear measures and an angle measure

if a person is injured at the hospital during a natural disaster a correct action to take is ​

Answers

first check that you and the casualty aren't in any danger. If you are, make the situation safe. When it's safe to do so, assess the casualty and, if necessary, dial 999 or 112 for an ambulance. You can then carry out basic first aid and shift to another hospital




That’s what I learnt sooo..

If a corporation is socially responsible, it will develop and implement a sustainability plan and communicate it to stakeholders.

True
False

Answers

Answer:

True

Explanation:

All big companies are pretty much required in today's day and ages to complete these reports whether they truly believe it.

A mechanic claims to have developed a car engine that runs on water instead of gasoline. What is your response to this claim?​

Answers

The claim will be impractical. The reason behind this is provided below throughout the explanation segment.

Inside the same combustion chamber, fresh water can't be pressurized even more than fuel as well as air. Consequently, the cylinder does not burn due to a problem with the compressor.To accomplish the development processes, a machine requires any sort of combustible which might cause combustion as well as create a tremendous quantity of power.

Thus, the idea of using water instead of petroleum appears unworkable throughout traditional engines.

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Which of the following is NOT an effective way for a person to boost their self-esteem?A. Learn to view failures as opportunities for learning and future growthB. Reframe negative thoughts of failure into positive ones of effort and progressC. Seek opportunities to learn, grow, and achieve without focusing on perfectionD. Surround yourself with people who stress achievement and perfection over anything else HELP ITS DUE IN THE MORNING AND ITS 3:57 Hi, help me solve/ hola me ayudan a resolver. imagine you are Aisha write two diary entries where you reavel your emotional, feelings Each day Jose spends 2/3 of an hour playing the piano and 1/4 of an hour practicing music theory. What is the total fraction of an hour that Jose spends playing the paino and practicing music theory each day? Find the vertex of the following equation: y = -0.25x2 + -1.5x + 6 a coin is tossed succesively three times times . determine tje probabiliy of getting all three heads a sum of money Doubles itself in 5 years what is rate of simple interest Find f(-2)..................................... Which behavior would best describe someone who has good communication skills with customers ? a) Following up with some customers b) Talking to customers more than listening to them c) Repeating back what the customer says d) Interrupting customers frequently Which statement is the best description of an electric motor? A. It moves magnetic fields relative to loops of wires to make electricity. B. It uses motion in a magnetic field to produce an electric current. C. It uses kinetic energy to rotate a loop of wire in a magnetic field. D. It uses an electric current in a magnetic field to produce motion. Which foods are not allowed on clear liquid diet Can you . me some new books on this subject?A. recommend toB. recommendC. offer toD. offer of [6] a) I haven't readied your book yet. (Into Affirmative) b) He'd rather find him noisy and restless. (Add question tag) c) People believe that the life in the city is easy and comfortable. (Change into passive voice) d) The teacher asked me whether I had completed the assignment the day before. (Change into direct speech) The manila folders are stored __________ the top of the shelf of the storage cabine A sporting equipment store expects to purchase $8,200 of ski boots in October. The store had $2,800 of ski boots in merchandise inventory at the beginning of October, and expects to have $1,800 of ski boots in merchandise inventory at the end of October to cover part of anticipated November sales. What is the budgeted cost of goods sold for October?a) $7,000.b) $9,000.c) $8,000.d) $12,000.e) $11,000. justify the statement that the constitution of Nepal ( 2072 ) was documents of political consensus. Which segment is parallel to ED? Using simplified language and numbers, using large font type with more spacing between questions, and having students record answers directly on their tests are all examples of _____. Group of answer choices universal design analytic scoring cheating deterrents guidelines to assemble tests What is the image of the point (4,7) after a reflection about the line y = 4.?