Ask question

Ask question

All categories

3 years ago

8

The temperature of a flowing gas is to be measured with a thermocouple junction and wire stretched between two legs of a sting,

a wind tunnel test fixture. The junction is formed by butt-welding two wires of different material. For wires of diameter D = 125 m and a convection coefficient of h = 700 W/m^2 K, determine the minimum separation distance between the two legs of the sting, L=L1+L2, to ensure that the sting temperature does not influence the junction temperature and, in turn, invalidate the gas temperature measurement. Consider two different types of thermocouple junctions consisting of (i) copper and constantan wires and (ii) chromel and aluminel wires. Evaluate the thermal conductivity of copper and constantan at T300 K. Use kCh =19 W/mK and kA = l29 W/mK for the thermal conductivities of the chromel and alumel wires, respectively.

1 answer:

ArbitrLikvidat [17]3 years ago

4 0

Answer:

minimum separation distance between the two legs of the sting L = L 1 + L 2 therefore L = 9.48 + 4.68 = 14.16 m

L = 1.14 m

Explanation:

D ( diameter ) = 125 m

convection coefficient of h = 700 W/m^2

Calculate THE CROSS SECTIONAL AREA

Ac = $\frac{\pi }{4} * D^2$ = $\frac{\pi }{4} * ( 125 )^2$ = 0.79 * 15625 = 12343.75 m^2

perimeter

p = $\pi * D$ = 3.14 * 125 = 392.5 m

at 300k temperature the thermal conductivity of copper and constantan from the thermodynamic property table are :

Kcu = 401 w/m.k

Kconstantan = 23 W/m.k

To calculate the length of copper wire of the thermocouple junction

L 1 = 4.6 ( $\frac{Kcv Ac}{h P}$ ) ^ 1/2 = 4.6 $(\frac{401 *12343.75 }{700 *392.5})^\frac{1}{2}$

L 1 = 4.6 ( 4949843.75 / 274750 )^1/2

L 1 = 9.48 m

calculate length of constantan wire

L 2 = 4.6 $(\frac{kcons*Ac}{hp} )^\frac{1}{2}$

= 4.6 ( (23 * 12343.75) / ( 700 * 392.5) ) ^1/2

L 2 = 4.6 ( 283906.25 / 274750 ) ^ 1/2

L 2 = 4.68 m

I) therefore the minimum separation distance between the two legs of the sting L = L 1 + L 2

L = 9.48 + 4.68 = 14.16 m

ii) Evaluating the thermal conductivity of copper and constantan

Kc ( thermal conductivity of chromel) = 19 w/m.k

Ka ( thermal conductivity of alumel ) = 29 W/m.k

distance between the legs L = L 1 + L 2

THEREFORE

L = 4.6 ( (Kcn * Ac ) / ( hp ) )^1/2 + 4.6 ( (Kac * Ac)/(hp) )^1/2

L = 4.6 $(\frac{Ac}{hp} )^\frac{1}{2} [ (Kcn)^\frac{1}{2} + (Kal)^\frac{1}{2} ]$

L = 4.6 ( 12343.75 /( 700 * 392.5) )^1/2 * [ 19^1/2 + 29^1/2 ]

L = 4.6 ( 12343.75 / 274750 ) ^1/2 * 5.39

L = 1.14 m

You might be interested in

Which of the following is true about the n-way analysis of variance (ANOVA)?

Ne4ueva [31]

Answer:

It is a type of ANOVA that can analyze several independent variables at the same time.

Explanation:

This is the statement that correctly describes the n-way analysis of variance (ANOVA). ANOVA is a type of analysis of variance that can analyze several independent variables at the same time. In this type of analysis, a dependent variable is measured by different levels of independent variables. When the results are obtained, these are assumed to be the consequence of the different levels of the independent variables, plus random error. The computation necessary for this analysis can be done in most types of statistical software.

7 0

3 years ago

Q9. A cylindrical specimen of a metal alloy 54.8 mm long and 10.8 mm in diameter is stressed in tension. A true stress of 365 MP

wolverine [178]

Answer:

σ = 391.2 MPa

Explanation:

The relation between true stress and true strain is given as:

σ = k εⁿ

where,

σ = true stress = 365 MPa

k = constant

ε = true strain = Change in Length/Original Length

ε = (61.8 - 54.8)/54.8 = 0.128

n = strain hardening exponent = 0.2

Therefore,

365 MPa = K (0.128)^0.2

K = 365 MPa/(0.128)^0.2

k = 550.62 MPa

Now, we have the following data:

σ = true stress = ?

k = constant = 550.62 MPa

ε = true strain = Change in Length/Original Length

ε = (64.7 - 54.8)/54.8 = 0.181

n = strain hardening exponent = 0.2

Therefore,

σ = (550.62 MPa)(0.181)^0.2

<u>σ = 391.2 MPa</u>

7 0

3 years ago

A driver traveling in her 16-foot SUV at the speed limit of 30 mph was arrested for running a red light at 15th and Main, an int

Lynna [10]

Answer:

(a) Yes

(b) 102.8 ft

Explanation:

(a)First let convert mile per hour to feet per second

30 mph = 30 * 5280 / 3600 = 44 ft/s

The time it takes for this driver to decelerate comfortably to 0 speed is

t = v / a = 44 / 10 = 4.4 (s)

given that it also takes 1.5 seconds for the driver reaction, the total time she would need is 5.9 seconds. Therefore, if the yellow light was on for 4 seconds, that's not enough time and the dilemma zone would exist.

(b) At this rate the distance covered by the driver is

$s = v_0t + \frac{at^2}{2}$

$s =44*1.5 + 44(4.4) - \frac{10*4.4^2}{2} = 162.8 (ft)$

Since the intersection is only 60 feet wide, the dilemma zone must be

162.8 - 60 = 102.8 ft

4 0

3 years ago

Implement a function called myFilter that does the following: Takes a sequence of integers with values from 0 to 100 Remove all

goldenfox [79]

Answer:

using System;

using System.Collections.Generic;

using System.Linq;

public class Problem1 {

public static IEnumerable < int > myFilter(IEnumerable < int > input) {

return input.Where((val, index) => {

//First remove all multiples of 6 less than 42

return !(val % 6 == 0 && val < 42);

}).Select((val, index) => {

//Then square each number

return val * val;

}).Where((val, index) => {

// Finally, remove any resulting integer that is odd

return !(val % 1 == 0);

});

}

public static void Main(string[] args) {

Random rnd = new Random(5);

//Takes a sequence of integers with values from 0 to 100

var listForProblem = Enumerable.Range(1, 100).Select(i => rnd.Next() % 101);

var answer = Problem1.myFilter(listForProblem);

foreach(int i in answer) {

Console.WriteLine(i);

}

}

}

Explanation:

The Problem 1 solution is explanatory enough.

Your problem 2 question is lacking details. However, i have written a code that sorts it.

6 0

3 years ago

List 6 different mechanisms in the Rube Goldberg cartoon and predict the purpose of each. Does the mechanism change speed, force

vodka [1.7K]

Answer: Rotary - because it has to

Around in a circle

Explanation:

i hope this helped u

7 0

3 years ago