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Finger [1]
2 years ago
14

Air enters a nozzle steadily at 280 kPa and 77°C with a velocity of 50 m/s and exits at 85 kPa and 320 m/s. The heat losses from

the nozzle to the surroundings medium at 20°C are estimated to be 3.2 kJ/kg. Determine (a) the exit temperature and (b) the entropy generation for this process. Assume that the air has variable specific heats.
Engineering
1 answer:
Arlecino [84]2 years ago
6 0

The input values are the following

\left.T_{1}=350 K\right\ then

h_{1}=350.49 \frac{k j}{k g}, s_{1}=1.85708 \frac{K j}{K g \cdot K}

By using the energy equilibrium

\dot{E}_{i n}-\dot{E}_{o u t}=\Delta \dot{E}_{s y s t e m}=0 , \dot{E}_{i n}=\dot{E}_{o u t}

we haveT_{2}=297.2 K

eq (1)  \dot{m}\left(h_{1}+\frac{V_{1}^{2}}{2}\right)=\dot{m}\left(h_{2}+\frac{V_{2}^{2}}{2}\right)+\dot{Q}_{o u t} ∴

0=q+h_{2}-h_{1}+\frac{V_{2}^{2}-V_{1}^{2}}{2}

Now, for specific energy h2:

h_{2}=h_{1}-q_{o u t}-\frac{V_{2}^{2}-V_{1}^{2}}{2}

By replacing the eq (1) we have

h_{2}=350.49 \frac{k j}{k g}-3.2-\frac{\left(320 \frac{m}{s}\right)^{2}-\left(50 \frac{m}{m}\right)^{2}}{2}\left(\frac{1 \frac{k j}{k g}}{1000 \frac{m^{2}}{s^{2}}}\right)

h_{2}=297.34 \frac{k j}{k g}

By using a standard ideal-gas properties of air we have

T_{2}=297.2 K

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Write multiple if statements: If carYear is before 1967, print "Probably has few safety features." (without quotes). If after 19
Free_Kalibri [48]

Answer:

The solution code is written in Python 3.

  1. carYear = 1995
  2. if(carYear < 1967):
  3.    print("Probably has few safety features.\n")
  4. if(carYear > 1970):
  5.    print("Probably has head rests. \n")
  6. if(carYear > 1991):
  7.    print("Probably has electronic stability control.\n")
  8. if(carYear > 2002):
  9.    print("Probably has airbags. \n")

Explanation:

Firstly, create a variable, <em>carYear</em> to hold the value of year of the car make. (Line 1)

Next, create multiple if statements as required by the question (Line 3-13). The operator "<" denotes "smaller" and therefore <em>carYear < 1967</em> means any year before 1967. On another hand, the operator ">" denotes "bigger" and therefore <em>carYear > 1970 </em>means any year after 1970.

The print statement in each of the if statements is done using the Python built-in function <em>print()</em>. The "\n" is an escape sequence that create a new line at the end of each printed phrase.

5 0
2 years ago
what is the advantage of decreasing the field current of a separately excited dc motor below its nominal value
enyata [817]

Answer:

Ability to rotate at higher speeds

Explanation:

Constant K1 becomes greater than the other constant K2

This translates to that the motor being able to rotate at high speeds, without necessarily exceeding the nominal armature voltage.

The armature voltage is the voltage that is developed around the terminals of the armature winding of an Alternating Current, i.e AC or a Direct Current, i.e DC machine during the period in which it tries to generate power.

6 0
2 years ago
Suppose we store a relation R (x,y) in a grid file. Both attributes have a range of values from 0 to 1000. The partitions of thi
leva [86]

Answer:

For (a) The total number of buckets from the given query for the relation is 25 buckets (b) the nearest neighboring query is (80, 200) (80, 150), (100, 150), (120,150) and (120, 200)

Explanation:

From the question stated, we need to define what a Grid file is

Grid File it is a structure of data that are used to divide the total space into a grid non-periodic, where set of point (small) are defined by more than one cells of the grid.

(a)Finding buckets for the query

The relation is divided into two parts which ranges from 0 to 1000, the first part is partitioned in every 20 units, at 20, 40, 60 etc; a second part is partitioned into every 50 units at 50, 100, 150 etc.

The total number of buckets from the given query for the relation is 25 buckets

(b)Finding the closest point or nearest point

The closest point discovered in the distance is little above 15

These points are are the points closer to the point target (110, 205) which can be found in five neighboring rectangles with left corners lower is stated as follows:

(80, 200) (80, 150), (100, 150), (120,150) and (120, 200)

3 0
2 years ago
A cylindrical drum (2 ft. dia ,3 ft height) is filled with a fluid whose density is 40 lb/ft^3. Determine (a. the total volume o
Ksivusya [100]

Answer:

a)V=9.42\ ft^3

b)Mass in lb = 376.8 lb

Mass in slug = 11.71 slug

c)v=0.025\ ft^3/lb

d)w=1276 \ lb/ft.s^2

Explanation:

Given that

d= 2 ft

r= 1 ft

h= 3 ft

Density

\rho = 40\ lb/ft^3

a)

We know that volume V given as

V=\pi r^2 h

V=\pi \times 1^2\times 3

V=9.42\ ft^3

b)

Mass = Density x volume

mass =40\times 9.42\ lb

mass= 376.8 lb

We know that

1 lb = 0.031 slug

So 376.8 lb= 11.71 slug

Mass in lb = 376.8 lb

Mass in slug = 11.71 slug

c)

we know that specific volume(v) is the inverse of density.

v=\dfrac{1}{\rho}\ ft^3/lb

v=\dfrac{1}{40}\ ft^3/lb

v=0.025\ ft^3/lb

d)

Specific weight(w) is the product of density and the gravity(g).

w= ρ X g

w = 40 x 31.9

w=1276 \ lb/ft.s^2

8 0
2 years ago
3.24 Program: Drawing a half arrow (Java) This program outputs a downwards facing arrow composed of a rectangle and a right tria
eimsori [14]

Answer:

Here is the JAVA program:

import java.util.Scanner; // to get input from user

public class DrawHalfArrow{ // start of the class half arrow

public static void main(String[] args) { // starts of main() function body

    Scanner scnr = new Scanner(System.in); //reads input

int arrowBaseHeight = 0; // stores the height of arrow base

int arrowBaseWidth  = 0; // holds width of arrow base

int arrowHeadWidth = 0; // contains the width of arrow head

// prompts the user to enter arrow base height, width and arrow head width

System.out.println("Enter arrow base height: ");

arrowBaseHeight = scnr.nextInt(); // scans and reads the input as int

System.out.println("Enter arrow base width: ");

arrowBaseWidth = scnr.nextInt();

/* while loop to continue asking user for an arrow head width until the value entered is greater than the value of arrow base width */

while (arrowHeadWidth <= arrowBaseWidth) {

    System.out.println("Enter arrow head width: ");

    arrowHeadWidth = scnr.nextInt(); }

//start of the nested loop

//outer loop iterates a number of times equal to the height of the arrow base

 for (int i = 0; i < arrowBaseHeight; i++) {

//inner loop prints the stars asterisks

      for (int j = 0; j <arrowBaseWidth; j++) {

          System.out.print("*");        } //displays stars

          System.out.println();          }

//temporary variable to hold arrowhead width value

int k = arrowHeadWidth;

//outer loop to iterate no of times equal to the height of the arrow head

for (int i = 1; i <= arrowHeadWidth; i++)

{     for(int j = k; j > 0; j--)     {//inner loop to print stars

       System.out.print("*");    } //displays stars

   k = k - 1;

   System.out.println(); } } } // continues to add more asterisks for new line

Explanation:

The program asks to enter the height of the arrow base, width of the arrow base and the width of arrow head. When asking to enter the width of the arrow head, a condition is checked that the arrow head width arrowHeadWidth should be less than or equal to width of arrow base arrowBaseWidth. The while loop keeps iterating until the user enters the arrow head width larger than the value of arrow base width.

The loop is used to output an arrow base of height arrowBaseHeight. So point (1) is satisfied.

The nested loop is being used which as a whole outputs an arrow base of width arrowBaseWidth. The inner loop draws the stars and forms the base width of the arrow, and the outer loop iterates a number of times equal to the height of the arrow. So (2) is satisfied.

A temporary variable k is used to hold the original value of arrowHeadWidth so that it keeps safe when modification is done.

The last nested loop is used to output an arrow head of width arrowHeadWidth. The inner loop forms the arrow head and prints the stars needed to form an arrow head. So (3) is satisfied.

The value of temporary variable k is decreased by 1 so the next time it enters  the nested for loop it will be one asterisk lesser.

The screenshot of output is attached.

3 0
2 years ago
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