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
Ulleksa [173]
3 years ago
7

A counter-flow double-piped heat exchange is to heat water from 20oC to 80oC at a rate of 1.2 kg/s. The heating is to be accompl

ished by geothermal available at 160oC at a mass flow rate of 2 kg/s. The inner tube is thin-walled and has a diameter of 1.5 cm. If the overall heat transfer coefficient of the heat exchanger is 640 W/m2.oC, determine the length of the heat exchanger required to achieve the desired heating using the effectiveness-NTU method.
Engineering
1 answer:
lawyer [7]3 years ago
3 0

Answer:

110 m or 11,000 cm

Explanation:

  • let mass flow rate for cold and hot fluid = M<em>c</em> and M<em>h</em> respectively
  • let specific heat for cold and hot fluid = C<em>pc</em> and C<em>ph </em>respectively
  • let heat capacity rate for cold and hot fluid = C<em>c</em> and C<em>h </em>respectively

M<em>c</em> = 1.2 kg/s and M<em>h = </em>2 kg/s

C<em>pc</em> = 4.18 kj/kg °c and C<em>ph</em> = 4.31 kj/kg °c

<u>Using effectiveness-NUT method</u>

  1. <em>First, we need to determine heat capacity rate for cold and hot fluid, and determine the dimensionless heat capacity rate</em>

C<em>c</em> = M<em>c</em> × C<em>pc</em> = 1.2 kg/s  × 4.18 kj/kg °c = 5.016 kW/°c

C<em>h = </em>M<em>h</em> × C<em>ph </em>= 2 kg/s  × 4.31 kj/kg °c = 8.62 kW/°c

From the result above cold fluid heat capacity rate is smaller

Dimensionless heat capacity rate, C = minimum capacity/maximum capacity

C= C<em>min</em>/C<em>max</em>

C = 5.016/8.62 = 0.582

          .<em>2 Second, we determine the maximum heat transfer rate, Qmax</em>

Q<em>max</em> = C<em>min </em>(Inlet Temp. of hot fluid - Inlet Temp. of cold fluid)

Q<em>max</em> = (5.016 kW/°c)(160 - 20) °c

Q<em>max</em> = (5.016 kW/°c)(140) °c = 702.24 kW

          .<em>3 Third, we determine the actual heat transfer rate, Q</em>

Q = C<em>min (</em>outlet Temp. of cold fluid - inlet Temp. of cold fluid)

Q = (5.016 kW/°c)(80 - 20) °c

Q<em>max</em> = (5.016 kW/°c)(60) °c = 303.66 kW

            .<em>4 Fourth, we determine Effectiveness of the heat exchanger, </em>ε

ε<em> </em>= Q/Qmax

ε <em>= </em>303.66 kW/702.24 kW

ε = 0.432

           .<em>5 Fifth, using appropriate  effective relation for double pipe counter flow to determine NTU for the heat exchanger</em>

NTU = \\ \frac{1}{C-1} ln(\frac{ε-1}{εc -1} )

NTU = \frac{1}{0.582-1} ln(\frac{0.432 -1}{0.432 X 0.582   -1} )

NTU = 0.661

          <em>.6 sixth, we determine Heat Exchanger surface area, As</em>

From the question, the overall heat transfer coefficient U = 640 W/m²

As = \frac{NTU C{min} }{U}

As = \frac{0.661 x 5016 W. °c }{640 W/m²}

As = 5.18 m²

            <em>.7 Finally, we determine the length of the heat exchanger, L</em>

L = \frac{As}{\pi D}

L = \frac{5.18 m² }{\pi (0.015 m)}

L= 109.91 m

L ≅ 110 m = 11,000 cm

You might be interested in
Water enters a boiler at a temperature of 110°F. The boiler is to produce 2000 lb/hr of steam at a pressure of 130 psia. How man
strojnjashka [21]
Yes it does the answer is no
5 0
2 years ago
In javaWrite a program that simulates flipping a coin to make decisions. The input is how many decisions are needed, and the out
Pavel [41]

Answer:

// Program is written in Java Programming Language

// Comments are used for explanatory purpose

import java.util.*;

public class FlipCoin

{

public static void main(String[] args)

{

// Declare Scanner

Scanner input = new Scanner (System.in);

int flips;

// Prompt to enter number of toss or flips

System.out.print("Number of Flips: ");

flips = input.nextInt();

if (flips > 0)

{

HeadsOrTails();

}

}

}

public static String HeadsOrTails(Random rand)

{

// Simulate the coin tosses.

for (int count = 0; count < flips; count++)

{

rand = new Random();

if (rand.nextInt(2) == 0) {

System.out.println("Tails"); }

else {

System.out.println("Heads"); }

rand = 0;

}

}

7 0
3 years ago
Which is the main material in a solar cell?
quester [9]
Crystalline silicon
hope this helps!! <3
5 0
3 years ago
Random ____ fluctuations in the early universe were stretched by a period of intense inflation, resulting in permanent density f
fgiga [73]

Answer:

Quantum

Explanation:

Appearance of energy particles from any where as allowed by uncertainty principle.

7 0
3 years ago
For every 3 packages that Marcella wraps she uses 1/2 of a roll of wrapping paper if she uses 2 1/2 rolls of wrapping paper how
hram777 [196]
She wrapped 5 packages
6 0
3 years ago
Read 2 more answers
Other questions:
  • A cylindrical drill with radius 4 is used to bore a hole through the center of a sphere of radius 5. Find the volume of the ring
    15·1 answer
  • Please read
    6·1 answer
  • 3 examples of technology transfer pls
    12·2 answers
  • A tool chest has 950 N weight that acts through the midpoint of the chest. The chest is supported by feet at A and rollers at B.
    15·1 answer
  • The assembly consists of two blocks A and B, which have a mass of 20 kg and 30 kg, respectively. Determine the distance B must d
    14·2 answers
  • A power of 100 kW (105 W) is delivered to the other side of a city by a pair of power lines, between which the voltage is 12,000
    9·1 answer
  • The spring has a stiffness k = 200 N&gt;m and an unstretched length of 0.5 m. If it is attached to the 3-kg smooth collar and th
    12·1 answer
  • The coefficient of performance of a reversible refrigeration cycle is always (a) greater than, (b) less than, (c) equal to the c
    12·1 answer
  • Technician A says that squeeze-type resistance spot welding (STRSW) may be used on open butt joints. Technician B says that repl
    14·1 answer
  • In a creep test, increasing the temperature will (choose the best answer) A. increase the instantaneous initial deformation B. i
    5·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!