heat exchanger design formula sheet

11
HXD FORMULA SHEET #ri7i#

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Formulas for heat exchanger design

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Page 1: heat exchanger design formula Sheet

HXD

FORMULA

SHEET

#ri7i#

Page 2: heat exchanger design formula Sheet

1 - For plane wall

UA= ���=

�� ���� ��� �� ��

2 - For a tubular pipe

UA= ����= ���� = ���=

�� ���� ������� �

���� ������

3 – For a unclean surface(Fouling /scaling)

∆��� = �� =

!"� = �$! ��%&'()*+, -.�*/(+'. ∆��%�.01 ,-(2*.+/ ('-3�� 4+').(+ �4-$('.

4 – For a fouled surfaces

56 = 7898 + 5; + 5<8=98 + 7>9> R@ = Wall resistance

5 – Overall heat transfer (taking efficiency in account)

Q = hA [1 - KLK (1 - ȠN )] ∆T

6 – Overall heat transfer coefficient

�� = �9Q 98 ȠR789Q 5;9Q 98 5<8ȠR 5<QȠS 7>9>

Page 3: heat exchanger design formula Sheet

*a=m(table)

Page 4: heat exchanger design formula Sheet
Page 5: heat exchanger design formula Sheet

In case of multipass arrangement

Ft= Correction Factor

=

Page 6: heat exchanger design formula Sheet

Series Coupling over all counter flow

T�K = U��V U��U��V U�� T�W = U�XV U��U�XV U�� T�Y = U�XV U��U�XV U��

Z� = U[\] ^_`a[ �b �`c�d�ce_f bfe�cU[\] ^_`a[ �b g�\h�`[c ij = U��V U��U�XV U�� =

U��V U��U�XV U��

� – l��� –�� l�� =

U��V U�XU��V U��

� – l�m� –�� l�m =

U�XV U�XU��V U��

nop

n�p

Temperature Effectiveness :

n��

no�

n�o

noo

n�p

nop

n��

no�

n�p

C A B

Page 7: heat exchanger design formula Sheet

� – l�q� –�� l�q =

� – l��� –�� l�� × � – l�m� –�� l�m =

U�XV U�XU��V U��

General formula for T�

T� = ∏ ( �V��l���)V ∏ ( �Vl���)��t���t�∏ ( �V��l���) V �� ∏ ( �Vl���)��t���t�

For R=1

P�= ∑ wx y���z�{y���|�∑ } y���z�{y���|~��t� ���̀%�

Series Coupling overall parallel flow

T�= ���� �1 − ∏ �1 − (1 + �)T�K� ��̀%� �

NTU = ∑ �n��K��̀%�

n��

no�

n�o

noo

n�p

nop

n��

no�

Page 8: heat exchanger design formula Sheet

DOUBLE PIPE HEAT EXCHANGER

Counter Flow

( Cold-Tube Side , Hot- Shell Side)

(�Vl)(�Vl�) =

U���V U� ��U� ��V U���

∆nf\ = (U���V U���) l (�V�)f`��{yy� �

��U�� =

(�V�)���1−TT� � NT�g = �����

For n- pass heat exchangers

1- Cold fluid in parallel and hot fluid in series flow

� = l(��V�)f`�( �(�{y�))� �� ��V �� �� � �� �� �

2- Cold fluid in series and hot fluid in parallel flow

� = l(�V`�) `⁄

f`w(�V`�)� ��{y���`��

Page 9: heat exchanger design formula Sheet

CHARTS

Page 10: heat exchanger design formula Sheet
Page 11: heat exchanger design formula Sheet