heat exchanger design formula sheet
DESCRIPTION
Formulas for heat exchanger designTRANSCRIPT
HXD
FORMULA
SHEET
#ri7i#
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>
*a=m(table)
In case of multipass arrangement
Ft= Correction Factor
=
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
� – 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�
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���`��
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