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Comparison of the heat transfer and pressure drop characteristics of packed beds and those of pall rings in a tube.
OW%293918M3MP7-U2Y13.W0 Q IPBZPemamon Prcrr Ltd.
PRELIMINARY
COMMUNICATION
Comparison of the Heat Transfer and Pressure Drop Characteristics
of
Packed Beds and those of Pall Rings in a Tube. D. Burfoot. P. Rice. Loughborough University, Loughborough, Leicestershire,
LEll 3TU. England.
Stainless steel pall rings of one inch diameter were adapted for insertion into a copper tube with an inside diameter of 20 mm by removing one fifth of the circumference of the rings and reforming. Such inserts were studied to investigate their heat transfer enhancement over that of an empty tube. The rings are easy to insert while integral roughness is often difficult to produce on the inside surface of a tube. The heattransfer and pressure drop characteristics of a copper tube containing pall rings, over the Reynolds number range of 15500 to 86500, with various spacings between the rings, were studied using a double tube heat exchanger. Both tube and annulus fluids were "ater; the average bulk fluid temperature of each stream was 35OC and 80°C, respectively. The pressure drop characteristics were correlated in the form: In
= In [Al + B In [Re]
(la) (lb)
9 $ = A ReB
Similarly the heat transfer data was correlated in the form:
In
[&]
=In H =
1x1 [Fl
N" +-
- F Re
+E
In
E
i&l
(2=) (2b)
Proe4 Whilst it would be difficult to calculate the equivalent diameter of the pall rings for use in the available correlations which apply to packed beds; Figs. 1-4 show interesting trends concerning the parameters A,B,F,hE. The fraction of the tube wall area, that was uncovered, was calculated by assuming that all of the circumference of each pall ring was in contact with the inner surface of the tube. The surface area of the rings does not include the surface area of their insets, The data of Leva, taken from Perry E = 0.75 for 0.35 < (D~/D~) < 0.60
[Z] shows that (3)
For the above diameter ratio limitations, it may be considered that the uncovered containing wall surface area will be relatively large, compared to that for (D /Dt),< 0.35, and this is similar to the pall ring Figs. 1 & 3 show that the exponents, E & B. change case considered here! from the empty tube values to the packed bed values as the covered fraction of the tube wall area increases, i.e. more rings are inserted into the tube. It is concluded that further work using pall rings with other inset surface areas should be performed to study the apparent analogies noted above. Literature Cited [I]
Chilton, T.H., Colburn, A.P., Ind. Eng. Che., 1931, 23, 913.
121 Perry, R.H.,
Chilton, C.H. (Eds.), 'Chemical Engineering Handbook', 5th Edition, 1973, 4-38.
Acknowledgements The authors thank Norton Chemical Process Products (Europe) Ltd. for supplying the pall rings. D.B. acknowledges the support of the ScienceResearch Council (Great Britain).
491
498
Preliminary Communication
_I
E
PRELIMINARY
COMMUNICATION
Comparison of the Heat Transfer and Pressure Drop Characteristics
of
Packed Beds and those of Pall Rings in a Tube. D. Burfoot. P. Rice. Loughborough University, Loughborough, Leicestershire,
LEll 3TU. England.
Stainless steel pall rings of one inch diameter were adapted for insertion into a copper tube with an inside diameter of 20 mm by removing one fifth of the circumference of the rings and reforming. Such inserts were studied to investigate their heat transfer enhancement over that of an empty tube. The rings are easy to insert while integral roughness is often difficult to produce on the inside surface of a tube. The heattransfer and pressure drop characteristics of a copper tube containing pall rings, over the Reynolds number range of 15500 to 86500, with various spacings between the rings, were studied using a double tube heat exchanger. Both tube and annulus fluids were "ater; the average bulk fluid temperature of each stream was 35OC and 80°C, respectively. The pressure drop characteristics were correlated in the form: In
= In [Al + B In [Re]
(la) (lb)
9 $ = A ReB
Similarly the heat transfer data was correlated in the form:
In
[&]
=In H =
1x1 [Fl
N" +-
- F Re
+E
In
E
i&l
(2=) (2b)
Proe4 Whilst it would be difficult to calculate the equivalent diameter of the pall rings for use in the available correlations which apply to packed beds; Figs. 1-4 show interesting trends concerning the parameters A,B,F,hE. The fraction of the tube wall area, that was uncovered, was calculated by assuming that all of the circumference of each pall ring was in contact with the inner surface of the tube. The surface area of the rings does not include the surface area of their insets, The data of Leva, taken from Perry E = 0.75 for 0.35 < (D~/D~) < 0.60
[Z] shows that (3)
For the above diameter ratio limitations, it may be considered that the uncovered containing wall surface area will be relatively large, compared to that for (D /Dt),< 0.35, and this is similar to the pall ring Figs. 1 & 3 show that the exponents, E & B. change case considered here! from the empty tube values to the packed bed values as the covered fraction of the tube wall area increases, i.e. more rings are inserted into the tube. It is concluded that further work using pall rings with other inset surface areas should be performed to study the apparent analogies noted above. Literature Cited [I]
Chilton, T.H., Colburn, A.P., Ind. Eng. Che., 1931, 23, 913.
121 Perry, R.H.,
Chilton, C.H. (Eds.), 'Chemical Engineering Handbook', 5th Edition, 1973, 4-38.
Acknowledgements The authors thank Norton Chemical Process Products (Europe) Ltd. for supplying the pall rings. D.B. acknowledges the support of the ScienceResearch Council (Great Britain).
491
498
Preliminary Communication
_I
E