proposal aproval

2. Experimental Investigation of
Fluid Elastic Instability in Cross
Flow Shell and Tube Heat
Exchanger Bundles
Research Supervisor : DR. Shahab Khushnood
Research Scholar : Muhammad Awais
12-MS-FT-TSE-03

3. Problem Statement
 Cross flow shell and tube heat exchangers are frequently used in
petrochemical industries, such as in oil refineries, fertilizer plants and in
different chemical industries.
 When the fluid passes over the tube bundle array, fluid elastic instability
mechanism occurs, which produces flow induced vibrations (FIVs) in the
tube bundle with large amplitude beyond a critical velocity of fluid flow.
 Due to this problem fretting wear and necking (at baffle holes) type
failures occur in the tube bundle. So, this mechanism of flow induced
vibrations in heat exchangers leads to equipment breakdown and hence
expansive repair and process shutdown.

4. Aims and Objectives
 The objective of this research is the experimental investigation of fluid elastic instability
in cross flow shell and tube heat exchanger tube bundle during partial admission of
liquid water in cross flow.
 Comparison of results for two different tube bundle arrays :
1- Triangular.
2- Square.
 Relation between the parameters on which this mechanism of flow induced vibrations
depends and which of these parameters are more influenced during fluid elastic instability
mechanism. Some of these parameters are:
 Mass-damping parameter.
 Tube frequency of vibration.
 Strouhal number.
 Critical velocity of fluid.
 Damping ratio.

5. Introduction
 Fluid elastic instability is the most catastrophic flow-induced vibration mechanism in
cylinder arrays subjected to cross-flow (Paidoussis 1980).
 During fluid flow across the flexible tube array, due to the fluid forces the tubes displaced
from the initial position.
 The damping force of the tubes that tries to restore the tubes back to their equilibrium
position opposes this change in fluid force.
 Thus, a competition results between the energy input by the fluid force and the energy
expended in damping.
 When the energy expended in damping is more than the energy input by the fluid, the
vibrations die down.
 However, if the fluid forces dominate, sufficient energy is imparted to the tube to sustain the
vibrations and an unstable situation is reached where the tube vibrates with large amplitude.
 In shell-and-tube heat exchangers, this limit is known as fluid-elastic instability and
leads to tube damage like fretting wear.

6. Fluid Elastic Instability Mechanism

7. Experimental Setup
TEST SECTION
BASIC SCHEMATIC OF EQUIPMENT SETUP

8. Expected Results:
The result expected in this research is to minimize
the flow induced vibrations (FIV) in tube bundle
during non-uniform cross flow of fluid around the
tubes.

9. Utilization of Research Results
By utilization of results of this experimental investigation
we can easily point out those parameters which are more
influenced during fluid elastic instability mechanism.
Through the results of this research it is easily visualized
that which mode of vibration occurs during each critical
velocity of non uniform fluid flow around the tubes.

10. Project Work Schedule
PROPOSED WORKING SCHEDULE (2013-2014)
ACTIVITY APRIL 2013 MAY 2013 JUN. 2013 JUL. 2013 AUG. 2013
SEP.
2013
OCT.
2013
NOV.
2013
DEC.
2013
JAN.
2014
Literature
Collection
Literature Study
Experimentation
Results
Formulation
Report Writing &
Submission

11. References
 Paidoussis, M.P., P rice, S. J., 1988, “The Mechanisms Underlying Flow Induced Instabilities
of Cylinder Arrays in Cross Flows”. Journal of Fluid Mechanics, vol.187, pp.45- 59 .
 Mitra, D.R., 2005, “Fluid Elastic Instability in Tube Arrays Subjected To Air-Water and Steam-
Water Cross-Flow”, Ph.D Thesis, University of California, Los Angles.
 Parrondo, J.L., Santolaria, C., Weaver, D.S., 1995, “ Fluid Elastic Instability in a Tube Array
Subjected to Partial Admission Water Cross Flow”. Journal of Fluid and Structures, Vol. 11,
pp.149-181.
 Olinto, C.R., Endres, L.A.M., Moller, S.V., 2007, “Experimental Study of the Characteristics
of the Flow in the First Rows of Tube Banks”, Transactions, SMIRT 19, Toronto.

12. Any questions…..?