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Improving the performance of shell-and-tube heat exchangers

Objective

To improve the performance of shell and tube heat exchangers by: investigating different baffle arrangements which could give a close approach to counterflow whilst achieving enhancement of heat transfer; comparing different alternative types with conventional baffle arrangements; increasing the tube-side heat transfer coefficient.
Research was carried out in order to improve the performance of shell and tube heat exchangers by:
investigating different baffle arrangements which could give a close approach to counterflow whilst achieving enhancement of heat transfer;
comparing different alternative types with conventional baffle arrangements;
increasing the tube-side heat transfer coefficient.

Comparative information was collected on the performance of segmental, disc and doughnut, rod and grid baffle arrangements and also on available augmentation techniques for shell side and tube side flows. Industrial applications were reviewed.

Numerical and local calculations for rod, grid and alternative baffle systems were carried out together with global calculations of flow and heat transfer in real heat exchangers.

To date the work has shown that the use of twisted tapes on the shell side of heat exchanger can give lower are requirements than both rod and grid baffles. The rod system was found to be marginally better that the grid system over the operating range investigated.
The heat exchanger market for EC countries has been estimated to approach 1.6 billion ECU/year in the late 1980s and early 1990s and about half of this market is of the shell-and-tube type. The energy efficiency of this heat exchanger type is therefore an important factor in achieving energy savings in industry. This coordinated project aims at studying shell and tube heat exchangers in the following ways.

Comparative information were collected on the performance of segmental, disc and doughnut, rod and grid baffle arrangements and also on available augmentation techniques for shell-side and tube-side flows. Industrial applications were reviewed (NEL, GRETh, CRES, ICI and COVRAD).

Numerical and local calculations for rod, grid and alternative baffle systems were carried out together with global calculations of flow and heat transfer in real heat exchangers; for this purpose the CFD code TRIO-VF were used (CRES, GRETh). The results of the calculations were compared with experimental data (GRETh, NEL). The heat transfer and pressure drop of rod and grid baffle systems will then be measured together with the performance of rod and grid baffled heat exchangers (NEL, GRETh, COVRAD). The field of novel "baffle" designs giving higher heat transfer performance with acceptable pressure drop will also be explored (NEL). With the most promising of these new concepts, full size heat exchangers were constructed and tested (NEL, GRETh, COVRAD); resulting data will also be used to validate the TRIO-VF code (GRETh). The possibilities for tube side enhancement were explored by NEL.

Funding Scheme

CSC - Cost-sharing contracts

Coordinator

National Engineering Laboratory (NEL)
Address

G75 0QU East Kilbride
United Kingdom

Participants (2)

Centre for Renewable Energy Sources
Greece
Address
Km 19Th,marathonos Avenue
19009 Pikermi Attiki
Commissariat à l'Energie Atomique (CEA)
France
Address
Centre D'études De Grenoble Avenue Des Martyrs
38041 Grenoble