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International Heat Transfer Conference 11

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

INVESTIGATION OF A NOVEL HELICAL FLOW SHELL AND TUBE HEAT EXCHANGER

Halfdan Knudsen
E&P Operations Norsk Hydro ASA N-5020 Bergen Norway

Anders Austegard
Department of Thermal Energy and Hydro Power The Norwegian University of Science and Technology N-7034 Trondheim Norway; SINTEF Energy Research

Erling Naess
Department of Energy and Process Engineering, Norwegian University of Science and Technology, N-7491 Trondheim, Norway

Otto K. Sonju
Department of Energy and Process Engineering, Norwegian University of Science and Technology, 7491 Trondheim, Norway

DOI: 10.1615/IHTC11.1700
pages 293-298

Abstrakt

A novel high-performance Helical Flow shell-and-tube Heat Exchanger (HFHE) is investigated. The HFHE is similar to conventional shell-and-tube heat exchangers, but includes a novel baffle layout. The HFHE concept shows high performance compared to other shell-and-tube heat exchangers, and represents an attractive alternative in many applications.
The thermal-hydraulic performance is investigated experimentally and theoretically. The experimental apparatus consisted of a full-scale heat exchanger connected to an air system and a combustion gas system.
Overall performance tests as well as measurements of local temperatures and static pressures on both shellside and tubeside were run with heat transfer rates varying from 140 to 335 kW. Heat balances determined from the performance tests were within ±5 per cent. Local velocities and heat transfer coefficients were measured throughout a typical baffle cell with fully developed isothermal flow. The local velocities were measured with a specially designed pitot tube. The local heat transfer coefficients were measured with an electrically heated copper rod with the same outer diameter as the heat exchanger tubes. Shellside Reynolds numbers varied from 7000 to 18000. The special helical flow shell-and-tube heat exchanger baffles set up a flow pattern with a high thermal hydraulic efficiency. The baffle design is very flexible, and within the same shell, the number of baffles can be varied by a factor of three without distorting the efficient flow pattern.
A separated flow model has been developed to characterize the shell side flow. Based on the separated flow model, a computer code for thermal-hydraulic rating for the novel concept has been developed. Good agreement has been obtained between experimental and theoretical results.
For a more detailed analysis of the shellside flow distribution a model using a three-dimensional finite-volume technique has also been developed, where the flow resistance is modeled using porosity models. There are separate flow-resistance models for crossflow, axial flow, shell-to-baffle and tube-to-baffle leakage flows. The crossflow resistance is modeled using a new approach, formulating a general pressure drop correlation intended to be valid for triangular, rectangular and non-standard tube layouts. Calculation results of velocity, pressure and temperature distributions compare well with experimental results.

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