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Thermo-performance evaluation of meso oscillatory baffled reactors

Lookup NU author(s): Safaa Ahmed, Dr Richard Law, Dr Anh Phan, Professor Adam Harvey

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Abstract

An Oscillatory Baffled Reactor (OBR) is an intensified design of continuous plug flow reactor (PFR) in which plug flow behaviour can be achieved at very low net flows (laminar flow regime). OBRs consist of tubes with periodically spaced baffles of various designs (orifice, helical, integral etc. baffles). There is a net flow through the reactor, and a superimposed oscillatory flow. The oscillatory flow interacts with the baffles to produce flow structures (usually vortices) that provide mixing. The mixing in the OBR is therefore independent of the net flow. As a result, the OBR's niche application is to operate “long” reactions in continuous mode. This is usually impractical in conventional tubular reactors. The oscillatory baffled reactor has been well-characterised in most areas of flow reactor performance (mixing, mass transfer, multi-phase operation etc), with the exception of heat transfer, where comparatively few data exist in the literature. The pressure drop in a single-orifice OBR has been measured in order to determine the power consumed as a result of the oscillatory flow applied [1]. The key finding in this study was the interesting behaviour of the pressure drop data which indicating to some power conservation. The heat transfer Nusselt number, Nu, has been improved in an OBR by 30-fold over the steady flow where the heat transfer rate was dominated by oscillation frequency and amplitude. In this study, performance of enhanced heat transfer for three designs of meso-scale oscillatory baffled reactors, oscillatory central-axial baffled (OCBR), oscillatory helical baffles reactor (OHBR), and oscillatory orifice baffled reactor (OOBR), have been evaluated over the net flow range (Ren = 61- 2500) and the oscillatory flow range (Reo = 0-1600). Interesting results were determined where the pressure drop in the OBRs decreased with the oscillatory flow confirming its feasibility in terms of restoring some energy. OHBR is shown lowest pressure drop, therefore, it is presented highest thermal performance. Unlike the conventional heat devices, the maximum enhancement of heat transfer achieved in OCBR, OHBR, and OOBR over steady unbaffled flow were 10-fold, 7-fold, and 5-fold respectively. New empirical correlations for predicting pressure drop and Nusselt number have been established for each design. The validity test has showed converge between the predicted data using the correlation and the experimental results collected in this work.


Publication metadata

Author(s): Ahmed SMR, Law R, Phan AN, Harvey AP

Publication type: Conference Proceedings (inc. Abstract)

Publication status: Published

Conference Name: ChemEngDay 2018

Year of Conference: 2018

Online publication date: 27/03/2018

Acceptance date: 24/01/2018


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