Chevron-type Plate Heat Exchangers Research Articles

New Plates for Different Types of Plate Heat Exchangers

The first patent for a plate heat exchanger was granted in 1878 to Albretch Dracke, a German inventor. The commercial embodiment of these equipments has become available in 1923. However, the plate heat exchanger development race began in the 1930s and these gasketed plate and frame heat exchangers were mainly used as pasteurizers (e.g. for milk and beer). Industrial plate heat exchangers were introduced in the 1950s and initially they were converted dairy models. Brazed plate heat exchangers were developed in the late 1970s. However, copper brazed units did not start selling until the early 80s. Nickel brazing came to market around ten years later, since copper presents compatibility problems with some streams (e.g. ammonia). All-welded and semi-welded (laser weld) plate heat exchangers were developed during the 1980s and early 90s. Shell and plate heat exchangers were recently introduced in the market and can withstand relatively high pressures and temperatures, as the shell and tube does. The fusion bonded plate heat exchangers (100% stainless steel) are a technology from the 21st century, these equipments being more durable than brazed plate heat exchangers. The plates are the most important elements from the different plate heat exchangers mentioned above. This paper initially introduces the gasketed plate and frame heat exchanger and common chevron-type plates. Resorting to computer fluid dynamics techniques, the complex 3D flow in cross-corrugated chevron-type plate heat exchanger passages is visualized. Recent patents related with the plates from different plate heat exchangers are then outlined.

Friction factors of power-law fluids in chevron-type plate heat exchangers

In the present work laminar flows of Newtonian and power-law fluids through cross-corrugated chevron-type plate heat exchangers (PHEs) are numerically studied in terms of the geometry of the channels. The plates area enlargement factor was a typical one (1.17), the corrugation angle, β, varied between 30° and 60° and the flow index behaviour, n, between 0.25 and 1. Single friction curves fRe g = K for both Newtonian and non-Newtonian fluids are proposed for each β by developing an adequate definition of the generalised Reynolds number, Re g. The coefficient K compares well with experimental data, for all (seven) values of β, and depends on the tortuosity coefficient, τ. It was found that, for each β, τ decreases with the decrease of n. Food fluids are frequently processed in PHEs and usually behave as non-Newtonian fluids. This study can be useful in engineering applications as well as in the characterization of transport phenomena in PHEs.

Laminar flow in chevron-type plate heat exchangers: CFD analysis of tortuosity, shape factor and friction factor

Laminar or low Reynolds number flows are usually obtained when liquid foods with high viscosity are processed in plate heat exchangers (PHEs). The tortuosity coefficient is a key parameter used by PHEs manufacturers to estimate Fanning friction factors and convective heat transfer coefficients. Using the finite-element computational fluid dynamics program POLYFLOW ®, fully developed laminar flows in double-sine chevron-type PHEs passages are analysed in this work. The corrugation angle and channel aspect ratio of the passages vary in a broad range, PHEs with common area enlargement factors and with high area density being studied. The tortuosity coefficient and the coefficient K (Kozeny's coefficient in granular beds) from the friction factor correlations increase with the increase of the channels aspect ratio and the decrease of the chevron angle. The shape factor from the PHEs passages also increases with the decrease of the chevron angle and is weakly influenced by the channel aspect ratio. In this paper, relations to predict the tortuosity coefficient and shape factor are proposed, the coefficient K being predicted resorting to the tortuosity coefficient and shape factor. The coefficient K compares well with literature data in the region of common chevron angles, channels aspect ratio and area enlargement factor.

The generalized Lévêque equation and its practical use for the prediction of heat and mass transfer rates from pressure drop

Based on the generalized Lévêque equation (GLE) a new type of analogy between pressure drop and heat transfer has been discovered, that may be used in the cross corrugated channels of chevron type plate heat exchangers, in packed beds, in tube bundles, in crossed rod matrices or in many other spacewise periodic arrangements. Experimental data on heat transfer in tube bundles in crossflow, both inline, and staggered arrangements, had been recently tested in greater detail. Using an empirical correlation for pressure drop in these arrangements from the literature that has been successfully tested against a large number of experimental pressure drop data, heat transfer data collected earlier could be very well represented from the pressure drop correlation and the GLE. The data for staggered bundles have been shown to be in better agreement with this new method, than with the existing empirical heat and mass transfer correlations. Somewhat larger deviations for inline tube bundles had been found at lower Reynolds numbers. Here a simple and physically reasonable correction function of Re is presented, which leads to a better agreement for the inline bundles, too. Additionally, it can be shown for a number of literature data on tube bundles and on crossed rod matrices that the agreement with the GLE prediction is even better if original pressure drop data from the same sources are available in place of a pressure drop correlation. The method results in reasonable heat or mass transfer predictions from frictional pressure drop, which may be widely used in chemical engineering applications.

96/06466 A theoretical approach to predict the performance of chevron-type plate heat exchangers

96/06466 A theoretical approach to predict the performance of chevron-type plate heat exchangers

A theoretical approach to predict the performance of chevron-type plate heat exchangers

Manufacturers of plate and frame heat exchangers nowadays mainly offer plates with chevron (or herringbone) corrugation patterns. The inclination angleof the crests and furrows of that sinusoidal pattern relative to the main flow direction has been shown to be the most important design parameter with respect to fluid friction and heat transfer. Two kinds of flow may exist in the gap between two plates (pressed together with the chevron pattern of the second plate turned into the opposite direction): the crossing flow of small substreams following the furrows of the first and the second plate, respectively, over the whole width of the corrugation pattern, dominating at lower inclination angles (lower pressure drop); and the wavy longitudinal flow between two vertical rows of contact points, prevailing at highangles (high pressure drop). The combined effects of the longer flow paths along the furrows, the crossing of the substreams, flow reversal at the edges of the chevron pattern, and the competition between crossing and longitudinal flow are taken into account to derive a relatively simple but physically reasonable equation for the friction factor ξ as a function of the angleand the Reynolds number Re. Heat-transfer coefficients are then obtained from a theoretical equation for developing thermal boundary layers in fully developed laminar or turbulent channel flow — the generalized Lévêque equation — predicting heat-transfer coefficients as being proportional to (ξ·Re 2) 1/3. It is shown, by comparison, that this prediction is in good agreement with experimental observations quoted in the literature.