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Backed by a 5,000m-2 manufacturing workshop at Nantong and more than 100 electrical, Mechanical engineers SME group have serviced the offshore and marine engineering industry for over 20 years and still deliver a high calibre and up todate service in this industry we perform over 500 jobs a year and supplying more than1,000 vessels per year. This blog will discuss the optimum pattern plate for the plate heat exchanger that forms the heart of the marine system and control how these optimum patterns deliver their thermal and economic efficiencies through a better understand of controlling fluid friction and heat flux in our cooling, heating and waste heat exchange systems.
Chevron Angle and Its Trade-Off Between Heat Transfer and Pressure Drop
The most important geometric parameter in the design of PHE is the chevron angle (or herringbone angle). As always, the greater the angle of the chevron (e.g. 60° to 75°), the more turbulence is created, and there will be increased heat transfer coefficient, but with a commensurate substantial increase in pressure drop and pumping power. On the other hand, smaller angles (30°–45°) are less resisting but have lower thermal performance. When viscous fluids such as lubricating oil are used in marine applications, SME is not commonly seen using a single plate. The range of Applications for SME to date can include use of mixed plate designs for high-water pass angle and lower angle of oil path or similar combination plates so to attain acceptable thermal performance without any high pressure loss. This hybrid design represents an overall, thermal-hydraulic optimal solution which is important in those retrofit and newbuild projects SME is involved with.
Corrugation Depth, Pitch, and Aspect Ratio
In addition to angle, the corrugation depth (h), pitch (P) and aspect ratio (2b/λ) have a direct effect on performance. The deeper the corrugations, the larger the heat transfer surface is, and the more it causes the separation of flows, so that the heat transfer amount in the local area can be enhanced by secondary mixing. However, they also increase the friction factor, leading to a higher pressure drop. An optimum relationship has been developed by studies based on the Taguchi method for marine gas heaters, such as the case of corrugation diameter 6 mm, corrugation depth 1 mm and corrugation inclination 45° which showed a 37.41% improvement in comprehensive performance index (TP) compared to conventional design. These data-driven optimization techniques are used in SME to specify plate geometry for vessel-specific operating conditions, in order not to give up thermal performance benefits because of the undue pumping costs.
Asymmetric and Modified Patterns for Variable Flow Demands
Hot-side flow In marine system’s hot side flow process can take advantage of the fact that it’s mass flow can be significantly different from that of other systems, for example the flow rate through the heating water’s flow can be up to multiples of a flow rate through a tap of accommodation. When this is done symmetrically, across all flow channels, the result is overall increase in pressure drop for the high flow circuit, but no changes to mechanical strength or thermal efficiency. Non-uniform flow channel plates – one with increased cross area by one channel has reduced press depth or varied ridges in one of those channels will have reduced press loss on this larger channel as much as mechanically permitted, and have good heat transferring ability. Moreover, recent studies have attained higher thermo-hydraulic performance in chevron plates ( >1 in separated herringbone plate), in which effect of turbulence enhancement on flow resistance exceeds. This very advanced optimisation is assessed by SME's engineers for ships with highly different operating scenarios and the value-added solutions proposed will enable ship owners to reduce energy usage.
Dimpled and Novel Surface Geometries
Studies in recent years have investigated the possibility of replacing the traditional herringbone patterns with dimpled (wave-point) plates with circular convex plates. Using numerical optimization with the response surface method, the optimum parameters (wave-point diameter of approximately 5.2 mm, depth of 0.9 mm and inclination of 42°) to achieve a maximum performance (JF factor) of 11.92% greater than the conventional herringbone designs were found . In this novel design, geometries are made to promote turbulence and thermal boundary layer and still maintain acceptable pressure drop. SME has continued to pay keen attention to such new developments, and applies proven innovations where relevant to the retrofit and newbuild solution to help clients remain compliant with the most recent efficiency and emissions standards.
Conclusion: Precision Plate Design for Marine Efficiency
The optimization of the plate patterns is not a standard operating procedure and demands detailed study of the fluid properties, flowrates, permissible pressure drops and thermal duty. SME Group is ISO 9001/14001/45001 certified, and provide over two decades of marine heat transfer experience to each project. Our local network ensures quick response at shipyards all over the world, particularly in the mainland China, allowing your heat exchangers to perform at their best. SME provides you with the 12-month warranty and the desire to do more than just meet and exceed your concern-the desire to save you even more energy due to its backing of optimizing plate patterns for measurable energy savings. Call our technical experts today to discuss your vessel's specific heating requirements.