Full steam ahead thanks to perfect cooling: VX plate heat exchangers
Small, compact, powerful: VX plate heat exchangers from GEA PHE Systems cool the new yacht engine generation from MAN
More power with simultaneous weight minimisation - that is the formula for success of the new V12 yacht engine, the most powerful unit in the MAN range of ship engine design. With a consistent programme of weight reduction measures the engineers of this traditional Nuremberg-based company have achieved a top rating of 1.78 kg per kW. The 1325 kW diesel engine is cooled by a modified VX plate heat exchanger (PHE) from GEA PHE Systems. The gasketed seawater cooler is a component in the closed cooling circuit, fixed firmly to the engine, which meant that it also had to undergo weight optimisation.
Only titanium plates guarantee corrosion protection on the high seas
The VX plate heat exchanger is installed on the front side of the engine block directly in front of the expansion tank of the fresh water circuit. The cooling water flows through the cylinder heads, charge air cooler and oil cooler at an operating pressure of around 4 bars. Here the fresh water takes up the complete waste heat from the engine and transfers it to the seawater in the PHE in counterflow. As the salt concentration of the seawater would quickly damage stainless steel grades, GEA PHE Systems always uses titanium plates in seawater coolers. Only this high-quality material guarantees the necessary corrosion protection and ensures process reliability on the ocean waves.
VX plate pressed in titanium for the first time
This was the challenge faced by the GEA engineers. Until now the VX plate had never been pressed in titanium. For a good three months they worked on how to achieve the required weight reduction of the VX plate without losing any of the pressure resistance as the second elementary parameter. As the raw material titanium cannot be easily deformed, it was necessary to optimise the pressing process. This was successfully achieved by specific modifications to the pressing tool.
Reduced plate thickness with simultaneous increase in heat transfer
Until now plate thicknesses of a minimum of 0.5 mm had been the lower limit, but now the engineers achieved a VX plate thickness of 0.4 mm and at the same time it was also possible to increase the heat transfer rate by a good 4%, representing a further optimisation of the engine cooling performance. The new MAN V12 unit has a cooling performance of 1060 kW, dissipated via 42 VX plates. VX-13 plates are fitted in the plate pack as their dimensions fit ideally to the engine geometry. The heat transfer surface per plate is 0.13 m2. NBR is used as the gasket material.
New gasket allows diagonal flow of the plates
A further challenge for the GEA engineers was the transverse installation of the seawater cooler required by MAN, because standard VX plates have parallel flow. A simple rotation through 90°C to achieve vertical installation couldn’t be the answer, if emptying and venting the unit was also to be possible.The solution here was a special gasket that meant that the flow across the plates could be deflected diagonally without much trouble.
Optimum combustion process with exemplary emission values
With its series based around the new V12 yacht engine for the very first time MAN is presenting high-performance models specially designed for pleasure craft and motor yachts, with the special feature being the bedplate concept. The bedplate replaces the individual crankshaft main bearing caps and makes a considerable contribution to the rigidity of the crankcase and to minimizing sound radiation. The result of the combination of second-generation common rail injection and an optimally designed combustion process is high performance combined with exemplary emission levels.
