Plate Heat Exchanger in Marine: Problems and Countermeasures

 Heat exchangers are widely used in marine turbines and become one of the indispensable important equipment. For example, in the main pump oil cooler, cylinder liner fresh water cooler, fuel heater, steam condensers, water heater and other equipment. However, the special working environment of the ship has very demanded on the heat exchanger. The special environment includes factors include instability on the sea, which may encounter vibration, shock, large angle tilt, and noise. The cooling medium is usually seawater. Something as high concentration, high humidity, the corrosion to the board, very strong place and very compact space itself, makes more stringent restrictions on the heat exchanger space and quality than traditional heat exchangers whose medium is often water and water, while heat transfer medium of ship heat exchanger is generally oil and water and so on. The emergence of plate heat exchangers effectively solves a large part of the problem.

(1) The use of equipment for ships requires a compact structure and a small quality

Compared with a variety of heat exchangers, due to small occupied space, light and other advantages, plate heat exchanger can get a good solution. The choice of hollow carbon steel plate plus rib structure also satisfies the conditions of overall comprehensive feasibility, process, and safety. Due to the complicated structure and cumbersome force condition, conventional calculation method can not accurately calculate the strength and stiffness of the work board. For this purpose, finite element analysis is used. At the same time, in order to meet the requirements of marine equipment, the unwanted parts of the plate are removed or reduced according to the actual stress and strain distribution, and the weak parts are locally thickened. Reduce the impact of welding deformation on the strength by the whole body gas cutting method, and then weld the inner side of the board and panel, at last eliminate the residual stress heat treatment.

(2) For the impact, large angle shaking, vibration and other issues.

Using the bottom of the board multi-point fixed method, that is, all fixed parts are used fixed connection, some important special parts also used to be strengthened, thereby increasing the stability of the equipment.

(3) For the cooling medium is sea water, nitrogen ion concentration is high.

Seawater concentration of salt is high, especially stainless steel corrosion is very strong, so the plate is usually selected high corrosion resistance of titanium whose quality is not smaller than stainless steel. In order to ensure the quality of titanium plate, in addition, to make routine testing of GB16409-1996 "plate heat exchanger", but also 100% color penetration test on the plate, to further eliminate the error. And the outer surface of the board also is carried out a special anti-corrosion, mildew phosphate treatment to extend the service life.

(4) For heat transfer media problems

Due to the difference between the specific heat capacity of water and oil, the difference in temperature difference during the heat transfer process, the heat transfer coefficient is greater. In order to make the product reliable and economical, to ensure oil and water heat transfer performance under the conditions of the ship, to ensure that the equipment has a certain heat margin.

Status and development of industrial production

At present, the heat exchanger scale for a new device and the transformation of the device in the domestic and foreign shipbuilding industry is growing. In order to achieve the large-scale and universal of heat exchanger device, and now the traditional heat exchanger has been unable to meet the needs of large-scale equipment. Plate heat exchanger as one of the highly efficient compact heat exchanger, with high efficiency, low-end temperature difference, low pressure, saving area, saving the cost of installation of engineering equipment, etc., suitable for large-scale production and installation of marine turbines.

Plate heat exchanger has its advantages, but its development is not very mature. Plate heat exchangers in the field of the ship will be used more widely, but also the following technical issues need to be solved.

(1) to strengthen the research and development of sheet structure. The plate is the most important part of the heat exchanger, pressed by the metal plate. In china, there are only three types been explored, so we should exploit a more space-saving one.

(2) to strengthen the corrosion treatment of sheet metal. At present, the main plate we used is 18-8 stainless steel and a small amount of industrial titanium plate, with fewer variety specifications. In the special environment of the ship, these plates are clearly not the most suitable. In metal materials, salt corrosion is very serious, so by improving the performance of the plate, or special treatment to achieve the effect of corrosion.

(3) Continue to improve the temperature of the heat exchanger. Ship industry running time is very long, safe using is generally about 180 degrees. So continually to improve the use of heat exchanger temperature, meet high temperature and high pressure of the special circumstances in the ship sailing.

Conclusion

The use of modern plate heat exchangers has been in various industries, also making a competition with the traditional shell and tube heat exchanger. As a highly efficient with compact structure, plate heat exchangers can replace shell and tube heat exchangers in addition to high temperature, high pressure and special medium conditions during heating, cooling, condensation, evaporation and heat recovery. Is has also been used in the shipbuilding industry, and because of its special advantages which are very suitable for the shipping industry. Plate heat exchanger started relatively late, technology is not very mature; especially in the shipping industry has just begun. However, with the type of plate heat exchanger are more and more, technical performance is getting better and better, in the field of the ship, plate heat exchangers will gradually replace the traditional heat exchangers.

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