Antifreeze and deicing: a "cold" topic in ship design ■ Ma Yubin, Jiang Zhuo, he Wenhai With the development of science and technology, the combat performance and endurance of modern ships have been greatly improved. At the same time, the cold and antifreeze tactics of ships are also increasing. As the polar region has become a military hot spot of concern to all countries, the frequency of ships going to high latitude ice and snow waters has increased. Antifreeze has become a problem that more national naval ships must face. In March last year, three Russian nuclear powered submarines broke through the ice at the same time within a radius of 300 meters in an Arctic sea area, demonstrating its underwater military strength and the country's achievements in ship antifreeze. So, how can ships freeze in winter or extremely cold sea areas? How to deal with the "cold" problem in ship design? Please see the relevant interpretation. The Russian norwind God class strategic missile nuclear submarine that broke through the ice in the Arctic sea. Data picture In ice and snow, the influence of low temperature on ship performance is almost everywhere For a ship, when the temperature in the sea area drops below the freezing point, frost and ice may appear in the deck platform and other areas. At the end of 2014, the South Korean Navy's missile destroyer Cui Ying, which visited Vladivostok, suffered severe icing due to low temperature. The surface of the ship was covered with a thick "ice coat", especially the 127 mm main gun at the bow was frozen into a "Popsicle". It is speculated that the reason is either that the South Korean naval ships that have always been active in low latitude waters lack experience in dealing with this extremely cold weather, or that the requirements in this regard are not highlighted in ship design. There are many reasons why ships freeze and frost in extremely cold weather or environment: ships are made of steel and have strong thermal conductivity. In cold weather, their temperature can easily reach below the freezing point and form ice in case of water; The ship deck pipeline system is complex. Once the pipeline leaks, it will freeze below the freezing point; The most common is from the splashing of waves and the freezing of ponding; In case of sudden snowfall, when the snow cannot be removed in time, the ship will also freeze. It can be said that the impact of extremely cold weather or low temperature environment on the ship is all-round, including personnel safety, equipment operation, the use of Shipborne weapons and the stability of the ship. Its influence on shipborne equipment is mainly reflected in the stress shrinkage of parts and the reduction of battery performance; The impact on personnel is mainly reflected in frostbite and potential safety hazards in operation on ice. The low temperature brought by extremely cold weather bears the brunt of the impact on the oil and water used by ships. When the temperature of fuel drops suddenly, the density will change, and finally solidify or the volume will become smaller; Due to the low freezing point, the lubricating oil generally will not solidify, but like the fuel oil, the volume will become smaller due to low temperature, which will affect the use effect; Sea water and fresh water will freeze and expand at low temperature, which is easy to lead to pipeline rupture. If no measures are taken to eliminate these effects caused by low temperature, the ship may be in trouble or even in danger in the joint attack of "ice knife and frost sword". Take multiple measures at the same time, and put on "warm clothes" for ship body and equipment The various effects of low temperature on the performance of ships determine that ships must make great efforts in cold prevention and deicing. These efforts should be made not only in some "face" projects, but also in some "inner" projects. For the need of navigation in ice water, ships should also take precautions in terms of ice breaking ability and handling dangerous situations. The ship body is immersed in seawater for a long time, which is most directly affected by extremely cold weather or low temperature environment. In order to reduce the damage caused by thermal expansion and cold contraction, the hull will generally choose low-temperature ductile materials. Many countries take measures to improve the low temperature toughness of hull materials in the process of ship design and construction. One is to add different proportions of metals to form alloys in iron and steel raw materials. The "combination" of these metal elements can improve the low-temperature toughness of iron and steel to a certain extent; The second is to change the content of carbon, nitrogen and oxygen in the steel itself, so as to improve the low-temperature toughness of the material. Russian delta class IV strategic missile nuclear submarine. Data picture South Korea's Cui Ying missile destroyer. Data picture The "face" project contains a lot of content. For example, in order to avoid frosting and freezing of glass windows due to excessive temperature difference inside and outside the cab, the windows usually use glass with charged hot wire; In order to ensure the normal operation of ship surface equipment, they are generally covered with "protective clothes" that can not only keep warm but also be easy to "wear" and "take off". On the one hand, they are covered for heat preservation, on the other hand, they are also convenient for anti ice and snow removal; Power distribution boxes and electric control devices on the deck and some low-temperature parts are equipped with electric heating devices to ensure power safety; The pipeline system located on the deck is usually wrapped with thermal insulation layer and equipped with anti freezing valve to ensure the normal discharge of seawater, fresh water, etc. in extremely cold environment. The content of "Lizi" project is more complicated. Some important cabins and oil and water tanks are usually set with double bottom, which can be used as ballast tank to increase the ship's sinking resistance. For ships sailing in extremely cold environment, it is like double-layer glass used in house windows in cold areas, which can reduce the heat exchange with the outside world and play the role of cold insulation and cold prevention. When sailing in extremely cold environment, the water tank will generally reserve about 10% of the volume to deal with the impact of cold expansion of seawater and fresh water. If the volume of the cabin is large, the proportion of space reserved for water storage will be larger. Steering gear, windlass and related control devices are the key "care" objects of cold prevention. Generally speaking, the relevant compartments of these key parts have corresponding heating devices. In some key parts, such as the hydraulic pipeline of the windlass, because it is close to the deck, the pipeline should be wrapped with warm materials to prevent freezing, so as to ensure that the windlass can be used normally at any time. The submarine gate valve box of the main and auxiliary engine and auxiliary mechanical cooling system is one of the key points of anti freezing. Generally, a heating coil will be set in the valve box to remove ice and ensure that what is inhaled is low-temperature seawater rather than crushed ice. For ships sailing in thick ice and frozen waters, it is not enough to only maintain their body temperature, but also to "exercise their muscles, bones and skin outside". Anti ice reinforcement measures are usually taken at the bow and bulbous nose to meet the needs of ice breaking. The hull of the bow shall be made of steel plate at least 5cm thick, which will be supported by dense steel members like the interior of the ball nose. The waterline is usually made of alloy steel to ensure that it can deal with the impact of solid ice. The emergency fire-fighting system is a "minimum" project, so its pipeline is usually located in the place with normal temperature on the ship, and the number of fire-fighting systems will be more than 2. For most ships, foam fire extinguishing systems, including outdoor foam tank, foam raw pipeline and pump body, will also take certain insulation measures to ensure safety, smooth and efficient use. Sustainable development requires antifreeze and deicing ability from science and technology The anti freezing technology and measures of ships are constantly improved and improved, but facing the ice formed by ships, the navies of most countries are still using the ancient and effective wooden mallet ice breaking method. In October 2018, the US Truman aircraft carrier battle group cruised the Arctic circle. The voyage with boundless scenery finally became a "Labor Day" on the aircraft carrier. The sailors had to wave baseball bats and shovels for deicing. Nowadays, the development of ship antifreeze and deicing technology mainly includes two aspects: on the one hand, it uses traditional technology, which is mainly deicing by machinery, electric heat or manpower. Mechanical deicing refers to mechanical deicing to generate destructive stress inside the ice, and then make the ice fall off from the hull surface; Electric energy deicing is to melt ice and defrost through heat. At present, mechanical deicing is mainly used in areas such as the upper deck of ships. This is because the deck position is low. If the ice is melted into water by heat, it is easy to freeze again and block when flowing through the cold outlet and drain pipe; For the deicing of important equipment, it is mostly realized by electric energy and thermal energy. Compared with the two methods, the energy consumption of mechanical deicing method is much lower than that of thermal deicing method, but this method requires the installation of corresponding mechanical parts. Manual deicing method is quite dangerous, and it is basically no longer used in various countries at present. The other is the application of new technologies. One is nanotechnology, that is, the combination of nano materials and resin is applied to the ship coating to make its surface show strong waterproof characteristics, so as to prevent the ship from icing. The second is memory alloy technology, which is widely used in aerospace. Its biggest advantage is that it can make use of the memory characteristics of the alloy to quickly restore the original state after the stress change on the ship surface, and achieve the deicing effect in the process of alloy deformation. However, its process is relatively complex, and there is still a way to go for its specific application to ship antifreeze. The third is the microwave heating deicing technology, that is, a layer of special material coating is laid on the hull, and the microwave is used to make the specific molecules in the material vibrate rapidly at high frequency to generate heat energy, so as to melt the ice in this part. These technologies, together with mechanical deicing, are expected to achieve ideal deicing effect. It can be seen that it is becoming a trend to ask for antifreeze and deicing ability from science and technology. Although some technologies are still a long way from mature application, it can be expected that with the continuous development of science and technology and its further integration with practice, ships will better solve the problems affected by extremely cold weather and low-temperature environment in the near future. Photo: Yangming (outlook new era)