The difference between cold storage aluminum row evaporator and seamless steel tube evaporator
When we choose to install cold storage, we usually encounter material selection problems. The advantages of the aluminum row evaporator are space saving, lightness, energy saving and environmental protection, convenient installation, etc.; while the seamless steel pipe row has the disadvantages of slow heat transfer performance, difficult installation, and short service life. Let's take a closer look at the difference between them!
1. The application prospect of aluminum row evaporator in cold storage
After bidding farewell to the original bulky copper tube refrigeration evaporator, the seamless steel tube evaporator was used for a period of time. In 2008, the new aluminum row evaporator was put into use. At present, nearly 80% of users in the freezer are using seamless steel tube evaporators, and more than 20% of users are using energy-saving aluminum row evaporators in new areas. In the past few years of promotion and use, aluminum row evaporators have gradually been accepted by new and old users, and are gradually being used nationwide. In the near future, it is believed that the aluminum row will gradually replace the seamless steel tube evaporator and be widely used.
Comparison of energy-saving aluminum alloy piping for cold storage and traditional seamless steel piping. With the development of economy and the improvement of science and technology, people pay more and more attention to energy saving and environmental protection. The shortage of resources and environmental pollution have become the bottleneck of economic development in the world today. The purpose of economic development is to improve people's quality of life, not to pursue economic development speed. Products that waste resources and pollute the environment are being eliminated. In recent years, in the refrigeration and refrigeration industry, a new type of energy-saving product-aluminum alloy pipe has been promoted and applied. This article attempts to compare energy-saving aluminum alloy platoon with traditional seamless steel pipe platoon to promote the application of energy-saving products.
2. The difference between aluminum row evaporator and steel pipe evaporator
(1) The heat transfer performance is different. Under the same temperature conditions, the thermal conductivity of aluminum alloy tube is 210w/m.℃, and that of seamless steel tube is 46w/m.℃. That is to say, under the same temperature conditions, the heat transfer of aluminum alloy pipe is 4.56 times that of seamless steel pipe. Aluminum alloy platoon pipes have better heat transfer performance than seamless steel pipes because of their good thermal conductivity and structural characteristics that are easy to sink cold air.
(2) The difficulty of installation is different. The aluminum alloy tube is formed by pressing aluminum alloy tubes and fins at one time. The tube is simple to manufacture, light in weight and easy to install. For seamless steel pipes, each seamless steel pipe needs to be derusted internally and externally. The production process is complicated. After the production is completed, it needs to be painted with anti-rust paint, and the weight is heavy, the labor intensity of the workers is high, and the installation is difficult.
(3) One-time investment is different. For low-temperature cold storage with the same nominal volume, aluminum alloy top row pipes are less one-time investment than seamless steel pipe top rows.
(4) Different energy saving effects. The aluminum alloy pipe is a longitudinally ribbed finned tube with a small refrigerant charge per unit length. This not only reduces the refrigerant charge of the entire refrigeration system, but also reduces the size or capacity of the auxiliary equipment of the refrigeration system. The probability of potential danger is relatively small. Due to the good thermal conductivity and its special structure, the aluminum alloy tube has high heat transfer efficiency, which is beneficial to reduce equipment investment and energy-saving operation. Seamless steel pipes have a large amount of refrigerant per unit length, the size or capacity of the auxiliary equipment of the refrigeration system, and the potential risk probability is relatively large. In addition, seamless steel pipes generally use smooth pipes, which have poor heat transfer efficiency, which is not conducive to reducing investment and energy-saving operation.
(5) Different levels of compliance with food hygiene requirements. There is a corrosion-resistant oxide film on the surface of the aluminum alloy pipe, which will not be rusted after long-term use, and will not pollute food and the environment. Although the seamless steel pipe is coated with anti-rust paint, it is easy to rust due to long-term use in a low temperature and humid environment. When frosting, rust may contaminate food and storage environment. Therefore, aluminum alloy pipes are more in line with food hygiene requirements than seamless steel pipes. Compared with seamless steel pipes, alloy pipes are more in line with food hygiene requirements.
(6) Safety performance. The destructive test pressure of aluminum alloy piping is 12Mpa, the strength test pressure is 2.4Mpa, and the tightness test pressure is 1.6Mpa. The pressure test of the aluminum alloy piping system is maintained for 24 hours. In cold storage, it is safe to use aluminum alloy pipes. In recent years, the practice of a large number of aluminum alloy platoon tubes used in cold storage projects has also proved that aluminum alloy platoon tubes, as a new type of energy-saving evaporator, are safe and reliable in application. Under normal use, the theoretical service life of aluminum alloy platoon is longer than that of seamless steel pipe.
(7) Different environmental performance. The manufacturing, processing, installation and use of aluminum alloy pipes do not produce rust or pollute the environment. It is an environmentally friendly product. After a certain number of years of use, seamless steel pipes are prone to rust and pollute the food environment.
(8) Different performance at low temperature. GB/T8163 stipulates: The lower limit of service temperature of 10#, 20# carbon steel seamless steel pipe is -29℃. The lower limit of the service temperature of aluminum alloy pipe is -269℃. Therefore, aluminum alloy platoon pipes have better and more stable performance at low temperatures than seamless steel pipe platoons.
(9) Flow resistance is different. The inner wall of the aluminum alloy pipe is smooth and clean, the refrigerant flow rate is large, the resistance is small, and it is not easy to accumulate grease and other dirt, which is beneficial to improve the heat transfer effect; the inner wall of the seamless steel pipe is not as smooth as the aluminum alloy pipe, and the refrigerant flow resistance is relatively high Large, it is easier to accumulate dirt and other dirt, which is not conducive to heat transfer.
(ten) Frost. Both aluminum alloy pipes and seamless steel pipes can be defrosted with hot ammonia (fluorine), and metal appliances (including pipes and pipe fixings) can not be used for manual defrosting, but softer can be used. Broom or special tools assist in sweeping frost. Some cold storage pipe users are experimenting to explore the use of low-pressure gas to assist defrosting the top pipe while hot ammonia (fluorine) is defrosted. The author believes that, as an exploration of flushing method, for safety reasons, it is advisable to use 0.01~0.07Mpa low pressure gas.
(11) Applicable working fluid. Aluminum alloy pipes are the same as seamless steel pipes, which can be used for ammonia and freon working fluids. There is a layer on the surface of the aluminum alloy pipe
(12) μm thick anti-corrosion layer, which is more suitable for low temperature and humid environment than seamless steel pipe.
(13) Effective utilization rate of cold storage warehouse. In low-temperature cold storage, aluminum alloy top row pipes are generally installed in a single row, which occupies less space in the warehouse than traditional double-layer seamless steel pipe top rows, which is beneficial to increase the storage height of goods in the low-temperature cold storage warehouse, which is actually effective. rate.
(14) Impact on the quality of refrigerated food. In low-temperature cold storage, the use of aluminum alloy top row pipes instead of air coolers can not only reduce power consumption and energy-saving operation, but also make the temperature of the cold storage more uniform and stable, thereby reducing the dry consumption of refrigerated food and improving the quality of refrigerated food .
(15) Applicable cold storage warehouse types. Aluminum alloy tube is generally suitable for low-temperature cold storage as the top tube evaporator. For freezing rooms, aluminum alloy pipe air coolers or shelf aluminum alloy pipes can be used as evaporators. For high-temperature warehouses, aluminum alloy pipe coolers can be used as evaporators. Aluminum alloy platoon air cooler and shelf-type aluminum alloy platoon have better heat transfer efficiency than seamless steel tube platoon air cooler and shelf-type steel platoon due to the heat transfer characteristics of the material.
(XVI) Precautions for aluminum alloy tube application:
A. The design, production, installation and commissioning of aluminum alloy pipes should be undertaken by an experienced company with cold storage design and installation qualifications. After the aluminum alloy platoon pipe is finished, the single pressure test and blowdown shall be carried out. Then, connect the refrigeration system to install. After the installation is completed, the refrigeration system should be tested for pressure leaks, draining, vacuum, and refrigerant filling.
B, the choice of the heat transfer area of aluminum alloy tube. The heat transfer area of aluminum alloy pipes in low-temperature cold storage is generally determined by 1.3~1.6 times the net area of the warehouse; the freezing room is generally selected and determined by 8-10 times the net area of the warehouse; the cooling room is generally 3.5~4 times the net area of the warehouse Choose OK.
C, the determination of the design length of the single-pass pipe pass of aluminum alloy row pipe. For liquid pump liquid supply systems, the length of a single pipe pass should be ≤40m; for gravity supply and direct liquid supply systems, the length of a single pipe pass should be ≤30m. If the length of the single-channel tube is designed to be too long, it will cause excessive flow resistance and affect the heat transfer effect.
D. Liquid supply and air return for aluminum alloy pipes. The liquid supply and return gas pipelines of aluminum alloy pipes should not be branched too much to prevent uneven liquid supply.
E. Tungsten argon arc welding should be used for welding aluminum alloy tube. Welding personnel should undergo professional technical training and pass the examination.
F. The connection between aluminum alloy piping and the refrigeration system is generally flanged.
G. During the production, transportation, installation and use of aluminum alloy pipe, it is strictly forbidden to hit or squeeze with metal objects. During the frosting process, it is strictly forbidden to knock with hard objects such as metal utensils to defrost.
h. Aluminum alloy pipes are used as top pipes in low-temperature refrigerators; in freezing rooms, they are used as rack pipes and air cooler pipes; in cooling rooms and high-temperature storage, they are used as air coolers Calandria. It is not recommended to use aluminum alloy pipes as wall pipes in cold storage unless effective safety measures are taken.
Third, the installation method of aluminum tube evaporator
(1) When the aluminum row pipe is installed on the roof of the storage, try to keep a certain slope at both ends, so as to facilitate the smooth flow of the aluminum drainage tank installed, and between the adjacent aluminum row and the aluminum row, the aluminum row and the storage board Keep a distance of 10-15CM between them to facilitate the flow of cold air; when welding aluminum row pipes, the welding machine current must be adjusted, otherwise it will easily cause welding through or surface welding; when welding elbows of aluminum row pipes, use sandpaper to weld The surface is polished clean, because argon arc welding will cause the surface of the aluminum row to oxidize; before the aluminum row pipe is welded to the elbow, the inside of the aluminum row pipe should be blown clean to prevent the internal aluminum slag from blocking the safety valve during use; When installing the heating wire in the tube, do not squeeze the heating wire with a hard object even if the fixing slot is narrow, because the heating wire inside the heating wire is not an aluminum tube evaporator.
(2) When the aluminum row pipe is installed on the roof of the storage, try to keep a certain slope at both ends, so as to facilitate the smooth flow of aluminum drainage of the water tank, and between the adjacent aluminum row and the aluminum row, the aluminum row and the storage board Keep a distance of 10-15CM between them to facilitate cold air flow;
(3) When welding aluminum row pipes, the current of the welding machine must be adjusted well, otherwise it is easy to cause weld penetration or surface welding;
(4) When welding elbows of aluminum row pipes, sandpaper should be used to polish the welding surface clean, because argon arc welding will cause oxidation of the aluminum row surface;
(5) Before welding the elbow of the aluminum row pipe, blow the inside of the aluminum row pipe to prevent the aluminum slag from blocking the safety valve during use;
(6) When installing the heating wire on the aluminum tube, even if the fixing groove is narrow, do not squeeze the heating wire with a hard object, because the heating wire inside the heating wire is very fragile and easy to break;
(7) When loading aluminum platoons, especially aluminum platoons over 6 meters, try not to let the stevedores hold the elbow with both hands. It is easy to crack the solder joints;
(8) A dispenser is needed when installing multiple aluminum pipes. The outlet of the dispenser must be uniform, free of burrs and equal in length.
