Plate heat exchanger is an ideal equipment for liquid liquid and liquid vapor heat exchange. It is a new type of effective heat exchanger which is composed of a series of metal sheets with a certain corrugated shape.

Structure and principle of plate heat exchanger: the detachable plate heat exchanger is made of a lot of stamping corrugated sheets at a certain interval, sealed by gaskets around, and overlapped and compressed by frame and compression screw. The four corner holes of plate and gasket form the distribution pipe and collection pipe of fluid, and at the same time reasonably separate the cold and hot fluid to make it flow in the flow channel on both sides of each plate, Heat exchange through plates.

The basic classification of plate heat exchanger in general, we mainly distinguish plate heat exchanger according to the structure, that is, according to the shape, which can be divided into four categories: ① removable plate heat exchanger (also known as plate heat exchanger with sealing gasket), ② welded plate heat exchanger, ③ spiral plate heat exchanger, ④ plate coil heat exchanger (also known as honeycomb heat exchanger). Among them, welded plate heat exchanger is divided into: semi welded plate heat exchanger, fully welded plate heat exchanger, plate shell heat exchanger, brazed plate heat exchanger.

Composition of plate heat exchanger

The plate heat exchanger is composed of heat transfer plate, gasket, compression plate, clamping bolt and other main parts.

In order to increase the stiffness of the plate, increase the turbulence of the fluid and improve the heat transfer efficiency, the surface of the heat exchange plate is pressed into corrugated or grooved shape. Its materials are mostly stainless steel, copper, aluminum, aluminum alloy, titanium, nickel, etc. The corner hole at the corner of the plate acts as a connecting channel.

The working medium alternately flows through the narrow and tortuous channels formed between the plates for heat transfer. As the plates are installed upside down, thousands of contact points formed by the cross corrugations are staggered and evenly distributed, which makes the fluid flow around these contact points, causing strong disturbance, forming a very high heat transfer coefficient, so that the heat exchanger has a very high heat transfer efficiency and pressure bearing capacity.

Common plate materials for plate replacement

① 304 stainless steel

This is * cheap, * widely used austenitic stainless steel (such as food, chemical, atomic energy and other industrial equipment). Suitable for general organic and inorganic media. For example, nitric acid with concentration < 30% and temperature ≤ 100 ℃ or concentration ≥ 30% and temperature < 50 ℃; Various concentrations of carbonic acid, ammonia and alcohols with temperature ≤ 100 ℃. The corrosion resistance is poor in sulfuric acid and hydrochloric acid; It is especially sensitive to crevice corrosion caused by chlorine containing medium (such as cooling water).

② 304L stainless steel

The corrosion resistance and use are basically the same as 304 type. Due to the lower carbon content (≤ 0.03%), the corrosion resistance (especially intergranular corrosion resistance, including weld zone) and weldability are better, which can be used for semi welded or full welded PHE.

③ Type 316 stainless steel

Suitable for general organic and inorganic media. For example, natural cooling water, cooling tower water, softened water; Carbonic acid; Acetic acid and caustic soda with concentration less than 50%; Alcohol, acetone and other solvents; Dilute nitric acid (concentration < 20%) and dilute phosphoric acid (concentration < 30%) with temperature ≤ 100 ℃. However, it is not suitable for sulfuric acid. Because it contains about 2% Mo, its corrosion resistance in seawater and other chlorine containing media is better than that of Type 304, which can completely replace type 304.

④ 316L stainless steel

The corrosion resistance and application are basically the same as type 316. Due to the lower carbon content (≤ 0.03%), the weldability and corrosion resistance after welding are also better, which can be used for semi welding or full welding PHE. The pre is 25.

⑤ 254 SMO * * stainless steel

This is a kind of ultra-low carbon * * stainless steel improved by increasing the content of mo. it has excellent resistance to chloride pitting and crevice corrosion, and is suitable for the medium that cannot use 316 type salt water, inorganic acid, etc. 254SMO is an austenitic stainless steel. Because of its high molybdenum content, it has high resistance to pitting corrosion and crevice corrosion. 254SMO also has good corrosion resistance. Especially in the acid containing halide, the steel is better than ordinary stainless steel. Its C content is less than 0.03%, so it is called pure austenitic stainless steel (< 0.01% is also called super austenitic stainless steel).

⑥ Duplex stainless steel 2205 alloy

Duplex stainless steel 2205 alloy is composed of 21% Cr, 2.5% Mo and 4.5% ni-n alloy. It has high strength, good impact toughness and good overall and local stress corrosion resistance. The yield strength of 2205 duplex stainless steel is twice that of austenitic stainless steel. This alloy is especially suitable for - 50 ° F/+600 ° F temperature range. This alloy can also be considered for applications beyond this temperature range, but there are some limitations, especially for welded structures. Compared with 316L and 317L austenitic stainless steel, 2205 alloy is superior to 316L and 317L austenitic stainless steel in pitting corrosion resistance and crevice corrosion resistance. It has high corrosion resistance. Compared with austenite, 2205 alloy has lower coefficient of thermal expansion and higher thermal conductivity. Compared with austenitic stainless steel, the compressive strength of 2205 duplex stainless steel is twice that of 316L and 317L duplex stainless steel.