what is a Stainless steel heat exchanger?

what is a Stainless steel heat exchanger?

Stainless steel heat exchanger is a universal industrial heat exchange equipment that uses austenitic stainless steel (304/304L, 316L as the main heat exchange element) to achieve heat transfer between two fluids without mixing the media.

Working principle of stainless steel heat exchanger

Cold and hot media are separated by stainless steel walls, and heat is conducted from high-temperature fluids to low-temperature fluids through stainless steel pipe walls/plates; Multiple counter current arrangements are used to increase the temperature difference in heat exchange, without direct contact between the medium, completing heating, cooling, condensation, and waste heat recovery.

Main structural types of stainless steel heat exchangers

1. Shell and tube (tubular) stainless steel heat exchangers are commonly used in the industry: shell+tube bundle, tube plate, baffle plate; Segmented fixed tube plate, floating head type, U-shaped tube type.

Fixed tube plate: Low cost, suitable for small temperature differences and clean media;

Floating head type: The tube bundle can be withdrawn for easy cleaning, suitable for working conditions that are prone to scaling and large temperature differences;

U-shaped tube: resistant to high temperature and high pressure, and the tube side is not easy to maintain and clean.

2. Multi layer corrugated stainless steel plates are stacked in a plate type stainless steel heat exchanger, which can be divided into detachable sealing plate type and fully welded/fusion welded plate type; High heat exchange efficiency, compact size, commonly used in sanitary grade; The disadvantage is that the upper pressure limit is lower than that of the shell and tube type.
3. Sleeve type (double tube) with two concentric stainless steel pipes inside and outside, simple structure, suitable for small flow, high pressure, and small working conditions.
4. Coil/Immersive Stainless Steel Heat Exchanger The stainless steel coil is immersed in a tank for heating and cooling the materials inside, with a simple structure.

Selection of commonly used materials for stainless steel heat exchangers

304/304L: ordinary water, weakly corrosive medium, food at room temperature; Not resistant to chloride ions, high chloride ions are prone to pitting corrosion, and have a high cost performance ratio.

316L: containing molybdenum, with stronger resistance to chloride ions and weak acid corrosion; Food, pharmaceuticals, seawater, and chemical weak acid systems are preferred, with prices 20-30% higher than 304; Low carbon, less prone to intergranular corrosion during welding.

Dual phase steel 2205/2507: high chloride ion, seawater, strong corrosion and harsh working conditions, high cost.

Advantages of Stainless Steel Heat Exchanger

1. Corrosion resistant, hygienic, non polluting medium, meeting the requirements of food and pharmaceutical cleanliness;
2. High temperature resistance, good mechanical strength, and can withstand high pressure;
3. Surface passivation film, not easily corroded or leaked, with a long service life;
4. Weldable and adaptable to various media;
5. Easy CIP online cleaning (sanitary grade).

Disadvantages of stainless steel heat exchangers

1. The thermal conductivity is lower than that of copper, and the heat transfer efficiency of the same heat transfer area is lower than that of copper;

Improper selection in chloride ion environments (seawater, high salt wastewater) can lead to pitting corrosion;

3. The material cost is higher than that of carbon steel heat exchangers;
4. Plate stainless steel has limited pressure bearing capacity.

Typical application areas of stainless steel heat exchangers

Food and beverage, pharmaceuticals (hygiene grade heat exchange, pasteurization)

Chemical and fine chemical industries, cooling and heating of acid-base and salt solutions

HVAC, hot water, waste heat recovery, water treatment

Environmental protection equipment, organic fertilizer/chemical production line heat exchange, condensation

Desalination of seawater, ships, oil and gas

Key parameters for selecting stainless steel heat exchangers

Medium composition (chloride ion concentration), design temperature/pressure, flow rate, inlet and outlet temperatures, allowable pressure drop, susceptibility to scaling, need for disassembly and cleaning, hygiene level requirements.