Tubular Shell and Tube Condenser Stainless Steel Heat Exchanger

Basic Structure and Principles

1. Core structure

Tube bundle: composed of multiple stainless steel tubes (e.g. 304, 316L stainless steel), as a heat transfer element, hot or cold fluid in or between the tubes.

Shell: the outer shell wrapped tube bundle, providing fluid flow space, the shell process is usually set to enhance turbulence and heat transfer efficiency of the folding baffle.

Tube plate and header: tube plate is fixed at both ends of the tube bundle, header is used for distributing fluid inlet and outlet, common forms are fixed tube plate, floating head, U-shaped tube, etc. (according to the demand for compensation of thermal expansion to choose).

2. Principle of operation

Hot fluid (such as high-temperature steam, hot oil) flows through the tube or shell process, cold fluid (such as cooling water, low-temperature media) flows through the other side, through the wall of the tube for heat exchange, to achieve the hot fluid condensation (such as condenser scene) or cold fluid heating.

Classification of Uses

Condenser: used for vapor condensation (such as refrigerant vapor condensation in the refrigeration system), the shell process away from the cooling water, the tube process away from the steam.

Evaporator: used for liquid evaporation and heat absorption (e.g. chemical solution evaporation and concentration), tube or shell passes into the heating medium (e.g. steam).

Cooler / Heater: Simply for fluid cooling or heating (e.g. temperature control of chemical reactors).

Advantages of stainless steel

Corrosion resistance

Stainless steel (such as 304, 316L) surface formation of chromium oxide passivation film, resistance to acid, alkali, salt solutions and atmospheric corrosion, suitable for the treatment of seawater, chloride-containing media, food and beverage, pharmaceutical solvents and so on.

Comparison: carbon steel heat exchanger is easy to rust, need frequent anti-corrosion treatment, while stainless steel can be long-term maintenance-free, suitable for high cleanliness scenes.

High and low temperature resistance

304 stainless steel can work stably in the range of - 196℃~800℃, 316L stainless steel has better corrosion resistance and is suitable for chemical high temperature corrosive environments (e.g. organic acid reaction).

Strength and cleanliness

Stainless steel has high strength and can withstand high pressure (e.g. high pressure refrigerant in refrigeration system); smooth surface is not easy to scale, easy to clean, in line with the hygienic requirements of the food and pharmaceutical industries.

Application Scenarios

1. Chemical and petroleum industry

Scenario:

Cooling / heating of corrosive media (e.g. temperature control of sulfuric acid, hydrochloric acid solution).

Condensation and evaporation of refrigerants (such as ammonia, Freon), commonly used in chemical refrigeration systems.

Case: A chemical plant uses 316L stainless steel floating head condenser to treat process wastewater containing chlorine ions to avoid tube bundle corrosion leakage.

2. Food and beverage industry

Scenario:

Pasteurization and cooling of fruit juice and milk (the tube course goes to the material, the shell course goes to the ice water).

Temperature control of beer fermenters (refrigerant fed through stainless steel u-tube heat exchanger).

Advantage: 316L stainless steel complies with FDA standards, no metal ion precipitation, to ensure product hygiene and safety.

3. Pharmaceutical and Biological Engineering

Scenario:

Concentration and evaporation of pharmaceutical liquids (e.g., decompression distillation of herbal extracts).

Temperature regulation of bioreactors (e.g. circulating cooling water is passed through during fermentation).

Requirements: Surface polishing treatment (Ra ≤ 0.8μm), to avoid material retention of breeding microorganisms, support CIP (online cleaning).

4. Refrigeration and air-conditioning system

Scenario:

Condenser of central air-conditioning chiller unit (shell course goes to cooling water, tube course goes to refrigerant such as R32).

Evaporator of low temperature cold storage (stainless steel tube bundle passes through liquid ammonia to cool the air in the storage).

Characteristics: refrigerant corrosion resistance, anti-vibration (such as compressor start and stop when the fluid impact).

5. Desalination and ocean engineering

Scenario:

Seawater cooling system (e.g. seawater cooler for ship's diesel engine).

Reverse osmosis seawater desalination device preheating / cooling link.

Material: 316L or duplex stainless steel (e.g. 2205), resistant to seawater chloride corrosion (Cl-concentration ≈ 19000ppm).

Selection and design points

1. Material selection

304 stainless steel: suitable for nitric acid, food grade medium, neutral solution, lower cost.

316L stainless steel: add molybdenum element, more resistant to acid corrosion (such as sulfuric acid, acetic acid) and seawater corrosion, used in highly corrosive scenes.

Special materials: such as 904L stainless steel (resistance to dilute sulfuric acid), Hastelloy (resistance to strong corrosion), for extreme working conditions.

2. Structural design

Anti-temperature stress: When the temperature difference is >50℃, floating head or U-tube structure is preferred.

Anti-fouling: shell program with large folding plate spacing or spiral folding plate, reduce fluid retention; pipe flow rate ≥ 1m / s, to prevent particle deposition.

Sealing: Gasket material matches the medium temperature (e.g. PTFE for low temperature, metal-wound gasket for high temperature).

3. Process parameters

Determine the fluid flow, inlet and outlet temperature, pressure, calculate the heat transfer and logarithmic mean temperature difference (LMTD), select the appropriate flow rate (1-3m/s for liquid, 5-15m/s for gas).

Example: In a refrigeration condenser, the temperature difference between the cooling water inlet and outlet is usually 5~8℃, and the refrigerant condensing temperature is 5~10℃ higher than the cooling water outlet temperature.

Maintenance and Precautions

Regular cleaning:

The heat transfer efficiency decreases after the shell or tube process is scaled, chemical cleaning (such as acid washing) or mechanical cleaning (such as high-pressure water jet) can be used.

Leak detection:

For corrosive media, regularly check the corrosion of the tube bundle with ultrasonic or coloring flaw detection to avoid media interlocking (such as cooling water into food materials).

Anti-corrosion treatment:

Shells not in contact with the medium can be coated with epoxy resin paint to extend service life.