Yangzhou Tongyang Chemical Equipment Co., Ltd.

News Center

Home

Types of heat exchanger scaling

Release time:

2024-06-17

Scaling can be defined as the deposition of unwanted material on a heat transfer surface.

　　Fouling is an unavoidable result of heat transfer between two flowing streams on a metal wall. The degree of fouling varies greatly with the nature of the fluid being treated.

　　Due to the deposition of unwanted material, there is an additional resistance to heat transfer, which results in a reduction of the total heat transfer coefficient. As the total heat transfer coefficient decreases, more heat transfer area is required to realize a given heat load.

　　The performance of the heat exchanger is degraded and fouling reduces the flow path, thereby increasing the pressure drop. Even worse, throughput is reduced due to partial blockage of the flow paths.

　　01. Negative effects of fouling

　　Increased capital costs, more heat transfer area must be provided to solve the fouling problem;.

　　Higher pumping costs; and

　　Lower thermodynamic efficiency of condensing and refrigeration cycles.

　　Higher maintenance costs.

　　Overall losses.

　　Downtime costs.

　　02. Types of fouling

　　Precipitation fouling

　　Precipitation fouling is caused by the presence of dissolved CaCO, Caso, and salts in the water, which lead to fouling of heat transfer surfaces. These salts have inverse solubility properties.

　　Particulate fouling

　　It is the accumulation of suspended particles present in the fluid on the heat transfer surface. It is known as deposit fouling. An example is rust particles contained in cooling water.

　　Chemical reaction fouling

　　It is the formation of deposits through chemical reaction between various components of the fouling stream. Examples of chemical reaction fouling are coking and cracking of hydrocarbons, polymerization etc.

　　Corrosion fouling

　　This occurs when the heat transfer surface itself reacts to form corrosion products. It contaminates the heat transfer surface.

　　Biofouling

　　It occurs due to attachment of microorganisms or macro organisms to the heat transfer surface.

　　Solidification Fouling

　　This occurs when a liquid solidifies on a supercooled heating surface. An example of solidification fouling is icing.

　　03. Factors affecting fouling

　　Fluid velocity

　　Fluid temperature

　　Material of construction

　　Material surface finish

　　Higher fluid velocities minimize fouling. Ideal fluid velocities are 1.5-2.1 m/sec inside the tube and 1.0-1.5 m/sec outside the tube.

　　04. When dirty fluids are to be used inside the tube, the following strategies can be followed to avoid scaling:

　　Use large diameter tubes.

　　Maintain high velocity.

　　Allow sufficient margin for pressure drop.

　　Keep a spare tube bundle or spare heat exchanger available.

　　Use two shells in parallel.

　　Use wire finned tube inserts.

　　Use in-line cleaning.

　　05. When dirty fluid is located on the shell side, the following strategies can be followed:

　　Use a U-tube or floating header design.

　　Use square or rotating square tube layout.

　　Minimize dead space with optimum baffle design; and

　　Maintain high velocity on the shell side.

Return to List →

扬州经济技术开发区通扬国际贸易有限公司

Business License