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Heat Transfer Enhancement Techniques

Many everyday appliances use heat transfer components, such as heat exchangers, within car radiators or refrigerators. Heat transfer involves moving heat from one liquid to another through a solid surface. However, appliance designers are constantly improving heat transfer techniques for more energy efficient and longer lasting products. Many enhancement techniques have been implemented in the heat transfer industry, operating in both passive and active capacities.

Internal Surface Alterations
- Heat transfer components use tubes or plates for movement of liquid through a heat exchanger assembly. Heat transfer is enhanced by altering the internal surface of the tube or plate. The surface can either be treated with a coating or modified with roughness, such as a grainy texture. Creating a rough texture or coating to the walls introduces turbulence to the flowing liquid. The disturbed liquid mixes more thoroughly with roughened wall surfaces, allowing more heat exposure to the fluid molecules for heightened heat transfer processes.
Increased Surface Area
- Some heat transfer components use extended surfaces, such as fins, within the liquid's flow. The fin provides more surface area, generating more heat transfer production since more fluid is in contact with the wall surface. In fact, many heat transfer components use multiple plate layers or smaller, coiled tubes. The fluid passing through these plates and tubes exposes more liquid molecules to the wall surface. Large, open plates or tubes cause many fluid molecules to remain in the liquid's center, possibly never contacting the wall surface, and inevitably hindering the heat transfer process.
Applied Movement
- Various industries use external influences on the heat transfer liquid. Mechanical stirring of the liquid creates the needed turbulence for enhanced heat transfer. The fluid, and even the wall surface, can have vibration or pulsation applied to them for generating turbulence as well. Fluid mixing is promoted by applying an electric or magnetic field across the heat transfer appliance. In addition, injection and suction processes are used for adding and subtracting fluid from the heat transfer appliance. This process also aids in creating a more turbulent fluid flow.
Cleaning
- One simple enhancement technique is maintaining the heat transfer appliance. Many industries use heavy machinery housing heat exchangers that run almost constantly for high production rates. However, heat transfer cannot function at peak levels if the internal wall surface accumulates fouling, regardless of the enhancement techniques applied to the assembly. Fouling is sediment and deposits that settle out of the moving liquid and onto the wall's surface. Slowly, it creates a layer along the wall, impeding the heat transfer process. For fouling prevention, the heat exchanger should be cleaned periodically for the best operation.

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