Heat transfer and fluid flow characteristics of the passive method in double tube heat exchangers: A critical review

Abstract

With the growing need for more energy, it is imperative to design efficient heat exchangers that are simpler, cheaper to manufacture, have higher heat transfer rates, and low in pressure drop. One of these heat exchangers is the double tube heat exchanger that is used in many industries. From past to present, double tube heat exchangers have caught the attention of researchers because of their simplicity and wide range of applications. This review paper contains a critical analysis of the impact of different passive methods on the heat transfer and fluid flow characteristics of the fluid in double tube heat exchangers. There are different techniques to increase the heat transfer rate in double tube heat exchangers, such as turbulator insertion, extended surface (fin), in tube geometry change, nanofluids and a combination of these techniques. All these techniques are reviewed in detail to determine the heat transfer rate and friction factor enhancement in the double tube heat exchangers. Statistical analysis was provided to compare the impacts of these different techniques on the heat transfer and fluid flow characteristics of the double tube heat exchanger performance. It was concluded that a combination of turbulator inserts and nanofluids is the best technique to increase the heat transfer rate. Also, this technique provides the highest potential for heat transfer enhancement based on the standard deviation. On the other hand, extended surface (fin) is the worst-performing technique because of the high friction factor. This review article provides new ideas and gaps in the present knowledge for further investigations.

Keywords

• Double tube heat exchanger
• Concentric tube heat exchanger
• Nanofluid
• Heat transfer rate
• Nusselt number
• Friction factor