Enhancing heat transfer surface are used in many engineering applications such as heat exchanger, air conditioning, chemical reactor and refrigeration systems, hence many techniques have been investigated on enhancement of heat transfer rate and decrease the size and cost of the involving equipment especially in heat exchangers. One of the most important techniques used are passive heat transfer technique. These techniques when adopted in Heat exchanger proved that the overall thermal performance improved significantly. This paper reviews experimental and numerical works taken by researchers on this technique since 2004 such as twisted tape, wire coil, swirl flow generator,… etc. to enhance the thermal efficiency in heat exchangers and useful to designers implementing passive augmentation techniques in heat exchange. The authors found that variously developed twisted tape inserts are popular researched and used to strengthen the heat transfer efficiency for heat exchangers. The other techniques used for specific work environments are studied in this paper. Twisted tape inserts perform better in laminar flow than turbulent flow. However, the other several passive techniques such as ribs, conical nozzle, and conical ring, etc. are generally more efficient in the turbulent flow than in the laminar flow.

A comprehensive review on passive heat transfer enhancements in pipe exchangers

Enhanced heat transfer in a triangular ribbed channel with longitudinal vortex generators

Heat transfer augmentation in a wedge-ribbed channel using winglet vortex generators

Heat transfer enhancement is an important matter of concern for energy conservation and also beneficial from economic point of view. The use of passive devices like twisted tapes, roughness elements, wires inserts etc. are effective methods of heat transfer augmentation. Many research studies on different types of twisted tapes geometries to increase heat transfer rate have been carried out. Also, several correlations were developed to determine heat transfer and friction factor for twisted tape inserts. In the present study, a review on work done in the area of heat transfer augmentation using twisted tapes has been carried out. Previous experimental and numerical studies on various types of twisted tapes (based on the literature survey) were discussed. These studies reveal that the future research in the area of twisted tapes will bring more development in the heat exchanger systems. The optimum shape for twisted tapes can also be developed based on maximisation of heat transfer and minimisation of friction factor regarding fluid used in the system.

Heat transfer augmentation using twisted tape inserts: A review

Turbulent flow heat transfer and pressure loss in a double pipe heat exchanger with louvered strip inserts

Heat transfer and friction characteristics in decaying swirl flow generated by different radial guide vane swirl generators

One of the most promising methods for reducing NO
 x
 emissions of jet engines is the lean combustion process. For realization of this concept the percentage of air flowing through the combustor dome has to be drastically increased, which implies high volume fluxes in the primary zone of the combustion chamber and represents a substantial challenge in regard to the flame stabilization. Swirl motion is thus applied to the air flux by the swirl generator and decisively contributes to the flame stabilization. The current paper reviews an atmospheric investigation of a burner configuration in regard to the weak extinction limit, comprising a confined non-premixed swirl-stabilized flame. The burner can be supplied with either kerosene or after a small adaption with natural gas (methane). Therefore, a comparison of a kerosene-fuelled flame (spray flame) to a natural gas fuelled one (methane flame) can be performed. Both are realized by almost identical burner configuration and at identical conditions. The main idea of this work is to align the stability characteristics of both flames by means of similarity. However, fundamental differences regarding the flame structures of the flames are detected through in-flame measurements. This determines the limits of the current approach and motivates an appropriate choice of flame modeling.

Similarity Issues of Kerosene and Methane Confined Flames Stabilized by Swirl in Regard to the Weak Extinction Limit

Present work reports the electrochemical diffusion coefficient (EDC) values of ferri-cyanide ions in an electrolytic system frequently used in mass transfer measurements. The measurement methods we...

Some Transport Properties of Potassium Ferri/Ferro-Cyanide Solutions in a Wide Range of Schmidt Numbers

In this study, polyurethane nanocapsules containing phase change material were synthesized by interfacial polycondensation polymerization method. Toluene-2,4-diisocyanate (TDI) and diethylenetriamine (DETA) were chosen as monomers. n-Nonadecane was employed as a core material. The properties of nanocapsules were characterized by DSC, FT-IR, and SEM. The results show that the nanocapsules were synthesized successfully and that the phase change temperature was about 29.6 °C, and the latent heat of fusion was about 82 Jg−1. The particle size was found to range from 100 to 340 nm.

O. Nuri Sara

Papers

Heat transfer and friction characteristics in decaying swirl flow generated by different radial guide vane swirl generators

Similarity Issues of Kerosene and Methane Confined Flames Stabilized by Swirl in Regard to the Weak Extinction Limit

Some Transport Properties of Potassium Ferri/Ferro-Cyanide Solutions in a Wide Range of Schmidt Numbers

Preparation and Characterization of Nanoencapsulated n-Nonadecane for Convective Heat Transfer