Review Paper on Forced Convection Heat Transafer Augmentation Using Annular Blockages

The study of improved heat transfer performance is\ud \ud referred to as heat transfer enhancement,\ud \ud augmentation, or intensification. In general, this\ud \ud means an increase in heat transfer coefficient.\ud \ud Energy- and materials-saving considerations, as well\ud \ud as economic incentives, have led to efforts to produce\ud \ud more efficient heat exchange equipment. Common\ud \ud thermal-hydraulic goals are to reduce the size of a\ud \ud heat exchanger required for a specified heat duty, to\ud \ud upgrade the capacity of an existing heat exchanger, to\ud \ud reduce the approach temperature difference for the\ud \ud process streams, or to reduce the pumping power. The\ud \ud study of improved heat transfer performance is\ud \ud referred to as heat transfer enhancement,\ud \ud augmentation, or intensification. In general, this\ud \ud means an increase in heat transfer coefficient. [1]\ud \ud General techniques for enhancing heat transfer can be\ud \ud divided in three categories. One is passive method\ud \ud such as twisted tapes, helical screw tape inserts,\ud \ud rough surfaces, extended surfaces, additives for\ud \ud liquid and gases. The second is active method, which\ud \ud requires extra external power, for example\ud \ud mechanical aids, surface fluid vibration, use of\ud \ud electrostatic fields. Passive methods are found more\ud \ud inexpensive as compared to other group