Experimental investigation on forcedconvection heat transfer augumentation using annular blockages

Abstract

Heat transfer intensify techniques ( Passive, Active & Compound methods ) are commonly used in areas such as process industries, heating and cooling in evaporators, thermal power plants, air-conditioning equipments, refrigerators, radiators or space vehicles, automobiles, etc. Passive techniques, where inserts are used in the flow passage to intensify the heat transfer rate, are advantageous compared with active techniques, because the insert manufacturing process is simple and these techniques can be easily employed in an existing heat exchanger. In design of compact heat exchanger, passive techniques of heat transfer augmentation can play an important role if a proper passive insert configuration can be selected according to the heat exchanger working condition ( Both flow and heat transfer conditions ). Many researchers have used different passive methods to improve heat transfer. Passive heat transfer methods are not only applicable in heat exchanger but also in solar air heater and cooling of electronic components. Experimental work on heat transfer augmentation using annular blockages. Inserts when placed in the path of the flow of the fluid, create a high degree of turbulence resulting in an increase in the heat transfer rate and the pressure drop. The work includes the determination of friction factor and heat transfer coefficient for various annular blockages and annular blockages having different diameter. The results of annular blockages having different diameter have been compared with the values for the plain tube. Four annular blockages (di=20%, 30%, 40% reduction in outer diameter) are used in the study.