Convective heat transfer can be improved by enhancing the thermal conductivity of the fluid. It has been established that fluids containing suspended solid particles of metallic origin in nanoscale dimensions, display enhanced thermal conductivity. Nanoparticle suspensions have superior qualities than suspensions of larger sized particles, such as more particle surface area, less possibilities of agglomeration and clogging and better stability. An experimental investigation on the effect of the inclusion of nanoparticles into the cooling fluid on the effectiveness of a heat exchanger is presented in this paper. An experimental double pipe heat exchanger with the hot fluid flowing through the inner tube was used in the study. Aluminum oxide and copper oxide nanoparticles with a size range of 20 to 30 nm suspended in water using ultrasonic agitation was used as the hot fluid, and water was used as the cold fluid passing through the annulus. The concentration of the suspended nanoparticles was varied to investigate its effect on the performance of the exchanger. The operating temperature is also used as a parameter in the study. Typically, an enhancement of 4.5 to 7 percent was observed in the effectiveness of the heat exchanger for 0.26% weight fraction of the nanoparticles in suspension, in an operating temperature range of 50–70°C. The effectiveness of the heat exchanger was found to increase with the concentration of nanoparticles for both materials used.

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