Experimental study on the heat recovery characteristics of a new-type flat micro-heat pipe array heat exchanger using nanofluid

This study aims to investigate the heat recovery characteristics of a new-type flat micro-heat pipe array heat exchanger using δ-Al2O3-R141b nanofluids as working fluids. δ-Al2O3-R141b nanofluids with volume fractions of 0.001%, 0.01%, and 0.1% were prepared. The experiments were performed with air volume flow rates ranging from 60 m3/h to 120 m3/h. The evaporator section inlet air temperature varied from 27 °C to 40 °C while the condenser section inlet air temperature remained at 24 °C. The results indicated that heat recovery efficiency is enhanced remarkably by using 0.01% volume fraction nanofluid as working fluid, and the maximum growth rate of effectiveness can reach 110%. The heat recovery effectiveness of the 0.001 vol% nanofluid was almost similar to that of R141b; however, the efficiency of 0.1% nanofluid declined significantly. The pressure drop ratio of the heat exchanger was tested subsequently, and the energy saved by the exchanger was analyzed to further evaluate the performance of heat exchanger.