Experimental Investigation of Overall Heat Transfer Coefficient in CuO/Water Nanofluids in the Compact Heat Exchanger

Overall heat transfer coefficient of CuO/water nanofluids has been measured experimentally according to the logarithmic mean temperature difference (LMTD) in a compact heat exchanger under laminar flow condition. Furthermore, using theoretical correlations we calculated the overall heat transfer coefficient of the nanofluid and compared the results.The concentration of 0.1 wt% nanofluid has been prepared. The nanofluid flows through the radiator consisted of 34 vertical tubes with elliptical cross sections and air makes a cross flow inside the tube bank with different speeds. Additionally, the effects of nanofluid inlet temperatures to the radiator, nanofluid flow rates and air flow rates on the overall heat transfer coefficient have also been analyzed. Results demonstrate that increasing the nanofluid circulating rates, inlet temperatures and also air flow rates can improve the overall heat transfer coefficient. Meanwhile, application of nanofluid with low concentrations (0.1 wt%) can enhance overall heat transfer coefficient up to 4% in comparison with the pure water, which is obtained at Reynolds numbers of 4100 and 750 for air and nanofluid, respectively at T=80˚C.

Keywords:

overall heat transfer coefficient , CuO , Water , nanofluid , compact heat exchanger