Abstarct: Improvement of heat transfer in the heat exchangers became an important factor in industry. For this purpose, various techniques have been proposed as the use of nano fluid, porous media and helically coil. This thesis is one of the first works which focuses on nanofluids flow and heat transfer in porous media and helically coil experimentally for wide range of Reynolds number from 700 to 5500. Transient natural convection of storage fluid around central tube is investigated experimentally. The CuO/Water nanofluid in two volume fraction of 0.1 and 0.2 dispersed and used as coolant flow of storage. The water at 70OC used as fluid storage that cooled by fluid flow in central tube. Tube Inlet temperature is constant in during the test and 27 OC is considered. The purpose of this study is to determine the relative advantage of using a helically coiled heat exchanger and porous media versus a straight tube heat exchanger. Measurment of temperature and pressure drop of nano fluids along with the test section is done at each test. Results were repoted with confidence intervals with 95% accuracy. Also for validate the test data; numerical simulation for empty tube was used. The result of this comparsion was shown an expectable error from correlations. Maximum decrease of storage temperature for empty tube, helically coil and porous tube are 15%, 20% and 6% respectively for the nanofluids compared to the baxse fluid and maximum decrease of storage temperature for helically coil and porous tube are 42% and 45% versus empty tube for 0.2% water/Cuo nanofluids. The results shows maximum heat lost from storage tank for helically coil and porous tube heat exchanger are 1.4 and 1.6 respectively versus empty tube. The measured pressure drop also shows significant increase in compare with empty tube.