Investigation of the effect of nanofluid flow on heat transfer in double pipe heat exchangers

In the present work, numerical investigation of heat transfer enhancement in double pipe heat exchanger embedded with fins on the outer surface of the inner tube and with addition of Alumina nanofluid have been carried out. Numerical work included construct the geometry which is consist from four pairs copper fins material of (35mm) height, (1mm) thickness, (8.5mm) distance between every two legs which fixed on the straight copper tube. The external and internal pipes have been manufactured from copper material of (51.78 ,20.4 mm) inner diameter, (1500, 1530 mm) length respectively. Cold water at various mass flow rates (0.03 to 0.07) kg/sec flows through annuli, and hot de-ionized water at Reynolds numbers ranging from (250 to 2500) flows through the inner tube. Performance of (smooth and finned) tube heat exchanger was investigated experimentally without nanofluids adoption. Numerical results showed (2.3 to 3.1) enhancement ratio when using finned tube heat exchanger. One type of nanoparticle (Al2O3) having volume concentrations (1%, 3%, and 5%) was used during simulation. Numerical results showed an increase in convective heat transfer coefficient by increasing both volume concentration and Reynolds number. Heat transfer coefficient and thermal conductivity increase at 5% volume concentration by (20%, 4.7%) respectively. Numerical simulation has been carried out on present heat exchanger to analyze both flow field and heat transfer using ANSYS FLUENT 20 package. The solution for conservation continuity, momentum and energy equations is utilized to predict the flow field inside the heat exchanger. A comparison of heat transfer for smooth, finned tube without nanofluids and finned tube with nanofluids was carried out. Steady state, Newtonian flow, incompressible and three dimensional were assumed. The results showed that adding fins enhanced the heat dissipation through heat exchanger. Heat transfer enhancement by adding nanoparticles to base fluid has been found during the simulation. This is due to the increase in thermo physical properties of base fluid. ANSYS FLUENT 20 package is successful for predicting both heat transfer and fluid flow in the present heat exchanger.