Experimental investigation of surface vibration effects on increasing the stability and heat transfer coeffcient of MWCNTs-water nanofluid in a flexible double pipe heat exchanger

Nanoparticles deposition is one of the most challenges for industrial use of nanofluids. In the present study, the heat transfer enhancement of Multi Wall Carbon Nano Tube, MWCNT-water nanofluid in a double pipe heat exchanger due to vibrating walls is examined for different mass fractions. This work is performed by a flexible double pipe heat exchanger made of PVDF. The forced vibration on the outer surface of the heat exchanger is imposed by electro-dynamic vibrators. Results demonstrate that imposing the vibrations increases the heat transfer coefficient remarkably, while decreases the nanoparticles deposition. Heat transfer increases by increasing the nanofluid temperature, mass flow rate, nano fluid mass fraction and vibtation level. The most increase in heat transfer coefficient is 100% which is obtained in the test of the lowest mass fraction (0.04%) with the highest vibration level (9 m/s(2)) in the experiment range.