(378e) Comparative Study of Graphene/Water Nano-Fluid in a Heat Exchanger System: Modelling and Simulation

The increase in demand for energy and more efficient systems has led to a greater demand of Heat exchanger with better performance. Historically more stress was led on developing high performance heat exchanger systems by working on its geometry. Recently researchers started working on the development of utility fluids which has higher thermal conductivity over the existing ones. Many such alternatives are reported in literature such as Nano-fluids, Dilute Emulsion and Emulsion etc., Nano-fluid is one of the most important solution for the enhancement of the thermal performance of heat transfer systems. Nano-fluids are prepared by suspension of nano particles and liquid in the specific proportion. The main feature of the nano-fluid is its high critical heat flux and boiling, better storage of thermal energy, and most importantly higher heat transfer coefficient. Because of the above mentioned reason the nano-fluid is known to be the most suitable and intelligent heating fluid in the world. With this the search for the better nano-particle started. Previously pure ethylene glycol, water oil etc., were mostly used in heat exchanger as a base fluid. Later on application of nano-fluid was found and it proved to be more promising in decreasing the dimensions of heat exchanger systems. Much time is invested for thermal performance improvement of heat exchanger using high thermally conductive material as a suspended particle such as nitride material, carbon nano tubes or diamond in a nano-fluid.

But with every new technology, there are some cons associated with it. The thermal conductivity of nano-fluid depends on the thermal properties of base fluids and shape, size of the particles suspended in it. The suspended solid nano particles in heat exchanger system significantly affect its performance but at the same time, it increases the pressure drop inside the heat exchanger. There are many reports exist in the literature showing the high thermal performance of Nano-fluid with the negative effect of pressure drop associated with it. The undesired effect of pressure drop reduces the overall system performance. So developing a nano-fluid with high thermal conductivity to counter the effect of equivalent pressure drop can provide the great advantage to its application in industries.

In the search for a nano particle with high thermal conductivity, scientists came with a remarkable material known as Graphene. It has SP2-bonded carbon atom hexagonally arranged with single atom thick sheet. Graphene particles in nano-fluid have 5 to 10 nano meter average thickness. It has a wide application in the field of heat exchange system and is itself one of the biggest breakthrough in the field of research that scientist named it as a miracle material. It has attracted many researchers with its remarkable properties. It has excellent thermal and electrical properties which makes it very useful as a nano-filler, nano-composite and nano-fluids. Recent studies on Graphene reveal that it has a very high thermal conductivity. Thus it shows the higher thermal performance in comparison to other nano particles.

In this paper, the modelling and simulation calculating thermal performance and Pressure drop analysis of a heat exchanger are done using MATLAB. Graphene oxide is taken as a nano particle and is compared with existing nano-fluids like TiO₂ (Titanium Oxide) and Al₂O₃ (Aluminium Oxide). The base fluid is pure water and concentration of nano particles is 0.025%, 0.05%, 0.075%, 0.1%. The two-dimensional steady-state momentum transfer and heat energy consumption by nano-fluids acting as a cooling media are modeled and simulated to compare the results with experimental data. The Reynolds number taken in the range of 3000-40000. The parameter is taken in the temperature range of (20-70)degree Celsius, with L/D ratio of tube dimensions greater than 10, Simulating the modeled equations, the Nusselt number, Peclet number, Pressure drop, friction factor along with the convective heat transfer coefficient is calculated. It is found that the Graphene/water nano-fluid can be used to enhance the thermal performance of heat exchanger without much compromising with the negative effect of the high-pressure drop. In order to validate the model, the result is compared with the experimental results of the existing literature and the result came with simulation is well fitting with the experimental results. Thus the present combination of nano-particle and fluid can be the solution for energy efficient heat transfer systems.