Improving heat transfer is a critical goal in many engineering fields, from electronics cooling to large-scale power generation. One of the most important applications is in solar ponds, which capture and store solar energy as heat in large bodies of water. To extract this energy efficiently, a special type of heat exchanger is needed. A Spiral Tube heat exchanger is an excellent choice because its coiled design provides a very large surface area in a very compact volume. To push the performance even further, modern engineering uses nanofluids. A nanofluid is a base fluid, like water, that contains tiny, suspended nanoparticles of a material with high thermal conductivity. This project explores a Nanofluid in Spiral Tube CFD simulation to see how a special water-graphene/platinum nanofluid can dramatically improve heat absorption. The entire study is based on the methods and data from the high-impact paper “Application of nanofluid to improve the thermal performance of horizontal spiral coil utilized in solar ponds” published in the Renewable Energy journal [1].

• Reference [1]: Khodabandeh, Erfan, et al. “Application of nanofluid to improve the thermal performance of horizontal spiral coil utilized in solar ponds: geometric study.” Renewable Energy122 (2018): 1-16.

Figure 1: The 3D geometry of the spiral tube used for the solar pond heat exchanger simulation.

Simulation Process: Modeling Advanced Heat Transfer in ANSYS Fluent

The first step in this Spiral Tube Fluent simulation was to create the complex, curved geometry using SpaceClaim. Because of the constant curvature, generating a high-quality mesh is challenging. We used Fluent Meshing to create a very fine grid of 5,704,311 elements to accurately capture the flow physics. The simulation was set up using a single-phase approach to model the nanofluid. The flow regime was defined as Laminar due to the low Reynolds number.

The boundary conditions are simple but critical: the nanofluid enters the tube at 34°C (307.1 K), and the outer wall of the tube is held at a constant hot temperature of 60°C (333.15 K). The most important part of the setup was defining the nanofluid’s properties. Its density, thermal conductivity, specific heat, and viscosity are not constant; they all change with temperature. These temperature-dependent properties were accurately programmed into Fluent to match the experimental data from the reference paper [1].

Figure 2:  The temperature-dependent thermophysical properties of the water-graphene/platinum hybrid nanofluid used in the simulation [1].

Post-processing: CFD Analysis of Heat Through the Spiral

The results of the simulation tell a clear story of superior thermal performance. The velocity field, shown in Figure 3, reveals a smooth and stable laminar flow pattern throughout the entire length of the spiral tube, with speeds peaking at a gentle 0.01941 m/s. This stable flow is the perfect vehicle for the heating process, as it ensures that the nanofluid moves predictably without any disruptive turbulence. This allows every particle of the fluid to have a long and consistent residence time, giving it the maximum opportunity to absorb thermal energy from the hot tube walls.

Figure 3: Contours of a) temperature and b) velocity, illustrating the effective heating within the stable laminar flow of the Spiral Tube CFD simulation.

This effective heat absorption is visualized perfectly in the temperature contours. As the nanofluid enters the coil at a cool 307.1 K, it begins its spiral journey. With every turn, its temperature steadily rises as it draws heat from the 60°C walls. The volume rendering vividly shows this progression, with the fluid color changing from blue to green and finally to red as it approaches the outlet. The simulation shows that the fluid reaches a final temperature of 333.2 K at the exit. The most significant achievement of this study is this impressive temperature increase of over 26 K. It is direct proof that the combination of the spiral tube’s large surface area and the nanofluid’s enhanced thermal properties creates a highly efficient heat transfer system, validating why this technology is so promising for applications like solar ponds.