Serpentine heat exchangers use coiled tubes that wind fluids. By increasing fluid-to-fluid contact in a small space, this design maximizes heat transfer surface area. Serpentine heat exchangers are used in HVAC, refrigeration, and industrial operations to control heating and cooling. Their design flexibility and strong thermal performance make them ideal for space- and efficiency-sensitive applications. On account of the reference paper entitled “ Computational assessment of Nano-particulate (Al2O3/Water) utilization for enhancement of heat transfer with varying straight section lengths in a serpentine tube heat exchanger [1]”, a CFD simulation is carried out to model serpentine heat exchanger.

• Reference [1]: Awais, M., et al. “Computational assessment of Nano-particulate (Al2O3/Water) utilization for enhancement of heat transfer with varying straight section lengths in a serpentine tube heat exchanger.” Thermal Science and Engineering Progress20 (2020): 100521.

Figure 1- Serpentine schematic taken from the Kaltra website

Simulation Process

The geometry is primarily modeled in Design Modeler from a sweep of a circular cross-section along a spiral curve. ANSYS Meshing can ease the meshing process, considering a boundary layer in the wall`s vicinity and 115404 tetrahedral cells. While 298K water flows inside a hot serpentine heat exchanger (324K), it is exposed to hot regions along the way.

Figure 2: Geometric dimensions and mesh of serpentine tube

Post-Processing

The serpentine heat exchanger’s CFD simulation results show important thermal performance features. With a temperature rise of 20.13K, the temperature contours show that the temperature rises steadily from 298K at the inlet to 318.13K at the exit. The velocity contour plot, which shows a range of velocity from 0 to about 9.23e-01 m/s, shows that the fluid is mixing well through the serpentine shape. The 115,404 tetrahedral cells in the mesh provide enough detail to show the complicated flow patterns and heat transfer processes happening inside the curved passages.

The temperature graph clearly shows how the thermal gradient changes along the curving path, with the coolest area (blue, about 298K) at the entrance and warmer areas (yellow-red, about 318K) moving away. The long flow path of the serpentine configuration increases the heat transfer surface area within a small footprint. This is shown by the fact that the temperature rises evenly through each bend. This geometric optimization improves the efficiency of heat transfer, and the modeling shows that the design works for situations where big temperature changes are needed in a small space.

Figure 3: Velocity & Temperature pattern through the serpentine heat exchanger CFD simulation