Toroidal tube latent heat exchanger: An experimental study

Concentric shell and tube latent heat exchangers integrated with phase change material (PCM) are widely used in many heat storage/transfer applications specially for building energy management due to their high energy storage density and fair simplicity in design. However, inadequate phase change in such systems reduces the thermal performance. The innovative geometric design is key in addressing this issue and accelerating the phase change process. The present work reports an experimental effort to investigate the progression of the melting process of PCM inside a novel design of toroidal tube embedded in the system as a shell and tube latent heat exchanger. The experimental setup consists of a toroidal enclosure filled with a bio-based PCM (i.e., coconut oil) and a constant temperature bath as a heat exchange environment. Digital images of melting progression and melting front at three different boundary temperatures (high, middle, and low temperature differences) are captured. Moreover, the time dependent temperature at a selected prob. point is also measured during the phase change process. As expected, decreasing temperature difference, decrease the melting rate, as the experiments show that the completed melting times are 20, 32, and 75 min for the high, middle, and low temperature differences. The melting front is sharper and more distinct to track for higher temperature differences as well. To observe the melting pattern and melting front inside the system (cross-sectional area of the tube) better, the melting progression in different selected times in a half-toroidal tube is also investigated. Furthermore, an extensive uncertainty analysis associated with measuring devices is reported.