Comparison of Heat Transfer Enhancement Techniques in Latent Heat Storage

Abstract

Latent Heat Energy Storage (LHES) using Phase Change Materials (PCM) is considered a promising Thermal Energy Storage (TES) approach as it can allow for high levels of compactness, and execution of the charging and discharging processes at defined, constant temperature levels. These inherent characteristics make LHES particularly attractive for applications that profit from high energy density or precise temperature control. Many novel, promising heat exchanger designs and concepts have emerged as a way to circumvent heat transfer limitations of LHES. However, the extensive range of experimental conditions used to characterize these technologies in literature make it difficult to directly compare them as solutions for high thermal power applications. A methodology is presented that aims to enable the comparison of LHES designs with respect to their compactness and heat transfer performance even when largely disparate experimental data are available in literature. Thus, a pair of key performance indicators (KPI), ΦPCM representing the compactness degree and NHTPC, the normalized heat transfer performance coefficient, are defined, which are minimally influenced by the utilized experimental conditions. The evaluation procedure is presented and applied on various LHES designs. The most promising designs are identified and discussed. The proposed evaluation method is expected to open new paths in the community of LHES research by allowing the leveled-ground contrast of technologies among different studies, and facilitating the evaluation and selection of the most suitable design for a specific application.

Numerical and Experimental Investigation of Wire Cloth Heat Exchanger for Latent Heat Storages

“…For the performance of heat exchangers, different parameters are described in literature. Next to the mean thermal power [27], the mean effectiveness [17], combined parameter like thermal power normalized to temperature step and heat transfer surface [27] or overall heat transfer coefficient to total volume [28] are used. Similarly, Lazaro et al describe in [36] the mean thermal power normalized to storage volume and temperature difference.…”

“…The investigated plate heat exchanger was rated to be not adequate for applications as it contains only a small amount of PCM due to the narrow channel structure in between the plates. A more extensive comparison of different technologies of heat transfer enhancement was done by Delgado et al based on data provided in literature [28]. As a performance parameter, a normalized heat transfer coefficient is introduced.…”

Special Issue “Advanced Phase Change Materials for Thermal Storage”

“…The second paper presented a methodology that allowed comparing latent heat energy storage (LHES) modules with different designs with respect to their compactness and heat transfer performance [2]. Nowadays, many novel and promising heat exchanger designs and concepts have emerged, aiming to enhance the heat transfer inside LHES devices.…”

Flow Field Simulation and Measurement in Packed Beds Based on 4D‐X‐Ray Computed Tomography

“…For physical processes such as absorption and leaching, the packed bed provides an extended interfacial surface between liquid and solid phases, to achieve the very high mass transfer rates 11. For thermal energy storage, on the other hand, the packed bed acts as an energy storage medium, where energy is transferred to the solid particles from the surrounding heat transfer fluid by convection and conduction mechanisms 12–16. As an example, the solid bed can be made up of encapsulated phase change materials packed in random fashion, thereby creating a latent heat thermal energy storage system 17.…”