It is widely recognized among specialists that PCMs (Phase Change Materials) typically have low thermal conductivity, which significantly restricts their commercial use. This study presents alternative, low-cost, yet effective approaches to enhance the average thermal conductivity of a PCM system (a commercially available paraffin wax with a phase change temperature around 40 °C) intended for thermal energy storage. The system contains 600 g of PCM within an annular space around an inner tube, through which heat is either added to or removed from the PCM. Experiments were conducted to assess the effects of water flow rate and temperature, used as the heat transfer fluid, on the system's performance. The flow rate was varied from 2 to 8 L/min, and the temperature was set between 45 and 55 °C. We tested three types of aluminum-based thermal enhancers: a commercial metal foam, a wire mesh, and irregular aluminum flakes (chips) produced as waste from machining processes. The PCM-only sample required the longest time for both charging and discharging, while the PCM with metal foam had the shortest times. The intermediate solutions, using chips and wire mesh, showed moderate phase change times. To evaluate the economic feasibility, we introduced a performance metric based on cost per phase change rate, showing that these two affordable thermal conductivity enhancers could play a vital role in promoting the broader application of latent thermal energy storage technology across various fields.

Among experts, it is well-known that the thermal conductivity of PCMs (phase change materials) is low hence a major limitation for their commercial application. This work proposes alternative, inexpensive, but nevertheless effective solutions to increase the average thermal conductivity of a PCM system (a commercial paraffin wax, having a phase change temperature of about 40 °C) used for thermal energy storage. 600 g of PCM fills an annulus wrapping an inner tube used to either charge or discharge heat to the PCM. The effect of the flow rate and temperature of the water used as heat transfer fluid was experimentally analysed. The flow rate was set to vary between 2 and 8 l min^-1 and the temperature between 45 and 55 °C. We tested three different aluminum-based thermal enhancers: a commercially available metal foam sample, a wire mesh, and irregular flakes (chips) obtained as waste product of machining operations. The PCM-only sample exhibited the longest charging and discharging times, while the PCM + foam sample shortened them the most. The two cost-effective solutions (chip and wire mesh) resulted in intermediate phase change times. A performance indicator, in terms of cost per phase change rate, is proposed to compare different enhancers. It demonstrated that these two cost-effective thermal conductivity enhancing solutions can become a key enabling method to widely deploy latent thermal energy technology widely in many different applications.

The transportation of perishable products is a crucial activity that must be carefully managed along the cold chain. The refrigerated transport aims at ensuring the suitable transportation conditions by maintaining the desired temperature level in the refrigerated compartment. Moreover, the carriage of perishable fresh foodstuffs calls for additional precautions due to the intrinsic metabolic activity of fresh foods which causes them to be highly temperature sensitive. About 30% of fresh products perishes on the route due to the loss of suitable temperature values. Recently, scientists have been focusing their efforts on the development of innovative solutions, which ensure a proper refrigerated products distribution and transportation in a more environmental-friendly and cost-effective way. Hence, in this work, a novel concept of a Latent Thermal Energy Storage (LTES) system consisting of an insulation layer of poly-urethane foam wrapping a second one of Phase Change Material (PCM) is proposed. In particular, the thermal performance is investigated by running numerical CFD analyses in Ansys Fluent. The effect of different product loads (25%-50%-75%) is studied. Besides, the contributions of the heat respiration and diverse food pre-cooling temperatures on the system performance are also analysed. For the long-distance route no door openings nor additional heat infiltrations are considered.