Thermal rectification based on phase transition materials

Significant loss of energy occurs every day in industrialized countries. For instance, in the United States alone, over 3000 TW of waste energy is lost annually. Going with the current trends, future waste energy loss is expected to escalate owing to continuous growth in the manufacturing sector. Interestingly, such huge losses are equivalent to billions of the oil barrel, that can be used in meeting the global energy demands. To this end, reclaiming the lost waste heat have attracted significant attention of researchers, as a way of solving the global energy crisis. Energy scientists proposed developing solid waste thermal devices as a potential and promising solution for recovering the waste heat.

Among the available devices, one stands out. A thermal diode which only allows heat flow in one direction has a great potential for efficient energy harvesting and heat controlling. Consequently, thermal rectification can be achieved not only at bulk scale but also at nanoscale levels. Recently, phase change materials have been used for controlling thermal flux due to their phase transition capability. This further permit control of the thermal conductivity either in the first order or second order transitions. However, thermal diodes based on organic phase transition materials have exhibited low thermal rectification factors. Therefore, the need to maximize their rectification factors to enhance their performance in various systems is highly recommended.

Recently, the Group of Embedded Nanomaterials for Energy Scavenging (GENES group) headed by Professor Jaime Alvarez Quintana from Research Center for Advanced Materials S.C. giving continuity to their pioneering works of thermal rectification based on phase transition materials^* (CIMAV) designed and developed a thermal diode based on first and second order phase transition materials. Specifically, neopentylglycol and gadolinium were utilized as first and second order phase transition materials respectively. Their research work co-authored by Dr. J. Leon, and Dr. J. Martinez is currently published in Journal of Materials Science.

In brief, the design entailed a composite of neopentylglycol and gadolinium transition materials which was used to validate the design. Next, the influence of both the transitions and temperature on the rectification factors were examined. Eventually, the authors investigated the feasibility of using the combined effects in fabricating high-performance thermal rectifiers.

The authors recorded a higher thermal rectification factor of 1.45 for the hybrid device as compared to 1.2 recorded in the initial devices that were based only on neopentylglycol. This was attributed to the manifestation of the influence of the transitions along the asymmetric temperature in the heat transfer axis of the thermal device as well as the molecular transformations in neopentylglycol and magnons deactivation in gadolinium. Furthermore, the developed model based on the continuum heat conduction laws indicated similarities in the experimental and predicted behaviors thus showing the accuracy of the model.

In summary, Professor Jaime Alvarez Quintana and the research team successfully fabricated a hybrid thermal diode based on the transition materials. To actualize their study, the results were further analyzed using finite element analysis based on ANSYS, from which the concept proved efficient for developing high-performance thermal rectifiers. In general, the CIMAV study will advance the efforts to reclaim waste heat and use to it produce electricity, an approach that will significantly enhance energy production and utilization.