José Matías Garrido

The decarbonisation of the energy sector requires efficient strategies to reduce fuel consumption and greenhouse gas emissions. Organic Rankine Cycles (ORCs) have emerged as a promising technology for waste heat recovery due to their flexibility and ability to operate with low- and medium-temperature heat sources. This work develops a general mathematical framework, grounded in the Helmholtz energy function, to characterise the limiting and optimal efficiency of ORCs equipped with an Internal Heat Exchanger (IHE) when operating with dry and isentropic working fluids. The framework is exemplified using the van der Waals equation of state and extended to real fluids through the PC-SAFT model. Results show that integrating an IHE significantly enhances efficiency for drier working fluids, which expand deeper into the superheated vapour region, enabling greater internal heat recovery. Efficiency gains diminish at condenser temperature extremes, defining operational boundaries where IHE integration is less effective. From a practical perspective, minimising the temperature difference at the IHE outlet (ΔT_min) is critical to maximise performance. The proposed framework provides theoretical insight and practical guidelines for fluid selection and operating strategies in ORC-based waste heat recovery systems.

Side-chain liquid crystal elastomers combine liquid-crystalline order with polymer-network elasticity, enabling anisotropic thermo-mechanical and transport responses. Here, we extend a coarse-grained side-chain liquid crystal polymer model to weakly cross-linked networks generated via a reproducible cross-linking protocol. Mesogens are coupled to a flexible backbone through spacers in end-on or side-on configurations, and we consider three representative attachment sequences: purely end-on, a random sequence containing 60% side-on units, and purely side-on. These architectures give rise to smectic-like, structurally disrupted, and columnar/tubular mesophases, respectively. We first quantify thermally induced strain and memory across the order–disorder transition, showing that network connectivity stabilizes architecture-dependent recovery pathways and can preserve stored anisotropic geometry even when global mesogenic alignment does not spontaneously recover. We then demonstrate that molecular shape and interaction anisotropy for the mesogens induce tunable biaxial ordering, including a robust biaxial nematic state in the purely side-on system under enhanced lateral interactions. Finally, equilibrium Green–Kubo calculations of the full thermal conductivity tensor reveal that anisotropic heat transport is governed not only by director alignment but also by mesophase topology and polymer connectivity. These results establish attachment geometry and interaction anisotropy as key molecular design parameters for programming memory, tuning biaxial correlations, and controlling anisotropic thermal transport in side-chain elastomer networks.

Organic Rankine cycles (ORCs) are one of the most prominent technologies for efficient energy use, from renewable or residual energy sources. These systems are widely used due to their simple design and flexibility. One interesting addition to an ORC is a thermal energy accumulator (TEA), which can improve the energy utilization efficiency. This contribution analyzes the thermal and exergetic efficiency changes when a TEA is added to an ORC. Seven novel deep eutectic solvent (DES)-based phase-change materials (PCMs) are studied and compared with paraffin wax used as a benchmark compound. The ORC uses ten different working fluids (WF), including fluorinated gases and hydrocarbons (HCs). The results show that R1233zd and n-pentane are the working fluids reaching the highest thermal and exergetic efficiency, while choline chloride plus suberic acid and choline chloride plus 4-hydroxybenzoic acid are the best PCMs, far exceeding the exergetic performance of paraffin wax. Furthermore, adding a TEA improves the quality of energy delivery, increasing the exergetic efficiency by up to 95%. These findings highlight the practicality of using hydrocarbons in ORCs in conjunction with TEAs. Additionally, the analysis indicates that PCMs with a higher-melting-temperature and fusion enthalpy offer the most promising solution for ORCs with TEAs, thereby providing valuable insights for the design and optimization of ORC systems.

Hydrotropy is a phenomenon where an amphiphilic molecule (i.e., the hydrotrope) is able to enhance the aqueous solubility of a hydrophobic solute. Understanding the molecular mechanisms behind this phenomenon is crucial to designing new hydrotropes aimed at enhancing the aqueous solubility of specific target solutes. This study investigates the hydrotropic behavior of 1,2-alkanediols in enhancing the aqueous solubility of syringic acid using molecular dynamics (MD) simulations. The analysis carried out here employs several computational methods, including Kirkwood-Buff integrals, solvation free energies, radial distribution functions, and hydrogen bonding number. The solvation free energy results reported in this work help explain the thermodynamic favorability of syringic acid solubilization in the presence of 1,2-alkanediols, aligning with experimental trends. In addition, MD simulations reveal a pronounced affinity between syringic acid and 1,2-alkanediols, particularly at low hydrotrope concentrations. This high affinity is driven by the alkyl chain of each hydrotrope when water is the main solvent, resulting in an increase in the solubility of the solute as the length of the hydrotrope alkyl chain increases. However, a shift in the solubilization mechanism is seen when water is no longer the main solvent, with the hydrogen bonding capabilities of the hydrotrope playing a larger role than its alkyl chains. Under low water concentration conditions, longer alkyl chains in the hydrotrope have difficulty forming hydrogen bonds, leading to an opposite trend compared to lower hydrotrope concentrations. This different behavior with composition results in a maximum solubility for systems with long alkyl chains at intermediate hydrotrope concentrations.

Optimizing the liquid reaction phase holds significant potential for enhancing the efficiency of biocatalytic processes since it determines reaction equilibrium and kinetics. This study investigates the influence of the addition of deep eutectic solvents on the stability and activity of α‐chymotrypsin, a proteolytic enzyme with industrial relevance. Deep eutectic solvents, composed of choline chloride or betaine mixed with glycerol or sorbitol, were added in the reaction phase at various concentrations. Experimental techniques, including kinetic and fluorometry, were employed to assess the α‐chymotrypsin activity, thermal stability, and unfolding reversibility. Atomistic molecular dynamics simulations were also conducted to assess the interactions and provide molecular‐level insights between α‐chymotrypsin and the solvent. The results showed that among all studied mixtures, adding choline chloride + sorbitol improved thermal stability up to 18 °C and reaction kinetic efficiency up to two‐fold upon adding choline chloride + glycerol. Notably, the choline chloride + sorbitol system exhibited the most substantial stabilization effect, attributed to the surface preferential accumulation of sorbitol, as corroborated by the computational analyses. This work highlights the potential of tailoring liquid reaction phase of α‐chymotrypsin catalyzed reaction using neoteric solvents such as deep eutectic solvents to enhance α‐chymotrypsin performance and stability in industrial applications.