Feature Papers of Thermo in 2023

The discrepancy between the calculated (CBS-4M/Jenkins) and experimentally determined enthalpies of formation recently reported for the 2:1 salt TKX-50 raised the important question of whether the enthalpies of formation of other 2:1 C, H, N, O salts calculated using the CBS-4M/Jenkins method are reliable values. The standard (p° = 0.1 MPa) enthalpy of formation of crystalline guanidinium 5,5′-azotetrazolate (GZT) (453.6 ± 3.2 kJ/mol) was determined experimentally using static-bomb combustion calorimetry and was found to be in good agreement with the literature’s values. However, using the CBS-4M/Jenkins method, the calculated enthalpy of formation of GZT was again in poor agreement with the experimentally determined value. The method we used recently to calculate the enthalpy of formation of TKX-50, based on the calculation of the heat of formation of the salt and of the corresponding neutral adduct, was then applied to GZT and provided excellent agreement with the experimentally determined value. Finally, in order to validate the findings, this method was also applied to predict the enthalpy of formation of a range of 1:1 and 2:1 salts (M⁺X⁻ and (M⁺)₂X²⁻ salts, respectively), and the values obtained were comparable to experimentally determined values. The agreement using this approach was generally very good for both 1:1 and 2:1 salts; therefore, this approach provides a simple and reliable method which can be applied to calculate the enthalpy of formation of energetic C, H, N, O salts with much greater accuracy than the current, commonly used method. Full article

Specific heat capacity at constant pressure c_p (J K⁻¹ g⁻¹) is an important thermodynamic property that helps material scientists better understand molecular structure and physical properties. Engineers control temperature (through heat transfer) in physical systems. Differential Scanning Calorimetry (DSC) is an analytical technique that has been used for over fifty years to measure heat capacities with milligram size samples. For existing procedures, such as ASTM E1269−11 (2018), the accuracy of molar heat capacity measurements is typically ±2–5% relative to the literature values, even after calibration for both heat flow and heat capacity. A comparison of different DSC technologies is beyond the scope of this paper, but the causes of these deviations are common to all DSC instruments, although the magnitude of the deviation (observed and accepted) varies with instrument design. This paper presents a new approach (Heat–Cool) for measuring more accurate and reproducible specific heat capacities of materials. In addition to better performance, the proposed method is faster and typically requires no additional calibration beyond the routine calibration of temperature and heat flow, with melting point standards common to all applications of DSC. Accuracy, as used throughout this paper, means deviation from the literature. The estimated standard deviation of repeated measurements of the c_p values obtained with the Heat–Cool technique typically falls in the ±1–2% range. Full article

Medazepam, citric acid and their binary mixtures were studied using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR) for thermal and structural properties. The DSC data show a simple eutectic peak at 370 K. To determine the exact mole fraction at which the eutectic occurs, Tamman’s triangle was used. The obtained results show that the eutectic mixture appears at a molar fraction of medazepam of approximately 0.85. The excess thermodynamic functions G^E, S^E and μ^E were calculated, and the results were interpreted to evaluate the interactions that occur between the components of the mixture. The FTIR results were used to confirm the eutectic formation. Solubility tests in deionized water show a 40-times increase in the medazepam solubility from the eutectic mixture, from 0.73 μg/mL to 28.61 μg/mL. However, further tests showed that the acidic character of the sample was the main factor responsible for this increase. Full article

Communities operating urban greenhouses need affordable solutions to reduce their heating consumption. The objective of this study was to compare the ability of different simple ground-based solutions to reduce the heating energy consumption of relatively small urban greenhouses operated all year round in a cold climate. An urban greenhouse located in Montreal (Canada) and its thermal interactions with the ground were modeled with the TRNSYS 18 software. The following greenhouse scenarios were simulated: partially insulating the walls, partially burying the greenhouse below the ground level, reducing the inside setpoint temperature, and using an air–soil heat exchanger (ASHE) or a ground-coupled heat pump (GCHP). The heat exchangers for the last two cases were assumed to be located underneath the greenhouse to minimize footprint. The results showed that reducing the setpoint temperature by 10 °C and burying the greenhouse 2 m below the surface has the most impact on fuel consumption (−33% to −53%), while geothermal systems with a limited footprint (ASHE and GCHP) can reduce the fuel consumption by 21–35% and 18–27%, respectively, depending on the soil thermal conductivity and ground heat injection during summer. The scenarios do not provide the same benefits and have different implications on solar radiation availability, growth temperature, electrical consumption, and operation that must be considered when selecting a proper solution. Full article

Group contribution (GC) methods to predict thermochemical properties are eminently important to process design. Following earlier work which presented a GC model in which, for the first time, chemical accuracy (1 kcal/mol or 4 kJ/mol) was accomplished, we here discuss classes of molecules for which the traditional GC approach does not hold, i.e., many results are beyond chemical accuracy. We report new ring-strain-related parameters which enable us to evaluate the heat of formation of alkyl-substituted cycloalkanes. In addition, the definition of the appropriate group size is important to obtain reliable and accurate data for systems in which the electron density varies continuously but slowly between related species. For this and in the case of ring strain, G4 quantum calculations are shown to be able to provide reliable heats of formation which provide the quantitative data which we can use, in the case of absence of experimental data, to establish group and nearest-neighbour interaction parameters to extend the range of applicability of the GC method whilst retaining chemical accuracy. We also found that the strong van der Waals that overlap in highly congested branched alkanes can be qualitatively investigated by applying DFT quantum calculations, which can provide an indication of the GC approach being inappropriate. Full article

In recent years, the European Union’s legislation about sustainable development has promoted the gradual decarbonization of all industrial sectors, pushing towards the final goal of a carbon-neutral European glass industry in 2050. Moreover, the COVID-19 pandemic, the war in Ukraine and the consequent natural gas supply crisis have led to significant increases in the costs of traditional energy commodities and CO₂ emission allowances. In this scenario, the European glass industry, which is both an energy-intensive sector and a large emitter of CO₂, needs to reduce its specific energy consumption, change its energy sources and decarbonize its production process. In order to understand and support this metamorphosis of the glass industry, the follwing questions must be answered: are the technologies reported in scientific publications merely theoretical exercises, or can they be adopted by the industry? In what timeframe can they be adopted? The aim of this study is to review consolidated and emerging technologies applicable to the glass industry and investigate which ones can be implemented in the short or medium term to reduce energy consumption and CO₂ emissions related to the glass production process. This study is based on a review of the literature, the materials presented in technical conferences and the opinions of interviewed experts. This study showed that the literature is not very substantial, lacking detailed information on technologies and their effects in terms of energy savings or emissions. More information can be found in the proceedings of selected specialist conferences. This study found that, on one hand, some technologies are mature and only adopted when economically viable, and appropriate boundary conditions are available; the state of the art regarding these technologies was already extensively covered in past publications (e.g., cullet pre-heating). On the other hand, there are many promising technologies in the research or testing phase (i.e., steam methane reforming, process electrification, use of hydrogen); in-depth studies about them are limited due to the novelty of the solutions that they propose or not available due to industrial secrecy issues. In addition to periodicals and specialized conferences, interviews were carried out with managers and technicians from industry, as well as technicians from the Italian glass research institute and industrial machinery producers (especially melting furnaces). The interviews represent added value of this publication, useful in helping us to truly understand the state of the art and degree of readiness of the technologies identified. In addition, the production values of the glass industry were studied: our research confirmed that the most important sub-sectors are flat and container glass, as well as the largest glass-producing nations/continents. Finally, a review of specific energy consumption and CO₂ emissions indexes was carried out. Full article

In recent years, there has been an increase in the use of renewable energy resources, which has led to the need for large-scale Energy Storage units in the electric grid. Currently, Compressed Air Energy Storage (CAES) and Pumped Hydro Storage (PHES) are the main commercially available large-scale energy storage technologies. However, these technologies are restricted geographically and can require fossil fuel streams to heat the air. Thus, there is a need to develop novel large-scale energy storage technologies that do not suffer from the abovementioned drawbacks. Among the in-development, large-scale Energy Storage Technologies, Pumped Thermal Electricity Storage (PTES), or Pumped Heat Energy Storage, stands out as the most promising due to its long cycle life, lack of geographical limitations, the absence of fossil fuel streams, and the possibility of integrating it with conventional fossil-fuel power plants. There have been a number of PTES systems proposed using different thermodynamic cycles, including the Brayton cycle, the Rankine cycle, and the transcritical Rankine cycle. The purpose of this paper is to provide a comprehensive overview of PTES concepts, as well as the common thermodynamic cycles they implement, indicating their individual strengths and weaknesses. Furthermore, the paper provides a comprehensive reference for planning and integrating various types of PTES into energy systems. Full article

3D-RISM-KH molecular solvation theory based on statistical mechanics has been an engine of the multiscale methods framework, which also includes molecular simulation techniques. Its applications range from the solvation energy of small molecules to the phase behavior of polymers and biomolecules. Molecular solvation theory predicts and explains the molecular mechanisms and functioning of a variety of chemical and biomolecular systems. This includes the self-assembly and conformational stability of synthetic organic rosette nanotubes (RNTs), the aggregation of peptides and proteins related to neurodegeneration, the binding of ligands to proteins, and the solvation properties of biomolecules related to their functions. The replica RISM-KH-VM molecular solvation theory predicts and explains the structure, thermodynamics, and electrochemistry of electrolyte solutions sorbed in nanoporous carbon supercapacitor electrodes, and is part of recent research and development efforts. A new quasidynamics protocol couples multiple time step molecular dynamics (MTS-MD) stabilized with an optimized isokinetic Nosé–Hoover (OIN) thermostat driven by 3D-RISM-KH mean solvation forces at gigantic outer time steps of picoseconds, which are extrapolated forward at short inner time steps of femtoseconds with generalized solvation force extrapolation (GSFE). The OIN/3D-RISM-KH/GSFE quasidynamics is implemented in the Amber Molecular Dynamics package. It is validated on miniprotein 1L2Y and protein G in ambient aqueous solution, and shows the rate of sampling 150 times faster than in standard MD simulations on these biomolecules in explicit water. The self-consistent field version of Kohn–Sham DFT in 3D-RISM-KH mean solvation forces is implemented in the Amsterdam Density Functional (ADF) package. Its applications range from solvation thermochemistry, conformational equilibria, and photochemistry to activation barriers of different nanosystems in solutions and ionic liquids. Full article