Le présent article propose tout d’abord une revue sélective dédiée aux travaux internationaux, puis ceux publiés dans International Journal of Thermal Services (ancienne Revue Générale de Thermique). Cette revue est la preuve du grand intérêt pour l’optimisation des moteurs thermomécaniques, mais pas seulement. Ainsi, de nombreux articles sont concernés par d’autres systèmes et procédés, dont les machines à cycle inverse (cryogénie, machines frigorifiques, climatisation, pompes à chaleur), mais aussi les systèmes et procédés thermochimiques (piles à combustible). Nous nous concentrons uniquement sur les moteurs thermomécaniques dont celui de Carnot. Nous proposons ici de revisiter les modèles de moteurs thermomécaniques complétés d’extension du modèle de Carnot, vers le modèle de Chambadal, en insistant sur le rôle fondamental de l’entropie de transfert thermique, conjointement à la production d’entropie rendant compte des irréversibilités internes ou externes au convertisseur. Cette partie reste originale à notre connaissance et génère de nouveaux résultats concernant l’efficacité au sens du premier principe correspondant à la puissance maximale du moteur, ainsi que des aspects plus fondamentaux (équipartition, minimum de production d’entropie).

This paper presents a comprehensive experimental study of gas-gas flows inside a bitubular (shell-and-tube) heat exchanger (HEX) subjected to various transient conditions, namely (1) increasing or decreasing the internal hot fluid temperature, (2) increasing or decreasing the mass flow rate of the external cold fluid by step variation. Surprisingly, there are very few results in the literature for this last case. However, it seems to be of fundamental interest for some applications. Two types of quantity, the temperatures of the fluids and the heat fluxes exchanged in the HEX, are subject to transient conditions, with a range of time constants from 20 to 80 s. A comparison of experimental results with the main existing analytical model proposed in the literature, essentially validated with liquid-liquid flows, is performed. Deviations from analytical models are given as uncertainties of the time constants. It is shown that one temperature time constant is not suitable for the gas-gas flows. Extension of the results to the heat fluxes responses of the HEX is also performed and confirms the observed results. A sensitivity analysis of the time constants to the main system parameters is reported. It allows the identification of the most important influences and the proposal of primary explanations for the observed results. Local experiments on the same HEX configurations are under development, as well as associated analytical and numerical models. However, the aim is to preserve the simplicity and robustness of the models, to successfully apply them to (real time) control and command of any type of HEX using the equivalent bitubular model. This practical implication, together with the main conclusions of the sensitivity analysis of time constants provides useful insights for modelling and control applications.

This paper presents a continuation of the Chambadal model optimization of the irreversible Carnot engine. We retrieved the results presented in the Special Issue “Carnot Cycle and Heat Engine Fundamentals and Applications II” and enriched them with new contributions that allowed comparing two points of view: (1) the now classical one, centered on entropy production in the four processes of the cycle, which introduces the action of entropy production, with several sequential optimizations; (2) the new one that is relative to an energy degradation approach. The same démarche of sequential optimization was used, but the results were slightly different. We estimate that the second approach is more representative of physics by emphasizing the energy conservation and the existence on an upper and a lower bound in the mechanical energy and power output of the engine.

The quality of the internal microclimate is a very important issue nowadays, considering that people in developed societies spend a good part of their day inside buildings and means of transport. But the poor quality of indoor air has a double effect; on the one hand, it can harm human health, and on the other hand, it can cause the degradation of materials. Thus, the current study considers the potential influence of a number of 20 pollutants on the exhibits, visitors, and employees of a synagogue that is over 140 years old in the Municipality of Oradea (Romania), which today is included in the list of historical monuments and is open to be visited. The monitoring period consisted of 9 months, during which parameters such as temperature, relative humidity, CO concentration, light intensity, concentration of particulate matter, and other pollutants were monitored. All the obtained values were then reported to the international standards in force for each indicator, both regarding the potential for human health and the integrity of the exhibits. The results indicate that the values of most pollutants respect the allowed thresholds, with more or less permitted exceptions. The most problematic are the values of temperature, relative humidity, HCHO, and VOC, which substantially exceed the allowed limits and vary a considerable difference. This can induce additional stress on the exhibits, leading over time to damage and premature aging; in terms of human health, the indoor microclimate can, in rare cases, cause discomfort associated with headaches, dizziness, and irritation, but the potential to cause persistent ailments is quite low. To maintain a clean internal microclimate, preventive conservation through the continuous monitoring of internal parameters as well as the establishment of long-term strategies to stabilize the values of pollutants are necessary actions.

Ce chapitre porte sur la thermodynamique à vitesse finie. Cette démarche qui combine1er et sd principe pour les processus a vitesse finie aboutit à la méthode dite directe. Elle est appliquée aux moteurs de Stirling, Carnot, Otto, diesel .il en résulte une étude analytique de la puissance optimale et l’efficacité du moteur. On insiste sur la production d entropie par forfait ou ratio.

The JETC Conference held in Salerno (June 12-17, 2023) was the opportunity to honor the two centuries anniversary of the booklet publication of Sadi Carnot. The paper reports on a selective review summarizing the evolution of the ideas and concepts proposed by Carnot. We consider mainly: a. The Carnot cycle relative to thermomechanical engine, b. The concept of efficiency (Carnot efficiency), c. The forms of energy (thermal energy or heat, Q, and mechanical energy or work, W), d. The concept of entropy, rediscovered and completed by Clausius. We show the importance of the energy conversion irreversibilities that started to be considered more recently by two methods, namely, the ratio method and the entropy production method. The second approach provides more significant results from a global point of view, also with more local modeling (cycle process modeling). Some examples are given that illustrate the proposal: Carnot cycle in endo-irreversible or exo-reversible configuration, Chambadal modeling, Curzon-Ahlborn modeling. More generally, the modeling is done in the frame of FTT (Finite Time Thermodynamics), FST (Finite Speed Thermodynamics), or FDOT (Finite physical Dimensions Optimal Thermodynamics). Preliminary conclusions and perspectives are proposed.

Ethnographic heritage textiles may be subject to risks generated in particular by various factors in close connection with the microclimate of the storage and exposure areas. In accordance with the current European trends of pest prevention and reduction and response to the infestation/contamination of the cultural heritage, the research direction of this study aimed at investigating the degradation of some women’s clothing items, around 80–100 year-old, made of natural fibres, namely cotton. Throughout this paper, an essential aspect was taken into account for establishing a preventive or curative conservation strategy, namely the characterization of the fabric from which the three shirts are made. Thus, some physical and structural characteristics were determined by making use of different types of analyses: FTIR spectroscopy, the spectra specific for cotton; the microbiological analyses showed the presence of Bacillus subtilis and Rhizobium radiobacter, Staphylococcus aureus and Streptococcus pyogenes, which are not considered pathogenic or toxigenic to humans with the normal function of the immune system.

The old fibers that make up heritage textiles displayed in museums are degraded by the aging process, environmental conditions (microclimates, particulate matter, pollutants, sunlight) and the action of microorganisms. In order to counteract these processes and keep the textile exhibits in good condition for as long as possible, both reactive and preventive interventions on them are necessary. Based on these ideas, the present study aims to test a natural and non-invasive method of cleaning historic textiles, which includes the use of a natural substance with a known antifungal effect (being traditionally used in various rural communities)—lye. The design of the study was aimed at examining a traditional women’s shirt that is aged between 80–100 years, using artificial intelligence techniques for Scanning Electron Microscopy (SEM) imagery analysis and X-ray powder diffraction technique in order to achieve a complex and accurate investigation and monitoring of the object’s realities. The determinations were performed both before and after washing the material with lye. SEM microscopy investigations of the ecologically washed textile specimens showed that the number of microorganism colonies, as well as the amount of dust, decreased. It was also observed that the surface cellulose fibers lost their integrity, eventually being loosened on cellulose fibers of cotton threads. This could better visualize the presence of microfibrils that connect the cellulose fibers in cotton textiles. The results obtained could be of real value both for the restorers, the textile collections of the different museums, and for the researchers in the field of cultural heritage. By applying such a methodology, cotton tests can be effectively cleaned without compromising the integrity of the material.

An improper indoor microclimate has adverse effects on the state of preservation of historical textiles arranged in them, favoring the development of bacteriological microflora. The current study aims to combine traditional and innovative methods for cleaning and preserving a 100-year-old traditional blouse from Bihor, Romania. The material of the blouse was impregnated with 30 and 70 ppm silver nanosuspensions and washed with a substance obtained from boiling natural wood ash (lye). The research goals were to determine the antimicrobial action of lye washing and silver nanoparticles applied to the analyzed textile material and identify the way in which the environmental factors (light) act upon the conservation degree of textile objects impregnated with silver nanoparticles. All these procedures are eco-friendly and do not cause any damage to the constituent material of the fabrics. The use of the hyperspectral imaging technique proved the permeation of both 30 and 70 ppm silver nanosuspensions into the textile, producing changes in the textile’s reflectance spectrum after being treated with them. The results showed anti-bactericidal/fungal properties of both silver nanoparticles and lye. Microbiological analyses revealed that bacterial colonies were reduced to more than 95% in both cases. The antibacterial effect of silver nanoparticles on the textile material of the blouse was maintained throughout the duration of the study, and under normal environmental conditions, the effects would remain active for a long period.

This paper reports on a review on combined heat and power (CHP). A historical examination points out that combined heat and power was primarily used for hot heat valorizing (CHHP). The technological aspects evolved with this configuration first in industrial size. More recently, configuration with cold heat and power production (CCHP) appeared. Then, the immediate extension of this configuration led to trigeneration configuration, providing three useful effects: power and hot and cold heat. We suggest in the paper that progress regarding this last approach remains to be achieved towards the extension of trigeneration to polygeneration, whatever the form of energy and substance (water uses, for example). More generally, we consider that the goal, regarding the energy uses, is the integration of all needs in the design stage of the whole system (design optimization). Then, the evolution of the system in time should be considered, this being the purpose of control command of the optimized concern. This part remains to be developed in the future. Currently, the optimized design is well-started from the thermodynamic point of view with good criterion (efficiency), completed with economic and environmental objectives or constraints, as is reported in the review.

Poor air quality inside museums can have a double effect; on the one hand, influencing the integrity of the exhibits and on the other hand, endangering the health of employees and visitors. Both components can be very sensitive to the influence of the internal microclimate, therefore careful monitoring of the physical parameters and pollutants is required in order to maintain them within strict limits and thus to reduce the hazards that can be induced. The current study considers the determination and analysis of 15 indicators of the internal microclimate in an Art Nouveau museum built at the beginning of the 20th century in the Municipality of Oradea, Romania. The monitoring spanned a period of seven months, between September 2021 and March 2022, targeting three rooms of the museum with different characteristics and containing exhibits with a high degree of fragility. The results show that, although there are numerous indicators that have exceeded the thresholds induced by international standards, the possible negative impact on the exhibits and/or on human health remains moderate. This is due to the fact that, most of the time, exceeding the permitted limits are small or only sporadic, the values quickly returning to the permitted limits. Thus, only 22 of the 212 days of monitoring recorded marginal conditions regarding the quality of the indoor air, the rest having acceptable and good conditions. To improve the indoor conditions, a more careful management is needed, especially regarding the values of temperature, humidity, particulate matters, natural and artificial light, volatile organic compounds (VOC) and formaldehyde (HCHO), which during the measurements recorded high values that fluctuated in a wide spectrum. The obtained results can represent the basis for the development and implementation of long-term strategies for stabilizing the microclimatic conditions in the museum in order to preserve the exhibits preventively and to ensure a clean and safe environment for people.

The digital revolution has been present in our lives more and more since the beginning of the third millennium and until now, has affected the way in which cultural heritage is valued, preserved and passed on. In this context, the present study aims to use digital technologies (digital radiography and Reflectance Transformation Imaging) to contribute to assessing the conservation status of a heritage textile fabric; a traditional women???s shirt about 100 years old from Bihor County (ie). The investigations concerned both the fine details that are not visible to the naked eye, regarding the internal structure of the material and external (damaged areas, embroidery with traditional motifs, etc.). The results obtained show high suitability of the methods used for the analysis performed on historical textiles, having major importance in identifying the visual representation of the weave, the fibres and the surface of the fabric, the deterioration and also the current state of preservation and contributing to the identification of optimal restoration-conservation solutions.

This paper presents a new step in the optimization of the Chambadal model of the Carnot engine. It allows a sequential optimization of a model with internal irreversibilities. The optimization is performed successively with respect to various objectives (e.g., energy, efficiency, or power when introducing the duration of the cycle). New complementary results are reported, generalizing those recently published in the literature. In addition, the new concept of entropy production action is proposed. This concept induces new optimums concerning energy and power in the presence of internal irreversibilities inversely proportional to the cycle or transformation durations. This promising approach is related to applications but also to fundamental aspects.

This paper is the logical follow-up to a work [1] whose results were presented at the 28th French Thermal Congress which was to be held in Belfort in 2020. The model developed at that time is completed in this proposal to consider the specificity of the geothermal heat pump. This is a machine operating upon a mechanical vapor compression cycle, the limit of which is an inverse Carnot cycle. Its specificity consists of a cold loop at the source with the geothermal exchanger and the evaporator, then a hot loop at the sink with the condenser and a floor heat exchanger in the application considered here. We are particularly concerned with the optimal sizing of these heat exchangers through their effectiveness. The parametric sensitivity of this distribution to various boundary conditions is studied, especially by focusing on different conditions at the source: (1) imposed soil temperature, corresponding to a Dirichlet condition, (2) imposed heat flux (including adiabatic case), corresponding to a Neumann condition, (3) imposed mechanical power consumed by the heat pump, and (4) imposed coefficient of performance COP, to all cases being associated a finite thermal capacity in thermal contact with the geothermal exchanger operating in steady-state conditions.

La litte ' rature disponible sur les pompes a` chaleur montre que les mode`les thermodynamiques donnent lieu a` minimisation de la de ' pense e ' nerge ' tique, tre`s souvent dans des configurations endore ' versibles, quelques fois irre ' versibles. La pre ' sente communication revisite en les comple ' tant les mode`les irre ' versibles des pompes a` chaleur, en ajoutant la contrainte de couplage entre le cycle et les re ' servoirs thermiques suppose ' s thermostats, condition essentielle d'existence du cycle. Cette approche conduit a` un ensemble de re ' sultats nouveaux, dont le COP au minimum de de ' pense e ' nerge ' tique. Les conse ' quences fondamentales de cette nouvelle approche montrent par ailleurs les limites du principe d'e ' quipartition de la surface d'e ' change thermique, de meme que de la me ' thode de minimisation de production d'entropie (EGM en anglais).

Monitoring the indoor microclimate in old buildings of cultural heritage and significance is a practice of great importance because of the importance of their identity for local communities and national consciousness. Most aged heritage buildings, especially those made of wood, develop an indoor microclimate conducive to the development of microorganisms. This study aims to analyze one wooden church dating back to the 1710s in Romania from the microclimatic perspective, i.e., temperature and relative humidity and the fungal load of the air and surfaces. One further aim was to determine if the internal microclimate of the monument is favorable for the health of parishioners and visitors, as well as for the integrity of the church itself. The research methodology involved monitoring of the microclimate for a period of nine weeks (November 2020–January 2021) and evaluating the fungal load in indoor air as well as on the surfaces. The results show a very high contamination of air and surfaces (>2000 CFU/m3). In terms of fungal contamination, Aspergillus spp. (two different species), Alternaria spp., Cladosporium spp., Mucor spp., Penicillium spp. (two different species) and Trichopyton spp. were the genera of fungi identified in the indoor wooden church air and Aspergillus spp., Cladosporium spp., Penicillium spp. (two different species) and Botrytis spp. on the surfaces (church walls and iconostasis). The results obtained reveal that the internal microclimate not only imposes a potential risk factor for the parishioners and visitors, but also for the preservation of the wooden church as a historical monument, which is facing a crisis of biodeterioration of its artwork.

Natural antimicrobials can eliminate fungi and prevent the aging of cotton fabrics. While fungi can cause severe infections to the fabric user etc, natural antimicrobials have the advantage of not being toxic to humans. The present study showed that the essential oils of lemon (Citrus limon), lavender (Lavandula angustifolia) and mint (Mentha piperita) have inhibitory effects on yeast and mould spores on a piece of textile from Romanian cultural heritage, “ie”, stored in a space within an ethnographic museum., inhibitory action against Botrytis sp., the inhibitory effect of lemon essential oil on Cladosporium sp. and that of peppermint essential oil on yeast species Rhododtorula mucilaginosa were demonstrated, respectively. Being environmentally friendly, these sources, can be tested on a large scale.

An irreversible Carnot cycle engine operating as a closed system is modeled using the Direct Method and the First Law of Thermodynamics for processes with Finite Speed. Several models considering the effect on the engine performance of external and internal irreversibilities expressed as a function of the piston speed are presented. External irreversibilities are due to heat transfer at temperature gradient between the cycle and heat reservoirs, while internal ones are represented by pressure losses due to the finite speed of the piston and friction. Moreover, a method for optimizing the temperature of the cycle fluid with respect to the temperature of source and sink and the piston speed is provided. The optimization results predict distinct maximums for the thermal efficiency and power output, as well as different behavior of the entropy generation per cycle and per time. The results obtained in this optimization, which is based on piston speed, and the Curzon–Ahlborn optimization, which is based on time duration, are compared and are found to differ significantly. Correction have been proposed in order to include internal irreversibility in the externally irreversible Carnot cycle from Curzon–Ahlborn optimization, which would be equivalent to a unification attempt of the two optimization analyses.

Poor air quality inside museums is one of the main causes influencing the state of conservation of exhibits. Even if they are mostly placed in a controlled environment because of their construction materials, the exhibits can be very vulnerable to the influence of the internal microclimate. As a consequence, museum exhibits must be protected from potential negative effects. In order to prevent and stop the process of damage of the exhibits, monitoring the main parameters of the microclimate (especially temperature, humidity, and brightness) and keeping them in strict values is extremely important. The present study refers to the investigations and analysis of air quality inside a museum, located in a heritage building, from Romania. The paper focuses on monitoring and analysing temperature of air and walls, relative humidity (RH), CO2, brightness and particulate matters (PM), formaldehyde (HCHO), and total volatile organic compounds (TVOC). The monitoring was carried out in the Summer–Autumn 2020 Campaign, in two different exhibition areas (first floor and basement) and the main warehouse where the exhibits are kept and restored. The analyses aimed both at highlighting the hazard induced by the poor air quality inside the museum that the exhibits face. The results show that this environment is potentially harmful to both exposed items and people. Therefore, the number of days in which the ideal conditions in terms of temperature and RH are met are quite few, the concentration of suspended particles, formaldehyde, and total volatile organic compounds often exceed the limit allowed by the international standards in force. The results represent the basis for the development and implementation of strategies for long-term conservation of exhibits and to ensure a clean environment for employees, restorers, and visitors.