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Abstract: Psychrometric-like charts for the energy analysis of VOC removal or recovery by means of combined adsorption and condensation were developed. These charts make use of conventional psychrometric parameters: dry-bulb temperature, specific mass content—or alternately mole fraction—, degree of saturation (relative “humidity”), enthalpy, etc., for toluene-nitrogen mixtures. In addition, they include information on the adsorption equilibrium, and particularly the adsorbed-phase enthalpy, in order to characterise the adsorbers behaviour. The graphical representations of unitary operations occurring in VOC treatment processes are presented: VOC condensation on a cool coil, adsorption or regeneration of an adsorber. This methodology is applied to a case study based on an indirectly heated and cooled adsorber and a heat pump. A proper design of this integrated process allows to use half of the heat available at the heat pump condenser, which is usually wasted. [Copyright &y& Elsevier]

Abstract: The performances of a recently developed TSA process for gaseous pollutant treatment, based on indirect heating and cooling by means of an internal heat-exchanger, have been investigated both numerically and experimentally. Heating is carried out by condensing steam, and cooling by water circulation. The cycle performances are usually better than those of competing processes, but with increased heat consumption. The sensitivity of the performances to the regeneration temperature and purge flow rates is discussed. Lastly, it is shown that in the conditions of an adsorber scaled-up to a typical practical size including a mass of adsorbent 1000 times higher than in the laboratory column, the specific heat consumption is in the same range as conventional TSA processes. [Copyright &y& Elsevier]

Most studies on industrial heat decarbonization by electrification focus on energy and greenhouse gas emissions. However, there are additional potential environmental impacts to be considered to make a fair comparison. The aim of the proposed work is therefore to highlight the benefits and drawbacks of switching to electricity, using life cycle assessment (LCA) methodology to explore more environmental issues. In addition, in order to evaluate the environmental sustainability of this transformation, the LCA results are compared with sustainability thresholds defined with two different methods, on a global scale using the "sustainable levels" concept. The first method is based on the current environmental impacts of industrial processes, while the second considers the economic added value. Industrial heat production levels for the Danish and French food industries are used as case studies. The results show a large number of environmental trade-offs associated with electrification, some of which are leading to unsustainable levels. Sustainability thresholds based on economic added value ensure a fairer distribution between sectors, in particular by preventing the most virtuous sectors and processes from being penalized. [ABSTRACT FROM AUTHOR]

Waste Heat Recovery in the industrial sector often requires to upgrade the temperature of the heat fluxes in order to make them useful for the process. Thermochemical Heat Transformer (THT) and especially 2-salt configuration, can play a major role as they can achieve high temperature lift when compared to alternative technologies. Despite various developments in recent years, this technology still suffers from several issues to make it fully attractive: rapid and reliable reactive salt selection, heat and mas transfer intensification, coupling with process heat demand, etc. This work is focused on a new methodology to achieve a rapid screening of salt pairs for a given application (i.e. source temperatures). Four criteria, based on thermodynamic considerations, are proposed allowing for an example to go from 4290 possibilities to only three most promising pairs at the end. A second part is dedicated to dynamic aspect considerations, exploring the robustness of the solution towards changes in heat transfer and kinetic coefficients as well as to changes in heat source temperatures. Knowledge on this last aspect is of great importance to achieve efficient integration to cover process heat demand. • A new methodology to achieve a screening of salt pairs for 2-salt THT is developped • 3 promising reactive pairs from 4290 candidates are selected. • A 0D dynamic model of 2-salts THT is developed and validated. • The relation between the driving forces and the THT heat power is highlighted. [ABSTRACT FROM AUTHOR]

To decarbonize the heating sector, the 4th and 5th generations of district heating networks have been identified as promising solutions. They offer superior energy efficiency, economic viability, and environmental advantages compared to decentralized, individual heating systems. However, they raise several challenges concerning their design and control optimization due to their size and the operational constraints of the production systems involved such as inertial heat generators, intermittent renewable energy sources and thermal energy storage. As a result, numerical simulations of these networks are computationally heavy which makes fast optimal control a complex and challenging task. A common strategy to address this limitation is to formulate reduced order models or to establish fast and yet accurate surrogate models. In this work, we present a novel surrogate modeling framework to rapidly predict district heating networks transients. Our model is based on a physics-guided spatio-temporal convolutional graph neural network. While similar work focused mainly on the prediction of thermal loads, this paper tackles the challenge of simulating complex and non-linear behaviors of the distribution network of district heating systems. The results show that the simulation time using our model is 99% less than a physical simulator while maintaining a high accuracy. In addition, we have conducted an ablation study and a residual analysis to test the robustness of the proposed model. Furthermore, the generalization ability of our approach is assessed by evaluating it against different district heating network topologies. • A spatio-temporal graph neural network is used to predict district heating network dynamics. • A framework enables interaction between physical simulator and surrogate model. • The model achieves high accuracy and captures diverse network dynamics. • Computation time reduction unlocks global optimization with full dynamics of the system. [ABSTRACT FROM AUTHOR]

Power generation faces the challenge of reducing its greenhouse gas emissions without shifting the burden to other environmental impacts. Energy and exergy-based environmental indicators have proven to some extent to be effective environmental proxies for the current energy mix but the robustness of this approach has barely been discussed in the frame of energy transition scenarios. Hence, the aim of this study is to analyse their relevance in the context of decarbonisation of industrial heat through electrification. To this end, we investigate the potential relationships between two different energy indicators and environmental indicators using life cycle assessment (Ecoinvent database, 16 environmental indicators, 2 energy indicators) for 28 pairs of energy sources shifting for the production of 1 kWh of electricity. For the reference French case, no similar trends across all sources of energy, for given environmental and energy indicators are found neither between all environmental and energy indicators. The extension to other cases is discussed, leading to the same conclusion. These results highlight the need for a multi-criteria assessment to evaluate the impacts of industrial heat in a context of intensive process electrification, which will be country dependent because of the various strategies in achieving net-zero electricity mix. [Display omitted] • Investigation of correlations between energy, exergy and environmental indicators. • Limited correlations found between energy and environmental indicators for decarbonated energy. • Electrification contributes to decarbonisation, but comes with environmental trade-offs. • Need for a multi-criteria approach for a complete analysis of the impact of electrification. [ABSTRACT FROM AUTHOR]

A series of experiments were carried out on an indirectly heated pilot scale rotary kiln. These experiments aimed at recording, while the solids flow, the temperature profiles of the freeboard gas, the solid particle bulk and the wall, as well as the power supplied for heating, over a range of operating conditions. Based on these data, the experimental wall-to-solid heat transfer coefficient was determined through an energy balance. The effects of operating conditions, namely rotational speed, filling degree, lifter shape and controlled temperature, on the heat transfer coefficient are discussed. A model based on dimensional analysis is proposed to calculate the wall-to-solid heat transfer coefficient for low to medium heating temperatures (100–500 °C). The experimental and calculated results are in good agreement. The experimental results are also compared to the predictions of some existing models. While the predictions are within a reasonable order of magnitude with regard to the experimental results, these models fail to represent actual variations with operating conditions satisfactorily. [ABSTRACT FROM AUTHOR]

In this paper, an exergoeconomic approach is proposed to assess the impact of the integration of a Borehole Thermal Energy Storage (BTES) in the existing district heating of the city of Chateaubriant in France. To do so, a dynamic simulation is run over ten years of operation. The model includes a new approach for cost calculation of short-term thermal storage, which is extended to seasonal BTES. The analysis of the system operation at yearly and daily scales revealed several issues. Hence, without redesigning the existing installation, it was found that a non-comprehensive control strategy results in an increase of fossil fuel share by 1.2%. At the BTES scale, from an exergoeconomic point of view, the charging stage is found particularly sensitive to the dynamic. For example, charging the BTES at low temperature increases of the specific cost of the heat stored. Hence, it is shown that some exergoeconomic indicators, like the specific cost of stored heat, could be relevant for designing and operating heating systems with borehole thermal energy storage. • Impact of seasonal thermal energy storage on an existing solar district heating is assessed. • A dynamic exergo-economic approach is proposed to identify the inefficiencies. • Yearly performance decrease because of improper operation between storage and generators. • Average and standard deviation values illustrate the wide spread distribution of indicators. • Several inefficiencies are identified during seasonal storage charging mode. [ABSTRACT FROM AUTHOR]

The aim of this paper is to study the influence of the thermodynamic conditions on the consequences of the rapid vaporization of C O 2 . This study is motivated by the lack of experiments characterizing those transient phenomena over a wide range of thermodynamic conditions. For that purpose, a complete test section was designed based on the Joule effect to deliver the energy discharge in pressurized C O 2 . The transient deposit of power in the liquid have two consequences: the generation of a pressure wave (of several bars) due to the transient creation of vapour, and a slow compression in the test section due to the creation and expansion of vapour (few cm 3). This experiment had been performed 200 times over a wide range of thermodynamic conditions : static pressure between 2.55 MPa and 6 MPa, liquid temperature between −12 ° C and 22 ° C and energy transmitted to the fluid between 70 J and 310 J. From this databank, significant tendencies are extracted from the maximum of overpressure generated and the mass of vapour created function of the test conditions. Lastly, a simple model permits to predict the first pressure peak as a function of the test conditions. This work, motivated by the so-called Fuel Coolant Interaction (FCI) nuclear safety related problematic, brings consistent data allowing to better characterize the small scale processes for such transient vaporization phenomena. [Display omitted] • Thermal shock implies the rapid creation of a layer of vapour. • The increase of pressure depends on the dynamics of creation of vapour. • The violence of the phenomena decreases with the pressure and the sub-cooling. • Peak pressure observed at onset of vapour formation is related to expansion dynamics of a vapour layer. [ABSTRACT FROM AUTHOR]

Compact evaporators like plate heat exchangers can play a significant role in reducing the investment cost of low cooling power sorption systems. If water is used as refrigerant, their design remains mainly empirical. The objective of this paper is thus to investigate the specific characteristics of water pool boiling in narrow channel at subatmospheric pressure in order to acquire the fundamental knowledge needed to improve the design of compact evaporators in these sorption systems. An experimental test setup was thus designed and built to study water pool boiling in narrow channel at subatmospheric pressure (from 5 to 1.2 kPa) on a vertical heated copper disk. The influence of the thickness of the narrow channel and of the pressure on the heat transfer is discussed. As the pressure and the channel thickness decrease the occurrence of a specific subatmospheric pool boiling regime is observed, degrading heat transfer coefficient. Nevertheless, the general trends of evolution are in agreement with those generally observed in the literature: heat transfer is enhanced as the thickness of the narrow channel decreases but, depending on the pressure, decreasing too much the channel thickness could lead to a deterioration of the heat transfer coefficient. A particle image velocity (PIV) device was implemented to the experimental setup in order to highlight the effect of the wake-induced flow on the heat transfer. [ABSTRACT FROM AUTHOR]

• Climate change footprint is studied taking the life cycle of the whole energy system. • Mechanical heat pumps (MHP) are considered as alternatives to natural gas boilers. • MHP can help to achieve the Paris Agreement targets in EU countries by 2050. • Energy price ratios to make MHP competitive are identified for different performance. • Impact of carbon tax on MHP competitiveness is assessed for several EU members. The recovery of waste heat represents a promising opportunity to reduce greenhouse gas (GHG) emissions from industrial sectors. The current development of heat recovery technologies can provide industries with several options for retrofitting their heat generation systems. Although past studies estimated the resulting savings in GHG emissions for specific industries or facilities, work is still needed to fully substantiate the expected benefit and the competitiveness of these alternatives, taking into account data at country scale (e.g. long-term reduction targets, energy cost, etc.). Hence, in this study, a new methodology is developed to determine the minimum conditions for waste heat recovery solutions to enable compliance with the targets from the Paris Agreement, taking 2030 and 2050 as reference years. It is applied to several industrial sectors for 24 EU countries, focusing on mechanical heat pump solutions (MHPs). Results indicate that all countries are compliant in 2050 for MHP integration with low temperature lift (like ammonia production) and 21 countries are compliant for high temperature lift (like food industry). The main constraint to the development of the MHP technology in 2030 is found to be economic, while in 2050, the main barrier for countries that do not reach the reduction targets is a too high carbon intensity of electricity generation. To accommodate the relatively long lifetime of the heat production system, the future MHP roadmap should therefore anticipate these potential barriers including carbon footprint of electricity network, working fluids and gas to electricity price ratio. In addition to meeting the 2030 requirements by a large margin, this strategy would factor in constraints associated with the long-term investments in MHPs. To further expand such foresight analysis, our methodology can be duplicated to other technologies than MHPs, so it can help industry decision-makers select the most suitable waste heat recovery options for a given industrial process in a specific country. [ABSTRACT FROM AUTHOR]

The objective of this paper is to underline the specific characteristics of water pool boiling at subatmospheric pressure compared to atmospheric pressure in order to optimize the design of evaporators dedicated to sorption systems. An experimental test set up was built to characterize the pool boiling of water at pressure down to 0.85 kPa. The major specificity of the pool boiling at low pressure lies in the non homogeneity of the boiling environment, both in terms of pressure and subcooling degree. This non-homogeneity makes really different boiling phenomena than those usually observed. That is why a particular shape and size of bubbles at low pressure is observed. Bubbles have centimeter size (up to 15 cm at 1.2 kPa) and are often followed by a liquid jet at the departure that confer them a “mushroom” shape. Boiling curves from 100 kPa to 0.85 kPa were plotted and related to specific subatmospheric pressure pool boiling regime. This regime is characterized by significant wall temperature fluctuations (up to 20 K for our experimental conditions) affecting the heat transfer coefficient and causing material fatigue. [ABSTRACT FROM AUTHOR]

• A violent solid/liquid thermal interaction has been experimentally initiated in saturated carbon dioxide. • High energy deposit creates a significant acoustic pressure peak. • Acoustic phenomena have a major impact on the vapour creation and motion. • Optical flow techniques show great results on velocity and diameter evolution calculations. The aim of this paper is to characterize two-phase phenomena occurring for a rapid energy discharge in the fluid leading to explosive vapour expansion. This study was motivated by the lack of macro-scale experiments characterizing those transient phenomena at high reduced pressure. For that purpose, a complete test section was designed based on the Joule effect to deliver the energy discharge. CO 2 was chosen as working fluid, allowing to work at saturation and under saturation conditions. Equipped with pressure sensors and a high-speed camera, the complete process is recorded during few seconds. The thermal shock in the carbon dioxide creates transient pressure peaks and sudden vapour production. The first observed pressure wave is well described as acoustics. This first wave is followed by a quick (60 ms) generation of vapour.The maximum volume of vapour produced is extracted from pressure fluctuations and matches the theoretical value. Following their creation, the bubbles flow upward in the test section as bubbly flow. Visual observation allows the characterization of the shape and the velocity of pertinent bubbles as part of a wobbling flow. This project, motivated by the so-called Fuel Coolant Interaction (FCI) nuclear safety related problematic, brings consistent data allowing to better characterize the small scale processes for such transient vaporization phenomena. This paper focuses on a single test performed under saturated conditions. [ABSTRACT FROM AUTHOR]