An application of latent heat thermal energy storage systems with phase change materials seems to be unavoidable in the present world. The latent heat thermal energy storage systems allow for storing excessive heat during low demand and then releasing it during peak demand. However, a phase change material is only one of the components of a latent heat thermal energy storage system. The second part of the latent heat thermal energy storage is a heat exchanger that allows heat transfer between a heat transfer fluid and a phase change material. Thus, the main aim of this review paper is to present and systematize knowledge about the heat exchangers used in the latent heat thermal energy storage systems. Furthermore, the operating parameters influencing the phase change time of phase change materials in the heat exchangers, and the possibilities of accelerating the phase change are discussed. Based on the literature reviewed, it is found that the phase change time of phase change materials in the heat exchangers can be reduced by changing the geometrical parameters of heat exchangers or by using fins, metal foams, heat pipes, and multiple phase change materials. To decrease the phase change material’s phase change time in the tubular heat exchangers it is recommended to increase the number of tubes keeping the phase change material’s mass constant. In the case of tanks filled with spherical phase change material’s capsules, the capsules’ diameter should be reduced to shorten the phase change time. However, it is found that some changes in the constructions of heat exchangers reduce the melting time of the phase change materials, but they increase the solidification time.

Important parameters used for adsorption chillers, e.g. cooling capacity, coefficient of performance, are strictly dependent on heat and mass transfer conditions between adsorbent mass and the cooling/heating medium. With the aim of energy efficiency increasing it is essential to reduce heat transfer resistance. Different bed configurations and heat exchangers constructions are recommended for adsorption bed application. In the paper the review of commonly used adsorption bed configurations, i.e. loose-grain beds or fixed beds, is presented. Also, different heat exchangers for adsorption technology were described. The characteristic features of commonly applied constructions, both for commercial use and scientific research, were presented. The experimental studies presented in the literature were investigated and the substantial conclusions from the literature review are mentioned. Also, the proposition of new adsorption bed construction using the binder and additives was mentioned.

Many attempts are made worldwide to create cheap, efficient, and eco-friendly water desalination systems. Passive solar stills (SS) are considered to be such. This paper presents the results of the experimental and theoretical investigation of the effects of using phase-change materials (PCM) on the performance of SS. The experiments were conducted for two paraffin waxes, as PCM and 1.0, 2.5, and 5.0 kg of PCM were used. The results of the experimental studies were used to validate a mathematical model, which was based on the energy balance ordinary differential equations. The equations were solved numerically since the approximate solutions obtained numerically are sufficient and relatively simple as compared to the exact analytical solutions. A theoretical analysis was then carried out and a novel and detailed dependence on the water evaporation rate as a function of water temperature and the difference between water and cover temperature was determined. It was also found that the productivity of the SS with PCM strongly depends on the operating conditions. For uniform initial temperatures of the SS, its productivity decreases with an increasing PCM-to-water mass ratio, and the maximum decrease is 10.8%. If the SS is not thermally insulated, the PCM can take the role of a thermal insulator and increase productivity by 1.1%, but there is an optimal PCM-to-water mass ratio. The greatest increase in productivity, by up to 47.1%, can be obtained when the PCM is heated outside the SS and inserted into the SS when the water temperature starts to decrease. In this case, the productivity increases with the increasing PCM-to-water mass ratio. These outcomes fill a knowledge gap caused by a lack of justification for why in some cases, the application of PCM fails to improve the productivity of SS.

This paper presents the results of numerical tests on the elements of an adsorption chiller that comprises a sorption chamber with a bed, a condenser, and an evaporator. The simulation is based on the data and geometry of a prototype refrigeration appliance. The simulation of this problem is unique and has not yet been performed, and so far, no simulation of the phenomena occurring in the systems on a real scale has been carried out. The presented results are part of the research covering the entire spectrum of designing an adsorption chiller. The full process of numerical modeling of thermal and flow phenomena taking place in the abovementioned components is presented. The computational mesh sensitivity analysis combined in the k-ε turbulence model was performed. To verify and validate the numerical results obtained, they were compared with the results of tests carried out on a laboratory stand at the AGH Center of Energy. The results of numerical calculations are in good agreement with the results of the experimental tests. The maximum deviation between the pressure obtained experimentally and by simulations is 1.8%, while for temperatures this deviation is no more than 0.5%. The results allow the identification of problems and their sources, which allows for future structural modifications to optimize the operation of the device.

Adsorption chillers are a promising alternative to traditional compressor-based devices. Adsorption chillers can be supplied with low- or medium-temperature waste heat or heat from renewable energy sources. In addition, they can be used for water desalination purposes. Thus, the adsorption chillers are unique devices that meet essential problems of the modern world: a need to limit the negative impact of humankind on the natural environment and growing problems with access to drinking water. However, adsorption chillers also have disadvantages, including ineffective operation and large size. Therefore, in this paper, the influence of steam utilization on the operation of an adsorption chiller with water desalination function was investigated experimentally, which has not been done before. The research was carried out on the adsorption chiller, working on a silica gel–water pair, installed in the AGH UST Center of Energy. The chiller was modified to preheat the sorbent with the use of steam. The results show that the use of steam instead of water for preheating the bed leads to higher temperatures in the heat exchanger and the bed. As a result, heat transfer from the heating medium to the bed is more intense, and a significant shortening of the desorption process is observed. In the case of using steam for preheating, the desorption time was about 30 s, while for water, it was 300 s. Thanks to this solution, it is possible to reduce the size of the device and increase its efficiency. The proposed solution opens a new course of research on adsorption chillers and broadens the horizon of their applications, as steam is a by-product of many industrial processes.

The paper presents the results of the optimization of the paper production process as a function of paper grade, basis weight and key operating parameters of paper machines, wire speed V_s and reel speed V_n, using computer simulation. Based on empirical data from 2015 to 2020, the analysis accounts for web breaks, downtimes, and grade changes, all of which affect production continuity and the operation of the plant’s combined heat and power (CHP) system supplying thermal and electrical energy. Production interruptions reduce CHP stability; therefore, the optimization criterion was profit maximization, including energy-related effects associated with forecasting the availability of surplus energy for sale when participating in the capacity market. The results were compared with those obtained using numerical taxonomy methods, which confirmed the effectiveness of their application to the problem under consideration.