Michał Pomorski

Thermal energy storage (TES) looks to be a promising technology for recovering waste heat or other intermittent heat sources, especially if it is coupled with the organic Rankine cycle (ORC) system. This system may use a variety of heat storage materials, including solids, liquids, and phase change materials (PCM). This article discusses the use of PCM as a thermal energy storage material in TES systems coupled with ORC systems. Other TES configurations may be used in ORC; however, in this article, the TES is solely used in heat exchangers, i.e., evaporator and liquid heater. The goal of this research is to establish a dimensionless storage mass parameter for sizing TES-evaporator (TES-EVA) or TES-liquid heater (TES-LH) devices for ORCs. Furthermore, the model of this system was created in the MATLAB environment using the chosen hydrocarbons as ORC working fluids. The obtained modelling results provide a novel point of view that scientists and engineers may employ while developing the TES-EVA or TES-LH utilizing PCM for ORC.

Objectives: The impact of infection with novel coronavirus — SARS-CoV-2 — on women's and fetus' was unclear; therefore, it was the reason for many worries. We wanted to understand and describe the worries of pregnant women, assess mental well-being, and analyse the problems affecting prenatal care and hospital stay in this unprecedented time. Material and methods: We designed an original 23-question survey aimed at women who were pregnant during the pandemic or who gave birth at that time. The survey included demographic data, questions about prenatal care, mental status and worries, and hospitalisation. Results: Our study included 1321 women: 1010 (76.5%) during pregnancy and 311 (23.5%) after the delivery in the studied time. For 1168 (88,4%) respondents, the pandemic had a negative impact on their mood. The three main concerns were: the need for isolation from the child (n = 498, 37.7%), the childbirth without a partner/trusted companion (n = 417, 31.6%) and the risk of infection of the child in hospital (n = 381, 28.8%). Conclusions: The novel coronavirus pandemic affects the mental health of pregnant women. Pregnant patients should be considered a group of particular concerns. Patients consider remote obstetrical consultations as an insufficient approach. The reason for the highest worries of pregnant patients is a lack of companionship during labour. There was no difference between the rate of childbirth via caesarean sections over vaginal delivery during the first wave of the pandemic. Objectives: The impact of infection with novel coronavirus — SARS-CoV-2 — on women's and fetus' was unclear; therefore, it was the reason for many worries. We wanted to understand and describe the worries of pregnant women, assess mental well-being, and analyse the problems affecting prenatal care and hospital stay in this unprecedented time. Material and methods: We designed an original 23-question survey aimed at women who were pregnant during the pandemic or who gave birth at that time. The survey included demographic data, questions about prenatal care, mental status and worries, and hospitalisation. Results: Our study included 1321 women: 1010 (76.5%) during pregnancy and 311 (23.5%) after the delivery in the studied time. For 1168 (88,4%) respondents, the pandemic had a negative impact on their mood. The three main concerns were: the need for isolation from the child (n = 498, 37.7%), the childbirth without a partner/trusted companion (n = 417, 31.6%) and the risk of infection of the child in hospital (n = 381, 28.8%). Conclusions: The novel coronavirus pandemic affects the mental health of pregnant women. Pregnant patients should be considered a group of particular concerns. Patients consider remote obstetrical consultations as an insufficient approach. The reason for the highest worries of pregnant patients is a lack of companionship during labour. There was no difference between the rate of childbirth via caesarean sections over vaginal delivery during the first wave of the pandemic.

The article deals with the experimental and numerical thermal-flow behaviours of a low-temperature Phase Change Material (PCM) used in Thermal Energy Storage (TES) industrial applications. The investigated PCM is a composition that consists of a mixture of paraffin wax capsuled in a melamine-formaldehyde membrane and water, for which a phase change process occurs within the temperature range of 4 °C to 6 °C and the maximum heat storage capacity is equal to 72 kJ/kg. To test the TES capabilities of the PCM for operating conditions close to real ones, a series of experimental tests were performed on cylindrical modules with fixed heights of 250 mm and different outer diameters of 15, 22, and 28 mm, respectively. The module was tested in a specially designed wind tunnel where the Reynolds numbers of between 15,250 to 52,750 were achieved. In addition, a mathematical model of the analysed processes, based on the enthalpy porosity method, was proposed and validated. The temperature changes during the phase transitions that were obtained from the numerical analyses in comparison with the experimental results have not exceeded 20% of the relative error for the phase change region and no more than 10% for the rest. Additionally, the PCM was examined while using a Scanning Electron Microscope (SEM), which indicated no changes in the internal structure during phase transitions and a homogeneous structure, regardless of the tested temperature ranges.

This article presents the results of a study into a packed bed filled with ceramic bricks. The designed storage installation is supposed to become part of a heating system installed in a single-family house and eventually to be integrated with a concentrated solar collector adapted to climate conditions in Poland. The system’s working medium is air. The investigated temperature ranges and air volume flow rates in the ceramic bed were dictated by the planned integration with a solar air heater. Designing a packed bed of sufficient parameters first required a mathematical model to be constructed and heat exchange to be analyzed, since heat accumulation is a complex process influenced by a number of material properties. The cases discussed in the literature are based on differing assumptions and different formulas are used in calculations. This article offers a comparison of various mathematical models and of system operating parameters obtained from these models. The primary focus is on the Nusselt number. Furthermore, in the article, the thermo-hydraulic efficiency of the investigated packed bed is presented. This part is based on a relationship used in solar air collectors with internal storage.

Gas pressure reduction stations are commonly applied to decrease the pressure of natural gas in the transmission pipelines. In such stations, natural gas is expanded in throttling valves without producing any energy. Through the use of expander in natural gas pressure reduction stations, it is possible to recover the pressure energy of the natural gas during expansion, and drive the electrical generator. Possible solutions include turbines and volumetric expanders. However, turbines are complicated and expensive, while volumetric expanders are simple and cheap. This paper presents an analytical modeling of rolling piston expander work conditions when adopted to natural gas expansion. The main objective of this research was therefore a comprehensive analysis of influence of varied sizes of the expander components and natural gas thermal properties at the inlet and at the outlet of the expander, on the expander output power. The analysis presented in this paper indicates that the rolling piston expander is a good alternative to the turbines proposed for energy recovery in natural gas pressure reduction stations.