Papers by Maciej Jaworski
E3S web of conferences, 2019
In the paper the equilibrium and non-equilibrium models of moisture transport across the wet buil... more In the paper the equilibrium and non-equilibrium models of moisture transport across the wet building material are proposed and compared. The equilibrium condition between gaseous and liquid moisture phases in the first model is relaxed in the second one, where evaporation and condensation are driven by the difference between the actual moisture partial pressure and its saturation value. In both models moisture is assumed in the gaseous phase as well as continuous (funicular) and discontinuous (pendular) liquid phase. Moreover, the transport of moisture is tightly coupled with heat transfer, which is treated as the fully equilibrium process in both models. The proposed models are verified with numerical results available in literature, namely with temporal variation of temperature in selected location in the building material. Additionally, predicted with both models temporal changes of the moisture content in three selected points and the total moisture content are compared. Both models produced similar results.
Energies, Jan 2, 2020
In the proposed paper, non-equilibrium and equilibrium models of heat and moisture transfer throu... more In the proposed paper, non-equilibrium and equilibrium models of heat and moisture transfer through wet building materials are presented and compared. In the former, the mass transfer between liquid and gaseous moisture results from the difference between the partial pressure of water vapor and its saturation value. In the second model, the equilibrium between both phases is assumed. In the non-equilibrium model, liquid moisture can be in the continuous (funicular) or discontinuous (pendular) form. The transfer of moisture for each proposed model is tightly coupled with the energy transfer, which is assumed to be an equilibrium process. The time step and grid size sensitivity analysis of both numerical models are performed primarily. The verification of the model is based also on the numerical data available in literature. Finally, obtained with considered models, temporal variations of moisture content in three locations in the computational domain are compared. Reasonable conformity of results is reported, and discrepancies related to differences in formulations of models are discussed.
Energies, Nov 30, 2021
Air pollution is a significant problem in city centers. According to public health care in Poland... more Air pollution is a significant problem in city centers. According to public health care in Poland, there is a need for local authorities to propose good purification solutions in both outdoor and indoor conditions. The main objective of this study is the development of an appropriate filtration system for public transport, especially for buses and bus stops. Firstly, the authors justify the need for air filtration in the capital of Poland, Warsaw. The average concentration level of PM 10 and PM 2.5 dust particles in large Polish cities is presented. In addition, it is underlined that PM 2.5 dust particles are carriers for coronavirus COVID-19 and easily inhaled by humans. In the next step, the authors introduce an experimental stand used in the examination of different filtration baffles. The filtration efficiency is defined and calculated according to experimental examinations. In these experiments, an antismog cover for air-conditioning split systems, an H13 HEPA filter and a three-stage filtration baffle (active carbon + F5 filter + EPA11 filter) were taken into consideration, and the efficiency of filtration under pressure-drop conditions and the influence of moisture were ascertained. The best filter setup was thereby determined to be the three-stage filtration baffle, being the most efficient in cleaning air on account of having the smallest mass concentration of PM 2.5 . This indicates that three-stage filtration is the most suitable air-filtration method for public transportation in cities where air pollution is a serious concern.
Archives of Thermodynamics, Sep 1, 2015
Adsorption refrigeration systems are able to work with heat sources of temperature starting with ... more Adsorption refrigeration systems are able to work with heat sources of temperature starting with 50 • C. The aim of the article is to determine whether in terms of technical and economic issues adsorption refrigeration equipment can work as elements that produce cold using hot water from the district heating network. For this purpose, examined was the work of the adsorption air conditioning equipment cooperating with drycooler, and the opportunities offered by the district heating network in Warsaw during the summer. It turns out that the efficiency of the adsorption device from the economic perspective is not sufficient for production of cold even during the transitional period. The main problem is not the low temperature of the water supply, but the large difference between the coefficients of performance, COPs, of adsorption device and a traditional compressor air conditioning unit. When outside air temperature is 25 • C, the COP of the compressor type reaches a value of 4.49, whereas that of the adsorption device in the same conditions is 0.14. The ratio of the COPs is 32. At the same time ratio between the price of 1 kWh of electric power and 1 kWh of heat is only 2.85. Adsorption refrigeration equipment to be able to compete with compressor devices, should feature COP ads efficiency to be greater than 1.52. At such a low driving temperature and even changing the drycooler into the evaporative cooler it is not currently possible to achieve.
Journal of Power of Technologies, 2001
W pracy omówiono prostą metodę określania temperatury przejścia fazowego (topnienia) oraz stopnia... more W pracy omówiono prostą metodę określania temperatury przejścia fazowego (topnienia) oraz stopnia przechłodzenia w procesie krzepnięcia materiałów, które są rozważane jako czynniki robocze w układach akumulacji ciepła (materiały PCM). Przedstawiono również wyniki pomiarów wymienionych wielkości fizycznych dla wodnych roztworów glikolu etylenowego i propylenowego w zakresie stężeń od 0 do 30% (ułamek objętościowy).
Journal of Power of Technologies, Apr 20, 2011
The paper presents the results of thermal conductivity measurement of gypsum-based composites inc... more The paper presents the results of thermal conductivity measurement of gypsum-based composites incorporating microencapsulated phase change material (PCM). Samples of different concentration of PCM were analyzed in the temperature range typical for building indoor conditions. The investigation showed the major impact of both PCM content and temperature on thermal conductivity. The materials under investigation are used in manufacturing structure elements for building applications. Gypsum wallboards, thanks to the contribution of PCM, have substantially increased thermal capacity (thermal inertia); properly incorporated in the building envelope such materials can stabilize indoor temperature (thereby improving thermal comfort) and, as they operate as thermal energy storage elements, reduce energy requirements of buildings.
Materials, Sep 9, 2021
Energy storage is one of the most effective ways to increase energy savings and efficiency of hea... more Energy storage is one of the most effective ways to increase energy savings and efficiency of heating and air conditioning systems. Phase change materials (PCMs) are increasingly used in latent heat thermal energy storage (LHTES) systems to increase their capacity. In such systems, costs are a very important factor of viability so the typical heat transfer elements like fin-and-tube heat exchangers are used to construct the LHTES. The problem of this approach is a possibility of corrosion of metals in contact with PCM that shortens the life cycle of LHTES. Therefore, the main objective of this work is an experimental study of the compatibility of metals typically used in fin-and-tube heat exchangers (copper and aluminum) with three commercially available organic PCMs (RT15, RT18HC, and RT22HC). Compatibility of PCMs with copper and aluminum was tested for a period of approximately two months, during which a total of 35 heating and cooling cycles were carried out, each with a complete phase transition of the tested materials. In the course of the tests it was assessed whether the PCM caused corrosion of the tested metals. The evaluation was based on the gravimetric method, calculation of corrosion rate, and visual observations and measurements of the features on the metal sample's surface using optical microscope. It was determined that RT15, RT18 HC, and RT22 HC show low corrosion rates for aluminum and copper samples. The visual tests indicate that there was no change in the PCM solutions during the tests, only a sediment was observed for the samples with the combination of copper and aluminum. Microscopic examination of the surface of the samples did not show any significant surface changes, except for the aluminum samples, on the surface of which local microdefects were observed. It follows from the present results that copper and aluminum can be used to design the heat transfer surface in contact with the chosen PCMs.
Proccedings of 10th International Conference "Environmental Engineering", 2017
The effect of standard means of thermal upgrading of buildings on energy performance indices is s... more The effect of standard means of thermal upgrading of buildings on energy performance indices is studied in the paper. The following was considered: improving thermal performance of the envelope (walls, roof, floors over unheated cellars or ground-floor slabs, windows, and doors); using exterior blinds during heating and cooling seasons; using heat recovery (recuperation) in a forced ventilation system; reducing the ventilation air flow rate; and improving air-tightness of a building. The calculations were performed for a number of variants. Seven locations in Poland were selected based on outdoor climate conditions. Various standards of thermal performance of the building envelope, internal heat capacities, and ventilation rates were applied. Variations in internal heat gains, depending on the presence of occupants (heat gains from occupants and from lighting) were considered. Due to a dynamic nature of the energy processes that take place in a building, the simplified hourly method...
Energies, 2021
Air pollution is a significant problem in city centers. According to public health care in Poland... more Air pollution is a significant problem in city centers. According to public health care in Poland, there is a need for local authorities to propose good purification solutions in both outdoor and indoor conditions. The main objective of this study is the development of an appropriate filtration system for public transport, especially for buses and bus stops. Firstly, the authors justify the need for air filtration in the capital of Poland, Warsaw. The average concentration level of PM10 and PM2.5 dust particles in large Polish cities is presented. In addition, it is underlined that PM2.5 dust particles are carriers for coronavirus COVID-19 and easily inhaled by humans. In the next step, the authors introduce an experimental stand used in the examination of different filtration baffles. The filtration efficiency is defined and calculated according to experimental examinations. In these experiments, an antismog cover for air-conditioning split systems, an H13 HEPA filter and a three-s...
The main goal of the paper is to provide a conditi on for which a maximum entropy generation occu... more The main goal of the paper is to provide a conditi on for which a maximum entropy generation occurs in a heat exchanger at constant i nlet parameters (temperatures and mass flow rates). Knowing this condition is essential during the design of the heat exchanger as it allows designers to avoid one of its most unfavourable opera ting conditions in terms of thermodynamics. Entropy generation resulting from the resistance of heat-transferring fluids to flow was not taken into account. Entropy generation was analysed as a function of a heat flow rate at constant parameters at the inlet of a condenser and a counter-flo w d uble-pipe heat exchanger. The analysis showed that for the condenser the entropy generatio n rate increases with the increase in the heat flow rate. The maximum entropy generation rate occu rs for the maximum flow rate of the heat that can be transferred according to the definition of heat transfer effectiveness. For the counterflow heat exchanger, the entropy generatio...
Materials, 2021
Energy storage is one of the most effective ways to increase energy savings and efficiency of hea... more Energy storage is one of the most effective ways to increase energy savings and efficiency of heating and air conditioning systems. Phase change materials (PCMs) are increasingly used in latent heat thermal energy storage (LHTES) systems to increase their capacity. In such systems, costs are a very important factor of viability so the typical heat transfer elements like fin-and-tube heat exchangers are used to construct the LHTES. The problem of this approach is a possibility of corrosion of metals in contact with PCM that shortens the life cycle of LHTES. Therefore, the main objective of this work is an experimental study of the compatibility of metals typically used in fin-and-tube heat exchangers (copper and aluminum) with three commercially available organic PCMs (RT15, RT18HC, and RT22HC). Compatibility of PCMs with copper and aluminum was tested for a period of approximately two months, during which a total of 35 heating and cooling cycles were carried out, each with a complet...
Archives of Thermodynamics, 2015
Adsorption refrigeration systems are able to work with heat sources of temperature starting with ... more Adsorption refrigeration systems are able to work with heat sources of temperature starting with 50 °C. The aim of the article is to determine whether in terms of technical and economic issues adsorption refrigeration equipment can work as elements that produce cold using hot water from the district heating network. For this purpose, examined was the work of the adsorption air conditioning equipment cooperating with drycooler, and the opportunities offered by the district heating network in Warsaw during the summer. It turns out that the efficiency of the adsorption device from the economic perspective is not sufficient for production of cold even during the transitional period. The main problem is not the low temperature of the water supply, but the large difference between the coefficients of performance, COPs, of adsorption device and a traditional compressor air conditioning unit. When outside air temperature is 25 °C, the COP of the compressor type reaches a value of 4.49, wher...
E3S Web of Conferences, 2018
The aim of this paper is to present a new concept of a high-temperature thermal energy storage (T... more The aim of this paper is to present a new concept of a high-temperature thermal energy storage (TES) for the application in the compressed air energy storage (CAES) systems. The proposed storage unit combines the advantages of pressurized containers with packed beds, e.g. of rocks, with the strengths of non-pressurized systems such as those encountered in CSP plants. Designed TES unit consists of the heat exchanger located inside a high-temperature thermocline-type vessel with molten HITEC® salt used as a heat storing material. In terms of the geometry of the designed heat exchanger, a tube-in-tube helical coil type was chosen due to its higher convective heat transfer coefficients in comparison with straight tubes. To find the most suitable case, four helical coils with different dimensions (diameter, pitch) were considered. Heat transfer and pressure drop analysis for each configuration were conducted. In particular, convective and overall heat transfer coefficients as well as fri...
Archives of Thermodynamics, 2015
The paper presents an analysis of relations describing entropy generation in a condenser of a ste... more The paper presents an analysis of relations describing entropy generation in a condenser of a steam unit. Connections between entropy generation, condenser ratio, and heat exchanger effectiveness, as well as relations implied by them are shown. Theoretical considerations allowed to determine limits of individual parameters which describe the condenser operation. Various relations for average temperature of the cold fluid were compared. All the proposed relations were verified against data obtained using a simulator and actual measurement data from a 200 MW unit condenser. Based on data from a simulator it was examined how the sum of entropy rates, steam condenser effectiveness, terminal temperature difference and condenser ratio vary with the change in the inlet cooling water temperature, mass flow rate of steam and the cooling water mass flow rate.
A short overview of basic problems connected with high power laser radiation interaction with sol... more A short overview of basic problems connected with high power laser radiation interaction with solids is presented. Physical phenomena occurring during absorption of laser beam energy in solid, basic fields of application of lasers, and mathematical model of the conversion of light energy into heat are described. There are also many examples of numerically calculated temperature fields in solids caused by the interaction of laser radiation of different parameters (different power densities and interaction times), which are the results of investigation of the laser interaction with solids. These investigations have been conducted in the Institute of Heat Engineering for several years.
The paper presents a short description of a numerical simulation for the transient heat transfer ... more The paper presents a short description of a numerical simulation for the transient heat transfer in a single heat storage element with phase change material PCM (Stefan problem -melting and solidification phenomena). Enthalpy method -a finite difference numerical discretization and explicit temporal discretization scheme -was chosen for the transient 3-D model. The results of numerical calculation of 3-D temperature fields for heating a single PCM vessel are presented in the graphic form. NOMENCLATURE с -specific heat L -latent heat i -enthalpy Τ -temperature τ -time r -radial coordinate ζ -axial coordinate λ -thermal conductivity ρ -density Q -heat flux α -the heat transfer coefficient
W pracy omówiono prostą metodę określania temperatury przejścia fazowego (topnienia) oraz stopnia... more W pracy omówiono prostą metodę określania temperatury przejścia fazowego (topnienia) oraz stopnia przechłodzenia w procesie krzepnięcia materiałów, które są rozważane jako czynniki robocze w układach akumulacji ciepła (materiały PCM). Przedstawiono również wyniki pomiarów wymienionych wielkości fizycznych dla wodnych roztworów glikolu etylenowego i propylenowego w zakresie stężeń od 0 do 30% (ułamek objętościowy).
The paper presents the results of thermal conductivity measurement of gypsum-based composites inc... more The paper presents the results of thermal conductivity measurement of gypsum-based composites incorporating microencapsulated phase change material (PCM). Samples of different concentration of PCM were analyzed in the temperature range typical for building indoor conditions. The investigation showed the major impact of both PCM content and temperature on thermal conductivity. The materials under investigation are used in manufacturing structure elements for building applications. Gypsum wallboards, thanks to the contribution of PCM, have substantially increased thermal capacity (thermal inertia); properly incorporated in the building envelope such materials can stabilize indoor temperature (thereby improving thermal comfort) and, as they operate as thermal energy storage elements, reduce energy requirements of buildings.
Inżynieria Bezpieczeństwa Obiektów Antropogenicznych, 2019
W pracy przedstawiono pasywną metodę mającą na celu ograniczenie zapotrzebowania na energię do c... more W pracy przedstawiono pasywną metodę mającą na celu ograniczenie zapotrzebowania na energię do celów klimatyzacji, której istotą jest zwiększenie bezwładności cieplnej struktury budynku przez zastosowanie materiałów zmiennofazowych PCM. Opisano różne metody wkomponowania materiałów PCM w różne elementy budynku. Przedstawiono również wyniki badań eksperymentalnych wybranych typów zasobników ciepła z PCM pokazujące wpływ zwiększonej bezwładności cieplnej struktury budynku na stabilizację temperatury wewnątrz pomieszczeń. W szczególności opisano badania zasobnika ciepła/chłodu zbudowanego z kompozytu gipsowego z dodatkiem PCM zintegrowanego z systemem wentylacji budynku.
Proccedings of 10th International Conference "Environmental Engineering", 2017
In the paper a special heat storage unit for building applications is presented. It has a form of... more In the paper a special heat storage unit for building applications is presented. It has a form of a ceiling panel that is made of PCM-gypsum mortar composite and it contains internal channels for air flow, since it is designed as a part of ventilation system of the building. The panel works as a regenerative heat exchanger with phase change material (PCM) as a prevailing heat storage medium. When a melting point of PCM is properly chosen it is possible that air temperature flowing into the building reach a level corresponding to thermal comfort conditions, regardless the temperature at the intake. Warm air (during a day) releases heat basically to PCM causing its melting. During night time cool ambient air is heated up while it takes back heat accumulated in PCM. An experimental set-up based on the above concept was developed. A series of tests in different conditions (for variable inlet air temperatures, air flow rates) were performed. Information on thermal performance of the ceil...
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Papers by Maciej Jaworski