The 42nd Symposium Chromatographic Methods of Investigating Organic Compounds : Book of abstracts

The 42nd Symposium Chromatographic Methods of Investigating Organic Compounds : Book of abstracts. June 4-7, 2019, Szczyrk, Polan

Heat transport solutions in rectangular shields using harmonic polynomials.

The search for the temperature field in a two-dimensional problem is common in building physics and heat exchange in general. Both numerical and analytical methods can be used to obtain a solution. Here a method of initial functions, the basics of which were given by W.Z. Vlasov i A.Y. Lur’e were adopted. Originally MIF was used for analysis of the loads of a flat elastic medium. Since then it was used for solving concrete beams, plates and composite materials problems. Polynomial half-reverse solutions are used in the theory of a continuous medium. Here solutions were obtained by direct method. As a result, polynomial forms of the considered temperature field were obtained. The Cartesian coordinate system and rectangular shape of the plate were assumed. The governing are the Fourier equation in steady state . Boundary conditions in the form of temperature (τ(x),t(y)) or/and flux (p(x), q(y)) can be provided. The solution T(x, y) were assumed in the form of an infinite power series developed in relation to the variable y with coefficients Cn depending on x. The assumed solution were substituted into Fourier equation and after expanding into Taylor series the boundary condition for y = 0 and y=h were taken into account. Form this condition a coefficients Cn can be calculated and therefore a closed solution for temperature field in plate

Numeryczna walidacja metody wyznaczania dyfuzyjności cieplnej bazującej na pomiarze profilu temperatury

The knowledge of dynamic thermal properties of building elements is necessary to investigate temperature and heat flux changes in natural daily and annual cycles. The basic dynamic parameter is thermal diffusivity. A method for determining its value for real objects has been proposed. This method is based on measuring the temperature in the element’s volume and on assuming that the obtained results meet the Fourier equation. Validation by a numerical experiment was made. The wall of the building with known thermal parameters was assumed and the temperature distribution was calculated over time in the process of non-stationary heat exchange. From the results, the diffusivity value was calculated and compared with the data entered into the model. Validations were performed for several accuracy of the temperature value and for two forms of function which approximated the temperature values obtained from calculation. A preliminary analysis of errors has been carried out.Znajomość dynamicznych własności elementów budynku jest konieczne do określania zmian temperatury i strumieni ciepła w naturalnych dziennych i rocznych cyklach. Podstawowym parametrem dynamicznym jest dyfuzyjność cieplna. Zaproponowano metodę wyznaczania tej wartości dla rzeczywistych obiektów budowlanych. Metoda bazuje na pomiarze temperatury w objętości obiektu i założeniu że wyniki pomiaru spełniają równanie Fouriera. Przeprowadzono walidację metody za pomocą eksperymentu numerycznego. Symulowano ścianę budynku o znanych parametrach cieplnych i wyznaczono zmienność temperatury w nieustalonym stanie wymiany ciepła. Z otrzymanych wyników obliczono dyfuzyjność cieplną i porównano z danymi wprowadzonymi do modelu. Walidacja została przeprowadzona dla kilku dokładności otrzymanych wyników i dwóch postaci funkcji aproksymującej wartości temperatury otrzymanych z obliczeń. Przeprowadzono również podstawową analizę błędu

Thermal Fluxes and Solar Energy Storage in a Massive Brick Wall in Natural Conditions

The thermal state of building elements is a combination of steady and transient states. Changes in temperature and energy streams in the wall of the building in the transient state are particularly intense in its outer layer. The factors causing them are solar radiation, ambient temperature and long-wave radiation. Due to the greater variability of these factors during the summer, the importance of the transient state increases at this time. The study analysed heat transfer in three aspects, temperatures in the outer, middle and inner parts of the wall, heat fluxes between these layers and absorption of solar energy, heat transfer coefficient on the wall exterior was also calculated. The analysis is based on temperature measurements at several depths in the wall and measurements of solar radiation. The subject of research is a solid brick wall. The results show that the characteristics of heat flow in winter and summer for the local climate show distinct differences. In the winter, the maximum temperature difference between the external and internal surface of the wall was 10 °C and in summer, 20 °C. In the winter, the negative flux on the internal surface reached 10 W/m2 and on the external 40 W/m2 and was constant throughout the day. The mean heat transfer coefficient on the exterior surface for winter week was 8 W/(mK). A Nusselt and Biot number for dimensionless convection analysis was calculated. The research contributes to the calculation of the variability of heat or cold demand in a daily period and to learn about the processes of energy storage in the wall using sensible heat

An experimental method for estimating the thermal diffusivity of building elements, depending on the resolution of temperature measurement

Thermal diffusivity, also known as temperature equalization coefficient, is the basic parameter in the Fourier equation for non-stationary heat exchange. Its values are known for homogeneous materials with a specific composition. Building elements made of reinforced concrete, for example, have a heterogeneous structure. For such cases, table values from the literature may differ significantly from the specific object for in real constructions. More accurate thermal diffusivity values can be obtained from measurements for a given element. Since these are usually large sized elements, the measurement method should take into account the material in the entire volume of the element. Proposals for such a method based solely on temperature measurement at several depths in the sample were presented. It consists in solving the inverse problem assuming a polynomial solution of the Fourier equation. An attempt was made to validate the method through a numerical experiment. Temperature variability was simulated with one-dimensional flow in the wall with assumed thermal diffusivity. Then the value of this diffusivity was determined from the calculated temperatures. On the inside of the partition, a constant temperature was maintained and on the outside it changed periodically. The dependence of the error in the obtained diffusivity value on the precision of temperature results was analyzed. Depending on the precision of the calculations, a minimum relative error of 2 to 6 percent was obtained. With the help of the data presented in the article, conclusions can be drawn as to the conditions that must be met to determine the value of diffusivity in real measurements with the required accuracy. The obtained results indicate that this method is worth further research

Measurement Method of Thermal Diffusivity of the Building Wall for Summer and Winter Seasons in Poland

The thermal diffusivity of building materials is an extremely important parameter influencing the subsequent thermal comfort of building users. By definition, thermal diffusivity describes how quickly heat from a hot source can flow through a material. Therefore, this parameter includes both the thermal conductivity and the heat capacity of the material. This parameter is often neglected in heat-related calculations which, in the case of dynamic problems, leads to unreliable results. It should be taken into account that heat flows through all materials at a finite speed. On the other hand, knowing the correct thermal diffusivity value of building materials, it is possible to accurately determine the internal parameters in rooms over time. There are several methods for determining thermal diffusivity, most of which are destined to determine this property in laboratories. The aim of the present research is to show how the thermal diffusivity of materials can be determined in existing buildings. The presented method can be used to determine more real thermal parameters used for thermal calculations in buildings, for example, during energy audits or when calculating the demand for cooling for air conditioning or heat for space heating. This research presents the results for a 60 cm brick wall. Thermal diffusivity was determined for specific summer and winter days—most representative of the whole year. This research has shown that the applied method should be used in the summer period, due to the fact that the wall has greater temperature fluctuations. The obtained results are comparable with the previously mentioned laboratory methods. However, due to the fact that the materials analyzed on the spot, the results are more reliable, and also take into account changes in the value of thermal diffusivity resulting from the use of binders, inaccuracies in joining and external layers made of other materials

Analytical model of wetting the porous medium

The purpose of this article is to develop an analytical model for determining the weakening of the thermal insulation capacity of porous materials - mineral wool and polystyrene because of increased water content. In the dry state, it was assumed that the sample consists of a skeleton and air-filled pores without process moisture content. In the second shot, however, dry material skeleton and pores with dry air and moisture content were taken into account. In addition, the results of tests involving the process of absorbing moisture in different moisturizing environments for both types of materials were presented. Based on the adopted calculation model, the value of the heat conduction coefficient in the dry state was determined based on the sum of the products of the volume shares of individual components of the material sample, i.e. the apparent volume of the sample material skeleton and the volume of air pores contained. The results of the thermal conductivity coefficient λ obtained in this way are consistent with those obtained from measurements during the experiment. This allowed to determine the validation of the adopted calculation model.Celem tego artykułu jest opracowanie modelu analitycznego do określania osłabienia zdolności izolacji termicznej materiałów porowatych - wełny mineralnej i polistyrenu z powodu zwiększonej zawartości wody. W stanie suchym przyjęto, że próbka składa się ze szkieletu i wypełnionych powietrzem porów bez zawartości wilgoci procesowej. W stanie wilgotnym wzięto pod uwagę szkielet i pory suchego materiału z zawartością suchego powietrza i wilgoci. Ponadto przedstawiono wyniki badań procesu absorpcji wilgoci w różnych środowiskach nawilżających dla obu rodzajów materiałów. Na podstawie przyjętego modelu obliczeniowego wartość współczynnika przewodzenia ciepła w stanie suchym została ustalona na podstawie sumy iloczynów udziałów objętościowych poszczególnych składników próbki materiału, tj. szkieletu i porów. Uzyskane w ten sposób wyniki współczynnika przewodzenia ciepła λ są zgodne z wynikami uzyskanymi z pomiarów podczas eksperymentu. Umożliwiło to weryfikację poprawności przyjętego modelu obliczeniowego

Hybrydowe układy ogrzewania

Wybór najlepszego rozwiązania ma na celu zbadanie ekonomiczności rozwiązań dla hybrydowych układów ogrzewania oraz wybór według kryterium najniższego kosztu. Poddany analizie budynek jest biurowym obiektem budowlanym o fasadzie szklanej. Przyjęte zostały dwa układy hybrydowe. Pierwszy z nich zakłada pompę ciepła oraz węzeł cieplny do spełnienia całego zapotrzebowania na ciepło. Drugi układ przewiduje zastosowanie pompy ciepła oraz węzła cieplnego do ogrzania budynku oraz kolektory słoneczne do zapewnienia ciepłej wody użytkowej.Choosing the best solution is to examine the cost-effectiveness of hybrid heating systems and the choice one of the criterion of the lowest cost. Analyzed building is an office building structure with a glass facade. We adopted two hybrid systems. The first of these involves the heating pump and the substation to meet total demand for heat. The second system provides for the use of heat pumps and district heating to heat the building and solar panels to deliver hot water

Uncertainty of PM10 concentration measurement on the example of an optical measuring device

The interest in the natural environment, in particular the ambient air, has been growing. For this reason, growing interest in measuring of concentration of pollutants in the air. To the reduction of costs and time of obtained results, increasingly are used non-reference, alternative methods and devices. However, it is necessary to ensure equivalence of results obtained by alternative methods with the results of the reference method. One of the equivalence issues is the assessment of the measurements uncertainty of the alternative method in relation to the reference method. This uncertainty is understood as the probability of obtaining a measurement result which differs from the real (reference) result by a predetermined value. Uncertainty can be caused by many reasons: imperfect implementation of the definition of the measurand, incomplete knowledge of the influence of external factors, heterogeneity of the analyzed phenomenon, errors of the measuring device and others. The paper presents methods for testing the uncertainty of measurements used in the study of equivalence and also proposed extending the test procedure with equivalence models, different from the linear regression models

Uncertainty of PM

The interest in the natural environment, in particular the ambient air, has been growing. For this reason, growing interest in measuring of concentration of pollutants in the air. To the reduction of costs and time of obtained results, increasingly are used non-reference, alternative methods and devices. However, it is necessary to ensure equivalence of results obtained by alternative methods with the results of the reference method. One of the equivalence issues is the assessment of the measurements uncertainty of the alternative method in relation to the reference method. This uncertainty is understood as the probability of obtaining a measurement result which differs from the real (reference) result by a predetermined value. Uncertainty can be caused by many reasons: imperfect implementation of the definition of the measurand, incomplete knowledge of the influence of external factors, heterogeneity of the analyzed phenomenon, errors of the measuring device and others. The paper presents methods for testing the uncertainty of measurements used in the study of equivalence and also proposed extending the test procedure with equivalence models, different from the linear regression models