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EN
The multi criterion decision making (MCDM) method and experimental investigation on free convective heat transfer performance of oxide-based water nanofluids along a vertical cylinder are the two methods used to compare the performance in this paper. Al2O3, CuO, TiO2, SiO2, Fe3O4, and ZnO were the metal oxide nanoparticles used in the study to make water-based metal oxide nanofluids with volume fractions ranging from 0% to 1%. Two step method was used to create nanofluids. Thermo-physical properties like density, specific heat, viscosity, and thermal conductivity were measured after the various nanofluids were synthesized. Then, the performance of each nanofluid was evaluated based on various attributes using the weighted sum model (WSM) method, and the ranking of nanofluids was given. To begin, water served as the medium for free convection heat transfer experiments to validate the experimental setup. Free convection heat transfer experiments were carried out using metal oxide-based water nanofluids as mediums at volume fractions ranging from 0% to 1% for various heat inputs in the range of 30 W and 50 W. The heat transfer coefficient augments with percentage volume concentration up to 0.1 % for all types of nanofluids and then decreases until it reaches 0.6% volume fraction. Al2O3-water nanofluid performs better than other metal oxide nanofluids in both WSM and experimental methods.
EN
Nanofluids have found widespread practical applications in heat transfer, including cooling oils for diverse uses like automobile radiators, solar and nuclear power systems, biomedical devices, ventilation, heating, air conditioning, refrigeration, engine cooling, and transformers. Extensive scientific studies have investigated the impact of exotic fluids when combined with traditional heat transfer fluids, revealing that this combination enhances heat transfer performance beyond that of conventional working fluids. Collectively, these studies demonstrate the impressive heat transfer abilities of nanofluids. To optimize the efficiency of flat plate solar collectors, a comprehensive approach integrating theory and experimentation is essential. The results of such research highlight that increasing both the mass flow rate and concentration of nanofluids can lead to significant efficiency improvements, with potential enhancements ranging from 20% to 85%.
PL
Nanociecze znalazły szerokie praktyczne zastosowanie w wymianie ciepła. Oleje chłodzące w tym oleje stosowane są w różnych zastosowaniach, takich jak chłodnice samochodowe, systemy energii słonecznej i jądrowej, urządzenia biomedyczne, wentylacja, ogrzewanie, klimatyzacja, chłodnictwo, chłodzenie silników i transformatorów. Celem szeroko zakrojonych badań naukowych było zbadanie wpływu egzotycznych cieczy w połączeniu z tradycyjnymi cieczami przenoszącymi ciepło, ujawniając, że ta kombinacja poprawia wydajność wymiany ciepła w porównaniu z konwencjonalnymi cieczami roboczymi. Badania wykazały imponujące zdolności przenoszenia ciepła przez nanociecze. Optymalizacja wydajności płaskich kolektorów słonecznych polega na kompleksowym podejściu łączącym metody teoretyczne oraz badania eksperymentalne. Wyniki takich badań podkreślają, że zwiększenie zarówno masowego natężenia przepływu, jak i stężenia nanocieczy może prowadzić do potencjalnej poprawy wydajności w zakresie od 20% do 85%. Celem tego artykułu jest zaprezentowanie osiągnięć naukowych w zakresie implementacji nanocieczy do zwiększenia efektywności cieplnej płaskich kolektorów słonecznych.
EN
Flat plate solar collector (FPSC) is popular for their low cost, simplicity, and ease of installation and operation. In this work, FPSC thermal performance was analyzed. It's compared to diamond/H2O nanofluids. The volume percentage and kind of nanoparticles are analyzed numerically that validation with experimental data available in the literature. The hot climate of Iraq is employed to approximate the model. The numerical study is performed by using ANSYS/FLUENT software to simulate the case study of problem. Due to less solar intensity after midday, temperatures reduction. The greatest collector thermal efficiency is 68.90% with 1% ND/water nanofluid, a 12.2% increase over pure water. The efficiency of 1% nanofluid is better than other concentrations because of a change in physical properties and an increase in thermal conductivity. Since the intensity of radiation affects the outlet temperature from the solar collector and there is a direct link between them, this increases the efficiency of the solar collector, especially around 12:30 pm at the optimum efficiency.
EN
The safety and reliability of the manned airship depend to a considerable extent on its thermal performance. In this paper, heat balance equations are developed and solved in the C++ programming language. The temperature variation of the enclosure, gasbag, and nacelles of the manned airship is investigated. In addition, the effects of season, latitude, and orientation on the thermal performance of the manned airship and the airship nacelle are investigated. The results show that: (1) The average temperature difference of the nacelle surface at the same time is 25 K, while the maximum temperature difference in the nacelle is 29 K during the day, (2) the temperature distribution in the nacelle is similar in spring and autumn, with maximum temperature between 306 K and 309 K. The maximum temperature in the nacelle is between 300 K and 303 K in winter while the maximum temperature in the nacelles is between 309 K and 315 K in summer, (3) as the flight position of the manned airship changes from 20°N to 60°N, the average nacelle temperature varies slightly by about 1 K. However, as the latitude increases, the high- temperature region shifts from the bottom of the nacelle to the side of the nacelle, and (4) the temperature distribution of the upper envelope of the airship varies considerably with orientation. However, the average temperature of the nacelle is less impacted by orientation. These results are useful for understanding the thermal performance of manned airships.
PL
Artykuł jest wprowadzeniem do badań dotyczących wpływu zastosowania materiałów budowlanych o ciemnych barwach w architekturze. Obecnie projektowanie architektoniczne kieruje się m.in. doktryną zrównoważonego rozwoju. Troska o zmiany klimatyczne zaleca kształtowanie środowiska zbudowanego tak, aby zapewnić najlepsze warunki dla osób przebywających w nim obecnie i w przyszłości. Badania środowiskowe potwierdzają wpływ materiałów budowlanych na mikroklimat przestrzeni zbudowanej i dlatego stanowią inspirację do analizy ich właściwości, a zwłaszcza współczynników odbicia i pochłaniania promieniowania słonecznego. Istotne jest również, dlaczego podejmowane są decyzje o stosowaniu bardzo ciemnych materiałów. Czy kreacja twórcy może to pomijać?
EN
The article is an introduction to research on the influence of the use of dark-colored building materials in architecture. Currently, architectural design is guided, among others, by the doctrine of sustainable development. Concern for climate change recommends shaping the built environment to provide the best conditions for people living now and in the future. Environmental research confirms the influence of building materials on the microclimate of the built space, hence the analysis of their properties, in particular the reflectivity and absorption of solar radiation. It is also important why decisions are made to use very dark materials. Can the designer creation skip this?
EN
A numerical investigation of thermal prediction of double-pass solar air heater of-counter flow is developed in the present study. The main idea of the current study is that the collector consists of two layers of glass so that the middle layer is glass instead of the usual metal plate. The performance of double-pass solar air heater is studied for a wide range of solar radiation intensities (600, 750 and 900 W/m 2). A FORTRAN-90 program is built to simulate the mathematical model of double-pass solar air heater based on solving steady state two-dimensional Navier-Stokes equations and energy equation based on finite volume method. Turbulence effect is simulated by two equations k-ε module. The results are compared with the results of a previous experimental study and a good agreement was found. From compression calculating efficiency of the present and traditional collector for each solar intensity, it was found that the efficiency of the current collector is higher than that of the traditional one, where the efficiency of the current collector at the solar intensity of (600, 750 and 900) W/m 2 are (0.529, 0.514 and 0.503), respectively, while those of the traditional collector (0.508, 0.492 and 0.481), respectively. In addition to this, the effect of the mass flow rate on the temperature difference of the current proposed collector was studied. Three values of the mass flow rate were studied (0.009,0.018, and 0.027) kg/s at solar intensity of 750 W/m 2. From this it was found that the temperature difference decreases with increasing mass flow rate. Accordingly, the efficiency decreases
EN
The mathematical model of heat generation and dissipation during thermal energy transmission employing nanoparticles in a Newtonian medium is investigated. Dimensionless boundary layer equations with correlations for titanium dioxide, copper oxide, and aluminium oxide are solved by the finite element method. Parameters are varied to analyze their impact on the flow fields. Various numerical experiments are performed consecutively to explore the phenomenon of thermal performance of the combination fluid. A remarkable enhancement in thermal performance is noticed when solid structures are dispersed in the working fluid. The Biot number determines the convective nature of the boundary. When the Biot number is increased, the fluid temperature decreases significantly. Among copper oxide, aluminium oxide, and titanium oxide nanoparticles, copper oxide nanoparticles are found to be the most effective thermal enhancers.
EN
Research and development of energy-efficient materials have been essential for sustainable infrastructure growth. A considerable amount of money is being spent on various energy stabilization techniques worldwide to attain thermal comfort in buildings. Thus, lowering the energy demand through green materials is vital to save energy and the environment. In this paper, a new form of Structural Insulated Panel (SIP) has been developed and referred to as Ferro Cellular Lightweight Concrete Insulated Panel (FCIP). Comparative thermal efficiency and acoustic performance of FCIP and brick masonry walls have been tested experimentally. The thermal results show that FCIP allows just 2ºC rise in the internal temperature of the room chamber in two hours, whereas the brick masonry allows 9.5ºC rise in the internal temperature of the room chamber for the same period. Similarly, the acoustic results show that FCIP has 0.85 sound absorption coefficient compared to 0.2 for brick masonry wall. Further, the cost-benefit analysis was conducted based on the electricity consumption results of a building produced by the eQuest energy simulation program. The outcome shows that the building’s lifetime running cost gets reduced to 50% when FCIP replaces the concrete/brick masonry envelope.
EN
Cooking is one of the most common activity in day-to-day life of every woman. In rural areas the transportation of fuel is major problem and the increasing demand of energy for cooking applications is gaining importance and various investigations are being carried out for performance enhancement of the solar cooker. The box-type solar cooker has a complex thermal analysis due to the transient heat transfer phenomenon involved in three dimensions. A comparison of the standard correlation available are analysed for accuracy of predicted results with experimental data. The investigation involves the experimental determination of the parameters viz. wind heat transfer coefficient, side and bottom loss coefficient, inner and outer glass temperature. The extensive data is analysed with that of standard correlations and the significance of the experimental data is checked. Analysis found to have deviation of 3%-20% in experimental and correlation data, which indicates that for accuracy of performance analysis the studied parameters should be determined experimentally.
EN
Solar cooking finds a major application in rural areas of Uttarakhand, India, yet its utilization is still limited due to certain limitation such as intermittent nature of solar radiations. This drawback limits solar cooker in becoming a viable alternate solution of LPG and other pollution causing resources such as wood. In order to cater this problem a numerical analysis of box type solar cooker with storage is carried out. The energy stored in the storage material will keep the cooker warm up to the time when food is consumed. Charging and discharging time analysis is performed in with an aim to understand the effect of storage on solar cooker. Heating and cooling characteristic time are being evaluated and analysed with storage. Thermal performance of box type solar cooker is measured in terms of figures of merit according to BIS standards. The effect of storage has also been analysed in terms of charging and discharging time and first figure of merit of box type solar cooker.it has been observed that during discharging the heat is stored for more duration as compared to the charging time as discharge time is approx. 4-5 hours while charging time for the same amount of insolation is around 3-4 hours.
PL
W artykule przedstawiono możliwości wykorzystania materiałów zmiennych fazowo jako przykład poprawienia zdolności akumulacji energii cieplnej wyrobów budowlanych, a także wyniki eksperymentu w zakresie oceny skuteczności działania materiału zmiennego fazowo w postaci mikrokapsułek Micronal®PCM firmy BASF, wprowadzonego w zróżnicowanej ilości do składu materiałów kompozytowych z matrycą gipsową i cementową. Oznaczono objętościową pojemność i przewodność cieplną w zmiennych warunkach temperaturowych, a także wykonano badania podstawowych parametrów technicznych analizowanych zapraw. Opisane rezultaty badań zaczerpnięto z prac dyplomowych, magisterskiej i inżynierskiej, zrealizowanych na Wydziale Budownictwa i Inżynierii Środowiska ZUT w Szczecinie.
EN
The article presents the possibilities of using phase changing materials as an example of improvement of thermal energy accumulation capacity of construction products, as well as results of an experiment regarding assessment of effectiveness of a phase changing material in the form of Micronal®PCM microcapsules, manufactured by the BASF company, introduced in varying amounts to the composition of composite materials with a gypsum and cement matrix. The volumetric capacity and heat conductivity were determined in changing temperature conditions, and the basic technical parameters of the analysed mortars were tested. The described research results have been taken from master's and engineer's dissertations, written at the Faculty of Civil and Environmental Engineering, at the West Pomeranian University of Technology in Szczecin.
EN
Solar air heater (SAH) is an important device for solar energy utilization which is used for space heating, crop drying, timber seasoning etc. Its performance mainly depends on system parameters, operating parameters and meteorological parameters. Many researchers have been used these parameters to predict the performance of SAH by analytical or conventional approach and artificial neural network (ANN) technique, but performance prediction of SAH by using relevant input parameters has not been done so far. Therefore, relevant input parameters have been considered in this study. Total ten parameters were used such as mass flow rate, ambient temperature, wind speed, relative humidity, fluid inlet temperature, fluid mean temperature, plate temperature, wind direction, solar elevation and solar intensity to find out the relevant parameters for ANN prediction. Seven different neural models have been constructed using these parameters. In each model 10 to 20 neurons have been selected to find out the optimal model. The optimal neural models for ANN-I, ANN-II, ANN-III, ANN-IV, ANN-V, ANN-VI and ANN-VII were obtained as 10-17-1, 8-14-1, 6-16-1, 5- 14-1, 4-17-1, 3-16-1 and 2-14-1, respectively. It has been found that ANN-II model with 8-14-1 is the optimal model as compared to other neural models. Values of the sum of squared errors, mean relative error, and coefficient of determination were found to be 0.02138, 1.82% and 0.99387, respectively, which shows that the ANN-II developed with mass flow rate, ambient temperature, inlet and mean temperature of air, plate temperature, wind speed and direction, relative humidity, and relevant input parameters performed better. The above results show that these eight parameters are relevant for prediction.
EN
For economic growth of nation, the energy plays an important role. The excessive use of fossil fuels results the increase in global warming and depleting the resources. Due to this reason, the renewable energy sources are creating more attraction for researchers. In renewable energy sector, solar energy is the most abundant and clean source of energy. In solar thermal systems, solar air heater (SAH) is the main system which is used for heating of air. As it is simple in construction and cheaper in cost, it is of main interest for the researchers. The concept of first law and second law of thermodynamics is used for the study of the energy and exergy analysis respectively. The energy analysis is of great importance for the study of process effectiveness while the exergetic analysis is another significant concept to examine the actual behavior of process involving various energy losses and internal irreversibility. For efficient utilization of solar energy, the exergy analysis is very important tool for optimal design of solar air heaters. The aim of the present work is to review the works related to energy and exergy analysis of various types of solar air heaters and to find out the research gap for future work.
EN
The objective of present work is to predict the thermal performance of wire screen porous bed solar air heater using artificial neural network (ANN) technique. This paper also describes the experimental study of porous bed solar air heaters (SAH). Analysis has been performed for two types of porous bed solar air heaters: unidirectional flow and cross flow. The actual experimental data for thermal efficiency of these solar air heaters have been used for developing ANN model and trained with Levenberg-Marquardt (LM) learning algorithm. For an optimal topology the number of neurons in hidden layer is found thirteen (LM-13).The actual experimental values of thermal efficiency of porous bed solar air heaters have been compared with the ANN predicted values. The value of coefficient of determination of proposed network is found as 0.9994 and 0.9964 for unidirectional flow and cross flow types of collector respectively at LM-13. For unidirectional flow SAH, the values of root mean square error, mean absolute error and mean relative percentage error are found to be 0.16359, 0.104235 and 0.24676 respectively, whereas, for cross flow SAH, these values are 0.27693, 0.03428, and 0.36213 respectively. It is concluded that the ANN can be used as an appropriate method for the prediction of thermal performance of porous bed solar air heaters.
PL
Powietrzne wielorurowe gruntowe wymienniki ciepła (PRGWC) o krótkich gałęziach i małych przekrojach kolektorów charakteryzują się nierównym rozdziałem powietrza pomiędzy równoległe gałęzie. W artykule przeprowadzono analizę wpływu wyżej wymienionej nierówności na całoroczną ilość ciepła i chłodu pozyskiwanego za pomocą PRGWC. W obliczeniach wzięto pod uwagę opór przewodzenia ciepła gruntu oraz wykraplanie wilgoci w rurach wymiennika. Nierówność rozdziału powietrza uwzględniono wykorzystując wyniki własnych badań doświadczalnych. Rozpatrzono dwa typy wymienników: Z i U. Obliczenia wykonano dla zmiennej ilości powietrza wentylacyjnego zakładając obniżenie dzienne i nocne. Stwierdzono, że w układach typu Z o krótkich gałęziach (L/d = 75) i średnicach kolektorów równych średnicom gałęzi (d = dkol), nierówny rozdział powietrza ma istotny wpływ na ilość pozyskiwanej energii. Wydajność tego typu wymienników okazała się o 3%-14% niższa niż wydajności wymienników o idealnie równym rozdziale. Z kolei wydajność wymienników typu U o krótkich gałęziach i średnicach kolektorów równych średnicom gałęzi była tylko nieznacznie (0%-2%) mniejsza niż wymienników o równym rozdziale powietrza. Tym samym ustalono, że w przypadku wymienników o większej długości gałęzi (L/d >> 75) i/lub odpowiednio większych średnicach kolektorów (d > dkol, dkol = f (L, n)), w których nierówność rozdziału powietrza jest mała, jej wpływ na wydajność cieplną wymiennika będzie pomijalny.
EN
Experimental investigations of multi-pipe earth-to-air heat exchangers (EAHEs) with short branches and small diameter of manifolds show a considerable non-uniformity in distribution of air between branches. In this paper an effect of this flow non-uniformity on the energy gains in the whole year EAHE operation is presented. In calculation, ground thermal resistance, water vapor condensation and changes of air flow rate were taken into consideration. The flow non-uniformity was described by means of experimentally obtained characteristics of Z-type and U-type EAHEs. The obtained results show that in Z-type heat exchangers with short branches (L/d = 75) and small collector diameters (d = dkol) the non- -uniform division of air between parallel pipes has significant influence on the thermal performance of such exchangers. The thermal performance of Z-type structures was 3-14% lower compared to the structures of uniform airflow distribution. On the other hand, the thermal performance of the U-type heat exchangers was only 0-2% lower in comparison to exchangers of perfect airflow division. Thus, it was found that for heat exchangers with long branches (L/d >> 75) and/or adequately large collectors (dkol > d, dkol = f (L, n)), in which the unequal distribution of air is small, the effect of this inequality on the abstracted energy will be negligible.
PL
W artykule dokonano przeglądu światowej literatury dotyczącej badań ogrzewania ściennego. Ponadto scharakteryzowano podstawowe typy grzejników ściennych. W kolejnej części zaprezentowano stanowisko służące do badania ogrzewania płaszczyznowego oraz obiekt badań, jakim był grzejnik ścienny wykonany w systemie suchej zabudowy. Grzejnik składał się z płyty gipsowo-włóknowej o grubości 15 mm rurkami polibutylenowymi o średnicy 8×1 mm i rozstawie 62,5 mm z umieszczonymi w wyfrezowanych kanałach. W ostatniej części artykułu zamieszczono wyniki badań charakterystyki cieplnej tego urządzenia.
EN
The article contains the international literature review on studies of wall heating. Basic types of wall heaters were described here. In the next part of this paper, laboratory research facility for testing the surface heating system and object of study as a wall heater integrated into dry construction panel were presented. The heater consisted of gypsum-fiber panel with a thickness of 15mm and embedded polybutylene tubes with a diameter of 8×1mm and spacing 62.5mm. The last part of the paper contains the thermal performance of this prototype device obtained by experimental testing.
EN
The assessment methodology for the sustainability of buildings is based on the analysis of environmental, social and economic performance. The main purpose of the paper is the presentation of energy-related conditions and envelope properties as well as methodology aspects. The first part of the paper presents the literature review on sustainability and zero-energy buildings. The second part is devoted to describe different energy indicators for the evaluation of primary energy requirements and energy characteristic. The last section describes the general methodology for characterization of energetic properties of the building envelope and gives examples from literature of the effect of applications in a building’s envelope an aerogel based thermal insulation for higher thermal transmittance and a PCM for higher latent heat capacity with general description of results obtained by other authors. The crucial measure is the use of high thermal performance components for the building’s envelopes combined with the heat storage potential. In the context of sustainability, energy related conditions constitute a new set of indicators for identifying the usefulness and the efficiency of new technologies.
19
Content available remote Wyniki badań ogrzewania płaszczyznowego typu B wykonanego w technologii suchej
PL
Artykuł prezentuje wyniki badań eksperymentalnych grzejników podłogowych wykonanych w technologii suchej - typu B. Analizie porównawczej poddano dziewięć wariantów, w konstruowaniu których użyto płyt Dual Floor i AQUAPANEL Floor oraz lameli wykonanych z folii aluminiowej i blachy stalowej. W artykule przedstawiono wpływ elementów rozpraszających ciepło na gęstość strumienia ciepła emitowanego z powierzchni grzejników. Analizowano również zmianę charakterystyki cieplnej wywołanej zastosowaniem jednej oraz dwóch płyt typu Dual Floor. Na zakończenie zaprezentowano wyniki porównania dwóch grzejników płaszczyznowych, z których jeden był przykryty płytą AQUAPANEL Floor a drugi dwiema płytami Dual Floor.
EN
The paper presents the results of experimental testing of floor heating system type B made in so-called dry screed technology. The comparative analysis included nine cases involving the heating panels consisting of Dual Floor and AQUAPANEL Floor boards and heat diffusers made of aluminum foil and steel sheet. The influence of the heat dissipating elements on the heat flux density emitted from the floor heating system is shown in this paper. Also it is analyzed the change in thermal characteristics caused by using one or two Dual Floor panels. At the end of the research report the results of comparison of two floor heating systems, one of which was covered AQUAPANEL Floor plate and the other two plates Dual Floor are presented.
20
Content available remote Wyniki badań grzejnika płaszczyznowego o bardzo małej wysokości
PL
Artykuł prezentuje wyniki badań eksperymentalnych nietypowego grzejnika podłogowego typu B. Charakteryzuje się on bardzo małą wysokością, gdyż nie zastosowano w nim warstwy jastrychu. Wyprofilowana płyta styropianowa z wężownicą została pokryta dwiema warstwami elastycznego kleju oraz siatką z tworzywa sztucznego. Górną warstwę grzejnika stanowiła terakota. W trakcie badań eksperymentalnych określono zależność gęstości strumienia ciepła emitowanego przez badany element od temperatury zasilania. W artykule zaprezentowano rozkład temperatury na powierzchni grzejnika oraz jej przebieg w trakcie nagrzewania się i chłodzenia. Do zalet badanej konstrukcji należy zaliczyć bardzo małą wysokość, niewielki ciężar, małą bezwładność cieplną, niski koszt oraz krótki czas montażu i oddania do eksploatacji. Główną wadą testowanego grzejnika jest zauważalna nierównomierność pola temperatury na jego powierzchni.
EN
The paper presents the results of experimental testing of an unusual floor heating system type B. It is characterized by a very small height, because the screed has not applied. Profiled styrofoam plate with heating coil has been covered with two layers of flexible adhesive and plastic mesh. Terracotta was a top layer of the heater. During the experimental studies dependence of a heat flux density emitted by the tested component on the supply temperature has been determined. The article presents the temperature distribution on the surface of the floor heating system and the temperature variation during the heating and cooling. Advantages of the tested structure is a very low height, light weight, low thermal inertia, low cost and short time of installation and starting of operation. The main disadvantage of the radiator is high nonuniformity of the temperature distribution on its surface.
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