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1

Investigations of the impact of the magnetic field on the process of formation of scaling in thermal devices

Ismailov Oybek, Khurmamatov Abdugaffor M., Ismoilov Mirzaakbar, Auesbaev Alisher U., Utegenov Usnatdin

Nafta-Gaz

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2024

|

R. 80, nr 2

115--121

EN

Water is used as working fluids in hydro and thermal power engineering, as well as in heat supply and cooling systems. In the process of heating water in water-heating boilers, scale forms due to the precipitation of crystals of mineral additives and mineral salts. Over time, the accumulation of scale with low thermal conductivity leads to a decrease in the internal diameter of the pipes. Consequently, the flow of liquid is hindered, the hydraulic resistance increases and the thermal conductivity of the device decreases. The scale layer is usually removed by acid washing of the internal heat exchange surfaces or mechanical washing. However, both methods involve the use of a substantial amount of chemicals and result in highly polluted wastewater. In addition, it significantly increases operating costs. The article uses statistical methods for processing experimental data, and generally accepted methods for conducting experiments to study the patterns of scale formation using control and measuring instruments and accurate methods for measuring technological parameters. The main purpose of the paper is to study the influence of a constant magnetic field on the formation of mineral salts deposits on the surface of walls of thermal appliances used in chemical, oil refining, and food processing industry. The influence of a constant magnetic field on the formation of scale on the surface of the walls of the heating element in a water heater has been established. According to the results of an experiment aimed at preventing the accumulation of mineral salt deposits on the surface of the heating element in a water heating boiler under the influence of a magnetic field, the amount of mineral salt precipitate deposited on such surface can be reduced up to 5.2 times. Consequently, the prevention of mineral scale formation is achieved, eliminating the need to use expensive chemicals. The stable operation of the devices contributes to enhanced thermal efficiency. Under the influence of a magnetic field, scale formation decreases on average by a factor of 5, as long as the water temperature does not exceed 70°C. However, if the temperature rises above 90°C, the scale formation rate gradually increases.

PL

Woda jest wykorzystywana jako płyn roboczy w energetyce wodnej i cieplnej, w systemach ciepłowniczych i chłodniczych. W procesie podgrzewania wody w kotłach wodnych powstaje kamień kotłowy w wyniku wytrącania się kryształów dodatków mineralnych i soli mineralnych. Z biegiem czasu wzrost grubości kamienia o niskiej przewodności cieplnej prowadzi do zmniejszenia wewnętrznej średnicy rury. W rezultacie przepływ cieczy staje się utrudniony, wzrasta opór hydrauliczny i maleje przewodność cieplna urządzenia. W celu usunięcia warstwy kamienia stosuje się zwykle mycie kwasem wewnętrznych powierzchni wymiany ciepła lub oczyszczanie mechaniczne. Wszystkie te metody wiążą się z użyciem dużej ilości chemikaliów i wytwarzaniem mocno zanieczyszczonych ścieków. Ponadto znacznie zwiększają one koszty eksploatacji. W artykule zastosowano metody statystyczne przetwarzania danych eksperymentalnych oraz ogólnie przyjęte metody prowadzenia eksperymentów do badania przebiegu powstawania kamienia kotłowego za pomocą przyrządów kontrolno-pomiarowych oraz dokładne metody pomiaru parametrów technologicznych. Głównym celem pracy jest zbadanie wpływu stałego pola magnetycznego na powstawanie osadów soli mineralnych na powierzchni ścianek urządzeń cieplnych stosowanych w zakładach przemysłu chemicznego, rafineryjnego i spożywczego. Określono wpływ stałego pola magnetycznego na powstawanie kamienia kotłowego na powierzchni ścianek elementu grzejnego podgrzewacza wody. Zgodnie z wynikami eksperymentu mającego na celu zapobieganie osadzaniu się osadów soli mineralnych na powierzchni elementu grzejnego w kotle wodnym pod wpływem pola magnetycznego, ilość osadów soli mineralnych osadzonych na powierzchni elementu grzejnego kotła wodnego można zmniejszyć nawet 5,2-krotnie. W rezultacie zapobiega się tworzeniu kamienia kotłowego i nie stosuje się drogich chemikaliów. Sprawność cieplna urządzeń osiągana jest dzięki możliwości stabilnej pracy urządzenia. Tworzenie się kamienia pod wpływem pola magnetycznego zmniejsza się średnio 5-krotnie, dopóki temperatura wody nie przekroczy 70°C. Jednakże, gdy temperatura wzrośnie powyżej 90°C, tempo tworzenia się kamienia stopniowo wzrasta.

2

Ocena przekształceń piętrowego, ceglanego domu z dachem półpłaskim z przełomu XIX-XX pod wpływem termomodernizacji na przykładzie gminy Puck, woj. pomorskie

Szarejko Magdalena, Górka Anna

Wiadomości Konserwatorskie

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2023

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Nr 73

102--116

PL

Ceglane budynki mieszkalne z przełomu XIX i XX wieku, które stanowiły charakterystyczny element krajobrazu wsi pomorskiej, obecnie powszechnie poddawane są modernizacji w celu poprawy warunków cieplnych. Przedmiotem badania jest stan zachowania najmłodszego, historycznego typu domu w zagrodzie chłopskiej na Kaszubach – piętrowego, ceglanego domu z dachem półpłaskim. Badanie przeprowadzono na obszarze gminy Puck. Zidentyfikowano i opisano 42 obiekty w 16 miejscowościach. Ponadto zaproponowano metodę klasyfikacji i oceny zmian architektonicznych pod wpływem termomodernizacji. Rezultaty potwierdziły znaczną skalę przekształceń: zaledwie dwa obiekty zachowały się bez zmian, podczas gdy 67% jest częściowo lub znacznie przekształconych. Uzyskane wyniki dowodzą trwałości wiejskich, historycznych budynków ceglanych oraz potrzeby poszukiwania i popularyzacji rozwiązań termomodernizacyjnych spełniających warunki ich ochrony.

EN

Brick houses dating back to the turn of the nineteenth and the twentieth centuries, which were a distinctive component of the Pomeranian countryside’s landscape, are now commonly being transformed to improve their thermal conditions. This study analyzed the state of preservation of the most recent historical type of house in peasant homesteads in Kashubia, namely a two-story brick house with a semi-flat roof. The survey was conducted in the Puck County area. As many as forty-two sites in sixteen locations were identified and documented. In addition, a method for classifying and evaluating architectural changes under the influence of thermal efficiency improvement has been proposed in the study. The results confirmed the significant scale of transformation: only two buildings remained unchanged, while 67% of them were partially or significantly transformed. The results demonstrate the durability of rural, historical brick buildings and the need to search for and popularize thermal efficiency improvement solutions that meet the conditions for the preservation of such buildings.

3

Effectiveness of using physical pretreatment of lignocellulosic biomass

Piątek Milena, Bartkowiak Anna

Journal of Water and Land Development

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2023

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no. 58

62--69

EN

Pretreatment is aimed at making lignin structures, which in turn causes decrystallisation and depolymerisation of cellulose. This treatment allows to increase the energy potential of substrates. A properly selected method allows for obtaining larger amounts of biogas with a high content of biomethane. The aim of the study was to analyse selected pretreatment methods (ultrasonic and hydrothermal) for biogas yield, including biomethane, and to demonstrate the effectiveness of obtaining additional electricity and heat from these methods. It was based on the literature data. On basis the study, the following information was obtained: average yield of biogas and biomethane before and after treatment, difference in yield of biogas and biomethane after treatment, and the effect of treatment on the substrate used. Moreover, an estimate was made of the effectiveness of obtaining additional electricity and heat from selected pretreatment methods compared to hard coal. Based on the analysis of the ultrasonic treatment analysis, it was shown that the best result was obtained with the ultrasound treatment of the mixture of wheat straw and cattle manure with the following parameters: frequency 24 kHz, temperature 44.30°C, time 21.23 s. This allowed a 49% increase in biogas production. The use of pretreatment would therefore allow the production of more electricity and heat capable of replacing conventional heat sources such as coal.

4

Thermal efficiency analysis of the rotary kiln based on the wear of the lining

Zeng Donghu, Shcherbina V. Yu., Li Jiaxiu

International Journal of Applied Mechanics and Engineering

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2023

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Vol. 28, no. 2

125--138

EN

The thickness of the lining is reduced from 230 mm to 80 mm due to long-term wear, resulting in low thermal efficiency of the rotary kiln. The thermal resistance, which is positively correlated with the thickness of the lining, is one of the most important factors determining the thermal efficiency of the rotary kiln. The thermal efficiency of the rotary kiln can be improved by introducing insulation material with lower thermal conductivity into the lining. The average heat flux is used as the thermal efficiency evaluation index of the 4×60 m rotary kiln under no-load conditions in this work. A numerical experiment was conducted for the temperature and heat flux of the inner surface of the lining, as well as the temperature of the outer surface of the shell during the wear of the lining. There are two cases considered, one with and one without insulation materials in lining. According to the analysis, when the lining in the high temperature zone of the rotary kiln wears to 80 mm, the average heat flux of the inner surface of the lining increases by 105.03%. However, after the addition of insulation material, the average heat flux on the inner surface of the lining increases by 40.38% (wears to 80 mm). Compared to the thermal efficiency of the rotary kiln without heat insulation material, the average heat flux of the inner surface of the lining is reduced by 36.36% (230 mm), and it is reduced by 99.01% (wears to 80 mm). A significant advantage of this solution is that it can increase the thermal efficiency of the rotary kiln, improve the insulation performance of the lining, reduce heat loss to the environment through the shell, and the results obtained can be used for the latest equipment design and existing equipment improvements.

5

Kominowe systemy odprowadzania spalin z gazowych kotłów kondensacyjnych

Tałach Zbigniew A., Nowak Roman

Gaz, Woda i Technika Sanitarna

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2023

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Nr 3

6--10

PL

Powszechne wprowadzenie gazowych urządzeń kondensacyjnych zapewnia wysoką efektywność energetyczną i jest zaliczane do urządzeń grzewczych z zamkniętą komorą spalania. Wysoka sprawność tych urządzeń wynika z zastosowania specjalnych koncentrycznych systemów kominowych. Efektem tego jest kominowa wymiana ciepła, gdyż ciepło z przewodu spalinowego przekazywane jest do koncentrycznego przewodu powietrznego, co powoduje, ze do komory spalania dostarczane jest podgrzane powietrze. Podczas użytkowania tego typu urządzeń, równie ważne są nie tylko zagadnienia dotyczące efektywności energetycznej, ale również aspekty bezpieczeństwa ich stosowania, poprzez eliminację zagrożeń zatrucia tlenkiem węgla. W artykule przedstawiono konstrukcje systemów powietrzno-spalinowych stosowanych dla urządzeń gazowych z zamkniętą komorą spalania typu C.

EN

The widespread introduction of gas condensing devices ensures high energy efficiency and is classified as a heating device with a closed combustion chamber. The high efficiency of these devices results from the use of special concentric chimney systems. The effect of this is a chimney heat exchange, because the heat from the flue is transferred to the concentric air duct, which causes the heated air to be supplied to the combustion chamber. When using this type of equipment, not only energy efficiency issues are equally important, but also the safety aspects of their use by eliminating the risk of carbon monoxide poisoning. The article presents the constructions of air-flue gas systems used for gas appliances with a closed type C combustion chamber.

6

Low Emission Power Plant Design Using R134a as Working Fluid Instead of Fossil Fuel to Mitigate Greenhouse Gas Effect

Simanjuntak Janter Pangaduan, Prayogo Wisnu

Ecological Engineering & Environmental Technology

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2023

|

Vol. 24, iss. 5

231--237

EN

This study investigates the potential of using R134a as a working fluid in a low-emission power plant instead of the conventional power plant to mitigate the greenhouse effect. The study explores the thermodynamic properties of R134a and its suitability for use in an Organic Rankine Cycle (ORC) power plant. A simulation model was developed using Aspen Hysys to evaluate the power plant’s performance using this working fluid. The results indicate that the ORC power plant can significantly reduce greenhouse gas emissions compared to conventional power plants while maintaining high energy efficiency. About 18.17 kW of electric power can be obtained at a working condition of 10 bar and an evaporator temperature of 130 °C with the highest thermal efficiency of 3.43%. The study provides valuable insights into the potential of R134a as a sustainable working fluid for low-emission power generation.

7

Exergetic performance analysis of solar air heater with inverted L-shape ribs as roughness element

Chaudhari Manmohan, Sharma Sohan Lal, Debbarma Ajoy

Archives of Thermodynamics

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2023

|

Vol. 44, no 3

241--267

EN

Improvement in the exegetic efficiency of a solar air heater (SAH) can be done by enhancing the rate of heat transfer. In this work, the exergetic efficiency optimization of an artificially roughened solar air heater having an inverted L-shape rib has been performed. The numerical analysis of the exergetic performance of the solar air heater was carried out at a constant heat flux of 1000 W/m2 . The study was conducted to investigate the effect of different relative roughness pitch (7.14–17.86) on the exergy losses, under the Reynolds number range of 3000 to 18 000. The roughness parameter of this geometry has been optimized and found to be among functional operating parameters like average solar intensity and temperature rise across the collector. The optimized value of relative roughness pitch is 17.86 at the isolation of 1000 W/m2 , and the parameter of temperature rise ranges from 0.005 to 0.04.

8

Investigation of thermal and air efficiency in trombe wall of modular building

Zhelykh Vasyl, Ulewicz Małgorzata, Furdas Yurii, Shepitchak Volodymyr

Archives of Civil Engineering

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2023

|

Vol. 69, nr 4

663--678

EN

The proposed Trombe wall design is an innovative and effective solution for addressing issues related to building energy efficiency. The Trombe wall can help reduce a building’s energy consumption, provide optimal indoor temperature, and minimize the building’s environmental impact by utilizing renewable energy sources. The article deals with the study of the heat-air characteristics of the Trombe Wall, which performs the functions of external protection of a modular house, with the aim of further evaluating the possibility of using it as a hybrid protection with additional heating and ventilation functions assigned to it. The results of experimental research conducted on one of the elements of external protection of a modular house in the form of the Trombe Wall are presented. The experimentally obtained graphic dependences were compared with the calculated data and the convergence was evaluated. The proposed design allows you to organize air exchange in the premises with a multiplicity within 1-1.5 h-1, and also provides an opportunity to provide additional thermal power in the amount of 250 W/m2. The article presents the results of experimental studies that allow to evaluate the thermal characteristics of the proposed design of external protection for a modular house. These results indicate that with the given geometric dimensions, in particular with a volume of 14 m3, the thermal power utilized by the Trombe wall is within 0.2-0.7 kW.

9

Dependence between nominal power deterioration and thermal efficiency of gas turbines due to fouling

Herdzik Jerzy

Zeszyty Naukowe Akademii Morskiej w Szczecinie

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2022

|

nr 69 (141)

45--53

EN

Deterioration in the performance of gas turbines is a well-known phenomenon occurring during their operation. The most important form is a decrease in the internal efficiency of the compressor and turbine due to fouling, which is the most significant deterioration problem for an operator. This article presents the effect of gas turbine fouling as a drop in airflow, pressure ratio, and compressor efficiency resulting in a reduction in power output and thermal efficiency. This resulted in a decrease in the nominal power of a gas turbine and an increase in the fuel consumption (heat rate). The fouling effects were described using the example of the MT30 marine gas turbine with a nominal power of 36 MW. The estimated profit loss during the operation of the gas turbine was within the range of 1–10% of the total fuel consumption cost. A 2% deterioration in the output of a gas turbine accounted for US$ 10,000–20,000 per year and 1 MW of gas turbine nominal power (according to marine fuel prices in 2019–2020) – this means at least US$ 300,000 annually for an MT30. Due to the low accuracy of fuel consumption measurements, another possibility was provided. The correlation between the gas turbine power deterioration and thermal efficiency was presented, which made it possible to estimate the increase in the specific and total fuel consumption when the nominal power deterioration is known. Two linear approximations were proposed to calculate increases in the annual operating costs for an MT30 due to fouling.

10

Air bottoming combined cycle performance analyses by the combined effect of variable parameters

Khan Mohammad N, Alzafiri Dhare

Archive of Mechanical Engineering

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2022

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LXIX, nr 3

497--517

EN

To meet the continuous demand for energy of industrial as well as commercial sectors, researchers focus on increasing the power generating capacity of gas turbine power plants. In this regard, the combined cycle is a better solution in terms of environmental aspects and power generation as compared to a simple gas turbine power plant. The present study is the thermodynamic investigation of five possible air bottoming combined cycles in which the topping cycle is a simple gas turbine cycle, regenerative gas turbine cycle, inter-cool gas turbine cycle, reheat gas turbine cycle, and intercool-reheat gas turbine cycle. The effect of pressure ratio of the topping cycle, the turbine inlet temperature of topping cycle, and ambient temperature on net power output, thermal efficiency, total exergy destruction, and exergetic efficiency of the combined cycle have been analyzed. The ratio of the net power output of the combined cycle to that of the topping cycle is maximal in the case when the topping cycle is a simple gas turbine cycle. The ratio of net power output and the total exergy destruction of the combined cycle to those of the topping cycle decrease with pressure ratio for all the combinations under study except for the case when the topping cycle is the regenerative gas turbine cycle.

11

Energetic & exergetic analysis of a parabolic trough: concentrated solar power plant

Nagpal Mohit, Maithani Rajesh, Kumar Suresh

Acta Innovations

|

2021

|

no. 40

19--30

EN

Solar energy is the most affordable source of energy. Parabolic trough systems are used to concentrate and extract heat, therefore it’s very significant to analyse its performance in terms of energy and exergy. Exergy based analysis of the system ensures the eradication of losses, resulting in the yield of energy of the highest quality. In this paper, an investigation has been carried out using numerical simulation with an objective of analysis of Parabolic Trough Collectors on the basis of energy and exergy. Detailed second law analysis has been performed by varying the system and operating parameters through computer simulation. Exergy output has been determined by analysing the effect of major system parameters, namely, mirror reflectivity, glass transmissivity, absorptivity, the diameter of glass envelop, and the receiver. The operating parameters considered in the investigation are insolation and temperature rise parameters. The extensive investigation of the parabolic trough of a concentrated solar power plant for various design parameters in the range of operating parameters reveals that it is beneficial to operate the system at higher temperature as opposed to the preference of the operating system at lower temperature from purely thermal considerations.

12

Solar collectors integrated into transparent facades

Zhelykh Vasyl, Venhryn Iryna, Kozak Khrystyna, Shapoval Stepan

Production Engineering Archives

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2020

|

Vol. 26, Iss. 3

84--87

EN

Due to the fact that the number of natural disasters in the world has increased in recent years, experts note that climate change is the cause. As a consequence of the nature of the needs to improve the fuel and energy complex in the countries in world. This solution could be solar energy and similar energy sources. The paper presents the classification of energy-efficient houses proposed by international standards and its critical analysis. Emphasis is placed on the problem of improving solar collectors integrated into the construction of buildings. The paper presents the temperature characteristics of an experimental solar collector. For the experimental solar collector combined with the translucent facade of the building, thermal characteristics are set, in particular, such as thermal capacity and thermal efficiency.

13

Experimental and Numerical Analysis of the Energy Efficiency of Transparent Partitions with a Thermal Storage Unit

Musiał Michał

Journal of Ecological Engineering

|

2020

|

Vol. 21, nr 6

201--211

EN

The article presents the results of experimental research and a mathematical analysis of the energy efficiency of a PCM-modified transparent partition. The study was carried out during the summer season and heating season for 5 months under temperate climate conditions in Rzeszów (Poland). The solution under investigation allows for short-term storage of heat within a building window, owing to the high value of melting/freezing enthalpy of approx. 185 J/g, and the phase change material (PCM) applied. The research was conducted in parallel over two identical windows, with only one of them being modernised with a phase change thermal storage unit. The obtained results showed the possibility of improving the thermal balance of the window by 9.99%, and a more favourable adjustment of gains from solar radiation to the profile of heat demand of the adjacent room by 15.02%, compared to the reference window. The obtained results also allowed the numerical model describing the non-stationary heat exchange within the phase change material to be verified, using the solution of a Stefan problem. The obtained model was created using the equations of finite difference method in the Matlab environment. The verified model is highly compatible with empirical quantities, and constitutes a useful tool for simulating the distribution of heat storage in a PCM storage unit over time. This allows the heat gains resulting from the use of the tested storage units in the building windows to be estimated.

14

Ewolucja norm badań odbiorczych kotłów wodnorurowych

Rataj Zbigniew Leon

Instal

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2020

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nr 1

7--14

PL

W artykule dokonano przeglądu norm badań odbiorczych kotłów wodnorurowych. Omówiono normę krajową PN-72/M-34128, normę DIN 1942 Pomiary odbiorcze kotłów parowych, Normę Europejską PN-EN 12952-15 Kotły wodnorurowe. Cześć 15 Badania odbiorcze, normę ASME PTC-4. Pokazano zmiany ewolucyjne wprowadzone w poszczególnych normach, związane z rozwojem konstrukcji kotłów i urządzeń pomocniczych. Podano klasyczną definicje sprawności kotła (metoda bezpośrednia i pośrednia). Zwrócono uwagę na istotę poprawnej definicji sprawności kotła, gdyż sprawność jest istotnym parametrem eksploatacyjnym i służy do oceny osiągów kotła oraz oceny zgodności parametrów i parametrów gwarantowanych w badaniach odbiorczych.

EN

The article reviews the acceptance standards for water-tube boilers. National standard PN-72/M-34128, standard DIN 1942 Acceptance Test Code for Steam Generators, European Standard PN-EN 12952-15 Water-tube boilers and auxiliary installations – Part 15: Acceptance tests, as well as ASME PTC-4 Fired Steam Generators. Performance Tests Codes have been discussed. Evolutionary changes introduced in individual standards, related to the development of boiler structures and auxiliary installations are shown. A classic definition of boiler efficiency is provided (direct and indirect method). Attention is paid to the essence of the correct definition of boiler efficiency, as efficiency is an important operating parameter and is used to assess boiler performance and assess compliance of parameters and guaranteed parameters in acceptance tests. The attention was turned onto possible errors, which might occur when estimating the mean year boiler efficiency.

15

Sprawność przeponowych wymienników ciepła

Rubik Marian

Ciepłownictwo, Ogrzewnictwo, Wentylacja

|

2020

|

T. 54, nr 10

9--14

PL

W artykule omówiono różne pojęcia sprawności przeponowych wymienników ciepła: sprawność cieplną, entropową i egzergetyczną. Opisano specyficzne cechy każdej ze sprawności oraz ich zastosowania w praktyce, a szczególnie do oceny efektywności energetycznej procesów intensyfikacji wymiany ciepła w wymiennikach.

EN

The article discusses various concepts of efficiency of diaphragm heat exchangers; thermal, entropic, and exegetic efficiency. The specific features of each efficiency are described, as well as their application in practice, especially for the assessment of energy efficiency regarding the processes of intensifying heat exchange in the exchangers.

16

Performance analysis of three sides solar air heater having roughness elements as a combination of multiple-v and transverse wire on the absorber plate

Kumar Dhananjay, Prasad Laljee

Archives of Thermodynamics

|

2020

|

Vol. 41, no 3

125--146

EN

Artificial roughness has been found to enhance the thermal performance from the collector to air in the solar air heater duct. This paper presents the results of experimental investigation on thermal performance of three sides solar air heater roughened with combination of multiple-v and transverse wire. The range of variation of system and operating parameters is investigated within the limits of relative roughness pitch of 10−25, relative roughness height of 0.018 −0.042, angle of attack of 30°−75° at varying flow Reynolds number in the of range of 3000−12000 for fixed value of relative roughness width of 6. The augmentation in fluid temperature flowing under three side’s roughened duct is found to be 36.57% more than that of one side roughened duct. The maximum thermal efficiency is obtained at relative roughness pitch of 10 and relative roughness height of 0.042, and angle of attack of 60°. The augmentation in thermal efficiency of three sides over those of one side roughened duct is found to be 46−57% for varying values of relative roughness pitch, 38−50% for varying values of relative roughness height, and 40−46% for varying values of angle of attack.

17

Experimental investigation of augmented thermal and performance characteristics of solar air heater ducts due to varied orientations of roughness geometry on the absorber plate

Sahu Mukesh Kumar, Matheswaran M. M., Bishnoi Pardeep

Archives of Thermodynamics

|

2020

|

Vol. 41, no 3

147--182

EN

This paper presents the outdoor experimental results for thermal performance analysis of artificially roughened solar air heaters (SAHs). Circular wire ribs have been arranged to form arc shape geometry on the absorber plates and have been tested for two configurations of SAHs named as arc shape apex-downstream flow and arc shape apex-upstream flow SAH. Roughness parameters have been taken as relative roughness pitch in the range of 8–15, angle of attack 45°–75°, and for fixed relative roughness height of 0.0454, duct width to duct height ratio of 11. During the experimental analysis the mass flow rate varied from 0.0100 to 0.0471 kg/s. Based on the experimental results it was found that roughness with apexupstream flow SAH is having higher value of thermal efficiency, heat removal factor and collector efficiency factor as compared to roughness with apexdownstream flow SAH and simple absorber plate SAH. In the range of the operating parameters investigated the maximum of thermal efficiency, heat removal factor, and collector efficiency factor have been found.

18

Determination of the operating parameters of steam jet injectors for a main boiler’s regenerative feedwater system

Adamkiewicz Andrzej, Grzesiak Szymon

Zeszyty Naukowe Akademii Morskiej w Szczecinie

|

2019

|

nr 60 (132)

171--176

EN

Due to the development of alternative propulsion systems, there is a need for LNG tanker turbine propulsion plants to regain their competitiveness. Previous research revealed effective methods to increase the thermal efficiency of the steam cycle based on quality assessment, and it was proposed that the latent heat of the main turbine exhaust steam could be recovered. Research was carried out for the steam cycle using regenerative heat exchangers fed by steam jet injectors. In this paper, an algorithm to determine the operating parameters of steam jet injectors, and the calculation results for different drive steam parameters are presented. The obtained results will be used as input parameters for further heat balance calculations of the proposed regenerative steam cycles.

19

Optoelectronic pressure dependent study of MgZrO₃ oxide and ground state thermoelectric response using Ab-initio calculations

Noor Naveed Ahmed, Rashid Muhammad Abdul Rehman, Mahmood Qasim, Ul-Haq Bakhtiar, Naeem M. A., Laref Amel

Opto-Electronics Review

|

2019

|

Vol. 27, No. 2

194--201

EN

The electronic, optical and thermoelectric properties of zirconia-based MgZrO₃ oxide have been studied theoretically at a variant pressure up to 25 GPa. Calculations for the formation energy and tolerance factor reveal the thermodynamic and structural stability of MgZrO₃. To tune the indirect band gap from to a direct band gap, the optimized structure of MgZrO₃ has been subjected to external pressure up to 25 GPa. The optical properties have been discussed in the form of dielectric constant and refraction that brief us about the dispersion, polarization, absorption, and transparency of the MgZrO₃. In the end, the thermoelectric parameters have been analyzed at variant pressure against the chemical potential and temperature. The narrow band gap and high absorption in the ultraviolet region increase the demand of the studied oxide for energy harvesting device applications.

20

Thermodynamic model of steam injection pipeline considering the effect of time and phase change

Zhao Xuan, Niu Chengcheng, Wang Jun, Zhu Xiuxing

Journal of Power Technologies

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2019

|

Vol. 99, nr 2

123--130

EN

Thermodynamic parameters in heavy oil thermal recovery wells form the basis for evaluating the thermal efficiency of steam injection. However, various factors in wellbores affect the variation law of thermodynamic parameters, hindering attempts to make an accurate description of them. A thermodynamic model of wellbores is proposed in this study which factors in the effects of time and phase change with a view to: (i) improving the accuracy of thermodynamic parameter analysis, and (ii) identifying the main factors and rules that govern thermal efficiency. With the time factor considered, the transient conduction function of a coupled wellbore-formation was established, and the heat loss during steam injection was analyzed. Meanwhile, a wellbore pressure gradient equation was established using the Beggs-Brill model with consideration of the influence of phase transformation in wellbore. Steam pressure, which varies with flow pattern, was also analyzed. The accuracy of the proposed model was verified by comparing the results of the analysis with the test data. Taking this approach, the influence of steam injection parameters on thermal efficiency was studied. The results demonstrate that the relative error of the pressure analysis result of proposed model is 1.06% and the relative error of temperature is 0.24%. The main factor affecting thermal efficiency is water in the annulus of the wellbore, followed by the steam injection rate. The thermal efficiency of the wellbore is about 80% when the water depth in the annulus is 300 m. An increase in the injection rate or extension of the injection time can improve thermal efficiency, whereas an increase in steam injection pressure reduces thermal efficiency. The proposed method provides good prospects for optimizing high efficiency steam injection parameters of heavy oil thermal recovery wells.