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1

Numerical assessment of solar air heater performance having a broken arc and broken S-shaped ribs as roughness

Haldia Shivam, Bisht Vijay Singh, Bhandari Prabhakar, Ranakoti Lalit, Negi Akashdeep

Archives of Thermodynamics

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2024

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Vol. 45, no 1

23--31

EN

This research article aims to provide a detailed numerical study of the multifaceted impact of S-shaped and broken arc roughness on solar air heaters. Therefore, a strong comparison was made between the modified heaters and smooth heaters for Reynolds numbers ranging from 2 00022 000. Also, the impact of two parameters, i.e. pitch and gap was analyzed to optimize the performance of the heater. The gap varies from 0.3 mm to 0.9 mm in both types of ribs with a step size of 0.2 mm. Afterwards, the pitch distance between both types of roughness was varied from 15 mm to 25 mm in the step size of 5 mm. Notably, it has been observed that among all the considered configurations, the gap length of 0.9 mm and pitch length of 25 mm have shown significant improvements in heat transfer characteristics. The specific combination of the gap of 0.9 mm and pitch of 25 mm has demonstrated better heat transfer capabilities at the expense of an increased friction factor. Lastly, the thermal performance factor of the systems was analyzed and reported. It was reported that the pitch length of 25 mm and gap length of 0.9 mm have shown a maximum thermal performance factor value from 2.9 to 3.3, while the pitch length of 25 mm and gap length of 0.3 mm have depicted the lowest thermal performance factor value. In terms of the overall performance, i.e. the thermal performance factor, the combination with a gap of 0.9 mm and pitch of 25 mm has shown the best performance, while a gap of 0.3 mm and pitch of 25 mm has yielded the worst performance.

2

Heat transfer and friction characteristics in three-side solar air heaters with the combination of multi-v and transverse wire roughness

Kumar Dhananjay

Archives of Thermodynamics

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2023

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Vol. 44, no 1

63--87

EN

The present paper describes the experimental analysis of heat transfer and friction factor for glass protected three-side artificially roughened rectangular duct solar air heaters (SAHs) having an arrangement of multiple-v and transverse wires (top wall multi-v and two side walls transverse) under the absorber plate, and compares their performance with that of one-side roughened solar air heaters under similar operating conditions. The investigated three-side solar air heaters are characterized by a larger rate of heat transfer and friction factor as compared to one-side artificially roughened SAHs by 24–76% and 4–36%, respectively, for the identical operating parameters. The air temperature below the three-side rugged duct is by 34.6% higher than that of the one-side roughened duct. Three-side solar air heaters are superior as compared to one-side artificially roughened solar air heaters qualitatively and quantitatively both.

3

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

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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.

4

Effect of D-shaped, reverse D-shaped and U-shaped turbulators in solar air heater on thermo-hydraulic performance

Ghildyal Abhishek, Bisht Vijay Singh, Bhandari Prabhakar, Rawat Kamal Singh

Archives of Thermodynamics

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2023

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Vol. 44, no 2

3--20

EN

As the cost of fuel rises, designing efficient solar air heaters (SAH) becomes increasingly important. By artificially roughening the absorber plate, solar air heaters’ performance can be augmented. Turbulators in different forms like ribs, delta winglets, vortex generators, etc. have been introduced to create local wall turbulence or for vortex generation. In the present work, a numerical investigation on a solar air heater has been conducted to examine the effect of three distinct turbulators (namely D-shaped, reverse D- and U-shaped) on the SAH thermo-hydraulic performance. The simulation has been carried out using the computational fluid dynamics, an advanced and modern simulation technique for Reynolds numbers ranging from 4000 to 18000 (turbulent airflow). For the purpose of comparison, constant ratios of turbulator height/hydraulic diameter and pitch/turbulator height, of 0.021 and 14.28, respectively, were adopted for all SAH configurations. Furthermore, the fluid flow has also been analyzed using turbulence kinetic energy and velocity contours. It was observed that the U-shaped turbulator has the highest value of Nusselt number followed by D-shaped and reverse D-shaped turbulators. However, in terms of friction factor, the D-shaped configuration has the highest value followed by reverse D-shaped and U-shaped geometries. It can be concluded that among all SAH configurations considered, the U-shaped has outperformed in terms of thermohydraulic performance factor.

5

Economic analysis of artificially roughened solar air heater with v-shaped ribs

Bahuguna Rahul, Chamoli Sunil, Barthwal Yogesh, Rana Sumit, Gupta Ashutosh, Bisht Vijay Singh

Acta Innovations

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2022

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no. 44

18--33

EN

Due to the minimal transfer of heat from absorber plate to moving air in the duct, solar air heaters have low performance. One of the procedures to augment the heat transfer by substantial amount is by utilizing artificial roughness, by which the performance can be improved considerably. In this study, an economic investigation of solar air heater embedded with artificial roughness is accomplished numerically employing v-shaped roughness, with the objective of optimising life cycle solar savings. The non-dimensional parameters of roughness, namely, angle of attack (α), roughness pitch (p/e) and roughness height (e/Dh) are examined by varying temperature rise over the solar air heater (∆T) and solar radiations (I) for different economic parameters values i.e., cost of collector, cost of roughness elements, and cost of conventional fuel.

6

An experimental study of solar air heater using arc shaped wire rib roughness based on energy and exergy analysis

Ghritlahre Harish Kumar

Archives of Thermodynamics

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2021

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Vol. 42, no 3

115--139

EN

In the present study, energy and exergy analysis has been evaluated for roughened solar air heater (SAH) using arc shaped wire ribs. To achieve this aim, two different types of flow arrangement have been considered. These arrangements are: apex upstream flow and apex downstream flo. In addition to this, a smooth duct SAH has been used for comparative study. The experiments were performed using the mass flow rate of 0.007– 0.022 kg/s on outdoor condition at Jamshedpur city of India. The absorber plate roughness geometry has been designed with relative roughness height 0.0395, rib size 2.5 mm, relative roughness pitch 10 and arc angle 60◦ . The energetic and exergetic performances have been examined on the basis of the first and second law of thermodynamics. According to the results, there is observed to be the maximum thermal efficiency and exergy efficiency as 73.2% and 2.64%, respectively, for apex upstream flow SAH at 0.022 kg/s, while, at same mass flow rate the maximum thermal efficiency and exergy efficiency is obtained as 69.4% and 1.89%, respectively, for apex downstream flow SAH. In addition to this, results reported that the maximum outlet temperature and temperature difference observed at lower mass flow rate. Also examined the outlet air temperature of SAH with various mass flow rates is very important for both analysis.

7

Evaluation of thermal performance factor for solar air heaters with artificially roughened channels

Siddique Waseem, Raheem Aneeq, Aqeel Muhammad, Qayyum Sualeh, Salamen Tareq, Waheed Khalid, Qureshi Kamran

Archive of Mechanical Engineering

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2021

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LXVIII, nr 2

195--225

EN

Heat transfer augmentation has become the utmost industrial desire. Turbulence promoters seems to be a better option for better heat transfer but at the expense of enormous pressure drop. In the current study, experimental optimization of heat transfer and pressure drop in various configurations of ribbed and corrugated surfaces on the bottom wall of the Solar Air Heater channel, having aspect ratio of 26:5 was performed. The results were evaluated in terms of enhancement in heat transfer (Nu/Nu s), friction factor ratio (f/f s) and thermal performance factor ( η). Three different cases and nine configurations with a pitch to rib/corrugation height ratio of 4.0 were studied. Case A consists of a smooth, continuous square rib, inline and staggered broken ribs. Case B comprises 30°, 45°, 60° and 90° trapezoidal corrugated geometries while Case C is the comparison of smooth, wavy corrugated and the best configurations of cases A and B. The results show that rectangular duct with staggered broken ribs and trapezoidal corrugation at 45° are the best configurations for case A and B, respectively. The 45° corrugated configuration is the best one amongst all, with values of 1.53, 1.5 and 1.33% for Nu/Nu s, f/f s and η respectively.

8

Solar air heater performance prediction using artificial neural network technique with relevant input variables

Ghritlahre Harish Kumar, Chandrakar Purvi, Ahmad Ashfaque

Archives of Thermodynamics

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2020

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Vol. 41, no 3

255--282

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.

9

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

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2020

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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.

10

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

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2020

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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.

11

A comprehensive review on energy and exergy analysis of solar air heaters

Ghritlahre Harish Kumar, Sahu Piyush Kumar

Archives of Thermodynamics

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2020

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Vol. 41, no 3

183--222

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.

12

Second law optimization and parametric study of a solar air heater having artificially roughened absorber plate

Sahu Mukesh Kumar, Prasad Radha Krishna

Archives of Thermodynamics

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2019

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Vol. 40, no 2

107--135

EN

In present article a mathematical model of arc shape wire roughened solar air heater, on the basis of energy and exergy output rates, entropy generation rate and augmentation entropy generation number, has been developed. A parametric study leading to entropy generation minimization has also been performed. In the analysis the geometric and operating parameters which have been considered as variable are: inlet air temperature, duct depth, collector width to duct depth ratio, mass flow rate per unit collector area, and temperature rise parameter. Results have been presented to see the effects of these values on the energy and exergy output rates of the roughened solar air heater. Effect of different values of wire rib roughness parameters on entropy generation has also been presented. Finally, design curves and optimization for different rib roughness parameters on the basis of minimum entropy generation number with temperature rise parameter, have been presented and optimum values also have been found out 0.004 to 0.010 (Km2 )/W. The entropy generation rate obtained for the system, in the present work has been compared with those obtained for solar air heater with different roughness geometries on absorber plates available in the literature for common roughness parameters and operating parameters which validate the present results.

13

Modelling of back propagation neural network to predict the thermal performance of porous bed solar air heater

Ghritlahre Harish Kumar, Prasad Radha Krishna

Archives of Thermodynamics

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2019

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Vol. 40, no 4

103--128

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.

14

Exergy based analysis of solar air heater duct with W-shaped rib roughness on the absorber plate

Patel Sumer Singh, Lanjewar Atul

Archives of Thermodynamics

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2019

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Vol. 40, no 4

21--48

EN

Exergy analysis is a powerful thermodynamic tool and it helps in computing the actual output of a system. It helps the researchers to optimize the roughened solar air heater design to compensate the present and also the future needs. In this study, investigation on exergetic performance evaluation of a solar air heater with W-shaped roughened absorber surface analytically by employing mathematical model and the results obtained are compared with smooth plate solar air heater under same operating conditions. The exergetic efficiency curves has been plotted as a function of different values of Reynolds number and temperature rise parameter for different roughness parameters. The maximum augmentation in the exergetic efficiency of the solar air heater with W-shaped roughened surface as compared to solar air heater with smooth surface has been obtained as 51% corresponding to the relative roughness height of 0.03375 and the rib angle of attack about 60°. Based on the exergetic efficiency the suitable design parameters of solar air heater with W-shaped roughened are determined.

15

Badanie wpływu kąta pochylenia powietrznego kolektora słonecznego na jego efektywność cieplną w warunkach konwekcji swobodnej

Fiuk J., Waligóra W.

Ciepłownictwo, Ogrzewnictwo, Wentylacja

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2017

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T. 48, nr 6

234--239

PL

W artykule przedstawiono wyniki badania wpływu kąta ustawienia powietrznego kolektora słonecznego względem poziomu na jego efektywność cieplną. Do badań wykorzystano ożebrowany, powietrzny kolektor słoneczny pracujący w warunkach konwekcji swobodnej. Badania wykonano w warunkach laboratoryjnych przy sztucznym źródle promieniowania cieplnego. Zmieniano kąt zawarty między kolektorem, a podłożem oraz wartość natężenia promieniowania. Wartość kąta ustawienia kolektora oraz natężenie promieniowania wynosiły odpowiednio: α = 45°- 90°, I = 0 W/m2-550 W/m2. W efekcie badań eksperymentalnych stwierdzono, że największą efektywność cieplną uzyskał kolektor ustawiony pod kątem 80° do podłoża.

EN

In the presented paper an experimental results of passive solar air collector is described. The collector is positioned at an varied angle towards incoming radiation, and its thermal efficiency is thus derived from measured data. For the research a finned absorber collector was used, which operates under natural Convection heat transfer regime. Artificial thermal radiation source was used in the laboratory. Angle between horizontal plane and collector was changed during experiment as well as irradiance value. The range of those parameters was: α = 45-90 deg; I=0-550 W/m2. The result of experimental research shows that highest thermal efficiency was obtained for collector at a 80 deg angle in regards to the floor.

16

Brief literature review on air solar collectors

Dutkowski K., Fiuk J., Sikora M.

Instal

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2016

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nr 12

25--28

EN

In this paper a short literature review on the solar collectors has been presented. A classification has been made according to application areas: heating in industrial processes (i.e. drying of agricultural products, biomass drying) or in civil engineering (i.e. air conditioning, space heating). Solar collectors have been classified in regard to their design: cover material, direction and type of flow, means of heat transfer intensification. Direction of future research in the field of solar collectors has been briefly discussed in both experimental and numerical research. The most popular trends in development of solar air collectors aiming at making the technology more common were specified. The most notable is heat accumulation through the utilization of phase changing materials (PCM).

PL

W artykule przedstawiono przegląd aktualnego stanu wiedzy na temat powietrznych kolektorów słonecznych. Dokonano podziału kolektorów ze względu na ich przydatność do celów grzewczych w procesach przemysłowych (np.: suszenie produktów rolnych, suszenie biomasy energetycznej) czy w budownictwie (wentylacja i klimatyzacja pomieszczeń). Przedstawiono podział kolektorów ze względu na: rodzaj pokrycia kolektora, kierunek i sposób przepływu powietrza, sposób intensyfikacji wymiany ciepła poprzez wydłużenie drogi jaką pokonuje czynnik roboczy, czy rozwinięcie powierzchni wymiany ciepła. Opisano kierunki badań eksperymentalnych oraz analiz numerycznych z wykorzystaniem komputerowych programów z zakresu CFD. Wskazano proponowane kierunki rozwoju powietrznych kolektorów słonecznych zmierzające do ich upowszechnienia, w tym te, które pozwalają na akumulację ciepła poprzez wykorzystanie np.: materiałów zmiennofazowych (PCM).

17

Modeling of thermal processes in the solar air heater

Zhelykh V., Kozak C.

Zeszyty Naukowe Politechniki Częstochowskiej. Budownictwo

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2014

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Z. 20 (170)

285--289

EN

The article sets out the place of solar energy in the world today. There are provided basic advantages and disadvantages of air quality heat capacity for solar heating system. Data for modeling heat flow system with passive energy use have been presented. Discussed methodology allows to determine the thermal characteristics of the air in the collector of the passive use of solar energy.

RU

Определено энергетическое положение в мире в настоящее время. Поданы основные преимущества и недостатки воздуха в качестве теплоносителя для солнечной системы отопления. Представлены данные по применению теории графов для моделирования тепловых потоков в пассивном солнечном воздухонагревателе. Приведена методика определения тепловых характеристик воздушного гелиоколлектора с пассивным использованием солнечной энергии.

18

Analysis of Heat Flow Distribution in the Room with Installed

Kozak C., Savchenko O., Zhelykh V.

Ciepłownictwo, Ogrzewnictwo, Wentylacja

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2014

|

T. 45, nr 9

359--362

EN

Regression equations are presented for finding the temperature of the heated air stream in a thermosiphon solar collector according to the intensity of the heat flux, the area of the collector holes and the inclination angle. It is proved that the greatest influence on relative temperature of the air stream has the angle of solar heater installation. The effectiveness of the flow turbulators installed along the coolant flow in the solar collector air channel is assessed. Availability of turbulators can improve the efficiency of the solar collector by 13%, as compared to a flat heat-absorbing plate.

PL

Przedstawiono równania regresji określające temperaturę strumienia ogrzanego powietrza w termosyfonowym kolektorze słonecznym w zależności od gęstości strumienia ciepła w obszarze otworów kolektora i jego kąta nachylenia. Zostało udowodnione, że największy wpływ na wartość względnej temperatury strumienia powietrza ma kąt montażu grzejnika słonecznego. Przedstawiono oszacowanie skuteczności turbulizatorów przepływu zainstalowanych wzdłuż przepływu powietrza chłodzącego w kanale kolektora słonecznego. Dostępność turbulizatorów może poprawić sprawność kolektora słonecznego o 13% w stosunku do płaskiej płyty absorbującej ciepło.