Collector Outlet Research Articles

Using ANN techniques to forecast thermal performance of a vacuum tube solar collector filled with SiO2/EG-water nanofluid

BackgroundThe ability to combine with the high-temperature applications even in less sunlight distinguishes vacuum tube solar collectors (VTSCs) from other collectors. Loading nanoparticles can lead to effectiveness enhancement. In this numerical study, using regression-based methods the thermal behavior of VTSCs filled with SiO2/EG-water was evaluated. MethodsFor this purpose, using the statistical parameters of R-square and margin of deviation (MOD), the appropriate number of neurons for the artificial neural network (ANN) was determined. FindingsThe results showed that using ANN for the prediction of outlet temperature was successful. Considering R2 > 0.99 and MOD < 0.3%, it was found that for all three coils (helical, U-tube and spiral) ANN can estimate collector outlet temperature with very little error.According to the output temperature predicted by ANN, the instantaneous/overall efficiencies were calculated with a maximum error of 7% and 0.298%. Moreover, the approved ANN for instantaneous efficiency has R2 > 0.886 while this figure for overall efficiency was greater than 0.9999.

Performance analysis and optimal charging time investigation of solar air heater with packed bed sensible heat storage device

The amount of stored thermal energy and the stratification in the packed bed thermal energy storage systems decrease in the afternoon because of the reduction in the solar power and solar-air heater panel's collector outlet temperature, so the charging process must be ceased at a particular instant. The optimal charging period is determined by considering the degree of stratification, energy/exergy stored, and the energy discharged during the 6 h of space heating. The proposed packed bed is divided into three sections lengthwise. Different bed materials have been placed separately in these regions regarding their volumetric heat capacity to promote stratification and sensible heat storage during charging. The bed's stratification level is determined via an exergy analysis to evaluate the discharge efficiency of the bed. The particle diameter and discharge air velocity on the system's thermal and hydrodynamic performance are inspected. The fan energy consumption during the discharge process is evaluated in the analyses. Distinctively, the air velocity is varied to obtain a minimum heat load of 18 kW for 6 h discharge process. A transient, one-dimensional finite-difference model is developed and validated with an experimental study conducted in the literature. Thermal energy storage and the stratification level are improved thanks to segmented bed by 85% and 135%, respectively.

Mathematical model of an innovative double U-tube sun-tracked PTC and its experimental verification

The paper describes in detail an in-house mathematical model, allowing to simulate the operation of an innovative double U-tube sun-tracked Parabolic Trough Collector (PTC). The analysed solar collector is characterized by a modular structure and is designed for low-temperature applications. A double U-tube pipe is used inside the evacuated collector tube, which is the study's main novelty. The energy balance equations are derived for a single U-tube, assuming the uniform flow of the Heat Transfer Fluid (HTF) through all collector U-tubes. The resulting differential equations are solved by approximating the derivatives with appropriate differential schemes. The proposed one-dimensional model with distributed parameters makes it possible to simulate the collector operation under transient conditions. A test stand with the analysed PTC is built to verify the obtained results accuracy and perform an extensive experimental verification. The measured and computed temperature courses of the HTF at the collector outlet are compared for different operation conditions. For all analysed cases, a fully satisfactory agreement between measurement and computational results is obtained. Estimating the accuracy of the developed model results with the measurements, the Root Mean Squared Errors (RMSE) are calculated for three measurement series (for selected days). The obtained RMSE values are 0.375 °C, 0.349 °C, and 0.632 °C for the selected day of January, May, and August, respectively. It proves the high efficiency of the proposed model. The proposed PTC model's main advantage is its simplicity and low computational cost, allowing for its online application.

CFD Modelling and Simulation of an Indirect Forced Convection Solar Dryer

Solar dryer is a conventional device used for solar drying products. There are several types of solar dryers being employed for drying fruits and vegetables. In this research, the indirect type solar dryer is studied and computational fluid dynamics is employed to simulate the process. Ansys fluent CFD software is used to simulate and obtain dynamic and thermal performance of the dryer at different operating conditions (mass flow rate). The predicted results are validated with the help of experimental results. The average velocity at the exit of the collector was 2.89 m/s for 0.0872 kg/s mass flow rate, while for a mass flow rate of 0.0447 kg/s was 1.36 m/s. The maximum temperature at the collector outlet was 44.6°C and the maximum absorber plate temperature was 69.57°C for a magnitude of 0.0872kg/s mass flow rate. The temperature profiles of the trays are also analysed and the tray closest to the collector is found to have the maximum average temperature. The results also revealed that CFD simulations are a reliable method to predict and design solar dryers.

Analysis of thermal-electrical performance of PVT collector with reflectors

&lt;span lang="EN-US"&gt;This work concerns numerical studies of PVT air collector operating in dynamic mode. We presented the temperature of the solar cells and of the air at the outlet of the PVT collector with and without reflectors. The obtained simulation results has been validated by comparating with the experimental results available in literature, where good agreement was been noted. In addition, we determine the optimal position of the reflectors by numerical calculation, in order to obtain the maximal concentration of the solar radiation intensity on PV/T collector. &lt;/span&gt;&lt;span lang="EN-US"&gt;The thermal and electrical efficiency of PV/T collector without reflectors and with reflectors in optimal position have been calculated for composite climate at Tetouan (-5°N, 35.5°E). &lt;/span&gt;&lt;span lang="EN-US"&gt;So, the effect of adding solar reflectors on the electrical and thermal performance &lt;/span&gt;&lt;span lang="EN-US"&gt;is showing&lt;/span&gt;&lt;span lang="EN-US"&gt;.&lt;/span&gt;

A case study of thermal analysis of a solar assisted absorption air-conditioning system using R-410A for domestic applications

Sustainable future and green environment goals quest for the development of technologies to utilize renewable energy resources to power the people. This study focuses on the designing, modelling, and simulation of an absorption solar air-conditioning system. Key performance parameters are identified, optimized for maximum efficiency and simulated in transient energy simulation software TRNSYS ®. The designed model comprises five thermal loops: a solar loop consisting of an evacuated glass tube solar collector having R-410A as heat transfer fluid in it and a heat exchanger heat tank, second loop has an absorption chiller, and an auxiliary furnace with hot water stream, third is the cooling tower loop, the fourth loop is of chilled water from the chiller and the final thermal loop is for air delivery of cooling to each room. The system is simulated using Lahore, Pakistan's climate conditions and offered a good tendency for the proposed system to meet air-conditioning demand at the domestic level. The average collector outlet temperature value of 78 °C has been recorded throughout the week. Collector provides useful energy gain at an average rate of 71,065 kJ/h. Average storage tank temperature at the outlet of heat exchanger is 92°C. Average room temperature values of three rooms are 27°C, 30°C and 19°C respectively.

Matlab graphical user interface (GUI) code for solar tower power plant performance calculations

In the present research, a Matlab program with a graphical user interface (GUI) has been established for studying the performance of a solar tower power plant (STPP). The program gives the ability for predicting the performance of STPP for different tower dimensions, ambient operating conditions and locations. The program is based on the solution of a mathematical model derived from the heat and mass balance for the tower components. The GUI program inputs are; tower dimensions, solar radiation, ambient temperature, pressure, wind velocity, turbine efficiency, emissivity and absorptivity for collector and ground and thermal conductivity and thickness for ground. However, the GUI program outputs are; temperature and pressure differences across the collector and tower, velocity in the tower, density of air in collector outlet, mass flowrate of air, efficiency for collector and tower, the overall efficiency and output power of STPP. The effect of the geometrical dimensions of STPP and some climatic variables on the plant performance was also studied. The results show that the output power increases with increasing the collector diameter, chimney diameter and solar radiation by an increasing of 0.282 kW/m, 0.204 kW/m and 0.046 kW/(W/m2) respectively.

A Sustainable model for the integration of solar and geothermal energy boosted with thermoelectric generators (TEGs) for electricity, cooling and desalination purpose

In this research paper, an integrated energy system for the production of cooling, hot water, and electricity along with desalinated water is proposed, simulated, assessed, and optimized. This integrated energy system is composed of a geothermal well, a single-effect Li/Br and water absorption chiller, parabolic trough collectors (PTCs), a steam Rankine cycle (SRC) and, a reverse osmosis desalination unit. Instead of the condenser, thermoelectric generators (TEGs) are used to increase the generated electricity by the SRC. The system's performance is evaluated in terms of energy, exergy, and exergoeconomic, and the cases with the TEG is compared to the system with the condenser, and results are discussed and investigated. Using the TEG instead of a condenser, results in reducing the total cost rate and enhancing the system's exergy efficiency. Also, the performance of the system was evaluated for four different days in Shiraz city. For the selected days in spring, summer, fall, and winter, the highest generated electricity of the system with the thermoelectric generator is 1087 kW, 1158 kW, 1133 kW, and 766.5 kW, respectively. Thus, the system with thermoelectric is selected for optimization. To optimize the system, seven decision variables are selected namel, the geothermal fluid temperature, the total solar aperture area, the collector outlet temperature, the inlet pressure of the turbines, the TEG figure of merit, the turbine outlet pressure, and the evaporator pinch point temperature difference. Total cost rate and system exergy efficiency are considered as two objective functions. To determine optimum values of the objective functions, a multi-objective genetic algorithm is applied, and also the Pareto frontier figure is obtained. In this figure, the best point is chosen from the technique for order of preference by similarity to ideal solution (TOPSIS) decision-making criterion, where the cost rate is 10.41 ($ / GJ), and the exergy efficiency is 20.52%.

Performance Investigation of a Solar Thermal Collector Based on Nanostructured Energy Materials

The convective and conductive heat transfer between the solar collector and working fluids make photothermal performance limited, and result in a higher rate of heat loss from the surface of the conventional absorber to the surroundings. Direct absorption solar collectors (DASC) are a favorable alternative for their improved photothermal performance. In this study, a simulation based on the performance of a nanostructured solar collector has been carried out using TRNSYS. The connective and conductive heat transfer from direct solar collectors were improved by using nanofluids and three different nanostructured materials, CuO, GO, and ZnO, in this study. The analysis determines the outlet temperature of the working fluids that passed through the direct solar collector. The TRNSYS model consists of a direct solar collector and weather model for Lahore city, the simulations were performed for the whole year for 1,440 h. The stability of these nanostructured materials in the water was investigated by using a UV‐Vis spectrophotometer. Various performance parameters of direct solar collectors were determined, such as variation in outlet collector temperature and heat transfer rates. The numerical model is validated with experimental results. A maximum outlet temperature of 63°C was observed for GO-based nanofluids. The simulation results show that for the whole year, nanofluids improved the performance of direct solar collectors. Significant improvements in the heat transfer rate of 23.52, 21.11, and 15.09% were observed for the nanofluids based on nanostructures of CuO, ZnO, and GO respectively, as compared to water. These nanostructured energy materials are beneficial in solar-driven applications like solar desalination, solar water, and space heating.

Optimum Utilisation of CuO Nanofluid in Flat Plate Solar Collector

The optimum utilisation of CuO-nanofluid in flat plate solar collector has been investigated under Malaysian climatic condition. To determine the optimum nanoparticle concentration required in the base fluid, a simulation was carried out using MATLAB program. From the simulation, it was found that, 0.5 vol.% of CuO nanoparticles in the base fluid yielded maximum collector efficiency. The test was conducted over six months following the ASHRAE standard with nanofluid in the flat plate collector to ascertain its efficiency. The maximum average solar radiation incident on the collector, collector outlet and ambient temperatures were observed about 1000 W/m2, 50 ºC and 38 ºC respectively. From the efficiency curve, the absorbed and removed energy parameters were found to be 0.501 and 24.23 respectively. At a mass flow rate of one litre per minute, the maximum average instantaneous efficiency was 51%. The result of experimental efficiency was compared with the result of simulation and the efficiency values were within 4% of each other. CuO nanofluid base collector increases the efficiency compared to water as the collector fluid. The experimental results revealed that the efficiency of FPSC with CuO nanofluid was 4.78% higher than water base collector at the same mass flow rate of 1 L/min. The uncertainty analysis of result has shown that instantaneous efficiency uncertainty was about 3.3%. The simulation result has indeed minimised number of experiments required to determine the optimum concentration of nanofluid for maximum efficiency.

Determination of the Toxicological Risk of Urban Waste from the City of Uvira Dumped into the North-Western Coast in Lake Tanganyika (Democratic Republic of Congo)

This study focuses on determining the toxicological risks of urban waste from the city of Uvira, discharged into Lake Tanganyika, on the surrounding population. Volatile organic compounds were measured in a variety of solid waste matrices, including inorganic micropollutants in wastewater and fish. The concentrations of Hg and Pb in the lake were found to be 1.21 and 1.42 μg/L respectively and between 0.83 to 18.36 μg/L of Hg and 8.25 to 670 μg/L of Pb, at the collector outlet. The presence of trace metallic elements, such as Cr, Co, Ni, Cu, Zn, As, Sb, Hg and Pb, were detected at high concentrations compared to the WHO standard. An ecotoxicology experiment herein on wastewater samples showed lethal pollutant concentrations of the order of 0.0055 mL/mL which killed at least 50% of fish (LC50), confirming the toxicity of the wastewater. These potentially harmful effluents also contain volatile organic compounds originating in high concentration from the pharmaceutical discharges of the general Uvira hospital, in particular: toluene, ethylbenzene, m-xylene/p-xylene, o-xylene and chloroform in higher concentrations compared to the norm. Other components such as benzene, bromodichloroethane and 1,1-dichloroethane were found to be present, but at a concentration below 0.05 ppb. A variety of trace organics can be suspected to be present as well.

Experimental investigation of suitable thin layer drying curve to solar maize dryer assisted for biomass back-up heater

A solar dryer assisted by biomass back-up heater was designed and manufactured from locally available materials to dry maize, and the drying model is selected, which better fits the dryer test results. This study tried to address the problem associated with the fact that solar dryers are efficiently operational only when there is sufficient solar energy. The dyer comprises a solar air heater, drying chamber, biomass back-up heater, and airflow systems. The solar heater has a length and width of 2 m × 1 m respectively and is enclosed with a transparent glass that allows the solar energy into the collector. The measurement taken to evaluate this dryer's performance is temperature, moisture content, solar irradiation, and airspeed. The average temperature difference between the ambient and the collector outlet was recorded as 9.6 °C, and 12.8 °C in the solar and biomass assisted dryer. The daily average solar insolation for the test periods of October and December at the site was 673 W/m2. When the system is loaded with 50 kg of wet maize grain at an initial moisture content of 21.3% and dried to 14.4% moisture content in 45 h drying time in the solar dryer, 4.03 kg of moisture is removed. A 50 kg of wet maize grain at an initial moisture content of 22.9% and dried to 14.2% moisture content in 27 h in solar dryer assisted by biomass back-up heater, 5.06 kg of moisture is removed. Solar dryer collector efficiency was estimated as 64.2% with an average drying rate of 0.0746 kg/hr. The solar dryer system efficiency was 20.8%, and solar assisted dryer efficiency was 4.3%.

Experimental analysis of thermal performance for flat plate solar water collector in the climate conditions of Yekaterinburg, Russia

Abstract Current experimental work studies the thermal performance of a flat plate solar water collector according to the weather conditions of the city of Ekaterinburg in Russia. All tests were carried within four months and four typical clear days were chosen for each month. Thermal efficiency, useful energy, and water temperatures at the inlet and outlet of the flat plate solar collector have been investigated in this study. The results were collected during summer and autumn have been analyzed to find out the effect of different weather conditions on the performance of the proposed flat solar water collector. The highest efficiency of the solar collector was recorded during midday when the collector receives the highest solar energy intensity and thus the highest rate of useful heat gained. The maximum efficiency observed by 66% in July compared to the other months included in the current study. The results showed good agreement between the previous studies and the current proposed solar water collector in terms of thermal efficiency.

Modeling and Simulation of a Parabolic Trough Solar Concentrator

This work consisted of the mathematical modeling of a parabolic trough concentrator. To this end, a heat balance has been established for the different parts of the parabolic trough concentrator, which are the heat transfer fluid, the absorber and the glass. This allowed us to establish a system of equation whose resolution was done by the finite difference method. This digital resolution made it possible to obtain the temperatures of the different parts of our parabolic trough concentrator, namely, the heat transfer fluid, the absorber and the glass. The simulation of the heating process of the fluid is done in time steps of one hour, from six hours to eighteen hours. The results obtained show that the temperature difference between the inlet and the outlet of the solar collector is very large. A computer program has been developed to simulate the temperatures of the heat transfer fluid, the absorber tube and the glass as a function of time and space. These results were obtained for a typical day with regard to the variation of the temperatures of the heat transfer fluid, the absorber and the glass, as well as the powers and efficiency of the parabolic trough concentrator and various factors for the sake of improve the performance of our prototype.

Design for New Type Centrifugal Fan and Passageway of the Air Conditioner Indoor Unit

This paper introduces a design flow for the low-speed high-efficient centrifugal impeller applicable to the new type indoor hanging unit, with the matching inlet collector and non-uniform outlet diffusion passageway being also designed. Under the influence of the inlet collector, the attack angle deviation and air intake distortion occur to the centrifugal impeller. While the unsteady pressure fluctuation generated by the non-uniform diffusion passageway can also affect the flow in the passage of the upstream blades. The preliminary design and optimization of the above three parts are described in this paper based on the needs of overall design, the outlet flow rate is also increased by adjusting the static pressure distribution in the inside centrifugal impeller, consequently the flow separation generated by the guide blade in the diffusion passage is improved and the outlet uniformity of the diffuser is enhanced. Finally, the feasibility analysis for the overall design is performed in this paper, to ensure the design requirements can be met.

Performance of Solar Adsorption Cooling System with Different Solar Collectors Technologies

The use of different technologies for collecting solar energy in the operation of the adsorption chiller unit is the topic of this article. A theoretical study was done through the simulation program TRNSYS. In this research, the effect of parabolic trough concentrator, compound parabolic concentrator, and the evacuated tube collector on the thermal performance of the absorption refrigeration unit was investigated in terms of cooling capacity, coefficient of performance a and the operating period of the adsorption chiller through the summer climatic condition of Cairo. The results proved that the parabolic trough concentrator (PTC) has the best effect on the performance of the 7 kW adsorption unit, where the maximum outlet collector temperature was 102 °C compare to 95.8 and 87.3 °C for the Compound Parabolic Concentrator (CPC) and the Evacuated Tube Collector (ETC) respectively. The collector type does not affect the COP of the adsorption unit but affects the operation time. For solar collectors of 20 m2, the weekly operation periods were 47, 32.24, and 25.75 hours for the PTC, CPC, and ETC respectively. These values increase with increasing the collector area. Also, for different storage tank capacities, the PTC has the best effect on the operation period of the adsorption unit compare to the other solar collectors.

Study of Dynamics of Heat Transfer in the Flat-Plate Solar Collector

Flat plate solar collector has been presented as an example of a heat-exchanger with two input signals, solar radiation intensity and temperature of working medium on the input, and one output signal, the temperature of a working medium on the output. The dynamics of heat exchange were analyzed for two models of a solar collector—an analog one using a thermoelectric analogy, and a digital one—determined experimentally in on-line mode using the parametric identification method. The characteristics of both models were compared in terms of their step and frequency response for selected construction and operational parameters. Tests of step responses determined for the analog model indicate that the dynamics of heat exchange in the solar collector depending on two input signals is varied. For step-forcing of input signals of the analog model, in both cases, a stable steady state is achieved, but while the first of the signals is inertial, the second one is oscillatory. The phenomenon of temperature oscillation at the collector outlet suggests the need to introduce a new physical quantity in the thermoelectric analogy-thermal inductance. Such an assessment of the dynamics of the solar collector can be useful for proper designing (construction parameters simulation) and diagnostics (operational parameters simulation) of the device.

Improving the Performance of A Flat Plate Solar Collector Using Nanofluid as Working Fluid

Solar energy is the best alternative to limited fossil fuels. The foremost important means of utilizing solar energy are solar collectors. The most common types of solar collectors are flat plate solar collectors. A great deal of theoretical research has been conducted to enhance the flat plate solar collector efficiency. One effective way to increase the efficiency is by using an improved thermal properties fluid as nanofluid. In this paper, a numerical study has been made to enhance the efficiency and improve the performance of solar collector via the use of (Multi-Wall Carbon Nano Tube-water) MWCNT-H2O nanofluid instead of traditional fluid like water as working fluid under the weather of Mosul city / Iraq (36.3489° N, 43.1577° E). One dimensional dynamic model using implicit finite difference method was used. Solving energy conservation equations through the various layers of the solar system is the basis upon which the current model was based. Effects of nanoparticle volume fraction and mass flow rate on the working fluid stream temperature differences, and the thermal efficiency were studied. The mass flow rate was varied from 0.004 kg/s to 0.03 kg/s, while the volume fraction was varied from 0% to 6%. The results of "Nanofluid Based Flat Plate Solar Collector" were compared with the experimental results presented by [1]. The comparison established a good match between the current results and experimental results. The results showed an increase in the working fluid outlet and inlet temperature difference and collector thermal efficiency due to the addition of MWCNT nanoparticles. The temperature difference of "Nanofluid Based Flat Plate Solar Collector" was found 28.8⁰C at 0.014 kg/s and 6% in April, while it was 25 ⁰C at the same condition in the "Water Based Flat Plate Solar Collector case". Also, the thermal efficiency of "Nanofluid Based Flat Plate Solar Collector" was found 2.41% to 6.68% more than the "Water Based Flat Plate Solar Collector case".

Temperature Performance of a Portable Solar Greenhouse Dryer with Various Collector Design

The two main components of a solar greenhouse drying system are the solar collector and drying chamber. Solar greenhouse utilized thermal energy to increase the temperature in the drying chamber at an optimum rate for drying purposes with the use of solar collectors. In this study the performance of a self-built portable solar greenhouse dryer using different types of solar collectors were evaluated, which are flat plate with insulator, V-groove with insulator, flat plate and V-groove with insulator and flat plate and V-groove without insulator. The experiment was conducted indoor, in the solar simulator laboratory using halogen lamps. Two parameters were varied, which are the mass flow rates at 0.011, 0.021, 0.030, and 0.041 kg/s, and the light intensities at 625, 708, 860, and 988 W/m2 . The collector outlet temperature for every solar collector design was compared to each other. The results showed that for all types of collector, the combination of the maximum solar radiation intensity of 988 W/m2 and the lowest mass flow rate of 0.011 kg/s produced the highest average maximum collector outlet temperature. Whereas, the highest efficiency is at the highest mass flow rate of 0.041 kg/s and the minimum solar radiation intensity of 625 W/m2 . In this study it was found that the solar collector that has the best performance of heat transfer is the combination of flat-plate and V-groove collector with an insulator under the V-groove while the best collector design for drying purpose is the combination of flat-plate and V-groove collector without insulator

TRNSYS simulation of flat plate solar collector based water heating system in Indian climatic condition

The primary component of the solar thermal system is solar collectors with flat plate collector (FPC) or evacuated tube collector (ETC) the most common ones. In the household solar hot water systems (SHWS) based on FPC are mostly used because of the low cost and minimum maintenance. Also, collector's outlet temperature matches with most household hot water requirement. The performance of the SHWS varies with the change in environmental conditions (Atmospheric temperature, solar radiation, wind velocity). In this paper, a domestic SHWS has been modelled using TRNSYS 18. The long term performance of the system is evaluated for Indian climatic condition and presented in the article. The performance parameters such as useful energy gain of the collector, collector hourly and monthly thermal efficiency are presented and discussed.