Glass Absorber Research Articles

Numerical analysis on performance evaluation of photovoltaic thermal systems using ternary hybrid nanofluids and forced convection around copper cylinders

This study evaluates the performance of a photovoltaic thermal (PV/T) system using forced convection and ternary hybrid nanofluids, comprising water with cobalt, zinc, and silver. The PV/T system includes a glass absorber, polycrystalline silicon, and a flow channel with eight copper cylinders, positioned at 20 %, 40 %, 60 %, and 80 % along the channel, both above and below the flow path for optimal thermal conductivity. The working fluid is modeled under turbulent, steady-state conditions using the κ−ε turbulence model.Numerical simulations via COMSOL Multiphysics 6.0 evaluate the system's thermal and fluid dynamics, focusing on local Nusselt numbers and photovoltaic cell thermal efficiency compared to a baseline. The investigation spans Reynolds numbers from 10,000 to 100,000, nanoparticle volume fractions of 1 %–20 %, and aspect ratios of 0.1–0.3. The aspect ratio in this study is defined as the ratio of the height of a square obstacle within the flow channel to the total height of the flow channel. A supervised machine learning framework develops predictive regression models for system analysis. Results show fluid force at the outlet increases by about 1200 % and 1300 % for aspect ratios of 0.1 and 0.3 as the Reynolds number rises. The Nusselt number enhances by 420 % and 466 % at a 20 % nanoparticle volume fraction for aspect ratios of 0.1 and 0.3, respectively, with a 9 % improvement in photovoltaic cell efficiency. This work uniquely applies machine learning to derive regression equations for fluid force, Nusselt number, and electrical efficiency, an approach not previously explored in laminar flow studies.

Enhancing thermal efficiency in flat plate solar collectors through internal barrier optimization

This study investigates the impact of introducing horizontal barriers within the internal cavity of flat plate solar collectors on their thermal efficiency. The primary objective is to enhance thermal performance by reducing convective heat loss. An experimental test bench was constructed to evaluate five solar collectors under controlled conditions. One collector was unmodified as a reference, while the other four had 1 to 4 horizontal barriers inserted between the absorber plate and glass cover. Each collector’s efficiency was assessed by measuring inlet and outlet water temperatures, incident solar radiation, ambient temperature, and water flow rate. Efficiency versus heat loss parameter curves were generated, and correction factors were applied to account for material and sensor differences. The collector with four barriers demonstrated the highest overall thermal efficiency, achieving an efficiency improvement of up to 12 % compared to the reference collector. Specifically, the efficiency of the reference collector was around 70 %, while the collector with four barriers reached an efficiency of approximately 82 %. Introducing two barriers resulted in a 9 % increase in efficiency, bringing it to about 79 %. Conversely, the collector with three barriers showed a slight decrease in efficiency to 68 %. The barriers effectively reduced internal convective heat loss, enhancing the collector’s ability to harness incident solar radiation. Inserting horizontal barriers within the internal cavity of flat plate solar collectors significantly improves thermal efficiency by reducing convective heat loss. The optimal configuration, based on this study, involves using four barriers. This method presents a straightforward yet effective approach to enhancing solar collector performance. Future research should focus on refining barrier design and placement for different collector sizes and geometries, potentially supporting broader adoption of solar thermal energy systems and contributing to sustainable energy solutions.

Theoretical and experimental investigation of the glass tube solar collector with inclined N-S axis and relative E-W single-axis tracking flat absorber

This paper presents a new solar collector design that combines flat absorber plates and glass tubes with a compacted automatic time-controlled (E–W) single-axis tracking mechanism. The mentioned design incorporates the advantages of the single-axis tracking system with a relatively small increase in the solar collector dimensions. According to it, a mathematical model was formed, and the test sample was fabricated. Using a bespoke test rig, the experimental investigation was carried out by simultaneously measuring the thermal performances of the solar collector in question and the flat plate solar collector with the same inclined position and absorber material. The experimental results (from July 15 to October 15, 2021) showed that compared to a reference collector, the new solar collector’s average daily specific useful heat was higher in the range of 14–23%, and the overall thermal efficiency was higher in the range of 9.7–17.9%. Using the obtained experimental and simulation data, the mathematical model was verified within an average deviation of 5.67%. Despite the partial reduction of the useful heat due to the mutual shading of absorbers, the mentioned solar collector shows promising results along with a compact design. We propose that this device will present promising opportunities in future applications.

Design and evaluation of a modified basin-type stepped solar- still under Malaysia climate conditions

ABSTRACT Distillation represents one of the earliest methods of treating water, and it remains as such in many parts of the world. A basin-type stepped solar-still remains the simplest desalination technology. It is simple, easy to construct, requires minimal maintenance, and is cost-effective. The objectives of this study were to design, fabricate and evaluate the performance of a modified stepped solar-still. The theoretical analysis was conducted to determine the optimum design of the still. The productivity and solar-still efficiency were obtained by solving the energy balance equations for the absorber plate, saline water, and glass cover, the temperature difference between saline water and the glass cover, and evaporation, convective, and radiative heat transfer coefficients under the climate of Malaysia. The experimental setup was constructed, and experiments were conducted at the Universiti Kebangsaan Malaysia (UKM), Selangor (Latitude 2°56‘22“North and Longitude 101°47’16” East). The basin area of the stepped solar-still was 1.m2 (0.5 m × 2.0 m). The basin of the still was constructed from a black-painted galvanized steel sheet to increase the absorptivity. The cover of the still was made up of glass. The absorber plate of the stepped still consisted of 5 steps (0.1 m × 2 m). The stepped solar-still has been modified to include external and internal reflectors, fins, and an external condenser. The performance of the modified stepped solar-still design has been investigated and compared with the unmodified stepped solar-still. The theoretical results show a significant improvement in the performance of the modified stepped solar-still. The productivity was higher than that for stepped solar-still before modification by approximately 29% under the same climate conditions. The experimental results have shown that the maximum temperature of saline water and glass cover were 62.1°C and 56.2°C, respectively. The maximum distillate water in the still was 6.10 kg/m2. The daily efficiency of the modified stepped solar-still was approximately 52.3%. Based on the experimental and theoretical results, the proposed design significantly enhanced the stepped solar-still thermal performance. A statistical t-test was conducted to establish the significance of the difference in the stepped solar-still experimental. It was found that there was a significant improvement in the stepped solar-still performance after modification. The techno-economic analysis showed that the product cost would be around USD0.07 per liter of distillate.

Energy and Exergy Investigation of a Solar Air Heater for Different Absorber Plate Configurations

In this paper, the effect of using different configurations of absorber plate, including one line finned flat absorber and two lines finned absorber plate, on the thermal performance of a flat plate – double passing solar air heater was investigated experimentally. L- shape fins are soldered on the absorber plate to roughen the absorber plate and generate vortices to enhance the heat transfer between the working fluid (air) and absorber plate to improve the thermal efficiency. The outdoor experimental test was carried out during February and May under the weather conditions of Baghdad city (Longitude 33.3 N and Latitude 44.44 E). The results show that the air temperature is 48 ℃, 47.5 ℃, and 58.5 ℃ at an air velocity of 1.7 m/s for a single line of fins which increased to 52 ℃, 57.5 ℃, and 66 ℃ at air velocity of 0.9 m/s for two lines of fins. The efficiency is increased by 28% for one line of fins and 66% for two lines of fins at an air velocity of 0.9 m/s while increased by 27% for one line of fins and 51% for two lines of fins at an air velocity of 1.7 m/s. The average exergy destruction rate increases by 37.6%, 60.6%, and 68.66% for the absorber plate, working fluid, and glass cover, respectively, for velocity increase from 0.9 m/s to 1.9 m/s. The exergy efficiency increased by 24.1% when the velocity increased from 0.9 m/s to 1.9 m/s.

Experimental comparison of evacuated tube solar air heater based on energy and exergy analyses with environmental and economic (4‐E) study

AbstractFor the purpose of low‐medium air heating applications like timber seasoning, HVAC, agricultural & food drying, space heating and desalination, there is requirement of hot air. Solar air heaters are the promising systems to satisfy these requirements in a very inexpensive manner. Due to higher efficiency at higher operating temperature and lower cost, evacuated tube collectors (ETCs) are preferred for solar air heating. In this manuscript, the comparative parametric study of two similar sets of evacuated tube solar air heater (ETSAH) is performed. The comparison is based on energy & exergy analyses, and also presents the environmental and economic study (4E analyses). Each set is fabricated using mild steel (M.S.) along with 50 evacuated tubes with total collector area of 8.46 m2. The experimental investigations are made at diverse flow rates, with and without using conventional reflectors. Without incorporating any additional heat storage unit, the system provides average hot air temperature of 76.13°C when average solar intensity was 502.68 W/m2 during 11 h of operation from 09:00 to 20:00 h. ETC's absorber glass and the M.S. material was observed to have significant energy storage and discharge. The single set of ETSAH has mitigation of 89.20 tons with 2.05 years of energy payback period, which is significantly low as compared to its 20 years of lifespan. For the optimum system performance the cost of generated hot air is 0.00048 $/kg, which is considerably low.

Performance Comparison of Solar Air Heater with Extended Surfaces and Iron Filling

The thermal performance of a solar air heater (SAH) is enhanced by producing air turbulence. The air turbulence is created by using either extended surface or iron filing between the black colour absorber plate and glass of the SAH. In this article, the thermal performance of a SAH in the case of without fins and with fins at a different location is compared with the SAH using an iron filling. The value of the overall heat loss coefficient in the case of iron filling is 2.1 W/m2K. The average thermal efficiency of the iron filling condition is 65.14%. The additional arrangement to increase the heat transfer also increases the pressure drop which leads to higher power consumption. Results show the thermal efficiency of SAH using iron filling is found best followed by fin arrangement above, below the absorber plate, and without fin.

Design a low-cost, medium-scale, flat plate solar air heater: An experimental and simulation study

The most efficient solar air heater is expensive, and attempts to reduce costs lead to reduced efficiency. The current study presents a low-cost, medium-scale, flat plate solar air heater's design, simulation, and experimental thermal analysis. Carbon steel, thermocol, window glass, and aerosol spray paint were utilized for fabrication to decrease manufacturing costs. Initially, a mathematical model was developed, and experimental tests on this system were carried out with different absorber plates and glass covers in various weather conditions. The air mass flow rate of the collector is set at 0.073 kg/s. According to the experimental results, the solar air collector with a finned steel absorption plate, black paint, and double-glazing exhibit optimal performance. Under average solar radiation and ambient temperature of 910 W/m2 and 29.44 °C, respectively, the maximum thermal efficiency is 60.81 %, the average thermal efficiency is 56.01 %, and the average air temperature difference between the inlet and outlet is 40 °C. Whereas, for the solar air collector with plain steel absorber plate and single glazing, the least desirable performance was observed with a maximum collector efficiency of 45.76 %, an average thermal efficiency of 39.22 %, and an average air temperature difference of 20.14 °C between inlet and outlet under average solar radiation and ambient temperature of 810 W/m2 and 29.98 °C, respectively. Compared to the results, the thermal performance of solar air collectors with a finned steel absorption plate, black paint, and double-glazing was improved by 14 % to 20 % under different conditions. In addition, the solar air heater was designed, and a simulation study was performed in COMSOL Multiphysics software to find the temperature distribution of the glass cover and absorber plate. The experimental findings demonstrated that this convenient and cost-effective solar air collector was designed successfully and can be utilized in heating applications.

Numerical transient modeling of a flat plate solar collector

The present study deals with numerical simulation of a typical flat plate solar collector. The transient two-dimensional governing differential equations of absorber plate, working fluid and glass cover were formulated to describe the thermal problem of the collector. The governing differential equations were solved numerically using Finite Differences Method and the transient problem was formulated using implicit scheme which gives a stable solution for any grid size and time step. The two-dimensional temperature distribution in absorber plate was achieved at 2211 nodes at every 10 s of the simulation period that extended for 1800 s. The variation of fluid exit temperature and glass cover temperature were also estimated. The estimation of top heat loss coefficient and collector efficiency becomes possible using the temperature distributions of absorber plate and working fluid along with cover temperature. The variations of mean plate temperature, fluid exit temperature, cover temperature, top heat loss coefficient and collector efficiency were drawn during the simulation period. Temperature distribution contours were also drawn at selected time intervals and irradiance values. It was concluded that the top heat loss coefficient of the solar collector is a strong function of the irradiance and working fluid mass flow rate. Increasing the value of mass flow rate shortened the transient period of the solar collector and rendered the transient curves of the collector parameters more flat. The study can be useful for further understanding the complex transient two-dimensional thermal problem occurring in flat plate solar collectors.

MICROTRON M-30 FOR RADIATION EXPERIMENTS: FORMATION AND CONTROL OF IRRADIATION FIELDS

The results of the formation and study of the parameters of the electronic accelerator microtron M-30 are presented. The absorbed dose and spatial-energy distribution of the density of the beam in the area of the opinion are installed, which is important for protocols of radiation tests of various materials and devices. Several variants of the radiation formation, as well as the spatial distribution of radiation density are considered. For the homogeneity of radiation investigation, a commercial glass is used as a recording medium. The analytical dependence of radiation dose from the distance to the output node M-30, the control of the energy of accelerated electrons is carried out using an aluminum and glass absorber. Control of the accelerator parameters is carried out remotely from the control panel with the help of the developed «Virtual Remote» program.

Solar-driven heterogeneous photocatalysis using a static mixer as TiO2-P25 support: Impact of reflector optics and material

Solar-driven heterogeneous photocatalysis using semiconductor thin-films immobilised on inert surfaces has restricted applicability, mainly due to the low catalyst surface per reactor volume and mass and photon transfer limitations. Furthermore, sunlight capture hardware presents some setbacks relating to high implementation and maintenance costs. Therefore, this work aims to overcome those limitations by using a stainless steel (SS) Kenics® static mixer (SM) coated with a thin-film of TiO2-P25 and assembled inside a borosilicate glass absorber tube (AT) placed above distinct solar collectors composed of different materials (uncoated [R85], coated [MS], and soiled anodised aluminium [R85s] and SS) and optics (traditional [DP] and [SP] simple double parabola, and flat [F]). The photon flux reaching/entering the AT (measured by 2-nitrobenzaldehyde actinometry) agreed with the theoretical light efficiency estimated for each reflective surface (based on material specular reflectance and geometry ray-wtrace analysis), increasing as follows: SS-F ≈ R85-F < R85s-DP ≈ SS-SP < SS-DP < MS-DP < R85-DP. The ability of each solar collector in combination with the Kenics® SM as TiO2-P25 support on promoting heterogeneous photocatalysis was compared using oxytetracycline (OTC) as the target pollutant. OTC degradation rates over time agreed with actinometric results, leading to similar apparent photonic efficiencies for all reflective surfaces, excepting R85-DP and MS-DP reflectors, which were slightly lower. Moreover, the semiconductor thin-film deposited on the Kenics® SM surface after calcination remained stable for at least seven consecutive cycles. Besides, the Kenics® SM geometry combined with flat reflectors allowed a more efficient absorption of solar UV photons by the catalyst when using two ATs, resulting in the highest volumetric treatment capacity per unit of time and collector surface. The enduring SS-F was found to be the most compact (37% fewer square meters) and cost-effective solution (50% less expensive).

PROPOSTA DE SOLUÇÃO PARA DESALINIZAÇÃO DE ÁGUA USANDO ENERGIA SOLAR

Water is abundant on Earth, only about 2.5% is freshwater, and because most of that water is stored as glaciers or deep groundwater, only a small amount of water is easily accessible to humans and animals. This study's motivation is to find a solution for lacking freshwater, converting brackish and seawater to potable water. The main goal was to produce potable water with high-efficiency production using solar energy. The system's main components were the absorber plate painted black, glass cover, insulation, and vessels to collect fresh water. The absorber plate is painted black to absorb solar radiation, preventing its reflection. The plate delivers higher temperatures for saline water to be evaporated and condensed afterward. The basin liner was made of an iron sheet, and the cover is made of ordinary glass, while the basin was covered with glass using silicon rubber. We used 30-degree single slope solar to identify the efficiency of using black stone without using black stone (control). The results showed that the maximum output with black stone and without it was respectively 750 ml and 600 ml; therefore, the use of black stone can increase the productivity for the single slope solar still.Keywords: Solar collector; Potable water; Brackish water.

Higher Order Accurate Transient Numerical Model to Evaluate the Natural Convection Heat Transfer in Flat Plate Solar Collector

The natural convection flow in the air gap between the absorber plate and glass cover of the flat plate solar collectors is predominantly evaluated based on the lumped capacitance method, which does not consider the spatial temperature gradients. With the recent advancements in the field of computational fluid dynamics, it became possible to study the natural convection heat transfer in the air gap of solar collectors with spatially resolved temperature gradients in the laminar regime. However, due to the relatively large temperature gradient in this air gap, the natural convection heat transfer lies in either the transitional regime or in the turbulent regime. This requires a very high grid density and a large convergence time for existing CFD methods. Higher order numerical methods are found to be effective for resolving turbulent flow phenomenon. Here we develop a non-dimensional transient numerical model for resolving the turbulent natural convection heat transfer in the air gap of a flat plate solar collector, which is fourth order accurate in both spatial and temporal domains. The developed model is validated against benchmark results available in the literature. An error of less than 5% is observed for the top heat loss coefficient parameter of the flat plate solar collector. Transient flow characteristics and various stages of natural convection flow development have been discussed. In addition, it was observed that the occurrence of flow mode transitions have a significant effect on the overall natural convection heat transfer.

Effect of humidity on the performance of rooftop solar chimney

A mathematical model of a solar chimney was developed considering moist air as a participatory media. This model coheres to the steady-state heat transfer equations derived for glass cover, moist-air between the glass cover and the absorber wall, and for the absorber wall separately. An in-house developed MATLAB code solves the equations via matrix method, utilizing the Gauss–Seidel iteration technique. A study was done on dry as well as moist air that flows between the glass and absorber plate of the solar chimney. Air absorbing heat by mode of convection, radiation, and both was considered. Performance of the system is characterized in terms of the mass flow rate of air. Variation of mass flow rate of air with the gap between the glass and the absorber plate is studied as a function of relative humidity. The effect of ambient temperature and radiation on solar chimney’s performance was reported. The result shows an improvement of 10% in the performance of solar chimney driven by moist air as compared to dry air at 45°inclination of chimney. Chimney inclination of 45°was found to be optimum for Bhubaneswar (India), as it has higher mass flow rate compared to other inclination for most duration. It is also concluded that the mass-flow rate through the solar chimney directly depends on the gap between absorber plate and glass cover. Compared to 0.1 m air gap, there is about 62% and 114% increase in mass flow for the gap of 0.2 m and 0.3 m, respectively.

A review on the simulation/CFD based studies on the thermal augmentation of flat plate solar collectors

The flat plate solar collectors (FPSCs) are widely used in heating applications due to their simple design and easy installation. Different methodologies and approaches have been used for efficiency improvement and thermal performance enhancement of FPSCs. Coating and thickness of glass cover; Transmittance and emissivity of glass cover influences the thermal performance of FPSCs. The efficiency of FPSC is reduced due to different type of heat losses occurring because of the temperature difference between absorber and surroundings. Transparent cover and Insulating materials such as CFC free polyurethane foam (PUF) collector are used in the FPSCs to minimize the heat loss. Air gap between the absorber plate and glass cover also affect the efficiency of FPSC due to reduction in natural convection. The insertion of twisted tapes, wire coil and foam are the most effective techniques to improve thermal performance of FPSCs. The insertion of twisted tapes results in increased fluid mixing and friction which increase the heat transfer. Porous materials are used in the solar collector system to enhance the heat transfer material because of their high thermal conductivity. The present work provides an overview of numerical/CFD based studies on various kinds of methods which have been used for efficiency improvement of FPSCs. Use of nanofluids, PCM and polymer, changing absorber plate design and use of inserts and reflector for escalating performance of FPSCs have been discussed. These articles also suggest the scope for future work in the domain of FPSCs.

Thermal characteristics of a flat plate solar collector: Influence of air mass flow rate and correlation analysis among process parameters

Present research focuses on the analysis of temperature profile, heat transfer characteristics and thermal efficiency of a flat plate solar air collector (FPSAC) at different air mass flow rates. Further, the interrelationship among several variables was also investigated using multivariate analysis. Experiments were performed with FPSAC at non-load conditions in the outdoor environment at natural convection (NC) and forced convection (FC) conditions. Air with mass flow rate (ṁ) of 0.01, 0.015 and 0.02 kg/s exhibited 30.73%, 57.88% and 96.40% enhanced convective heat transfer coefficient (hc,p-a) than 0.006 kg/s. Moreover, increase of ṁ from 0.006 kg/s to 0.02 kg/s augmented the thermal efficiency (ηth) from 22.53 to 32.3%. With regard to 0.006 kg/s, air mass flow rate of 0.02 kg/s produced 8.6% and 4.3% reduced heat transfer coefficient from absorber plate to glass due to convection (hc,p-g) and radiation (hr,p-g). Pearson correlation analysis indicated a strong positive effect of solar intensity on the temperature of absorber plate, glass cover and outlet air of collector, but a weak correlation with collector inlet air temperature, useful heat gain, ηth, and hc,p-a. Further, a positive correlation of solar intensity with hc,p-g and hr,p-g was also noticed. Principal component analysis enabled the visualization of association among solar intensity, temperature of different components of collector, heat transfer coefficients, thermal efficiency and time of the day. The analysis indicated that useful heat gain, heat transfer coefficient of air and thermal efficiency of the collector were not highly influenced by solar intensity.

Optimization of a solar water heating system for vapor absorption refrigeration system

AbstractIn this work, the optimization study of the solar collector integrated, with a thermal energy storage tank for the vapor absorption refrigeration system, was studied using TRNSYS. The performance of the integrated system was evaluated considering major contributing parameters such as solar collector area, the mass flow rate of the operating fluids, storage tank volume and height, absorber plate thickness, tube spacing, absorber tube diameter, insulation thickness, and glass thickness/properties, respectively. A physical model of the complete solar water heating (SWH) and refrigeration system was developed followed by simulation studies of the major components for optimization, and finally, the obtained results were compared with the reported data for validation. The results indicated that, by using the solar power with a serpentine tube type flat plate collector of area 24 m2 and a storage volume to a specific collector area of about 60 Lm−2, the optimized system could meet 65% of the annual thermal energy requirement for the refrigeration unit. Further, the annual performance of the optimized solar collector in terms of collector efficiency, heat removal factor, and overall heat loss coefficient was found to be about 0.32, 0.87, and 2.99 W m−2 K, respectively. In addition, the optimization approach that is adopted using TRNSYS in the present study could be used for optimizing the solar‐based energy system for various applications.

Performance of segmented lead glass absorber calorimeter prototype

Sampling calorimeter is essential for physics measurements in high-energy frontier collider experiments using particle-flow-algorithm (PFA) . Three-dimensional information is used to separate the particles in a jet incident on the calorimeter. Therefore, in calorimeters optimized for PFA, both energy information and position information data are essential. Location information can be improve by creating a very finely granulated detection layer, however, the energy resolution is principally determined by the sampling ratio. Energy resolution can be dramatically improved if energy information can read using lead glass as the absorption layer. To independently observe energy in the narrow area required to use the PFA, it is necessary to divide the lead glass into small pieces that are independent of each other. A small optical sensor is required to read out the Cherenkov light from a small lead-glass block. To read maany small lead-glass blocks, the dead volume between layers can be reduced by using MPPC, and by keeping the optical sensor thickness small. This sampling calorimeter using lead-glass blocks as its absorption layers is useful for experiments that requiring the high-energy resolution in the future. We are developing a calorimeter prototype with a segmented-lead-glass absorption layer that takes the PFA into account. The prototype absorber layer's size is 9 × 9 × 4 cm3 and consists of nine 3 × 3 × 4 cm3 lead-glass blocks. The detection layer can read position information with a 1 × 1 cm2 resolution using a plastic scintillator with a width of 1 cm. Backward energy leakage is measured with a tail catcher using a single 12 × 12 × 25 cm3 lead-glass block. All detectors are optically readout using MPPCs. We tested this prototype using the positron beam at Research Center for ELectron PHoton Science, Tohoku University. First, a positron beam was injected into each lead-glass block channel for calibration. Then, the full prototype's performance was evaluated by injecting the beam. As a result of the beam-injection test of the prototype with three segmented lead-glass absorption layers, the overall energy resolution was found to be 13%. We will report upon the performance of this prototype.

Experimental and theoretical analysis of hybrid concentrated photovoltaic/thermal system using parabolic trough collector

In the current work, a hybrid concentrated photovoltaic thermal system was designed and coupled with a parabolic trough collector and investigated theoretically and experimentally for combined heat and power output. In the design, a photovoltaic module was mounted on a flat surface of parabolic trough absorber tube having semi cylindrical shape. A provision was made to cool photovoltaic panel from both the surfaces by flowing water through the absorber tube as well as the annulus of between absorber tube and glass cover. The model was developed using first law of the thermodynamics and then validated using experimental data generated through the fabricated setup. During the experimentation, the annulus flow rate was varied from 0.008 kg/s, 0.017 kg/s and 0.025 kg/s and inner flow rate was varied from 0.075 kg/s, 0.083 kg/s and 0.091 kg/s. The field testing results showed the mean overall efficiency of system obtained as 61.42%, 64.61% and 66.36% for inner tube flow rate of 0.075 kg/s, 0.083 kg/s and 0.091 kg/s respectively for annulus flow rate of 0.008 kg/s. The theoretical results of hybrid system obtained from the simulation are in good agreement with the experimental data. In the end environmental cost analysis was also carried out for the proposed system.

Effect of absorber plate surface shape and glass cover inclination angle on the performance of a passive solar still

Purpose Solar-driven water desalination technologies are rapidly developing with various links to other renewable sources. However, the efficiency of such systems severely depends on the design parameters. This paper presents results from an investigation on the effect of the glass cover inclination angle on the performance of two stepped solar still geometries (flat and convex) and the amount of produced distilled water. Design Methodology Approach Studied inclination angles of 25°, 27.5°, 30°, 32.5° and 35° were chosen, while other design parameters were fixed. Findings The investigation showed that the unit with the convex absorber plate had higher average water daily production rate, compared to the output of the flat absorber plate unit. The results also depicted that the inclination angle of the still has a noticeable effect on the performance of solar stills. The value of the critical angle is 32.5°, and the higher inclination angle results in less heat transfer coefficient. This value can be used for design purposes and erases the typical assumption to use lower angles to optimize the productivity of the still. Practical Implications Finally, obtained data were used to correlate the Nusselt number for the flat and convex surfaces with different inclination angles of the glass cover. Originality Value The outcome of this investigation may find applications to develop highly efficient solar stills to secure more drinkable water in warm, dry lands.