Low thermal conductivity solar domestic water heater Porta-Gándara, Miguel Ángel; Fernández-Zayas, José Luis; Villa-Medina, Juan Francisco ...
Case studies in thermal engineering,
December 2022, 2022-12-00, 2022-12-01, Letnik:
40
Journal Article
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Odprti dostop
Solar domestic water heaters (SWH) with thermosyphon circulation are the most common commercial applications of solar energy in Mexico. They are also becoming popular in the rest of the world, given ...their simplicity, good economic returns, and sustainability. Traditionally the solar collector, the piping, and the storage tank are built of copper and steel. However, water quality in many parts of the Mexican Northwest has high mineral contents and, when heated, results in early metal pitting corrosion of SWH parts. Short-lived water heaters are bad promoters of the technology. In this work, a SWH thermoplastic Chlorinated Polyvinyl Chloride (CPVC) is built and tested under real operating conditions in La Paz, BCS, Mexico. The optimal design is detected with the aid of a suitable numerical model. Results reveal that a full SWH-CPVC can be technically and economically convenient for the weather conditions of the Northwestern states of Mexico.
•A novel method for designing water-in-glass evacuated tube SWHs was proposed.•3.538125×108 combinations of extrinsic properties were screened by a machine learning model.•Two new designs with high ...predicted heat collection rates (HCRs) were installed & measured.•The two new designs had higher measured HCRs than all the 915 samples in our previous database.
How to design water-in-glass evacuated tube solar water heater (WGET-SWH) with high heat collection rates has long been a question. Here, we propose a high-throughput screening (HTS) method based on machine learning to design and screen 3.538125×108 possible combinations of extrinsic properties of WGET-SWH, to discover promising WGET-SWHs by comparing their predicted heat collection rates. Two new-designed WGET-SWHs were installed experimentally and showed higher heat collection rates (11.32 and 11.44MJ/m2, respectively) than all the 915 measured samples in our previous database. This study shows that we can use the HTS method to modify the design of WGET-SWH with just few knowledge about the highly complicated correlations between the extrinsic properties and heat collection rates of solar water heaters.
Solar thermal systems are an efficient utilization of solar energy for hot water and space heating at domestic level. A Solar Water Heater (SWH) incorporating an Evacuated Glass Tube Collector (EGTC) ...is simulated using TRNSYS software. Efficiency parameters are pointed, and a parametric optimization method is adopted to design the system with maximum conceivable efficiency. In the first part, the selection of refrigerant for heat transportation in SWH loop is presented. A set of 15 working fluids are chosen, and their chemical properties are computed using NIST standard software (REFPROP). The selected working fluids are tested in the system under study and plots for energy gain and temperature are plotted using TRNSYS. Results showed that ammonia (NH3) having specific heat 4.6kJ/kg-K and fluid thermal conductivity 2.12 kJ/hr-m supplies peak energy gain of 7500 kJ/h in winter and 8900 kJ/h in summer season along 120 °C temperature rise. On the other hand, R-123 having specific heat 0.65kJ/kg-K and fluid thermal conductivity 0.0293kJ/hr-m showed inferior performance during the simulation. A solar-hydrogen co-generation system is also designed and simulated under low solar insolation and warm climate regions to study annual hydrogen produced by the hybrid system. System comprises main components: a PV array, an electrolyzer, a fuel cell, a battery, a hydrogen storage unit and a controller in the complete loop. Results of Hydrogen cogeneration system provide 7.8% efficiency in the cold climate of Fargo North Dakota state due to lower solar insolation. While hot climate condition of Lahore weather provides efficiency of 11.8% which satisfy the statistics found in literature.
•Simulation based performance analysis has been carried out using TRNSYS® software.•Proposed model is tested for 15 fluids for hybrid solar hydrogen production.•TRNSYS shows an excellent choice for solar based hydrogen simulation.
•Integrating phase change materials (PCM) within the evacuated solar tube collectors.•Heat pipe is immersed inside the PCM, where heat is effectively stored.•We examined the novel approach during ...both normal and on-demand operation.•Improved functionality during on-demand operation or insufficient solar intensity.•The feasibility is tested via large scale commercial solar water heaters.
This paper presents a novel method of integrating phase change materials (PCMs) within the evacuated solar tube collectors for solar water heaters (SWHs). In this method, the heat pipe is immersed inside the phase change material, where heat is effectively accumulated and stored for an extended period of time due to thermal insulation of evacuated tubes. The benefit of this method includes improved functionality by delayed release of heat, thus providing hot water during the hours of high demand or when solar intensity is insufficient. The proposed solar collector utilizes two distinct phase change materials (dual-PCM), namely Tritriacontane and Erythritol, with melting temperatures of 72°C and 118°C respectively. The operation of solar water heater with the proposed solar collector is investigated during both normal and on-demand operation. The feasibility of this technology is also tested via large scale commercial solar water heaters. Beyond the improved functionality for solar water heater systems, the results from this study show efficiency improvement of 26% for the normal operation and 66% for the stagnation mode, compared with standard solar water heaters that lack phase change materials.
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•Recent advances in solar water heating (SWH) systems have been systematically reviewed.•The design criteria of the major components of the SWH system were discussed elaborately.•The ...potential applications based on thermal performance were studied thoroughly.•Nanofluids selection criteria for a specific SWH system were reviewed extensively.
The solar water-heating (SWH) system is one of the most convenient applications of solar energy, which is considered an available, economical, and environmentally friendly energy source to fulfill the energy demands of the world. In this review, existing SWH systems and design aspects of major components e.g., solar thermal collector, storage tank, heat exchanger, heat transferring fluid, absorber plate, etc. were extensively studied. Recent research to further improve SWH systems and potential practical applications are critically reviewed. Moreover, a relatively new concept in SWH systems, which is using nanofluids in solar collectors as heat transfer fluid has been studied in terms of design criteria for the development of SWH systems. Stationary flat plate collector (FPC) and single-axis tracking compound parabolic collector (CPC) exhibit thermal efficiencies of 45–60 % (operating range: 25–100 °C) and 30–50 % (operating range: 60–300 °C), respectively. The use of thermal stratification structures e.g., diffusers, baffles, membranes, fabrics, etc. is an effective tool to reduce heat losses from the storage tank as well as to harvest the highest energy from the solar collector. Coating of nanomaterials e.g., nickel, copper, etc. was found to reduce the backside heat loss in SWJ systems which eventually increases the thermal performance of the system. Nanofluids consisting of multiwall carbon nanotubes (MWCNTs) and Al2O3 increased the effectiveness of FPC by 28.3 and 35 %, respectively. Moreover, using CuO nanofluids, the collector efficiency of a typical evacuated tube collector (ETC) was increased by up to 12.4 %. Several potential future recommendations for improving the performance of the SWH system were stated.
The effect of thermal conductivity of the absorber plate of a solar collector on the performance of a thermo-siphon solar water heater is found by using the alternative simulation system. The system ...is assumed to be supplied of hot water at 50
°C and 80
°C whereas both are used in domestic and industrial purposes, respectively. According to the Rand distribution profile 50, 125 and 250
l of hot water are consumed daily. The condition shows that the annual solar fraction of the planning functions and the collector's configuration factors are strongly dependent on the thermal conductivity for its lower values. The less dependence is observed beyond a thermal conductivity of 50
W/m
°C for the solar improper fraction and above 100
W/m
°C for the configuration factors. In addition, the number of air ducts and total mass flow rate are taken to show that higher collector efficiency is obtained under the suitable designing and operating parameters. Different heat transfer mechanisms, adding natural convection, vapor boiling, cell nucleus boiling and film wise condensation is observed in the thermo-siphon solar water heater with various solar radiations. From this study, it is found that the solar water heater with a siphon system achieves system characteristic efficiency of 18% higher than that of the conventional system by reducing heat loss for the thermo-siphon solar water heater.
•Drum still integrated with water heater, condenser and CuO nanofluid was studied.•Effect of different drum speeds on drum solar still performance was investigated.•The maximum increase in ...productivity was 350% under optimum conditions.•Optimum conditions are drum speed of 0.1 rpm and using condenser, heater, and CuO.•The highest efficiency was 85.5% under the optimum conditions.
In this study, the thermal performance of the solar still was aimed to be improved in successive stages. This improvement was achieved via using a rotating drum inside the basin still to be nominated as drum distiller. The drum helps to increase the evaporative surface area and decrease the thickness of the saline water film. In the next stage of experimentations, a solar water heater was integrated into the drum distiller. After that, an external condenser was incorporated with drum still. Then, in the last stage of experiments, the effect of copper oxide nanoparticles on the performance of drum distiller was investigated. Different rotational speeds such as 0.02, 0.05, 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, and 4.0 rpm were investigated. A theoretical model was built to predict the performance of the distillers under different conditions. An acceptable agreement was noticed between the experimental and theoretical values (7–13%). Results revealed that the maximum productivity was obtained at 0.1 rpm and using the condenser, heater, and nanofluid. Under these conditions, the freshwater productivity was 9220 L/m2 for the drum still compared to 2050 L/m2 for the conventional still with an enhancement percentage of 350%. Additionally, the estimated cost of 1 L of distillate for traditional and drum stills are about 0.05 and 0.039 $, respectively.
Solar water heating system proves to be an effective technology for converting solar energy into thermal energy. The efficiency of solar thermal conversion is around 70% when compared to solar ...electrical direct conversion system which has an efficiency of only 17%. Hence solar water heaters play a vital role in domestic as well as industrial sector due to its ease of operation and simple maintenance. Extensive works on improving the thermal efficiency of solar water heaters resulted in techniques to improve the convective heat transfer. Passive technique has been used to augment convective heat transfer. These techniques when adopted in solar water heaters proved that the overall thermal performance improved significantly. This paper reviews various techniques to enhance the thermal efficiency in solar water heater. In addition to this, a detailed discussion on the limitations of existing research, research gap and suggested possible modifications is made.
The solar water heating system (SWHS) is one of the most common application of solar energy utilization system. The usage of solar water heating system is not commonly employed throughout the globe, ...due to its high initial cost. The advancement in SWHS will lead to be beneficial over conventional system over the long span of time. The eco-friendly nature of such system promotes these systems to be used frequently in both domestic and industrial heating. The investigators throughout the globe focusing on technical advancement as well as economic feasibility of SWHS. The present study focused on to report such studies, which demonstrates the economic feasibility of SWHS in the long run. The payback period of SWHS varies from one origin to other as it depends on numerous factors like price of fossil fuels, rate of subsidy, solar insolation etc. Initially the paper reported the basic components of SWHS, and their advancements, further the global scenario of SWHS is discussed, followed by the studies reported on a techno economic analysis of SWHS, which shows that the economic feasibility is equally important as technical feasibility for its implementation. The last section inculcates the recent studies on the technical advancement of SWHS and the future research trends of SWHS were discussed.
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