Heat Loss Coefficient Research Articles

Experimentation, Taguchi and machine learning-based optimisation of parameters concerning heat losses from the trapezoidal box-type solar cooker

ABSTRACT The optimal design parameter combinations for a trapezoidal solar cooker that yield the lowest heat loss coefficient have been determined using a thorough Taguchi and Machine learning-based optimization approach that has been established for this study. Data for the previously described optimization have been generated through the use of an experimental approach in a laboratory environment. Numerous influencing factors are taken into account, including the temperature of the bottom plate, the depth of the cavity, the emissivity of the bottom cover, and the wind-induced heat transfer coefficient on the top glass cover. For the current investigation, the ideal factor combination is found to be a parametric combination plate temperature of 350K with 0.4 plate emissivity, 15W/m2 convective heat transfer coefficient, and 0.25 m height. To determine the percentage contribution of each control element to the heat loss coefficient, analysis of variance (ANOVA) has been used for the collected data and signal-to-noise ratios. Plate temperature at 74.72% and emissivity at 23.84% are the primary contributing variables found. Likewise, the least contributing factors like height (0.57%) and convective heat transfer coefficient (0.32%) are discovered. A regression equation is used to represent the connection between the response and the control factor. This formula is suggested as a forecast formula for calculating the heat loss coefficient.

Thermal and exergy analysis of solar air heater enhanced with sodium carbonate decahydrate and Magnesium sulfate heptahydrate PCM: Performance evaluation

The advancement of renewable solar energy is prospective for energy, heat exchanger, and air heater applications. The main objective of the present research is enhancing the solar air heater thermal performance by the modification of a collector absorber-like plain absorber featuring rectangular fine (SAH 2) and sodium carbonate decahydrate (Na2CO3·10H2O) and Magnesium sulfate heptahydrate (MgSO4·7H2O) PCM with rectangular fin (SAH 3). During the experimental evaluation, the airflow varied by 0.042 and 0.059 kg/s. Influences of collector modification on the functional behaviour of solar air heaters (SAH) are evaluated. Its results are compared to the system of conventional setup without modification of the solar collector with a plain absorber (SAH-1). With the excellence of Na2CO3·10H2O/MgSO4·7H2O with fin setup performed with 0.059 kg/s found better heat transfer performance including heat gain, thermal & exergy efficiency, heat loss coefficient, and PCM temperatures like 927.3 W, 78.6 %, 33.6 %, 16.9 W/m2K, and 68.3 ⁰C respectively. Moreover, Increasing the airflow rate leads to improved heat transfer, and the SAH proves to be effective at higher flow rates when equipped with fins and PCM.

An energy analysis methodology for residential heat pump retrofits

The government has targets to upscale domestic heat pump retrofit as part of the strategy to decarbonise heat. There are significant barriers to uptake including installation cost together with a lack of expertise in predicting and reporting energy and carbon performance. As a result, end user confidence in heat pumps can be low. This paper presents analysis of two monitored domestic properties using high resolution data. The aim is to develop reliable prediction and in-use diagnostic tools to improve transparency and reliability of heat pump performance. This paper focuses on a method drawn from theory as set out in CIBSE TM41, and shows how real building heat loss coefficients can be determined from regression analysis over different time frame resolutions. Practical application This research aims to provide residential heat pump retrofit providers with cost effective methods for assessing the suitability of dwellings to accept heat pump retrofit solutions, and to extend these techniques for the effective monitoring and performance evaluation of heat pumps post installation.

Empirical investigation and performance evaluation of flat-plate solar water heating systems: a comparative analysis with and without heat exchangers

Abstract Harnessing solar energy through flat-plate solar water heating systems offers an efficient and sustainable solution for residential water heating needs. This study aims to assess and compare the thermal efficiency of two flat-plate solar water heating systems designed for residential use: one with a heat exchanger and one without. Each system features a flat-plate collector with a dark absorber, a transparent cover to reduce heat losses, and a heat-transport fluid. A thin copper sheet with a selective coating forms the absorber. According to the standards of the Indian Ministry of New and Renewable Energy (MNRE), the evaluation revealed that the system without a heat exchanger achieved a higher efficiency (50 %) compared to the system with a heat exchanger (46 %). This device demonstrated notably lower thermal loss efficiency relative to previous studies, as evidenced by heat loss coefficients of 2.89, 2.66, 1.77, and 2.13 W/m2 k. Despite the higher efficiency of the system lacking a heat exchanger, the importance of heat exchangers in mitigating issues related to water hardness must be acknowledged. This study offers novel insights into the design and optimization of solar water heating systems, highlighting the trade-offs between efficiency and practical considerations.

Experimental study on a direct-expansion micro-channel PV/T evaporator using water-ZnO nanofluid as the spectral beam splitter

Introducing nanofluid (NF) as the spectral beam splitter (SBS) in photovoltaic/thermal (PV/T) evaporators can significantly enhance their performance and energy flexibility. In this study, a novel direct-expansion micro-channel evaporator using water-ZnO nanofluid as SBS (i.e., NF-MC-PV/T evaporator) was manufactured. Particularly, the stability of low-viscosity water-ZnO nanofluid was first optimized and natural convection within the NF-MC-PV/T evaporator was directly formed. Further, a direct-expansion heat pump system based on the NF-MC-PV/T evaporator was developed and tested. According to the findings, adding sodium hexametaphosphate as a dispersant with the dispersion ratio of 1:5 and ultrasonic treatment for 1.5 h can achieve the optimal stability of water-ZnO nanofluid. The nanofluid's natural convection can reduce the evaporator's operating temperature and improve the PV module's temperature distribution uniformity. Specifically, the NF-MC-PV/T evaporator's operating temperature was lower than the environment temperature and a pure PV module. Besides, the PV module's temperature distribution was uniform in the direction perpendicular to the refrigerant flow with a max temperature gradient of only 4.59 °C. The typical photothermal efficiency of the NF-MC-PV/T evaporator reached 102.55 % while the heat loss coefficient was only 4.37. Moreover, the average photothermal efficiency, photovoltaic efficiency, and COP of the system were 103.58 %, 12.03 %, and 5.09, respectively.

Energy and exergy analysis for a laboratory-scale closed-loop spray drying system: Experiments and simulations

Improving exergy efficiency is crucial to the drying process, especially in reducing costs and carbon dioxide emissions. A closed-loop drying system with a condenser-reheater system was built and analyzed using a numerical simulation to explore the optimal drying conditions, such as inlet air temperature and the air flow rate. Heat-loss coefficients in the simulation were fitted to experimental measurements. The study found that increasing the inlet temperature led to an increase in energy inflow and exergy loss in the system. With an increase in air flow rate from 0.005 to 0.01 kg/s, the exergy loss of the chamber decreased (0.07–0.04 kW), and the exergy efficiency increased (69–92%). The exergy loss was mainly concentrated in the drying chamber, that is, the drying process, and the newly connected condenser and reheater had good exergy efficiencies, exceeding 60%.

A new human metabolic rate sensing model optimization and wearable sensor realization

Accurate assessment of metabolic rate is crucial for predicting human thermal comfort. However, many existing instruments are bulky, invasive, and inconvenient. Additionally, wearable metabolic rate measurements have faced long-standing challenges due to a lack of a comprehensive theoretical model with easy-to-measure parameters. This paper optimizes our previously proposed theoretical approach for wearable metabolic rate measurement that incorporates heart rate, whole-body unit heat loss, skin resistance, and body muscle percentage. We have improved the evaluation approach for whole-body unit heat loss by introducing a newly designed convective heat loss coefficient from various body segments. Regarding the wearable sensor design, a heat loss measuring system with serpentine channel was verified as the most suitable design following calibration experiments. We also integrated a modified square-wave-based skin resistance design, resulting in an upgraded integrated metabolic sensor. To validate our sensor and model performance, we conducted experiments with ten subjects of both genders at three temperature conditions (22, 25 and 28 °C) and four levels of activities (rest, tiptoe heel, slight walk, and moderate walk). First, our results demonstrate a strong positive relationship between the metabolic rate obtained by our optimized sensor and Quark CPET instrument, with high coefficients of determination (highest:0.97 from the male group, 0.98 from the female group). Our approach achieved at least 96 % accuracy and less than 2.5 % uncertainty for both groups. Second and increasingly, we found that only one metabolic rate model was required across combined temperature conditions when the person was fixed. Third, the positive relationship was further improved by incorporating whole-body unit heat loss. Finally, we obtained information from different segments on skin temperatures. In summary, our study provides a powerful methodology for predicting and evaluating human metabolic rate through an innovative wearable approach. Our approach and sensor have the potential to substantially contribute to energy-saving efforts in smart buildings.

Decarbonization Potential of Energy Used in Detached Houses—Case Study

The main objectives of this study were the energy assessment of detached houses built in different periods in a central European city. A total of 236 detached houses built between 1930 and 2023 in Debrecen (Hungary) were analyzed from an energy perspective, and their CO2 emissions were measured. It was found that the net floor area of family houses built in recent years has increased but that the compactness of buildings has increased as well. The specific heat loss coefficient and the specific energy demand for heating in new buildings have decreased to 15.2% and 18.5%, respectively, over the last 90 years. Furthermore, around one third of the analyzed buildings built several decades ago must have already been renovated at least once for energy efficiency, as their heat demands are 27.6–41.4% lower than estimated. Energy consumption in six houses built in recent years was measured and studied. It was found that the occupants’ behavior may increase CO2 emissions from heating by 26%, while CO2 emissions from hot-water preparation may decrease by 38.2%. The potential of the locally available sources of renewable energy was calculated, and the costs of decarbonization packages for eight building groups were evaluated.

Amplifying thermal performance of solar flat plate collector by Al2O3/ Cu/MWCNT/SiO2 mono and hybrid nanofluid

Flat plate collectors (FPCs) have garnered widespread usage in applications such as water heating, space heating, and various thermal systems, presenting an eco-friendly and sustainable approach to harnessing solar energy. However, the thermal performance of FPCs has been adversely affected by the improper selection of Heat Transfer Fluids (HTFs). The purpose of the work is to explore and demonstrate the potential advancements in solar flat plate collector (FPC) technology through the use of nanofluids to Enhance Energy Conversion, Explore Synergistic Effects, Contribute to Sustainable Energy Solutions and Address Technological Challenges. That is to optimize the thermal performance of FPCs by incorporating standalone and hybrid nanoparticles into the base fluid to augment their thermal properties. This approach explores new possibilities for synergistic effects and enhanced thermal properties, offering a novel contribution to the field of nanofluid research. The standalone and hybrid nanofluids encompass nanoparticles such as Al2O3, Cu, multi-walled carbon nanotubes (MWCNT), and SiO2 at a concentration of 0.5 wt%. In the preparation of hybrid nanofluids, equal volume fractions (25 % each) of Al2O3, Cu, MWCNT, and SiO2 nanoparticles were employed. The investigation includes the evaluation of thermal performance parameters, namely heat gain, heat loss coefficients, and thermal efficiency of FPCs, comparing these values with those of water. Hybrid nanofluids exhibit significantly improved thermal performance compared to both plain water and monodisperse nanofluids. Employing hybrid nanofluids yields results that indicate a peak outlet temperature of approximately 83.2 °C, a higher heat gains of 2385 W, a reduced heat loss coefficient of 25.5 W/m2K, and a peak thermal efficiency of 70.4 %. The use of hybrid nanofluids, as opposed to monodisperse nanofluids, offers superior thermal performance for flat plate collector-based solar heating systems.

Investigation of the effect of dimensional and non-dimensional parameters on the performance of pitch-varied staggered arranged dimple solar air heaters

In this study, the efficacy of a single pass, single glazed, five different types of absorber plate incorporated solar air heater (SAH) was experimentally examined in outdoor test conditions on alternative days. The experiment was carried out for flat plate solar air heater (FPSAH) and staggered arranged dimple imprinted absorber plate solar air heater (SDPSAH) maintained at four different pitch ratios (Pt/Pl: 1.0, 1.11, 1.25, and 1.67) by varying the air mass flow rate (ma) from 0.01-0.05 kg/s (corresponding Re range: 1971.66–10466.45). The results show that the performance of both FPSAH and SDPSAH improves when the ma increases. For the tested range of ma, SDPSAH outperforms FPSAH regardless of pitch ratio. SDPSAH, with a pitch ratio of 1.25, on the other hand, has a greater air temperature difference, efficiencies, heat removal factor, collector efficiencies, and averaged Nusselt number (Nuavg) while having a lower global heat loss coefficient and top loss. The Nuavg of SDPSAH at a pitch ratio of 1.25 is 1.01–1.17, 1.16–1.24, 1.26–1.57, and 1.44–1.88 times higher than SDPSAH at pitch ratios 1.0, 1.11, 1.67, and FPSAH, respectively. The higher averaged friction factor (favg) of 0.0443 is attained for SDPSAH at a pitch ratio of 1.25 due to the presence of the largest number of dimples. The ηth and ηd of SDPSAH at a pitch ratio of 1.25 are 34.5 and 35.5 % higher than those of FPSAH. The global heat loss coefficient of SDPSAH at pitch ratios 1.11, 1.0, and 1.67 is 1.05–1.84, 1.09–2.15, and 1.11–2.92 times higher, respectively, than that of SDPSAH at a pitch ratio of 1.25.

Performance characterization of nano-enhanced PV/T systems in various cross-sections, extended flow turbulators, fins, and corrugated patterns

Photovoltaic thermal (PV/T) systems may generate both heat and electricity from the sun. Modifying the collector's thermal performance by passive methods is a reliable approach to making them more effective. This study compares the impact of different cross-sections, extended surface turbulators, fins, and corrugated patterns based on the ISO criterion when the working fluid is enriched by MWCNT-water nanofluid at φ=0.3%. The multi-angle yet passive techniques used here, including the nanofluid in Longitudinal Fin (LF), Flat Plate Turbulator (FPT), Wedge Plate Turbulator (WPT), Triangular Corrugated Channel (TCC), and Wavy Corrugated Channel (WCC), and smooth channels, improve the optical efficiency (η0) and reduce the heat-loss coefficient (a1) by 6.8 % and 19.6 %, 12.5 % and 29.3 %, 12.5 % and 27.7 %, 11.7 % and 23.6 %, 10.81 % and 22.9 %, and 3.2 % and 10.71 % compared to the base case (i.e., the smooth channel with pure water) respectively. Pump power in WCC, TCC, and LF is negligible, leading to enhancement in electrical efficiency (ηelec) up to 4.7 % for the former two and 2.9 % for the latter cases. However, plate turbulators show a decline in ηelec at higher inlet velocities due to increased pressure drop. A parametric study of FPT reveals that reducing height and periodic ratios effectively decreases pump power while slightly affecting the performance parameters (η0anda1). The system's performance is also evaluated using the overall exergy efficiency (ηex,ov) concept. The study finds the FPT configuration with the highest ηex,ov of 16 %.

Pathway to Multi-Response Characterization of the Improved Elliptical Vessel Solar Receiver for Efficiencies Maximization

Studies on the pathway to multi-response characterization of the improved elliptical vessel solar receiver for environmental sustainability has been studied. The materials were sourced based on categories of components element: support mechanisms made of mild steel plates, bolts, nuts, clamps, and water as heat transfer fluid. The reflector was made of aluminum foil tape while the vessel has a glass cover fitted with bolts and nuts, the receiver is made of copper pipe, aluminum pipe, galvanized iron pipes, and stainless steel pipes. They are fitted into the vessel with chlorinated polyvinyl chloride 3⁄4 pipes, and journal-bearing mechanisms. Furthermore, glass cover attachment reduces radiative heat loss coefficient by eliminating wind influence and increases heat flux inside the vessel thereby improving heat transfer, hence improving the overall system's efficiency. The pathway to multi-response characterization showed that the average experimental thermal efficiency rose from 9.83% to 12.55% and from 4.42% to 7.03% for Polyurethane coated Copper and Aluminum respectively. It reduced from 9.83% to 8.53% and from 8.10% to 6.50% respectively for Polyurethane coated Galvanized Iron and Aluminum. This depicts the gleam appearance of Polyurethane coating on Galvanized Iron and stainless steel thus reducing their heat absorption coefficient and in turn reducing their efficiency.

Thermal assessment of cylindrical parabolic integrated collector storage using input-output and dynamic system testing procedures: Experimental and numerical study

The main limitation of Integrated Collector Storage systems lies in their low efficiencies and high loss coefficients. In this paper, experimental and numerical setups are conducted to assess the thermal performances of low cost Cylindrical Parabolic Integrated Collector storage (CP-ICS). The conceived system has two aluminum plates in parabolic form serving as reflectors, each with a surface area of 2 m2. The storage tank has a volume of 160 L covered with a layer of black paint with single and double transparent insulations. Results of the experimental tests using Input-Output method showed that the daily thermal efficiency ηd of the developed systems is equal to 48.21% and 49.46% for single and double insulation cover configurations, respectively. The total store heat capacity Cs, the useful collector surface Ac* and the storage tank heat losses coefficient Us of the system found using Dynamic System Testing procedure are equal to 0.56 MJ/K, 0.74 m2 and 1.59 W/K, respectively. Even if the energy efficiency of the system is slightly lower than that recorded in conventional systems, numerical results of long-term study using TRNSYS software showed that the system provides a reasonable solar fraction for the needs of a family in Tunisian climate. A comparative assessment of the developed solar collector performances in different representative climates showed that the use of the CP-ICS system presents a promising solution for countries with annual ambient temperatures fluctuating from 13°C to 33°C, such as Araxos with a solar coverage of 30.65% for a daily supply volume of 160 L. More importantly, in Faya-Largeau location, presenting Chadian climate data, the solar fraction is found to be the highest and reached an average of 67.25%.

Prediction of the minimum heat loss coefficient for safe operation of a Li-ion cell: A machine learning approach

The operating conditions, either C-rate or DoD, of all the Li-ion cells in the battery pack of EVs are subject to continuous change. In addition, the cells’ ambient temperature (Tamb ) is also not constant due to geographical or day/night conditions. As the generation and transfer of heat from the cells are vital functions of C-rate, DoD, and Tamb , choosing an appropriate heat loss coefficient for the given conditions is imperative to maintain the operating temperature of the cell below a specified Set Point Temperature (SPT). The selected heat loss coefficient must be the minimum possible such that overcooling of the cells can also be eliminated. The present study employed a machine learning based surrogate model called Gaussian Process Regression (GPR) to achieve this objective for an AMP20M1HD - A0 Li-ion pouch cell. The training and validation of the surrogate model are conducted with the samples generated using Latin Hypercube Sampling and simulated using the NTGK model available in the Ansys Fluent. The model’s accuracy is further tested for three new combinations of the operating conditions, which are not used for training or validation. Using the present model, the predicted minimum heat loss coefficient successfully regulates the cell’s maximum temperature below a user-specified SPT for the same user-given operating conditions. The developed model immensely helps in designing a cost-effective battery thermal management system with optimum cooling capacity by predicting the nature of heat loss coefficients for all plausible combinations of the operating conditions.

The Impact of System Sizing and Water Temperature on the Thermal Characteristics of Floating Photovoltaic Systems

Accurately calculating the annual yield of floating PV (FPV) systems necessitates incorporating appropriate FPV-specific heat loss coefficients into the calculation, including both wind-dependent and wind-independent factors. The thermal behavior of several FPV systems has been investigated within this study, through the analysis of heat loss coefficients across various system sizes and configurations. Over a one-year period, data were collected from two measurement sites with three distinct systems: two ~50 kWp demonstrator-scale setups of Solarisfloat (azimuthal tracking) and Solar Float (East-West orientation) and a 2 MWp commercial-scale East–West system by Groenleven. The Solarisfloat demonstrator revealed a wind-dependent heat loss coefficient of 3.2 W/m3Ks. In comparison, the Solar Float demonstrator system displayed elevated wind-dependent heat loss coefficients, measuring 4.0 W/m3Ks for the east-facing module and 5.1 W/m3Ks for the west-facing module. The Groenleven system, which shares design similarities with Solar Float, showed lower wind-dependent heat loss coefficients of 2.7 W/m3Ks for the east-facing module and 2.8 W/m3Ks for the west-facing module. A notable discrepancy in the wind-dependent coefficients, particularly evident under a north wind direction, indicates a more efficient convective cooling effect by the wind on the demonstrator scale system of Solar Float. This could possibly be attributed to improved wind flow beneath its PV modules, setting it apart from the Groenleven system. Additionally, a thermal model founded on a ‘balance-of-energy’ methodology, integrating water temperature as a variable was introduced. The heat loss coefficient, dependent on the surface water temperature, fluctuated around zero, depending on whether the water temperature surpassed or fell below the ambient air temperature. It can be concluded that it is not of added value to introduce this floating specific heat loss coefficient parameter, as this parameter can be integrated in the wind speed independent Uc parameter.

Estimating the as-built thermal performance of dwellings using simulated on-board data: From ideal to limited monitoring

Advancement in non-intrusive monitoring of energy usage in households presents an ideal opportunity to get insight into the as-built performance of buildings and assess performance indicators such as the Heat Loss Coefficient (HLC) of the building fabric. The availability of in-use monitored data contributes to bridging the energy performance gap while avoiding costly and exhaustive dedicated measurement campaigns. Methodologies to assess the building performance by combining on-board monitoring and statistical data-driven models are widely accepted. However, their unsupervised and automated applicability on a large scale, with limited data and no insight into the building characteristics and occupants’ behaviour still needs to be investigated. Therefore, this work aims at assessing the reliability and performance of statistical black-box AutoRegressive with eXogenous input (ARX) models on artificial measurement campaigns starting from idealistic setups and progressing towards limited ones. In this investigation, the uncertainty in the estimate inherited from inputs, such as different heat sources or weather data, and their post-processing is combined with the uncertainty originating from different monitoring packages, which results in a thorough overview of the statistical modelling limitations. Results show that disaggregation of the final heating usage poses a major challenge. In cases where gross gas usage is measured, and the system efficiency and domestic hot water consumption are not taken into account, the HLC can deviate by 49% in low-performing houses and by 106% in well-performing houses. However, by applying data pre-processing methods the discrepancy can be lowered to 8% and 23% respectively, but with high uncertainty. On the other hand, the installation of an additional heat meter could yield deviations from the target of 26% for low-performing and 11% for well-performing dwellings without data manipulation, both with low uncertainties.

Investigation of combined parallel and triple-pass v-corrugated solar air heater: A numerical and experimental study

Renewable and safe energy sources have been used more in recent years because of rising energy needs and finite fossil fuel resources. A solar air heater (SAH) is a device that utilizes solar energy to warm air for diverse applications, including room heating, drying procedures, or ventilation. The major aim of the current study is investigating the performance of the combined utilization of grooved absorber and triple-flow air channel modification in a SAH using numerical modeling. Accordingly, CFD method has been used to model the heat and flow characteristics inside a parallel-flow v-grooved SAH (PFVSAH), a triple-flow v-grooved SAH (TFVSAH), and a combined-SAH. The experimental and numerical evaluation of PFVSAH was conducted under different climatic conditions and mass flow rates of 0.019 kg/s, 0.015 kg/s, and 0.012 kg/s. Additionally, a numerical comparison was made between PFVSAH, TFVSAH and combined-SAH. According to the numerical results, the calculated temperature differences in a TFVSAH are greater than those in a PFVSAH and less than in a combined-SAH. According to the experimental results, when the mass flow rate is 0.012 kg/s, the PFVSAH shows average thermal and exergy efficiencies of 59.51% and 29.09%, respectively. In PFVSAH, the highest temperature difference between the outlet and the inlet was 28 °C. The recorded values for the top heat loss coefficient (THLC) of the PFVSAH varied between 4.3 and 8.93 W/m2.

Outdoor performance investigation of a thermoelectric cooler-integrated solar air heating collector

Solar air heating systems are continuously being improved by combining them with other energy conversion technologies. In this paper, outdoor tests were carried out on a thermoelectric heat-pumping solar air heater (TE-SAH), with four (04) TECs (TEC1–12706) attached to the backside of the absorber plate, and powered by a 40Wp mono-Si PV module to pump heat from the absorber plate into the heated air. The thermal energy production, energy efficiency, heat loss coefficients, and heat removal factor were evaluated and compared with a reference system without TECs. The heat collection and energy efficiency of the solar air heater were improved by 7.14 % and 66.71 %, respectively, with the integration of TECs. Heat losses also decreased by 0.46 MJ. Furthermore, the estimated heat removal factor for the TE-SAH was 0.55, higher than 0.49 obtained for the reference SAH. These results showed that PV-TE heat-pumping is a viable means of improving the thermal performance of solar air heaters.

Solar Hybrid System: Innovations in Cooking, Drying, and Power Generation

A hybrid system has been designed and developed which comprises the principle of solar thermal and photovoltaic. Flat plate collector and concentrating trough collector were incorporated under solar thermal technology. Solar thermal device which makes the most using infrared radiation out of solar spectrum. Black copper sheet at focal point of the solar trough served as a stand for cooking pan was able to gain direct as well as high intensity reflected solar radiation to expedite the cooking process. The electric unit of the system worked on the principle of photovoltaic effect. Main components of the hybrid system were collector housing, solar trough reflector, triangular shaped glazing surfaces, copper sheet to place cooking pots and dedicated insulation to prevent heat loss. The dual concept hybrid system was found exceptionally speedier as compared to traditional box type cooker. Results revealed that cooking pot attained maximum temperature of 104.50 C at 12.30 pm, which was sufficient for cooking nutritious food. The experiment was conducted in winter season on 18th January, 2018. Average thermal efficiency (ηtherm) was estimated as 35.1%, cooking power (P) was estimated 47.68 W and the overall heat loss coefficient was calculated 3.03 W/m2°C. Average cooking time found to be just 130 minutes which was otherwise more than 3 hrs in case of traditional box type cooker. Electric power which was stored in the battery can operate 5W dc bulb for 9 hours in single charging. It also could operate smart phone charger and a dc fan (12V, 4Ah) for 60 minutes each.

Unveiling the potential of concentric tubular solar stills (CTSS) through comprehensive thermodynamic modeling and analysis

ABSTRACT The present research work delves into the thermodynamic modeling and analysis of concentric tubular solar stills (CTSS) using a rigorous mathematical approach. The primary objective is to gain a comprehensive understanding of the system’s behavior by formulating and analyzing various crucial parameters. These parameters include the basin water temperature, inner and outer glass cover temperatures, heat transfer coefficients, heat loss coefficients, thermal efficiency, exergy efficiency, hourly yield, and cumulative yield. The study is specifically conducted under the environmental conditions of Nagpur city (21.1458° N, 79.0882° E), India, in the month of May 2022. By selecting this location, the present study ensures that their findings are contextually relevant and applicable to the local conditions. To facilitate the computation of results and generate informative visualizations, MATLAB code has been developed. This code allows for efficient analysis, processing, and presentation of the obtained data, enabling a comprehensive interpretation of the research findings. Results of the study indicate that hourly yield, considering only bottom losses, is 5.071 k g / m 2 and 3.012 k g / m 2 when water and air are used as cooling mediums, respectively. However, when all losses are taken into account, the hourly yield decreases to 4.575 k g / m 2 and 2.555 k g / m 2 for water and air as cooling mediums, respectively. The percentage error when water and air are used as the cooling medium by considering bottom losses is 1.05 and 3.06, while considering all losses, the error is 10.73 and 18.26.