Variation Of Mass Flow Rate Research Articles

Computational fluid dynamics analysis of flat plate type solar collector under different fin variables to enhance air-based heat transfer

Purpose This study begins by outlining the core principles of how flat plate solar collectors (FPSC) operate and the underlying mechanisms of heat transfer. It underscores the pivotal role of fin patterns in enhancing convective heat transfer. Design/methodology/approach The primary objective is to examine the impact of diverse fin patterns on the thermal performance of FPSCs. The study involves the development of a 3D-CFD model for FPSC using the computational fluid dynamics (CFD) software ANSYS FLUENT. The analysis is conducted for variable mass flow rates (mf) ranging from 0.01 to 0.05 kg/s with an interval of 0.02 kg/s. Each flow rate is assessed for three distinct fin patterns: straight plate fins, V-shaped fins and wavy fins. Recognizing the variation in solar radiation intensity throughout the day, the analysis is executed at six different time points ranging 10:00 a.m. to 03.00 p.m. with a time interval of 1.00 h. Findings It is observed that the wavy fin pattern with a mass flow rate of 0.01 kg/s exhibited the highest outlet temperature, showing a significant temperature difference of 12.4 K at noon. Conversely, the V-shaped fin pattern with a mf of 0.05 kg/s has the lowest temperature difference value, measuring only 3 K. The analysis included the calculation of thermal efficiency for each case, revealing that the V-shaped fin pattern at a mf of 0.05 kg/s and a sun radiation intensity of 885.42 W/m2 achieved the maximum instantaneous thermal efficiency (ηth) of 34.7%. The study records the outlet air temperature for all of these combinations and presents the data graphically in the paper. Originality/value The findings of the simulations indicate that the thermal performance that is ηth and maximum temperature of outlet air of FPSCs can be improved through the utilization of variable fin patterns.

Advanced model for a non-adiabatic capillary tube considering both subcooled liquid and non-equilibrium two-phase states of R-600a

Previous empirical correlations have largely failed to predict the mass flow rate variations of R-600a during the transient pull-down operation of household refrigerators. This shortcoming is attributed to the fact that these correlations were developed for specific thermodynamic states of the refrigerant at the capillary inlet, whereas the thermodynamic state varies during transient operations, particularly involving non-equilibrium two-phase states. To address these limitations, a novel model has been developed. This model comprises two distinct sub-models corresponding to the refrigerant state at the capillary tube inlet: one for the subcooled liquid state and the other for the non-equilibrium two-phase state. These sub-models are integrated to account for the transitions in the thermodynamic state of R-600a at the capillary inlet. The integrated model demonstrates excellent agreement with observed variations in the R-600a mass flow rate during the pull-down operation of actual refrigerators. The mean absolute percentage error between the measured and estimated mass flow rates is approximately 10 % over the entire period of pull-down operations tested under various environmental conditions.

Modeling of Liquefied Natural Gas Cold Power Generation for Access to the Distribution Grid

Cold energy generation is an important part of liquefied natural gas (LNG) cold energy cascade utilization, and existing studies lack a specific descriptive model for LNG cold energy transmission to the AC subgrid. Therefore, this paper proposes a descriptive model for the grid-connected process of cold energy generation at LNG stations. First, the expansion kinetic energy transfer of the intermediate work mass is derived and analyzed in the LNG unipolar Rankine cycle structure, the mathematical relationship between the turbine output mechanical power and the variation in the work mass flow rate and pressure is established, and the variations in the LNG heat exchanger temperature difference, seawater flow rate, and the turbine temperature difference in the cycle system are investigated. Secondly, based on the fifth-order equation of state of the synchronous generator, the expressions of its electromagnetic power, output AC frequency, and voltage were analyzed. Finally, the average equivalent models of the machine-side and grid-side converters are established using a direct-fed grid-connected structure, thus forming a descriptive model of the overall drive process. The ORC model is built in Aspen HYSIS to obtain the time series expression of the torque output of the turbine; based on the ORC output torque, the permanent magnet synchronous generator (PMGSG) as well as the direct-fed grid-connected structure are built in MATLAB/Simulink, and the active power and current outputs of the grid-following-type voltage vector control method and the grid-forming-type power-angle synchronous control method are also verified.

Experimental study of CO2 jet field and CO2-MQL-assisted turning of Ti-6Al-4V based on mass flow rate and pressure

The effectiveness of jet cooling is significantly influenced by both mass flow rate and pressure, which are interrelated and exhibit a coupled relationship. This study examined the effects of mass flow rate and pressure from the perspectives of thermodynamic theory, jet field temperature, micromorphology, and the performance of CO2-MQL-assisted turning of Ti-6Al-4V alloys. Comparative experiments demonstrated that a small mass flow rate of CO2 (1.00 g/s) can achieve cooling and lubrication effects comparable to those of a larger mass flow rate (1.83 g/s) when applied at pressures of 7.38 and 6.00 MPa, respectively. For varying pressures, the maximum differences in improving the CO2-MQL on turning force, turning zone temperature, and surface roughness were 2.36%, 26.31%, and 39.63%, respectively. Conversely, the maximum differences for varying mass flow rates were 1.32%, 17.53%, and 19.66%. The results indicate that pressure has a more significant impact and that optimizing the combination of pressure and mass flow rate is substantial for cooling and lubrication. This study offers a reference for reducing CO2 consumption in CO2-MQL applications, thereby enhancing the alignment of CO2-MQL with sustainable manufacturing practices.

Using froude and weber numbers to represent the changes in the flow pattern from stratified to stratified-wavy or plug for wire-on-tube condenser

According to manufacturing data, a theoretical study of condensation inside a heat exchanger with wires on tubes.examined flow patterns with variable refrigerant mass flow rates. Wire-on-tube condensers are adopted with tubes, which have multiple diameters (3.25, 4.83 and 6.29 mm). In addition to the use of two refrigerants (R-134a, R-600a) working at condensing temperatures of (54.4, 45, and 35 °C). The Equal Equation Solver software (EES) was used to obtain the results for the mass velocity range from 8 to 167 kg s−1m−2. Using the non-dimensionless numbers, the model determines the refrigerant flow pattern. Weber number (We) and Froude number (Fr) were used for mass velocity in a range below 100 kg s−1 m−2, which is recommended flow inside the wire-on-tube condenser. The initial transition of the two-phase flow pattern from stratified to stratified-wavy occurred at beginning of condensation for the quality range (0.78-0.42) was Fr (2.7-2.0) and We (6.1-4.0) for R-134a, while the quality range (0.85-0.39) was Fr (5.0-2.4) and We (7.0-4) for R-600a. Second, as the quality range approached, the stratified-wavy flow was replaced by a plug at quality (0.23-0.06) were Fr (1.5-0.4) and We (3.8-2.1) for R-134a and for R-600a the quality range (0.22-0.05) were Fr (1.7-0.55) and We (3.7-2.2).

Hydrogen storage and refueling options: A performance evaluation

This study focuses on the comparative modeling and refueling simulations of hydrogen refueling stations for hydrogen-powered vehicles and high-pressure hydrogen storage options in tanks. The study further aims to simulate these under actual conditions in Ontario, Canada for better assessment which can be treated as a case study as well. The specific tests explore the modeling of hydrogen flow between the recharging station to the car's tank, as well as the optimization of transient variations in temperature, pressure and mass flow rate of hydrogen throughout the process of refueling a fuel cell electric vehicle. The H2FILLS program is utilized to assist for the simulation studies. The primary objective is to replicate various practical weather conditions, tank pressures, flow rates, and refueling periods for different categories of high-pressure hydrogen storage tanks and analyze their storage efficiency. The three different commercially available high-pressure type-IV hydrogen storage tanks were considered in the study as tank-I, tank-II and tank-III with working pressures of 500 bar, 700 bar, 700 bar, and hydrogen storage capacity of 9.5 kg, 4.6 kg, and 5 kg, respectively. Seven different ambient temperatures were selected to mimic seasonal effects. When the power output is constant, with temperature increases, flow rate decreases, and therefore time required to refuel also increases. There is a linear relationship between the final mass flow rate and the ambient temperature, where the mass flow rate drops by approximately 1.8 kg/h for every 10 °C rise in temperature. The variation in ultimate mass flow rate between the highest and lowest ambient temperatures is roughly 5.4 kg/h. Based on the refueling time and docking, undocking, downtime it’s been found that approximately five minutes is wasted between each vehicle. This can help reduce average of 230.02 kt, 231.70 kt, and 235.06 kt CO2 emission per year for vehicle-III, vehicle-II, and vehicle-I, respectively. Lastly, yearly CO2 reduction forecast shows that it may reach 0.9 Mt, 1.6 Mt, 2.7Mt, 3.76 Mt, and 4.73 Mt in the year 2030, 2035, 2040, 2045, and 2050, respectively corresponding to the Global Net-Zero scenario.

Part-load analysis and preliminary annual simulation of a constant inventory supercritical CO2 power plant for waste heat recovery in cement industry

The present work investigates the part-load performance of a MW-scale sCO2 power plant designed as waste heat recovery unit for an existing cement plant located in Czech Republic, in the framework of the H2020 funded project CO2OLHEAT. The study first presents the selected power plant configuration and then focuses on the evaluation of its part-load operation due to variation of flue gas mass flow rate and temperature. The range of flue gas conditions at the outlet of the upstream process is retrieved from a preliminary statistical analysis of historical trends obtained through the cement plant monitoring. The numerical model developed for this study aims at providing realistic results thanks to the adoption of turbomachinery performance maps provided by the turbomachinery manufacturer of the project. Moreover, heat exchangers have been modelled through a discretized approach which has been validated against manufacturer data, while piping inventory and pressure losses have been assessed through a preliminary sizing that considers the actual distances to be covered in the cement plant. Performance decay is estimated for the whole range of flue gas conditions, reporting the most significant power cycle parameters, and identifying the main causes of efficiency loss. The part-load analysis is carried out considering a constant CO2 inventory, in order to reduce the system complexity and capital cost and simplify plant operation. Results show that the operation entails minor variation of the compressors operative points in the whole range of operating conditions of the cement plant, avoiding the risk of anti-surge bypass activation. Moreover, the plant is able to work close to the nominal thermodynamic cycle efficiency (20.5 %–23.0 %) for most of the year and benefits from part-load operation in terms of overall performance. In the last part of the work, a preliminary techno-economic analysis of the plant is also presented to highlight the potential advantages of sCO2 technology for waste heat recovery applications. The results of the part-load performance of the plant are combined with the flue gases data obtained from the preliminary statistical analysis and the cement plant historical monitoring. An annual electricity production equal to 13′909.7 MWh is obtained, corresponding to 6560 equivalent hours and a system capacity factor of 74.9 %. The investment cost of each CO2OLHEAT plant component is estimated by means of cost correlations obtained from literature and the non-discounted payback time is computed as a function of the electricity selling price. The results show that, even considering electricity prices before 2022, the payback time of the CO2OLHEAT plant is estimated to be lower than 8 years, justifying the industrial interest in the proposed technology.

Experimental comparative analysis of an air-breath direct methanol fuel cell (DMFC) using serpentine and spiral flow fields

In the present study, an experimental comparative analysis of Air Breathe Direct Methanol Fuel Cells (DMFC) was conducted using two different flow field patterns, namely spiral and serpentine. The impact of flow field plates on cell performance, CO2 gas bubble behavior and pressure drop was examined at various mass flow rates and current densities. The experiments were conducted with the same hydraulic diameter and channel length for both flow field patterns, varying mass flow rates from 0.25 to 4 ml/min, and exploring reactant concentrations ranging from 0.25 M to 4 M. From the results it is observed that, for both the flow field patterns, pressure drop increases and CO2 bubble formation decreases with increase in mass flow rate. It is also observed that, under identical operating conditions, the serpentine flow field exhibits higher values for both pressure drop and peak power density compared to the spiral flow configuration. The study reveals that, the serpentine flow appears more efficient in terms of peak power density, while the spiral flow outperforms in terms of minimizing pressure drop under the specified operating condition.

Experimental investigation of Triply Periodic Minimal Surfaces for high-temperature solar receivers

This study experimentally investigates Triply Periodic Minimal Surfaces (TPMS) as structured porous media for concentrated solar power systems. Two mock-up planar solar receivers with different TPMS lattices, Diamond and SplitP, were fabricated using Additive Manufacturing. Testing was conducted within the SFERA III project, funded by the EU, utilizing a solar simulator facility at IMDEA Energy Institute in Madrid, Spain. Thermal performance was evaluated under varying mass flow rates and heat flux levels, using synthetic air as the working fluid. Results show superior performance of the SplitP lattice over the Diamond lattice, exhibiting higher heat absorption, lower heat loss, and improved thermal and exergetic efficiencies. SplitP achieved a maximum thermal efficiency of approximately 70 %, compared to 60 % for Diamond, and an exergetic efficiency of approximately 12 %, compared to 8 % for Diamond.

Thermal performance analysis of a double-pass solar air heater with lava rock as porous and sensible heat storage material

This study investigates the utilization of lava rock as a sensitive heat storage material in a double-pass solar air heater. Three configurations were examined: (i) Double-pass solar air heater without the lava rock, (ii) Double-pass solar air heater with a 50 % lava rock packed bed, and (iii) Double-pass solar air heater with a 100 % lava rock packed bed. The experiments were performed indoors under the solar simulator with solar irradiances ranging from 590 to 1000 W/m2 with varying mass flow rates of 0.02, 0.06, and 0.12 kg/s. Results indicate a significant improvement in thermal efficiency with the addition of lava rock. At 1000 W/m2 solar irradiance, the configurations (i), (ii), and (iii) exhibited thermal efficiencies ranging from 18.2 % to 65.02 %, 25.27 % to 72.17 %, and 26.28 % to 76.41 %, respectively. Lava rock's integration into the double-pass solar air heater significantly lowered the temperature of the absorber plate as compared to the conventional double-pass solar air heater, showcasing the thermal storage properties of the lava rock. Under solar irradiance of 1000 W/m2 and a mass flow rate of 0.06 kg/s, the temperature of the absorber plate dropped from 91.3 °C in configuration (i) to 80.0 °C in configuration (ii), a decrease of 12.56 %, and to 71.4 °C in configuration (iii), a decrease of 21.74 %, respectively. The configuration (iii), utilizing a 100 % lava rock packed bed, exhibited the most enhanced thermal performance, representing the potential of lava rock as a sensible heating storage material in double-pass solar air heaters for improved heat retention and utilization under varying solar conditions. Moreover, the use of a double-pass solar air heater with lava rock results in a consistent and even distribution of temperature throughout the heater.

Electrical and thermal performance analysis of hybrid photovoltaic/thermal water collector using meta-heuristic optimization

The photovoltaic/thermal (PV/T) flat-panel technology has numerous advantages over PV modules and separately mounted solar thermal collectors regarding overall effectiveness and space-saving. Hybrid PV/T solar collectors’ thermal and electrical performance is influenced by design parameters like mass flow rate, tube diameter, tube spacing, packing factor, and absorber conductivity. This paper focused on using several meta-heuristic optimization techniques, incorporating the following: multiverse algorithm, dragonfly algorithm, sine–cosine algorithm, moth-flame algorithm, whale algorithm, particle swarm algorithm, ant-lion algorithm, grey wolf algorithm, and particle swarm optimization algorithm in PV/T collector optimal design according to maximum total efficiency obtained. The outcomes of the various algorithms revealed that the maximum electrical efficiency of the PV/T collector ranged from 13.85 to 14.28%, while the maximum thermal efficiencies ranged from 41.41 to 52.08% under standard test conditions (1000 W/m2 and 25 °C). The optimized values for the design parameters of the PV/T collector were as follows: the absorber conductivity was determined to be 356.6 W/m K, the packing factor was optimized to 0.7, the mass flow rate was set at 0.019 kg/s, the tube width was determined to be 0.035 m, and the tube spacing was optimized to 0.0524 m. The results indicated that the grey wolf optimizer (GWO) algorithm proved to be highly effective in optimizing the design parameters of PV/T collectors. Furthermore, the study examined the relationship between the temperature of PV modules and PV/T collectors by considering variations in mass flow rate, packing factor, and tube width at different solar radiation levels. The results confirmed that the PV/T collector temperature exhibited improvements compared to the PV module temperature. As a result, this led to higher electrical efficiency and an overall increase in the total efficiency of the PV/T collector.

Impact of Mass Flow Rate on Thermal Behavior of PCM-Based SWH during Charging Operations

Using phase change materials in solar water heaters presents an intriguing prospect due to their notable energy density and potential for substantial thermal energy storage capacity. In the context of active-type solar water heaters, careful consideration must be given to the water flow rate as a crucial parameter. This paper investigates the thermal dynamics of active-type solar water heaters equipped with phase change materials, examining variations in mass flow rate during the charging process. Indoor experiments utilized horizontal tanks, flat plate collectors, pumps, and solar simulators. Cylindrical capsules filled with paraffin wax were employed and arranged horizontally within the tank, while K-type thermocouples were utilized to monitor water and paraffin wax temperatures. Charging procedures were executed over 160 minutes with mass flow rate adjustments. Data analysis was performed to evaluate the system's thermal performance during charging. Results indicate higher mass flow rates correspond to increased instantaneous, cumulative heat storage, and charging efficiency. The mass flow rate notably affects the thermal efficiency of solar water heater systems incorporating phase change materials.

Numerical Simulation and Thermal Analysis of Pressurized Hydrogen Vehicle Cylinders: Impact of Geometry and Phase Change Materials

This comprehensive study investigates the nuanced aspects of pressurized hydrogen vehicle cylinders during refueling, employing numerical simulation and thermal analysis. The examination encompasses the intricate dynamics influenced by cylinder geometry, mass flow rate variations, and the integration of phase change materials (PCMs). Simulations involving cylinders with diverse length-to-diameter ratios and inlet diameters highlight the impact of these parameters on temperature control. Notably, smaller length-to-diameter ratios prove effective for temperature regulation, while larger inlet diameters mitigate temperature rise. The study further explores the role of varying mass flow rates, revealing that an increasing flow rate during refueling results in the lowest temperature rise. In addition to geometry and mass flow rate considerations, the integration of PCMs is a focal point. Modeling and parametric analysis are employed to assess the feasibility of incorporating these materials. The study contributes valuable insights into optimizing the thermal performance and safety of hydrogen fuel systems. The holistic approach considers the interplay of geometry, mass flow rate dynamics, and the innovative use of PCMs, offering a multifaceted understanding of the factors influencing pressurized hydrogen vehicle cylinders.

Performance Evaluation and Cost Analysis of Photovoltaic Thermal (PVT) System Using the Triangular Shape of Absorber with Different Water-based Nanofluids as Coolants

The worldwide energy demand is continuously increasing, prompting experts to recommend using alternative energy sources to conserve natural gas, fossil fuels, and electricity. Photovoltaic thermal (PVT) systems emerge as a viable solution, generating electrical and heat energy simultaneously while freeing carbon dioxide (CO2) emissions. These systems offer sustainable green technology for supplying renewable electricity and heat to commercial and domestic applications. This study delves into the performance of a photovoltaic thermal (PVT) system featuring an isosceles triangular-shaped absorber design. It considers size variations of 0.02 and 0.03 m while maintaining a constant aspect ratio. Water-based nanofluids such as CuO/w, MgO/w, and ZnO/w, with a nanoparticle volume portion of 4%, alongside pure water as a coolant, are utilized with a variation of mass flow rate ranges from 0.028 kg/s to 0.11 kg/s, allowing for an exploration of its impact on performance parameters. A numerical model is established to comprehensively analyze the system's performance, applying an energy balance equation to its components. An economic analysis is also conducted to assess the system's cost-effectiveness and determine the energy payback time. Results indicate that the highest overall daily performance is achieved with ZnO/w nanofluid at a mass flow rate of 0.112 kg/s and a fluid flow channel size of 0.02 m. Comparatively, compared to other nanofluids and pure water, the average electrical, thermal, and overall performances achieved are 14.57%, 22.36%, and 36.40%, respectively. The energy payback periods are 5.5, 5.2, 5.4, and 4.8 years for CuO/w, MgO/w, ZnO/w, and Pure water, respectively. Furthermore, it is observed that a higher mass flow rate correlates with higher system performance parameters.

2D thermo-fluidynamic rotary model of an elastocaloric cooling device: The energy performances

Elastocaloric cooling has been considered a promising solid-state technology for cooling and heat pumping among the alternatives to vapor compression, at room temperature range. The technology is based on elastocaloric effect that is a thermophysical phenomenon occurring in materials like Shape Memory Alloys (SMA). The effect is detectable as a temperature change in the material if adiabatically subjected to a forcing field of mechanical nature. The latter provokes to the materials a stress that can derive from tension, compression, bending, torsion solicitations. As a result, the SMA experiments a structural phase change from austenite to martensite (coupled with heat addition) and temperature rise. Dually when the stress is removed, the SMA releases heat with a temperature decrease. In this paper the SUSSTAIN-EL rotary elastocaloric heat pump has been deeply investigated to test the energy performances while it works on open loop and closed loop, through a 2D numerical model based on the finite element method, for cooling and heating operation modes. The device employs a binary NiTi SMA as elastocaloric refrigerant and air as heat transfer medium. A wide set of working conditions has been considered like variable inlet mass flow rate, rotation frequency and thermal loads. The acquired results demonstrate that, both in open and closed loop, the prototype’s energy performances are promising and highly favourable for the intended macroscale collocation of the device.

Integrating computational models and machine learning for corrugated absorber plate solar collector thermal predictions

This research provides a computational analysis, development, and empirical testing of a Corrugated Absorber Plate Solar Collector (CAPSC) with fins inserted Thermal Energy Storage (TES) system outlet temperature and thermal efficiency, which is then predicted employing machine learning techniques. For computational analysis, the governing equations of the CAPSC device have been generated and integrated into Computational Fluid Dynamics (CFD) software. Several experimental tests were conducted in both summer and winter seasons during the year, with varying mass flow rates ranging from 0.014 to 0.064 kg/s. The maximum average temperature difference among computational and experimental CAPSC outlet temperatures has been 1.72 °C at 0.044 kg/s. However, to enhance the thermal efficiency forecast of the CAPSC with fins inserted TES system, machine learning techniques such as Multiple Linear Regression (MLR), Random Forest (RF), K-Nearest Neighbors (KNN), eXtreme Gradient Boosting (XGBoost), and Artificial Neural Network (ANN) have been used. A substantial empirical dataset of 288 samples was utilized to analyze the machine-learning approaches. The observed statistical error and regression values in all techniques indicate the adequacy of the approaches presented. When compared to MLR, KNN, and RF techniques, ANN, followed by XGBoost, provides the most accurate forecast. Notably, XGBoost demonstrated superior accuracy due to its ability to handle complex non-linear relationships and interactions within the dataset. Furthermore, to improve the thermal efficiency forecast of the CAPSC with fins inserted TES system by integrating the computational model with the machine learning techniques by utilizing computational CAPSC output temperature as one of the inputs. This CFD with machine learning integration technique considerably enhanced the thermal performance forecast accuracy.

[formula omitted]-Functions for fields of series- and parallel-connected boreholes with variable fluid mass flow rate and reversible flow direction

A new methodology is developed for the calculation of g-functions for the simulation of geothermal bore fields in non-stationary conditions. The g-functions are able to represent the variations of fluid mass flow rate and reversible flow direction, and model the effect of these variations on the long-term ground temperature response. The thermal model is constructed by coupling an axially-discretized finite line source solution for the ground heat transfer, a thermal resistance circuit model for the interior of the boreholes, as well as connectivity relations between parallel- and series-connected boreholes. Simulation experiments show that the new g-functions are required for the accurate prediction of fluid temperatures in series-connected boreholes with variable mass flow rate and reversible flow direction. A simulation of a borehole thermal energy storage system of 144 boreholes over a period of 20 years shows a maximum absolute error of 0.65 °C. The new g-functions thus extend the simulation capabilities of g-functions to borehole thermal energy storage systems.

Liquid droplet entrainment in an annular flow boiling regime—A Bayesian regularization algorithm based study

Accurate prediction of the entrained liquid droplet fraction in an annular two-phase flow regime plays a crucial role for estimating the dryout type critical heat flux to identify the optimized flow characteristics in the thermal systems across different industries. Existing studies have provided different correlations based on the limited experimental data. However, these correlations are applicable to certain operating conditions. Therefore, the present study aims at applying a deep learning method, specifically an artificial neural network (ANN), to enhance the prediction of the entrained liquid droplet fraction. Experimental data from various works on annular flow, covering a wide spectrum of pressure and flow conditions, are utilized for training the ANN model. Eight input variables, viz, superficial gas velocity (JSG), superficial liquid velocity (JSL), gas viscosity (μG), liquid viscosity (μL), gas density (ρG), liquid density (ρL), pipe diameter (d) and liquid surface tension (σLV) are considered as input features. The entrained liquid droplet fraction is the single output feature. The present model employs the Bayesian regularization backpropagation algorithm for training. The present ANN model is compared against the performance of linear regression, decision tree and support vector machine algorithms, and found that the performance of the present Bayesian regularization neural network (BRNN) model is superior within ∼7.5% deviation. Further, the BRNN model is coupled with the film mass flow rate model to obtain the axial variation of the liquid film mass flow rate and good agreement is noticed when compared against the experimental data.

Development of characteristic equations of conical solar still by incorporating N identical concentrator collectors with/without photovoltaic panel: A comparative investigation

This paper focuses on the development of characteristic equations and performance analysis of a conical solar still (CSS) connected to N identical compound parabolic concentrator (CPC) collectors, with or without photovoltaic thermal (PVT) integration. The objective is to achieve sustainable solar distillation in line with the United Nations' sustainability goals. The thermal model is developed by formulating energy balance equations for each part followed by its experimental validation considering N=0and1. A fair agreement between analytical and experimental results is observed having correlation coefficients as 0.996, 0.993, 0.992, and 0.97, 0.98, 0.99 for water temperature, yield, and glass temperature for N = 0 and 1, respectively. The study considers three cases: CSS integrated with N identical partially covered PVTCPCs (case (i)), CSS integrated with N identical fully covered PVTCPCs (case (ii)), and CSS integrated with N identical CPCs (case (iii)). The performance of these cases is compared using climate conditions in New Delhi on a typical day in June. The findings indicate that the mean value of instantaneous efficiency for case (i) is higher by 67.75 % than case (ii), however lower by 22.22 % than case (iii). The study also investigates the influence of variations in mass-flow rate and N on the output of the active CSS.

The augmentation of the heat recovery by using evaporative cooling in HVAC applications: Experimental study

An experimental study was conducted to investigate the impact of evaporative cooling on heat recovery within HVAC systems. This study involved the development of a specialized test rig comprising two air passages connected by a wickless heat pipe heat exchanger (wickless HPHE). Additionally, an evaporative cooling pad was integrated into the cold air return duct. The evaporative cooling process effectively lowered the temperature of the cold air, which was subsequently directed through the wickless HPHE condenser. This occurred at a variable mass flow rate ratio, in contrast to the constant mass flow rate of warm air passing through the wickless HPHE evaporator section. The study encompassed a range of mass flowrate ratios, specifically 1, 1.5, and 2. The thermosiphon heat pipe was charged with acetone at a 60 % filling ratio. The results clearly demonstrated that evaporative cooling played a pivotal role in enhancing the heat exchanger's performance. Notably, the temperature differential observed in the wickless HPHE evaporator surpassed that in the HPHE condenser, primarily due to the influence of evaporative cooling. The highest temperature difference recorded in the HPHE evaporator was 17.8 °C, indicative of the most substantial heat recovery achieved. Importantly, the effect of evaporative cooling significantly improved the performance of the wickless HPHE by more than 48 %.