Thermal Efficiency Of System Research Articles

Thermodynamic properties of non-azeotropic refrigerant heat pumps under full operating conditions with non-phase-change heat sinks and heat soucres

ABSTRACT When using pure refrigerants in heat pump, a significant temperature mismatch arises between hot and cold fluids within the evaporator and condenser, adversely impacting the thermal efficiency of system. To mitigate this issue, we incorporated non-azeotropic refrigerant blends such as R1233zd(e)/R152a, 1224 yd(z)/R152a and 1234ze(z)/R152a into heat pumps devoid of phase-change heat sinks and sources. Through rigorous examination of the temperature glide characteristics of these refrigerants, we determined an optimal R152a composition of 0.3, resulting in COPs of 3.326, 3.36, and 3.605 for the respective heat pumps. Our analysis further delved into heat pump configurations, revealing that the COP of the regenerative configuration could be substantially elevated from 3.36 (in the simple configuration) to 3.79. Additionally, the maximum temperature observed in the two-stage compression configuration was significantly lower compared to the regenerative setup. A comprehensive thermodynamic assessment = across all operating conditions indicated that COP of all configurations decreases markedly as heat production diminishes below 50% of full load. Conversely, when heat production exceeds 50% of full load, the COP remains relatively stable across different heat production levels. Notably, the COP of the regenerative configuration closely approximates that of the two-stage configuration. Considering factors such as investment cost, system complexity and operational efficiency, the regenerative configuration stands out as the optimal choice across all operating conditions.

The Role of Heater Size and Location in Modulating Natural Convection Behavior in Cu-Water Nanofluid-Loaded Square Enclosures

Enhancing the energy efficiency of thermal systems reduces their consumption, lowers costs, and reduces undesired environmental impact, thus making these systems more sustainable. The current work introduces a passive method for heat transfer enhancement that is carried out using natural convection by nanofluid. This work introduces a computational study of the process of natural convection within a square cavity containing Cu/H2O nanofluid. The cavity wall on the left side undergoes partial isothermal heating, while the opposing side is fully cooled isothermally, with all other boundaries maintained adiabatic. A mathematical model formulated based on a 2-D model was used to provide the solution for the system of governing equations of mass, momentum, and energy conservation, employing the finite element technique. A commercial CFD package is utilized to perform the computational simulation. The present investigation delves into the impact of the Rayleigh number, nanoparticle concentration, heater length, and heater location on the flow field and heat transfer characteristics. The model outcomes were displayed for a wide range of the pertinent parameters as 103 ≤ Ra ≤ 106, 0.25 ≤ lh ≤ 1.0, 0.125 ≤ hc ≤ 0.875, and 0.02 ≤ ϕ ≤ 0.10. Also, correlation equations relating the average Nusselt number to these crucial parameters are derived. These equations are simple and can be applied in practice easily in many fields, such as electric and electronic equipment cooling and thermal management of heat sources. Also, these equations gather all the parameters that affect the heat transfer process. They are shedding light on the intricate interplay between these parameters in the natural convection heat transfer process.

Effect of working fluid charging amount on system performance in an ocean thermal energy conversion system

In ocean thermal energy conversion (OTEC) systems, the initial working fluid charging amount is crucial as it relates to the system’s performance and economic cost. But currently, there is no clear standard for it, and as the working fluid circulating pump is the most direct and only means to regulate the working fluid flow, it is necessary to investigate the coupled effects of it and the working fluid charging amount on the system performance. To this issue, a corresponding experimental facility was established. The coupled effects were investigated by energy and exergy analysis under varying temperature difference. The results showed that varying working fluid charging amount changed the physical state of the working fluid, and the effect on the system varied under dissimilar temperature difference conditions. Compared to the standard charge (8 kg), 75 % of the standard charging amount diminished the system thermal efficiency by 17 % and exergy efficiency by 16 % at small temperature difference (20 °C), whereas a charging amount of more than 100 % resulted in improved thermal efficiency by 14 % and exergy efficiency by 13 %. At large temperature difference (28 °C), 75 %, 125 % and 150 % of the standard working fluid charging amount all improved system performance (thermal efficiency by maximum 16 %, exergy efficiency by maximum 21 %). Besides, an increase in circulating pump frequency improved system performance regardless of the temperature difference and working fluid charging amount. This research innovatively investigates the above problems in the application scenario of OTEC, and provides theoretical and data support for the development of OTEC technology.

The effect of added wire mesh on the thermal efficiency of the flat plate solar water heater collector

The current study looks into the effects of using wire mesh to expand the flat plate solar collector (FPSC) on the system's thermal efficiency under transient heat-flux without changing its dimensions and its placement to minimise the shadows cast on the collector while utilising passive methods to circulate the working fluid. Thus, the traditional model was investigated numerically (using ANSYS fluent) and experimentally to establish the accuracy of simulation results. Then, the three models, A, B, and C, were tested numerically. In model A, the mesh is used to cover the riser pipe. In model B, the mesh covers the collector plate; in model C, the mesh is placed on both the riser pipe and the plate. The wire mesh placement in all three models improved the thermal efficiency of the FPSC. In addition, model C proved to be paramount to all models under study, classical models A and B, by having a higher thermal efficiency of 41.4 %, 14 %, and 31.2 %, respectively.

Development and Optimization of a Micro-Baffle for the Enhancement of Heat Transfer in Film Boiling

This study represents the development and optimization of a micro-baffle design to enhance heat transfer in film boiling. Numerical simulations are performed using an open-source computational fluid dynamics (CFD) model, which incorporates the Lee model for momentum source associated with the phase change, and the Volume of Fluid (VOF) method to capture bubble dynamics. A comparison of the numerical results with the previous numerical and experimental data confirmed the validity of the numerical model. The influence of key design parameters was systematically investigated. The results revealed that a vertical baffle provided the maximum performance. The optimal baffle design achieved a 57.4% improvement in the Nusselt number and a 66.4% increase in critical heat flux (CHF). Furthermore, the proposed design facilitated continuous bubble formation, even with a reduced temperature difference between the heated surface and the subcooled liquid, which is crucial for energy-efficient thermal management in engineering systems. Ultimately, this study demonstrates the potential of micro-baffle designs in controlling bubble dynamics and improving heat transfer in film boiling, thereby aiding the design of efficient thermal systems.

Energy-economic-environmental analysis of bifacial photovoltaic thermal (BPVT) solar air collector with jet impingement

Jet impingement cooling enhances photovoltaic (PV) system efficiency by using high-speed fluid jets to reduce panel temperatures, improving performance and longevity. The effectiveness depends on factors like fluid flow rate, nozzle placement, and distance from the panel. While it boosts energy output, it may increase energy use for fluid circulation and add complexity to the system. This research explores a groundbreaking approach to enhancing the efficiency of bifacial photovoltaic thermal (BPVT) systems by integrating jet impingement technology. A novel design featuring a jet plate reflector is introduced, offering the dual benefit of cooling the PV panels while simultaneously reflecting light to optimize energy capture. The study comprehensively analyses the system’s performance, including energy output and a detailed techno-economic and environmental-economic evaluation. The modelling in this study was validated and reasonably consistent with experimental results. The system's output air temperature and thermal efficiency are 302.07–318.75 K and 33.83–62.28 %, respectively. The temperature and electrical efficiency range for PV systems are 304.39–339.54 K and 9.39–11.22 %. Reduced mass flow rate and increased solar irradiation are the most economically advantageous operating parameters for the proposed system, resulting in lower annual pumping costs and more significant annual energy gains for the system. CBR variations range from 0.1363 to 9.3445, with an average of 2. Additionally, by using BPVT with jet impingement to generate electricity rather than fossil fuels, it is possible to reduce annual carbon dioxide emissions by approximately 1.61 tons and save RM93.51 annually. In general, the proposed method should be used to minimize environmental pollution.

Experimental investigation of heat transfer coefficient and frictional pressure drop in flow boiling of R513A: Comparative analysis of micro-fin and smooth tubes

The heat transfer coefficient (HTC) and frictional pressure drop (FPD) of R513A in flow boiling conditions experimentally investigated in the present article. The study employed micro-fin tubes (MFT1 and MFT2) and smooth tubes (ST1 and ST2) as testing tubes under various operational parameters. The test sections featured standardized tube lengths (1000 mm) and outer diameter (9.52 mm) across all tubes, with variations in mass flux (50–300 kg·m−2·s−1), vapor quality (0.02–0.96), saturation temperature (12°C, 17°C, and 22 °C) and heat flux (6, 18, and 30 kW·m−2). Research focused on evaluating influence of micro-fin enhancement on flow boiling characteristics, specifically comparing HTC and FPD between micro-fin and smooth tubes. Results indicate significant improvement on HTC within micro-fin tubes compared to smooth tubes, accompanied by reasonable increase in FPD. Additionally, the study validated experimental data against established correlations and conducted sensitivity analysis to understand influence of key parameters on HTC and FPD. Overall, findings contribute valuable insights for optimizing heat exchanger design and thermal system efficiency in flow boiling applications.

A novel boiler partial flow arrangement and partial load control strategies of a S-CO2 coal-fired power generation system

This work aims to address the technical issue of continuously decreasing reheat temperature in the S-CO2 coal-fired power system under partial-load operation. A novel partial flow arrangement of heating surfaces that uses part of the cooling walls in the furnace chamber as reheating surfaces was proposed. The steady-state model of a 300 MW S-CO2 coal-fired power system was developed to predict the partial-load operating characteristics. It is found that the proposed partial flow arrangement can effectively alleviate reheat temperature deviation. For the deviation of 10 °C, the present boiler operating load can be reduced to as low as 40 % whereas at least an 80 % load ratio for the traditional arrangement. According to the effects of four regulation measures, the comprehensive control sequence is suggested as 1) flue gas damper angle, 2) split ratio of the stream to FGC, 3) burner angle, and 4) split ratio of the stream to recompressor. This strategy can stabilize the reheat temperature at 620 °C for the load ratio decreasing from 100 % to 37 %, and achieve the higher system thermal efficiency. For load ratios from 37 % to 20 %, the reheat temperature cannot remain stable, and adjusting the reheat temperature will decrease the thermal efficiency.

Application of artificial intelligence to predict energy consumption and thermal efficiency of hybrid convection-radiation dryer for garlic slices

This study aims to examine the energy-related aspects of a hybrid convection-radiation drying technique employed in the drying process of garlic slices. Several factors, including infrared radiation intensity (1500, 2000, and 3000 W/m2), air temperature (40, 50, and 60 °C), and airflow rates of the drying chamber (0.7, 1.0, and 1.5 m/s) were evaluated to optimize the responses of drying time (min), energy consumption (kJ), thermal efficiency (%), and specific energy consumption (MJ/kg). Furthermore, an Artificial Neural Network model was employed to predict the effects of the parameters above on the drying system's specific energy consumption, energy consumption, drying time, and thermal efficiency. The obtained data were analyzed using a self-organizing map and principal component analysis. Interestingly, the findings showed that increasing the air temperature and infrared radiation intensity led to shorter drying times, while higher airflow rates resulted in longer drying durations. Additionally, it was found that higher infrared intensity and air temperature, combined with lower airflow rates, improved the energy indices. Increasing the air velocity to 1.0 and 1.5 m/s at the same air temperature and radiation intensity resulted in a considerable increase in drying time by 9 and 22.7%, respectively. The lowest efficiency value of 10.1% was observed at 40 °C temperature and an air velocity of 1.5 m/s. The Artificial Neural Network model demonstrated high accuracy with a Root Mean Square Error of 0.05 and an overall accuracy of (95%) in predicting the drying parameters. Notably, the self-organizing map visualization revealed that higher air temperatures and radiation corresponded to lower drying times, energy consumption, and specific energy consumption. Conversely, higher airflow rates resulted in increased drying time and energy consumption. The present study suggested that 60 °C, 3000 W/m2 and 0.7 m/s are optimum conditions for efficiently drying garlic slices under the hybrid dryer. This investigation addresses the limitations and deficiencies of previous work on energy optimization and efficiency analysis of garlic under a hybrid dryer with infrared heating systems. Further studies on the economic feasibility of applying such a system for sample drying and the impact of drying on the thermal behaviors of the products need additional investigation.

Energy and exergy optimization of Kalina Cycle System-34 with detailed analysis of cycle parameters

This study proposes a novel methodology for optimizing the Kalina Cycle System-34, providing new insights into the existing literature on the cycle. The research highlights the cycle's key variables and identifies the most critical parameters that require improvement while proposing a practical and effective optimization method. The effects of parameters on thermal and exergy efficiency were quantified using Taguchi and ANOVA methods. The study focuses on critical parameters such as evaporator outlet temperature, turbine inlet pressure, ammonia concentration, turbine efficiency, and pump efficiency. The optimal values of these parameters were determined within specified ranges. Furthermore, the study employed the L25 orthogonal array to create case scenarios that reduced the computational cost of the Kalina cycle. The best-case scenario was not included in the 25 cases in the orthogonal array, which significantly reduced computational costs. The results showed that the system's thermal efficiency increased to 16.2 %, and exergy efficiency increased to 27.8 %, with the case conditions for the best case being an evaporator outlet temperature of 120 °C, ammonia concentration of 0.9, turbine inlet pressure of 40 bar, turbine efficiency of 0.9, and pump efficiency of 0.8.

Design optimization of heat exchanger using deep reinforcement learning

A micronuclear reactor is currently being developed using 3D printing technology, with a focus on refining the design of its heat exchanger. The objective is to optimize the topology of heat exchangers to improve their performance. The initial thermofluidic topology design is a crucial factor influencing the efficiency of the final optimized heat exchanger. This paper presents a novel approach for the topology optimization of heat exchangers using initial designs generated via deep reinforcement learning (DRL). A printed circuit heat exchanger (PCHE) served as the target for this optimization. Extensive simulations demonstrated that the DRL-assisted optimization method enhanced the heat exchange efficiency by 14.8% compared with that of conventional topology-optimized PCHEs. The optimized heat exchanger was fabricated using 3D printing, and its feasibility was confirmed by comparison with simulation data. The integration of DRL into the topology optimization and production processes via 3D printing lays the groundwork for the development of more efficient thermal systems and demonstrates a viable method for complex engineering applications.

Multi-objective optimization and life cycle assessment of mass-integrated combined heat and power system

As the effects of climate change become more widely recognized, technical innovation and green energy will promote the growth of combined heat and power systems. This study proposes a novel mass-integrated combined heat and power system and conducts energy analysis, exergy analysis, and techno-economic analysis for the system. The optimization strategy integrated polynomial regression and non-dominated sorting genetic algorithm III is established, with system thermal efficiency, exergy efficiency, and return on investment (ROI) as objective functions. The system's environmental consequences are then assessed throughout its life cycle using life cycle assessment (LCA) under ideal operating circumstances. The findings reveal that the waste heat recovery heat exchanger has the highest exergy destruction in the system, with a value of 674.61 kW. Furthermore, the intermediate heat exchanger 1 and intermediate heat exchanger 2 (IHX2) with lesser exergy efficiency have an exergy destruction of less than 32.00 kW. The IHX2 is the most expensive equipment in the system, costing $90,931.19, but it also provides the most potential for system improvement. The multi-objective optimization findings suggest that the thermal efficiency, exergy efficiency, and ROI for the system are 0.17, 0.97, and 0.30, respectively. The LCA demonstrates that the system has a negligible influence on global warming and ozone generation with corresponding LCA findings of less than 4.20. The construction and operation phases of the investigation system have the most significant environmental consequences. The correlation between the raw materials necessary for the construction of the equipment in the system and the reaction temperatures, conditions, and waste composition during the preparation of the working fluids is large, so it is necessary to take corresponding environmental protection measures during production and processing to reduce the system's environmental emissions from the source and promote ecologically sustainable development.

Machine learning optimization of a zero energy building (ZEB) by waste heat recovery in a co-generation system

Waste heat recovery is known as one of the newest methods to increase the energy and exergy efficiencies of thermal systems. The concept has been also developed in co-generation systems where productions of electricity, cooling and heating are considered, simultaneously. This study investigates tri-generation system with a co-generation ammonia-water cycle (AWC) and an organic Rankine cycle (ORC) to supply cooling, heating, and power, simultaneously. As novelty, six different working fluids of Ammonia, R124, R134a, R152a, R245fa and R290 were investigated, as six scenarios for ORC. As result, the R124 was found as the best one and the next investigations were followed just with this fluid. Minimizing total cost and maximizing exergy efficiency at the same time are the main aim of this paper. Design Expert software was used to find out about this optimum point. Four cities in Australia were selected and the effect of annual ambient temperatures of them were studied on the outputs of the system, using TRNSYS software. Also, the optimum values of the effective parameters, including the isentropic efficiencies of pumps, compressor, and turbines, heat source temperature, ammonia concentration, utmost pressures of ORC and AWC, were obtained and reported by means of TOPSIS. As results, the monthly generations in electricity, heating and cooling were estimated. It was revealed that the lower ambient temperature, the higher electricity generation, according to the thermodynamic cycle of the proposed co-generation system. Finally, the results showed that application of the suggested co-generation system can cover the electricity demand of 294 apartments, heating for 208 apartments, and cooling load for 18,999 apartments.

Thermal slip and variable viscosity analysis on heat rate and magnetic flux through accelerating non-conducting wedge in the presence of induced magnetic field

The focus of present study is to incorporate the variable viscosity and temperature slip impact on heating rate and induced magnetic gradient along the moving non-conducting wedge under magnetic field. In industrial and engineering procedures, the impact of induced magnetization improves the efficiency of thermal systems to main the heating rates. The similarity transformations and stream functions are applied to reduce the governing equations into ordinary form. During this transformation, the pertinent parameters such as wedge parameter, moving parameter, Prandtl factor, viscosity parameter and temperature-slip parameter is obtained. These parameters play a prominent role on the physical values of fluid velocity, induced magnetic field and temperature distributions. The skin friction, Nusselt coefficient and induced magnetic gradient are incorporated through these parameters. The numerical values are executed by using the Keller box analysis with Newton–Raphson technique. It is depicted that the maximum slip in fluid velocity and temperature distribution is obtained for each values of thermal-slip parameter. It is noticed that maximum magnitude in induced magnetic field is reported for each wedge factor. The maximum velocity slip and temperature slip is observed for each choice of moving parameter. It is reported that the maximum variation in heating rate and induced magnetic gradient is obtained for magnetic force and viscosity parameter. The enhancing behavior of skin friction is observed for maximum values of Prandtl number.

Integration and Optimization of a Waste Heat Driven Organic Rankine Cycle for Power Generation in Wastewater Treatment Plants

The study focuses on achieving energy self-sufficiency in Wastewater Treatment Plants by proposing a comprehensive model for integrating, sizing, and optimizing an Organic Rankine Cycle system. The Organic Rankine Cycle system is designed to utilize waste heat from the gensets at As Samra Wastewater Treatment Plant in Jordan, where it will contribute to the overall electrical energy supply of the plant. Real data from As Samra Wastewater Treatment Plant is used to model and calculate the available waste heat using TRNSYS® software. The Organic Rankine Cycle model is then developed using ASPEN PLUS® software to explore the impact of operational parameters and determine their optimal values for maximizing the plant's energy profile. An economic analysis is conducted to assess the feasibility of the proposed model, considering system components, installation, operation, and maintenance costs. To optimize the Organic Rankine Cycle system, the study employs the Multi-Output Support Vector Regression technique to capture nonlinear relationships between independent variables (fluid type, turbine inlet pressure, turbine inlet temperature, turbine outlet pressure, and mass flow rate) and dependent variables (pump power input, waste heat input, and turbine specific work). The Osprey optimization algorithm is used to address the multi-objective optimization problem, with the proposed Pareto-based Osprey Optimization Algorithm and the Multi-Objective Particle Swarm Optimization technique being employed to evaluate critical performance and economic parameters such as system thermal efficiency, net power output, and the levelized cost of electricity. The results of the optimization strategies indicate that the M-SVR model's prediction accuracy is significantly improved after parameter optimization, with the model returning high R2 and low Mean Square Error values of 0.991 and 0.00216, respectively. The Pareto-Based Osprey Optimization Algorithm optimizer identifies the best working fluid as Isobutane/Isopentane in a ratio of 66:34, with optimal turbine inlet pressure and temperature of 15 bars and 218 °C, respectively. The Organic Rankine Cycle model at these optimal conditions achieves a cycle efficiency of 19.93 % and an Levelized Cost of Electricity value of 0.0353 USD/kWh.

4E experimental investigation of concentrated solar cell cooling via system of heat dissipator-phase change material

Low-concentrator solar cell (SC) experimentally cooled using a new composite thermal regulation system of heat dissipator (HD) and phase change material (PCM) is investigated. The impact of area ratio (AR; HD area/SC area) of 1.5 and 2 at different HD thicknesses (h) on the system performance is reported. An energy, exergy, economic, and enviroeconomic assessments for the different cooling systems used for the SC thermal regulation are presented. The results show that the SC temperature reduction increases with increasing the HD thickness and AR. Compared with reference SC, SC-PCM/HD (AR=2/h = 3) achieves a maximum temperature reduction of 24 °C compared with 9.1 °C and 21.8 °C for SC-PCM and SC-HD, respectively. Moreover, SC-PCM/HD cooling system achieves the maximum enhancement in the average electrical efficiency and power output of 11.88 % and 12 %, respectively, compared with reference SC. The PCM thermal energy storage rate and PV system efficiency increase with increasing area ratio and decreasing the HD thickness. Using HD of (AR=2/h = 1) in conjunction with PCM yields the most favorable PCM thermal performance where it enhances the thermal energy storage, rate of energy storage, and overall thermal system efficiency by 9.5 %, 40 %, and 20.36 %, respectively, compared with using PCM only. Moreover, the PCM/HD cooling system is more economical than using PCM or HD only, and reference SC, with a maximum cost saving of 41.7 % compared with reference SC. The SC-PCM/HD cooling system is the most eco-friendly option with net CO2 mitigation and ψCO2 of 146.2 kg and 5.84$, respectively compared with 143.7 kg and 5.74$, respectively for SC-PCM.

Performance characteristics of two-phase impulse turbines for energy recovery in thermal systems

The two-phase impulse turbine (TPIT) can improve the efficiency and economy of various thermal systems, because it can directly convert the internal energy of thermal fluids into the shaft power of the turbine with no needs of additional low-temperature sub-systems. However, current efficiency of reported TPITs is much lower than gas or water turbines, due to unknown characteristics of the two-phase flow in TPITs. This paper comprehensively analyzed the performance characteristics of a TPIT, which was used in the refrigeration system. CFD methods were employed to analyze the two-phase flow based on flashing models and validated with experimental results. Three average methods were used to derive the Euler power and compared with the output power derived by the torque on each blade, while the average method based on the modified factor can evaluate the Euler power accurately. The non-uniform flow caused by the nozzle position was significant, while the liquid film near pressure side and the shroud were also three dimensional and affected by wall effects. The liquid layer on the shroud was related to the negative torque on blade tips. Results presented in this paper are constructive for designing efficient thermal systems without additional energy recovery devices.

An experimental study on fuel reforming waste heat recovery engine system fueled with methane

The effects of various operating parameters on a fuel reforming waste heat recovery engine system fueled with methane were experimentally investigated. Steam methane reforming was employed in the system because it is endothermic. Experiments were conducted on the parameters of methane flow rate to reformer and steam-to-carbon ratio to study their effects on the conversion of methane and resulting the overall thermal efficiency of the system. The components of the reformed gas were analyzed, and their effects on the combustion characteristics and thermal efficiency factors of a spark-ignition gas engine were discussed. The effects of engine operating parameters such as spark timing and excess air ratio on the exhaust gas heat recovery effect by fuel reforming and the improvement of system thermal efficiency were also investigated through experiments.

Unraveling heat transfer mechanisms in MoS 2/SO−water nanofluid for flow over a stretching cylinder

Nanofluids, advanced heat transfer fluids with improved thermophysical properties, have proven effective in enhancing the efficiency of various devices. Widely applied in electronic devices and automotive industry, consisting of nanoparticles and base fluids, serve as efficient coolants to optimize heat transfer performance. This article investigates the physical effects of magnetohydrodynamic (MHD) boundary layer flow of H 2 O base fluid over a stretched cylinder subjected to heat generation and thermal radiation. The present nanofluid investigation incorporate Mo S 2 nanoparticles into a base fluid mixture of SO / H 2 O . The mathematical model, employing similarity transformations, is developed, leading to the formulation of similarity equations. Simulations are conducted using MATLAB’s bvp4c solver to analyze the resulting flow patterns. Simulation results for various physical parameters demonstrate that the inclusion of hybrid nanoparticles in the fluid mixture significantly enhances heat transfer compared to the conventional nanofluids. Our finding highlights the necessity of considering hybrid nanoparticles over single-type counterparts for creating efficient thermal systems. Moreover, investigation underscores the vital role of hybrid nanofluids in fluid transmission, showcasing their ability to achieve higher temperature distribution.

Improving the photovoltaic thermal system efficiency with nature-inspired dolphin turbulators from energy and exergy viewpoints

The main purpose of this study is to enhance the efficiency of the photovoltaic thermal (PVT) system using nature-inspired dolphin turbulators designed based on thermal images of the dolphin dorsal fin. The turbulators are placed in the cooling channel of the PVT. The effects of the number and length scale of the turbulators are investigated on electrical, thermal, and overall efficiencies from energy and exergy perspectives, as well as the photovoltaic cell temperature at different times of the day. The dolphin turbulator enhances heat transfer to the coolant by preventing the boundary layer growth, accelerating the fluid flow, directing and impacting the coolant to the absorber plate, and improving the mixing of coolant. Consequently, turbulators reduce the photovoltaic cell temperature, increase the coolant temperature, and improve efficiencies. The enhanced PVT improves the electrical, thermal, and overall efficiencies by about 2.59 %, 16.9 %, and 14.78 % from the energy viewpoint and 2.59 %, 12.87 %, and 3.77 % from the exergy viewpoint compared to the conventional PVT. In addition, this study investigates how operational conditions, such as the coolant Reynolds number, the coolant inlet temperature, and ambient wind speed, affect the efficiencies from energy and exergy viewpoints.