Fluid Inlet Temperature Research Articles

Global sensitivity analysis of borehole thermal energy storage efficiency for seventeen material, design and operating parameters

The effect of seventeen parameters (material, design and operating) on the efficiency of the long-term operation of borehole thermal energy storage (BTES) has been investigated in this paper. Global sensitivity analysis was used to determine this effect and the use of the fast meta-model to predict the thermal efficiency of BTES has also been proposed. Carrying out research on the real object using this many input parameters is impossible, therefore, the use of 3D transient simulation studies of heat and mass transport in the BTES was chosen. An efficient numerical technique, coupled with the design and analysis of the computational experiment method was used to significantly reduce the required calculation time.The results showed that the temperature of the inlet fluid during charging and discharging, as well as the thermal conductivity of the rock mass and the arrangement of the borehole heat exchangers, had a crucial impact on the efficiency of the BTES. In order to obtain high efficiency values for the BTES, it is necessary to produce the highest possible inlet fluid temperature during charging and the lowest possible temperature of the inlet fluid during discharging. The highest values of BTES efficiency can be achieved using a compact arrangement of the borehole heat exchangers (BHE spacing 1.5–3.5 m) and for low values of the thermal conductivity of the rock mass (less than 2.45 W/(m⋅K).

Composite crystallization fouling characteristics of normal solubility salt in double-pipe heat exchanger

The fouling behavior of normal solubility pure salt (Na2SO4) and mixed salt (Na2SO4 and NaCl) in counter-current double-pipe heat exchanger was investigated. Through real-time monitoring of inlet and outlet temperatures of hot and cold fluids, the influences of various factors such as the inlet temperature, inlet velocity of hot solution and solute mass ratio on the fouling thermal resistance were determined. The results show that the fouling thermal resistance is determined by the sodium sulfate content at the experimental temperature and the change of the solubility of sodium sulfate within the temperature difference of heat transfer. With the increase of the inlet velocity of hot solution, the thermal resistance of fouling decreases gradually, indicating that the fouling process is controlled by chemical kinetics. In the fouling experiment of mixed salt solution, the main deposition material is sodium sulfate. Due to the common ion effect, sodium chloride greatly affects the saturated solubility of sodium sulfate, with the increase of the mass ratio of sodium chloride, the fouling thermal resistance and the fouling rate decreases gradually, and the time when the fouling thermal resistance reaches the asymptotic value is prolonged. The research results can provide theoretical guidance for scale inhibition of cooling surface of double-pipe heat exchanger in the treatment of wastewater containing sodium sulfate.

Numerical investigation on the effect of toroidal rings in a parabolic trough receiver with the operation of gases: An energy and exergy analysis

In this study, the influence of toroidal rings in an absorber tube of a solar parabolic trough collector (SPTC) operating with air, carbon dioxide (CO2) and helium (He) is investigated with detailed energy and exergy analysis. Nine different cases of the modified absorber have been investigated and compared with the smooth absorber tube (SAT). Under varying fluid flow rate and inlet temperatures, the heat transfer tendency in the absorber tube has been numerically studied and validated. The modified absorber having a diameter ratio (H) of 0.88 and 0.90 are the thermally and exergetically efficient optimal cases, respectively, with ˋH′ being the ratio of inner to outer diameter of the toroidal ring. The bottom periphery temperature difference for the case H = 0.88 operating with He is found to be 8 K, and it is the lowest among all the examined cases. A maximum exergy efficiency of about 41.23% is achieved for the case H = 0.90 with He. For thermal efficiency, air has higher magnitude with tremendous increase in pressure drop followed by CO2 and He. Hence, the outcomes reveal that He is the appropriate working fluid exhibiting higher exergetic performance and lower pressure drop followed by CO2 and air.

Development of correlation for critical heat flux for vertically downward two-phase flows in round tubes

ABSTRACT Critical Heat Flux (CHF) is one of the catastrophic failure modes encountered in two-phase flows in nuclear, chemical, and power industries. Considerable research was carried on CHF in last few decades in horizontal, inclined, and vertically upward flows. Only limited information, mostly at atmospheric pressure conditions and including CHF enhancers like inlet throttling, was available on CHF in vertical pipes with flow directed downwards. The complexity associated with vertically downward two-phase flows, due to flow instabilities and premature tube burnout, dictates for stringent design considerations, especially, from CHF perspective. As a result, accurate estimation of CHF is a requirement not only from performance, but also more significantly from safety perspective. The objective of this paper is to develop a correlation for CHF in vertical tubes in which the fluid flow was directed downward. As part of these investigations, a versatile test rig was designed and developed. Experiments were conducted in the pressure range of 1 to 5 bar and a CHF correlation is proposed as a function of inlet fluid temperature, mass flux and pressure in the absence of inlet throttling or other similar effects. The new correlation developed agrees well with the data from current experiments with a mean deviation of 13.87% and standard deviation of 18.71%. The uncertainty analysis revealed a 90% confidence level on the CHF estimate due to variation in the input variables.

Comparison of different dynamic thermal performance prediction models for the flat-plate solar collector with a new V-corrugated absorber

The flat-plate solar collector with a V-corrugated absorber (VFPC) has been shown to be able to improve the steady-state optical and thermal efficiency by up to 15.8% and 10.7%, respectively. To predict the dynamic thermal performance of VFPC, the Quasi-Dynamic Test Model (QDTM), Transfer Function Model (TFM) and Dynamic Heat Transfer Model (DHTM) are compared in this study. The coefficients of the dynamic test models (including QDTM and TFM) are obtained by the regression of experimental data, and the DHTM is presented based on the analysis of detailed heat transfer processes inside collector. Tested data under four kinds of test conditions is selected to identify parameters in the dynamic test models, and tested data under one more test condition with varied solar irradiances, fluid inlet temperatures and mass flow rates is selected to validate the prediction accuracy of the three models. For the short-term prediction results by QDTM/TFM/DHTM, the maximum absolute value of relative error of fluid outlet temperature Tfo and rate of useful heat gain Qu are 6.8%/5.5%/3.0% and 64.9%/43.8%/29.6% respectively. While for the long-term prediction results with the operation period of about 1 h, the averaged absolute value of relative error of useful heat gain Qu.o are 1.4%/1.0%/1.2% and the averaged absolute error of averaged thermal efficiency ηt.o are 1.1%/0.8%/0.9%. Results indicate that the DHTM has the most potential to predict the short-term thermal characteristic of VFPC accurately, followed by the TFM and QDTM, while the three kinds of models have the similar accuracy level to predict the long-term thermal characteristic of VFPC.

An evacuated receiver partially insulated by a solar transparent aerogel for parabolic trough collector

A modified evacuated receiver partially insulated by a solar transparent aerogel was proposed for the parabolic trough collector. An optical-thermal model was developed and validated to investigate the optical and thermal performance of the modified receiver and a traditional evacuated receiver. Firstly, it was revealed that different heat transfer modes among the aerogel, absorber and glass can obviously influence the heat loss from the absorber. Based on adjusting these modes through varying the aerogel thickness, an optimal receiver design was obtained. Then, the effects of the direct normal irradiance and the coating emittance were analyzed. Finally, the optimal receiver was compared with two existing modified receivers which are insulated by an opaque material and a radiation shield, respectively. Optical study shows that the optical efficiency of receiver just decreases by 0.16% when the aerogel thickness increases from 0 to 24.5 mm, which indicates the aerogel influences slightly on the optical performance. Thermal study indicates the modified receiver with the aerogel thickness of 20 mm has the best insulating performance. Compared with the traditional receiver, it can reduce the heat loss from the absorber by 7.3–10.1% when the inlet fluid temperature is within 583–823 K, and the direct normal irradiance is within 400–1000 W·m−2. As a result, the receiver efficiency can be improved by 0.01–2.92%, and the collector efficiency is improved by 0.01–2.75%. Moreover, it is found that the higher the coating emittance or the fluid temperature is, more obvious the improvement in the receiver efficiency becomes. Finally, comparison of different receivers indicates the optimal receiver with the aerogel can achieve higher receiver efficiency than the two existing modified receivers under all examined typical conditions.

Thermodynamic Performance Evaluation of Concentrating Solar Collector with Supercritical Carbon Dioxide (sCO2) Base Nanofluids

The use of supercritical carbon dioxide as a working fluid is an important alternative to enable the use of parabolic collectors in the high-temperature applications field. In the present paper, the effects of carbon black nanoparticles dispersed in supercritical carbon dioxide (sCO2) base fluid on the energetic and exergetic performance of parabolic trough collectors are theoretically investigated. Thermal modeling and performance analyses are performed through the developed model in the Engineering Equation Solver software. To present operating conditions of the system, all working fluids are tested under a pressure of 80 bar at a mass flow rate of 1.1 kg/s. In these analyses, the fluid inlet temperature, ambient temperature, and nanofluid concentration are determined as the variable indicators. Up to approximately working fluid inlet temperature of 705 K, the exergy efficiencies of the concentrating collectors using the sCO2 nanofluids are higher than that of the concentrating collector using the sCO2 base fluid. Additionally, the exergy efficiency increases in the systems using nanofluids with 2% and 4% concentration ratio are between 0.34–6.96% and 0.49–11.44%, respectively, according to the system using base fluid. Besides, at the working fluid inlet temperature values greater than 705 K, the exergy efficiency of the collector of using the sCO2 working fluid is found higher than the collectors using the nanofluids. However, at the same working fluid inlet temperatures, the fluid outlet temperatures of the collectors with the sCO2 nanofluids are higher than the system with sCO2 working fluid.

Experimental and Computational Study of Melting of Paraffin Wax Inside a Cylindrical Capsules of Elliptical Cross Section

This paper focuses on the melting of phase change material capsulated in the elliptical cross-section horizontal cylinder under convective boundary conditions. Different parameters are discussed namely, the HTF inlet temperature and velocity and the aspect ratio of the capsule cross-section. The effect of HTF inlet temperature, inlet velocity, and encapsulant aspect ratio was studied using the CFD software FLUENT6.3.26. A comparison between the numerical and experimental results was made for the system. The experimental results matched well with the heat transfer model. It is shown that the inlet temperature of the heat transfer fluid (HTF) has a great effect on the process of paraffin wax melting. The increase of HTF inlet temperatures increases the PCM liquid fraction and decreases at the same time the total time of melting the capsulated paraffin wax. The geometry of the capsule cross-section represented by its aspect ratio has a sensible effect on the process of paraffin wax melting. Decreasing the aspect ratio of the capsule, i.e elongated the capsule in the direction of flow increasing the PCM liquid fraction and decreases the total time of melting the capsulated paraffin wax. The increase of HTF inlet velocity has a very weak effect on the process of paraffin wax melting.

Entropy generation distribution characteristics of a supercritical boiler superheater during transient processes

A 1D dynamic modeling approach for surface heaters is developed and validated by comparing the calculation results with data from the available literature. Subsequently, the modeling approach is used for a superheater case study. The entropy generation of the superheater is calculated after undergoing step increasing the cold or hot inlet flow rate/temperature by 20%. The entropy generation for the hot side, the metal inside, the cold side, the entire heat transfer unit in different positions and the integral heater (ΔS˙TH) are presented and analyzed. Results show that increasing the cold/hot fluid flow rate enhances the heat transfer quantity (QT) and ΔS˙TH increase accordingly. With the increase in cold fluid inlet temperature, QT and ΔS˙TH decrease. For hot inlet temperature increasing, QT and ΔS˙TH increase. Additional entropy generation (ΔΔSTH) occurs due to the deviation between the real-time and the steady-state thermal status. The shares of ΔΔSTH are 0.7% and 6.7% during the transient process for the step increase in cold fluid inlet temperature and flow rate, respectively. ΔΔSTH accounts for 1.5% and 3.0% at the beginning of the step increase in the hot fluid inlet temperature and flow rate, respectively.

Influences of different factors on the three-dimensional heat transfer of spiral-coil energy pile group with seepage

Abstract Energy pile group is an important component of ground source heat pumps with foundation piles as ground heat exchangers. Among different energy piles, those with spiral pipes have a large heat exchange area between the pipe and the concrete, achieving good heat exchanging performance and wide applications. To analyze the influence of geometrical parameters (pile layout, pile spacing and pile depth) and external parameter (groundwater velocity) on the heat transfer of spiral-coil energy pile groups, a three-dimensional analytical model of spiral-coil energy pile groups with seepage is used, considering the thermal interaction among different piles, the geometry of spiral pipe and the velocity of groundwater. The soil temperature distribution in the energy pile group is studied under conditions with different factors (pile layouts: 3 × 2, L shape and line shape; pile spacing distances: 3, 5 and 7 m; pile depths: 10, 30 and 50 m; and groundwater velocities: 0, 1.2 × 10−6 and 2.0 × 10−6 m/s). The 3-year outlet fluid temperature of energy pile group affected by the above different factors under different inlet fluid temperatures and velocities or soil thermal exchange ratios is investigated. Results show that for the low fluid velocity inside the piles, the influence of above factors on the thermal performance of energy piles is more obvious. Large groundwater velocity, line shape pile layout, large pile spacing distance and short pile depth can alleviate the long-term temperature variation caused by unbalanced soil heat exchange. This work will facilitate the research, design and application of the energy pile group in ground source heat pumps.

Heat Transfer Enhancement of an Automobile Engine Radiator using ZnO Water Base Nanofluids

In this research paper, the forced convective heat transfer enhancement of a Suzuki Mehran (VXR) 2016 radiator (heat exchanger) along with pressure drop and friction factor by utilizing Zinc oxide (ZnO) water based nanofluids has been experimentally studied. Three types of nanofluids with different volumetric concentrations of ZnO nanoparticles (0–0.3%) were employed in order to understand its effect on heat transfer enhancement. The experimental setup was completely designed as closely as possible to the car cooling system. The experimentation has been done under laminar flow conditions (186≤Re≤1127) at different fluid volume flow rates (2–12 L/min) and constant fluid inlet temperature (70°C) to the automobile radiator. A maximum enhancement in heat transfer rate, overall heat transfer coefficient and Nusselt number was obtained up to 41%, 50% and 31% by using nanofluid with 0.2% volumetric concentration of nanoparticles respectively. On the other hand, the mean enhancement in pressure drop and friction factor was obtained up to 47% and 46% by using nanofluid with the same volumetric concentration of nanoparticles i.e. 0.2% respectively. The experimental results also revealed that the heat transfer rate, overall heat transfer coefficient and Nusselt number of nanofluids increases by increasing the volume flow rates and volumetric concentration of nanoparticles. However, these thermal performance parameters of nanofluids started to decline when the volumetric concentration of nanoparticles was increased from 0.2% to 0.3%. Furthermore, pressure drop and friction factor of nanofluids increase by increasing the volumetric concentration of nanoparticles, while pressure drop increases and friction factor decreases by increasing the volume flow rate of nanofluids respectively. At the end, the thermal efficiency of automobile radiator with high cooling rates was obtained by using nanofluid with 0.2% volumetric concentration of nanoparticles.

Performance on Buoyancy Driven Flow in Square Duct Fitted with Twisted Strip

This experimental investigation aims to study the effect of inlet fluid on flow and heat transfer characteristics for buoyancy driven flow in square tube fitted with twisted strips. Twist pitch, heat supply, inclination of the tube and Inlet fluid temperature were changed during experimentation. The study revealed that with increase in pitch the percentage enhancement in heat transfer coefficient decreases. With decrease in the pitch the flow rate decreases. Moreover with increase in inlet fluid temperature both heat transfer coefficient and flow rate tends to decrease. Perhaps it is due to higher heat loss at the tube surface which results in reduction in Rayleigh number.

Investigation the effect of various factors in a convective heat transfer performance by ionic liquid, ethylene glycol, and water as the base fluids for Al2O3 nanofluid in a horizontal tube: A numerical study

Abstract The present research investigates the heat transfer enhancement by adding alumina nanoparticle to water, Ethylene glycol, and 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM][EtSO4] ionic liquid (called ionic liquid-based nanofluid or INf in synonym) as a base fluid. A horizontal tube with constant heat flux was modeled in two-dimensional geometry with a diameter and length of 4.0 mm and 6.0 m, respectively. Al2O3 (20 nm in diameter) nanoparticles added to the base fluid in 0.5, 1.0 and 2.5 weight fraction percent. Various factors such as Reynolds number, nanofluids concentration, type of base fluid, and especially fluid inlet temperature studied in this research. Impressive results observed with variation in fluid temperature which for the temperature below room temperature (278.15 K) IL-based nanofluid shows greater heat transfer coefficient than water and Ethylene glycol-based nanofluids because of its higher thermal conductivity and viscosity at a lower temperature. And also, by adding nanoparticles to the base fluids and increasing the concentration of nanofluids, the heat transfer coefficient increased. Both the maximum heat transfer coefficient and heat transfer enhancement observed for IL-based nanofluid at 2.5 wt% concentration of nanoparticle. Finally, a correlation proposed for Nu number that satisfies for all studied nanofluids with R2 = 0.971 and AREP = 7.9%.

Experimental investigation in the pressure drop characteristics of supercritical carbon dioxide in the uniformly heated horizontal miniature tubes

This study investigates experimentally the pressure drop characteristics of supercritical carbon dioxide uniformly heated in horizontal circular smooth tubes. The results illustrate that channel pressure drop would be enlarged with increases in mass flux and inlet fluid temperature, while it would decrease with increases in outlet pressure and tube diameter. Frictional pressure drop is the most dominant contributor (51%–85%) for total pressure drop, while accelerational pressure drop, up to 28%, and form loss, up to 24%, would contribute substantially with the increase of tube diameter due to significant reduction of fluid density at the channel outlet. Several classic correlations for turbulent flow and non-isothermal correlations for supercritical fluids are examined in smooth tubes. In overall, the existing empirical correlations could reasonably predict the frictional pressure drop within a relative error of about 30% against the present data set under uniform heating conditions.

Solar-driven melting dynamics in a shell and tube thermal energy store: An experimental analysis

The integration of an array of two evacuated-tube solar collectors with a latent thermal energy storage system has been accomplished, in order to study the heat transfer characteristics during solar-driven melting. A shell-and-tube heat exchanger is employed for energy storage purposes, using 30 kg of paraffin RT70HC in the shell side. A tube bundle uniformly distributed accommodates 12 tube passes, allowing a total mass flow of 100–1000 kg/h of water for inducing turbulent-flow in the tube side. A Coriolis flowmeter is employed for measuring the mass flow through the tubes, and PT100 temperature sensors are used for measuring the inlet and exit temperature of the heat transfer fluid. Outside wall temperature is measured in different cross-sections of the tubes using T-type thermocouples, which capture the buoyancy plume of the PCM induced over the tubes during phase change. Vertical and horizontal temperature probe arrays in the shell characterize the thermal stratification that occurs during melting. Liquid fraction and energy storage during three different scenarios of solar irradiance are computed. The relation between the primary energy source and the heat transfer dynamics of the LTES are described, considering the constraints in terms of maximum PCM operating temperature and achievable liquid fraction.

Transient heat transfer simulation, analysis and thermal performance study of double U-tube borehole heat exchanger based on numerical heat transfer model

This paper proposes numerical unsteady heat transfer model that predicts the transient heat transfer in the double U-tube borehole heat exchanger (BHE) where the U-tubes can operate with either different or equal mass flow rate and inlet fluid temperature. The implicit numerical method applied on heat transfer equations, obtained from energy balance on fluid, grout and ground nodes, was utilized to get the solution. The profile of the borehole loading as well as the net heat exchange on each leg of the U-tube along the borehole depth were obtained for simultaneous charging, discharging, and charging-discharging conditions. Axial variation of the mean fluid temperature, grout and borehole wall average temperature for charging and discharging cases were investigated. The model is extended to consider the axial and radial variation of ground temperature outside the borehole. Dynamic simulation was performed for different operating conditions to investigate various temperature response, borehole thermal resistance as well as thermal performance of the BHE. The proposed model was verified with the previously published experimental results. The performed modeling, simulation and analysis are important for the vertical BHE system optimization, efficiency testing as well as for the quick investigation of the impact of the borehole parameters and thermal properties on the overall performance of the BHE. The model is crucial in the design, optimization and performance study of ground source heat pump and borehole thermal energy storage systems.

A Study on Thermal-Hydraulics Characteristics for Designing a Shell and Tube Conderser for a 1200 MWe Nuclear Power Plant

The study explores the thermal-hydraulics parameters of a condenser of a nuclear power plant with 1200MWe net electric output and 37% thermal efficiency using empirical correlations of pressure drop and heat transfer coefficient both for the tube and shell sides. Considering a two-phase fluid system, a shell and tube condenser with coolant water on the tube side and condensing steam on the shell side has been selected. For designing a condenser with a thermal load of 2060MWth, the input temperature data of cold fluid inlet and outlet temperatures are taken as 29.4ºC and 40ºC while the condensation temperature is taken as 53.97oC. Transverse, two-pass condenser with 4 shell tanks has been considered in this study and the length of each shell tank is taken as 14m. Based on these input data, this work finds heat transfer area, logarithmic mean temperature difference (LMTD), and convection heat transfer coefficient inside the tubes as 549536m2, 18.74°C, and 2869.85W/m2.ºC respectively for 20mm tube outer diameter. Hydrodynamic parameters relating to the friction factors and pressure drops on tube side are found as 0.031 and 14.86kPa respectively. Similar design data have been generated for varying coolant inlet temperatures and tube inner diameters. Results reveal that velocity of flow inside the tubes as well as the number of tubes in a bundle decrease with the increase in tube diameter. Finally, the thermal-hydraulic data may be used to design a large scale commercial condenser to be applicable for a large scale nuclear plant since limited design data are available in the literature.
 Journal of Bangladesh Academy of Sciences, Vol. 43, No. 2, 181-189, 2019

Thermal performance of a flat-plate solar collector using aqueous colloidal dispersions of graphene nanoplatelets with different specific surface areas

The effects of using aqueous nanofluids containing covalently functionalized graphene nanoplatelets with triethanolamine (TEA-GNPs) as novel working fluids on the thermal performance of a flat-plate solar collector (FPSC) have been investigated. Water-based nanofluids with weight concentrations of 0.025%, 0.05%, 0.075%, and 0.1% of TEA-GNPs with specific surface areas of 300, 500, and 750 m2/g were prepared. An experimental setup was designed and built and a simulation program using MATLAB was developed. Experimental tests were performed using inlet fluid temperatures of 30, 40, and 50 °C; flow rates of 0.6, 1.0, and 1.4 kg/min; and heat flux intensities of 600, 800, and 1000 W/m2. The FPSC’s efficiency increased as the flow rate and heat flux intensity increased, and decreased as inlet fluid temperature increased. When using nanofluids in the FPSC, the measured temperatures of absorber plate and tube wall decreased down to 3.35% and 3.51%, respectively, with the increase in weight concentration and specific surface area, while the efficiency increased up to 10.53% for 0.1- wt% TEA-GNPs nanofluid with specific surface area of 750 m2/g, in comparison with water. When using water as heat transfer fluid, very good agreement was obtained between the experimental and predicted values of absorber plate temperature, tube wall temperature, and collector’s efficiency with maximum differences of 3.02%, 3.19%, and 3.26%, respectively. While, when using nanofluids, higher differences were found, up to 4.74%, 4.7%, and 13.47% for TEA-GNPs nanofluid with specific surface area of 750 m2/g, respectively. Accordingly, the MATLAB code was capable of simulating the thermal performance of FPSCs utilizing nanofluids as their heat transfer fluids with acceptable accuracy. Values of performance index were all greater than 1, and increased as weight concentration increased up to 1.104 for 0.1- wt% TEA-GNPs nanofluid with specific surface area of 750 m2/g, implying higher positive effects on efficiency than negative effects on pressure drop. Accordingly, the investigated nanofluids can efficiently be used in FPSCs for enhanced energy efficiency, and the 0.1- wt% water-based TEA-GNPs nanofluid with specific surface area of 750 m2/g was comparatively the superior one.

The suitability of microscale compressed air axial turbine for domestic solar powered Brayton cycle

Despite the fact that concentrated solar power technology was first studied about 55 years ago, it is just in recent times that this knowledge has achieved the attention of both investors and researchers all over the world. The turbine is considered to be one of the most important components of any power cycle, and it always needs to be improved to operate at a very high performance. This paper tries to typify the structural and aerodynamic analyses of a microscale axial turbine worked with the “Brayton cycle”, at several working conditions, by means of both the 3D CFD and FEM. First of all, the turbine was proposed to have 0.5–1.5 kW as output power and 83.3% as efficiency. At that time, the rotor’s hub and the blades were geometrically examined at a range of boundary conditions, with the aim of picturing the influence of various operational and geometrical parameters on the stress contours and values as well as the deformations across the rotor’s hub and the blades. The results indicated that the highest maximum principle and von Mises stresses are significantly guided by the “rotor stagger and trailing edge wedge” angles, as well as the rotor’s rotational speed and the working fluid inlet temperature. Moreover, the fatigue life was calculated, as well, and together the “rotor stagger and trailing edge wedge” angles considerably affected its value. Like these, results could open the doors for further analyses and market research to make this (domestic) system applicable.

A numerical study on a photovoltaic thermal system integrated with a thermoelectric generator module

In this work, a three-dimensional numerical model is developed to investigate the performance of a photovoltaic thermal system integrated with a thermoelectric generator module (PVT/TE). Furthermore, the effects of various operating parameters such as solar radiation, coolant mass flow rate, and inlet and ambient temperatures on the performance of both the PVT and PVT/TE systems are investigated and compared. Based on the obtained results, the electrical efficiency of the PVT/TE system, when exposed to solar radiation of 600 and 1000 W/m2, is 6.23% and 10.41% higher than that of the PVT system, respectively. Besides, the electrical efficiency of the PVT and PVT/TE by increasing the inlet fluid temperature from 26 °C to 34 °C, reduces by 2.58% and 4.56%, respectively. Furthermore, by increasing the ambient temperature from 26 °C to 34 °C, the electrical efficiency of the PVT reduces by 1.43%, the electrical efficiency of the PVT/TE increases by 0.82%. Based on the simulation results, the electrical efficiency of the PVT/TE system is much higher than that of the PVT system, while the PVT system benefits from higher thermal efficiency in comparison to the PVT/TE system.