Using computational fluid dynamics for different alternatives water flow path in a thermal photovoltaic (PVT) system

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
S. Hoseinzadeh ◽  
Ali Sohani ◽  
Saman Samiezadeh ◽  
H. Kariman ◽  
M.H. Ghasemi
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Solar Cell ◽  
Pressure Drop ◽  
Water Flow ◽  
Solar Collector ◽  
Flow Path ◽  
Electrical Performance ◽  
Working Fluid ◽  
Content Type

Purpose This study aim to use the finite volume method to solve differential equations related to three-dimensional simulation of a solar collector. Modeling is done using ANSYS-fluent software program. The investigation is done for a photovoltaic (PV) solar cell, with the dimension of 394 × 84 mm2, which is the aluminum type and receives the constant heat flux of 800 W.m−2. Water is also used as the working fluid, and the Reynolds number is 500. Design/methodology/approach In the present study, the effect of fluid flow path on the thermal, electrical and fluid flow characteristics of a PV thermal (PVT) collector is investigated. Three alternatives for flow paths, namely, direct, curved and spiral for coolant flow, are considered, and a numerical model to simulate the system performance is developed. Findings The results show that the highest efficiency is achieved by the solar cell with a curved fluid flow path. Additionally, it is found that the curved path’s efficiency is 0.8% and 0.5% higher than that of direct and spiral paths, respectively. Moreover, the highest pressure drop occurs in the curved microchannel route, with around 260 kPa, which is 2% and 5% more than the pressure drop of spiral and direct. Originality/value To the best of the authors’ knowledge, there has been no study that investigates numerically heat transfer, fluid flow and electrical performance of a PV solar thermal cell, simultaneously. Moreover, the effect of the microchannel routes which are considered for water flow has not been considered by researchers so far. Taking all the mentioned points into account, in this study, numerical analysis on the effect of different microchannel paths on the performance of a PVT solar collector is carried. The investigation is conducted for the Reynolds number of 500.

Numerical investigation of fluid flow structure and heat transfer in a passage with continuous and truncated V-shaped ribs

2015 ◽  
Vol 25 (1) ◽  
pp. 171-189 ◽  
Author(s):  
Shian Li ◽  
Gongnan Xie ◽  
Bengt Sunden
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Thermal Performance ◽  
Internal Cooling ◽  
Transfer Enhancement ◽  
Content Type ◽  
Flow And Heat Transfer

Purpose – The employment of continuous ribs in a passage involves a noticeable pressure drop penalty, while other studies have shown that truncated ribs may provide a potential to reduce the pressure drop while keeping a significant heat transfer enhancement. The purpose of this paper is to perform computer-aided simulations of turbulent flow and heat transfer of a rectangular cooling passage with continuous or truncated 45-deg V-shaped ribs on opposite walls. Design/methodology/approach – Computational fluid dynamics technique is used to study the fluid flow and heat transfer characteristics in a three-dimensional rectangular passage with continuous and truncated V-shaped ribs. Findings – The inlet Reynolds number, based on the hydraulic diameter, is ranged from 12,000 to 60,000 and a low-Re k-e model is selected for the turbulent computations. The local flow structure and heat transfer in the internal cooling passages are presented and the thermal performances of the ribbed passages are compared. It is found that the passage with truncated V-shaped ribs on opposite walls provides nearly equivalent heat transfer enhancement with a lower (about 17 percent at high Reynolds number of 60,000) pressure loss compared to a passage with continuous V-shaped ribs or continuous transversal ribs. Research limitations/implications – The fluid is incompressible with constant thermophysical properties and the flow is steady. The passage is stationary. Practical implications – New and additional data will be helpful in the design of ribbed passages to achieve a good thermal performance. Originality/value – The results imply that truncated V-shaped ribs are very effective in improving the thermal performance and thus are suggested to be applied in gas turbine blade internal cooling, especially at high velocity or Reynolds number.

Effects of different roughness elements on friction and pressure drop of laminar flow in microchannels

2018 ◽  
Vol 28 (7) ◽  
pp. 1664-1683 ◽  
Author(s):  
Fakhrodin Lalegani ◽  
Mohammad Reza Saffarian ◽  
Ahmadreza Moradi ◽  
Ebrahim Tavousi
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Laminar Flow ◽  
Friction Factor ◽  
Specific Effect ◽  
Working Fluid ◽  
Elementary Geometry ◽  
Content Type ◽  
Pressure Drops ◽  
Roughness Elements

Purpose According to very small dimensions of the microchannels, producing a microchannel with smooth surfaces is approximately impossible. The surface roughness can have a specific effect on microchannel performances. This paper aims to investigate the changes in friction and pressure drop in the microchannels by considering the different roughness elements on microchannel wall and changes in elementary geometry and flow conditions. Results show a significant effect of roughness on the pressure drop and friction. Design/methodology/approach Two-dimensional fluid flow in the rough microchannels is analyzed using FLUENT. Microchannels have a height of 50 µm. Water at room temperature (25°C) has been used as working fluid. The Reynolds numbers are considered in laminar flow range and from 50 to 300. Findings The results show that the value of friction factor reduces nonlinearly with an increase in Reynolds number. But, the pressure drops and the Poiseuille number in the microchannels increase with an increase in Reynolds number. The values of the pressure drop and the friction factor increase by increasing the height and size of the roughness elements, but these values reduce with an increase in the distance of roughness elements. Originality/value The roughness elements types in this research are rectangular, trapezoidal, elliptical, triangular and complex (composed of multiple types of roughness elements). The effects of the Reynolds number, roughness height, roughness distance and roughness size on the pressure drop and friction in the rough microchannels are investigated and discussed. Furthermore, differences between the effects of five types of roughness elements are identified.

Single-Phase Heat Transfer and Pressure Drop of Water Cooled Inside Horizontal Smooth Tubes in the Transitional Flow Regime

2010 ◽  
Author(s):  
Josua P. Meyer ◽  
Leon Liebenberg ◽  
Jonathan A. Olivier
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Pressure Drop ◽  
Transition Region ◽  
Heat Exchangers ◽  
Operating Conditions ◽  
Transitional Flow ◽  
Working Fluid ◽  
Tube Heat Exchanger ◽  
Smooth Tubes

Heat exchangers are usually designed in such a way that they do not operate in the transition region. This is usually due to a lack of information in this region. However, due to design constraints, energy efficiency requirements or change of operating conditions, heat exchangers are often forced to operate in this region. It is also well known that entrance disturbances influence where transition occurs. The purpose of this paper is to present experimental heat transfer and pressure drop data in the transition region for fully developed and developing flows inside smooth tubes using water as the working fluid. The use of different inlet disturbances were used to investigate its effect on transition. A tube-in-tube heat exchanger was used to perform the experiments, which ranged in Reynolds numbers from 1 000 to 20 000, with Prandtl numbers being between 4 and 6 while Grashof numbers were in the order of 105. Results showed that the type of inlet disturbance could delay transition to a Reynolds number as high as 7 000, while other inlets expedited it, confirming results of others. For heat transfer, though, it was found that transition was independent of the inlet disturbance and all commenced at the same Reynolds number, 2 000–3 000, which was attributed to secondary flow effects.

Analysis of heat transfer and fluid flow of a slot jet impinging on a confined concave surface with various curvature and small jet to target spacing

2019 ◽  
Vol 29 (8) ◽  
pp. 2885-2910 ◽  
Author(s):  
Dandan Qiu ◽  
Lei Luo ◽  
Songtao Wang ◽  
Bengt Ake Sunden ◽  
Xinhong Zhang
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Fluid Flow ◽  
Thermal Performance ◽  
Flow Characteristics ◽  
Target Surface ◽  
Surface Curvature ◽  
Content Type ◽  
Curvature Effects ◽  
Target Spacing

Purpose This study aims to focus on the surface curvature, jet to target spacing and jet Reynolds number effects on the heat transfer and fluid flow characteristics of a slot jet impinging on a confined concave target surface at constant jet to target spacing. Design/methodology/approach Numerical simulations are used in this research. Jet to target spacing, H/B is varying from 1.0 to 2.2, B is the slot width. The jet Reynolds number, Rej, varies from 8,000 to 40,000, and the surface curvature, R2/B, varies from 4 to 20. Results of the target surface heat transfer, flow parameters and fluid flow in the concave channel are performed. Findings It is found that an obvious backflow occurs near the upper wall. Both the local and averaged Nusselt numbers considered in the defined region respond positively to the Rej. The surface curvature plays a positive role in increasing the averaged Nusselt number for smaller surface curvature (4-15) but affects little as the surface curvature is large enough (> 15). The thermal performance is larger for smaller surface curvature and changes little as the surface curvature is larger than 15. The jet to target spacing shows a negative effect in heat transfer enhancement and thermal performance. Originality/value The surface curvature effects are conducted by verifying the concave surface with constant jet size. The flow characteristics are first obtained for the confined impingement cases. Then confined and unconfined slot jet impingements are compared. An ineffective point for surface curvature effects on heat transfer and thermal performance is obtained.

scholarly journals Numerical simulation of concentrating solar collector P2CC with a small concentrating ratio

2012 ◽  
Vol 16 (suppl. 2) ◽  
pp. 471-482 ◽  
Author(s):  
Velimir Stefanovic ◽  
Sasa Pavlovic ◽  
Marko Ilic ◽  
Nenad Apostolovic ◽  
Dragan Kustrimovic
Keyword(s):  
Mathematical Model ◽  
Fluid Flow ◽  
Solar Radiation ◽  
Solar Energy ◽  
Radiation Intensity ◽  
Solar Collector ◽  
Numerical Procedure ◽  
Working Fluid ◽  
Flow Rates ◽  
Solar Radiation Intensity

Solar energy may be practically utilized directly through transformation into heat, electrical or chemical energy. A physical and mathematical model is presented, as well as a numerical procedure for predicting thermal performances of the P2CC solar concentrator. The demonstrated prototype has the reception angle of 110? at concentration ratio CR = 1.38, with the significant reception of diffuse radiation. The solar collector P2CC is designed for the area of middle temperature conversion of solar radiation into heat. The working fluid is water with laminar flow through a copper pipe surrounded by an evacuated glass layer. Based on the physical model, a mathematical model is introduced, which consists of energy balance equations for four collector components. In this paper, water temperatures in flow directions are numerically predicted, as well as temperatures of relevant P2CC collector components for various values of input temperatures and mass flow rates of the working fluid, and also for various values of direct sunlight radiation and for different collector lengths. The device which is used to transform solar energy to heat is referred to as solar collector. This paper gives numerical estimated changes of temperature in the direction of fluid flow for different flow rates, different solar radiation intensity and different inlet fluid temperatures. The increase in fluid flow reduces output temperature, while the increase in solar radiation intensity and inlet water temperature increases output temperature of water. Furthermore, the dependence on fluid output temperature is determined, along with the current efficiency by the number of nodes in the numerical calculation.

Effect of Cross Aspect Ratio on Flow in Diverging and Converging Microchannels

2017 ◽  
Vol 139 (6) ◽  
Author(s):  
V. S. Duryodhan ◽  
Shiv Govind Singh ◽  
Amit Agrawal
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Numerical Study ◽  
Three Dimensional ◽  
Hydraulic Diameter ◽  
Working Fluid ◽  
Cross Sectional ◽  
Flow Acceleration ◽  
Three Dimensional Models

Aspect ratio is an important parameter in the study of flow through noncircular microchannel. In this work, three-dimensional numerical study is carried out to understand the effect of cross aspect ratio (height to width) on flow in diverging and converging microchannels. Three-dimensional models of the diverging and converging microchannels with angle: 2–14 deg, aspect ratio: 0.05–0.58, and Reynolds number: 130–280 are employed in the simulations with water as the working fluid. The effects of aspect ratio on pressure drop in equivalent diverging and converging microchannels are studied in detail and correlated to the underlying flow regime. It is observed that for a given Reynolds number and angle, the pressure drop decreases asymptotically with aspect ratio for both the diverging and converging microchannels. At small aspect ratio and small Reynolds number, the pressure drop remains invariant of angle in both the diverging and converging microchannels; the concept of equivalent hydraulic diameter can be applied to these situations. Onset of flow separation in diverging passage and flow acceleration in converging passage is found to be a strong function of aspect ratio, which has not been shown earlier. The existence of a critical angle with relevance to the concept of equivalent hydraulic diameter is identified and its variation with Reynolds number is discussed. Finally, the effect of aspect ratio on fluidic diodicity is discussed which will be helpful in the design of valveless micropump. These results help in extending the conventional formulae made for uniform cross-sectional channel to that for the diverging and converging microchannels.

Numerical study of the dimensionless characteristics and modeling experiment of a molten salt pump that transports viscous fluids

2017 ◽  
Vol 27 (9) ◽  
pp. 2131-2153 ◽  
Author(s):  
Chunlei Shao ◽  
Yang Zhao
Keyword(s):  
Reynolds Number ◽  
Molten Salt ◽  
High Speed ◽  
Critical Reynolds Number ◽  
Numerical Study ◽  
Working Fluid ◽  
High Speed Photography ◽  
Content Type ◽  
Modeling Experiment ◽  
External Characteristics

Purpose The purpose of this paper is to study the dimensionless characteristics of a molten salt pump and propose an approach to carry out the modeling experiment by using water instead of molten salts. Design/methodology/approach External characteristics of the pump were estimated by using the steady flow model and compared with the experimental results. By taking water as the working fluid, the pathlines in the volute of the model pump were validated by the results obtained of high-speed photography. According to the derived dimensionless characteristics of the molten salt pump, the modeling experimental schemes were proposed. Adopting the validated numerical simulation model, the performance of the molten salt pump was studied in detail. Findings The modeling experimental schemes designed according to the dimensionless characteristics are theoretically feasible. However, to carry out the experiment successfully, factors such as rotational speed, geometric size, flow rate and head should be taken into account. The flow in the pumps is similar under the similar operating condition and the external characteristics of the similar pump can be converted to each other. Compared with transporting water, the decline of the head and efficiency is within 5 per cent when the viscosity is lower than 0.01453 Pa · s. The pump is not suitable for running under the critical Reynolds number of 1.0 × 107. Originality/value The current work revealed the relationships among the dimensionless performances of a molten salt pump and proposed a critical Reynolds number ReQcr for the pump running.

scholarly journals Drag Reduction with Biopolymer-Synthetic Polymer Mixtures in Oil-Water Flows: Effect of Synergy

2020 ◽  
Vol 24 (6) ◽  
pp. 1-10
Author(s):  
Lawrence Chukwuka Edomwonyi-Otu ◽  
Muhammed Muhammed Gimba ◽  
Nurudeen Yusuf
Keyword(s):  
Reynolds Number ◽  
Pressure Drop ◽  
Pressure Gradient ◽  
Drag Reduction ◽  
Water Flow ◽  
Transport Systems ◽  
Test Fluid ◽  
Polymer Mixture ◽  
Water Flows ◽  
Oil Water

The search for lower cost materials that reduce pressure drop in fluid transport systems in oil and gas industries to conserve pumping energy is of paramount importance. Polymers are known to reduce pressure drop in pipeline oil-water flows in a process referred to as drag reduction (DR). The effect of partially hydrolysed polyacrylamide, polyethylene oxide, Aloe Vera mucilage and their mixtures as drag reducing polymers (DRPs) on pressure gradient (pressure drop; Δp) in pipeline oil-water flows were studied. The experiment was carried out in flow rig with 0.02-m diameter straight unplasticised polyvinylchloride (uPVC) pipe, two centrifugal pumps, control valves and two storage tanks. Tap water (ρ = 997 kg/m3 and µ = 0.89 cP) and diesel (ρ = 832 kg/m3 and µ = 1.66 cP) were used as the test fluid at ambient condition. The polymer mixture total concentration (MTC) of 30 and 400 ppm at different mixing proportion, mixture Reynolds number (Remix) and oil input volume were investigated. The results show increase in pressure gradient with increase in oil input volume in both single-phase water flow and oil-water flow before adding drag reducing polymers (DRPs). However, Δp decreased after adding DRPs with increase in Reynolds number (Re) or Remix and decrease in the oil-phase Re, and vice versa. The results further showed higher reduction in pressure drop by the polymer mixture than in each of the polymer used at the same conditions. The rigidness of the biopolymer was improved by adding synthetic polymers which resulted to increase in DR efficiency.

A Semianalytical Model for Horizontal-Well Productivity With Pressure Drop Along the Wellbore

SPE Journal ◽  
2018 ◽  
Vol 23 (05) ◽  
pp. 1603-1614 ◽  
Author(s):  
Wanjing Luo ◽  
Changfu Tang ◽  
Yin Feng
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Horizontal Well ◽  
Horizontal Wells ◽  
Productivity Index ◽  
Type Curves ◽  
Penetration Ratio ◽  
New Type ◽  
The One

Summary This study aims to develop a semianalytical model to calculate the productivity index (PI) of a horizontal well with pressure drop along the wellbore. It has been indicated that by introducing novel definitions of horizontal-well permeability and conductivity, the equation of fluid flow along a horizontal well with pressure drop has the same form as the one for fluid flow in a varying-conductivity fracture. Thus, the varying-conductivity-fracture model and PI model can be used to obtain the PI of a horizontal well. Results indicate that the PI of a horizontal well depends on the interaction between horizontal-well conductivity, penetration ratio, and Reynolds number. New type curves of the penetration ratios with various combinations of parameters have been presented. A complete-penetration zone and a partial-penetration zone can be identified on the type curves. Based on the type curves, two examples have also been presented to illustrate the advantages of this work in optimizing parameters of horizontal wells.

Nanotechnology: new hope of efficiency enhancement for solar evacuated tube collector

2016 ◽  
Vol 13 (3) ◽  
pp. 199-205 ◽  
Author(s):  
Rupeshkumar V. Ramani ◽  
Bharat M. Ramani ◽  
Anjana D. Saparia ◽  
Nikesh A. Shah ◽  
Pinank Kacha ◽  
...  
Keyword(s):  
Solar Collector ◽  
Pure Water ◽  
Sol Gel ◽  
Chemical Vapor ◽  
Working Fluid ◽  
Physical Vacuum ◽  
Fluid Temperature ◽  
Alternative Source ◽  
Content Type ◽  
Evacuated Tube

Purpose In the twenty-first century, the use of fossil fuels has increased drastically because the necessity of energy is increasing day by day which affects the world’s economy. The solar energy (photo-thermal energy conversion) system is the most economical and eco-friendly alternative source. To increase the use of domestic as well as commercialization purpose, the authors have reviewed this paper on the solar water heater along with its structural mechanism for energy enhancement and to create easier stair steps for climbing on the green world dream. Design/methodology/approach In this study, nanotechnology has remarkably built its own use for extending thermal efficiency by using some gradual experiments. It is a phenomenon, like nanofluid (as a working fluid for a direct solar collector), nanocoating (on the surface of a solar-evacuated tube by using the chemical vapor deposition/physical vacuum deposition/sol–gel technique) and nanorod-based solar collector tube. Findings This invention gives greater efficiency rather than the conventional systems, but also this advancement is not too much supported in a low- temperature environment also, we can consider the poor light absorption characteristics of the pure water (Bencic, et al., 2000). Originality/value The basic idea and understanding of this phenomenon to improve solar collecting performance for obtaining a high working-fluid temperature are discussed in this paper.

Sign in / Sign up

Export Citation Format

Share Document