scholarly journals Parametric Analysis of a Polygeneration System with CO2 Working Fluid

2021 ◽  
Vol 11 (7) ◽  
pp. 3215
Author(s):  
Evangelos Bellos ◽  
Christos Tzivanidis
Keyword(s):  
Heating Temperature ◽  
Operating Conditions ◽  
Critical Parameters ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Present System ◽  
High Heating ◽  
Pressure Medium ◽  
Polygeneration System ◽  
Temperature Levels

The objective of the present work is the investigation of a novel polygeneration system for power, refrigeration and heating production at two temperature levels. The present system uses CO2 as the working fluid, which is an environmentally friendly fluid. The total configuration is a combination of a transcritical refrigeration cycle coupled to a Brayton cycle with recompression, which is fed by a biomass boiler. The examined system, at nominal operating conditions, produces refrigeration at 5 °C, and heating at 45 °C and 80 °C. Additionally, the system can be converted into a trigeneration system where the two heating outputs are produced at the same temperature level. The system was studied parametrically by changing the following seven critical parameters: turbine inlet temperature, high pressure, medium pressure, heat exchanger effectiveness, refrigeration temperature, heat rejection temperature and high heating temperature. In nominal operating conditions, the system energy and exergy efficiencies were 78.07% and 26.29%, respectively. For a heat input of 100 kW, the net power production was 24.50 kW, the refrigeration production was 30.73 kW, while the low and high heating production was 9.24 kW and 13.60 kW, respectively. The analysis was conducted with a developed model in Engineering Equation Solver.

scholarly journals Experimental and Theoretical Analysis of a Linear Focus CPV/T System for Cogeneration Purposes

Energies ◽  
2018 ◽  
Vol 11 (11) ◽  
pp. 2960 ◽  
Author(s):  
Carlo Renno
Keyword(s):  
Focal Length ◽  
Concentration Field ◽  
Operating Conditions ◽  
Working Fluid ◽  
Fluid Temperature ◽  
Atmospheric Conditions ◽  
High Concentration ◽  
Environment Temperature ◽  
Temperature Levels ◽  
T System

The knowledge of the actual energy performances of a concentrating photovoltaic and thermal (CPV/T) system with a linear focus optics, allows to evaluate the possibility of adopting this type of system for cogeneration purposes. Hence, the main aim of this paper is the design, realization, setting and modeling of a linear focus CPV/T system in the high concentration field. An experimental linear focus CPV/T plant was created in order to determine its electrical and thermal performance under different working conditions in terms of environment temperature, sunny and cloudy conditions, focal length, etc. Moreover, a theoretical model of the linear focus CPV/T system was also studied. This model evaluates the temperatures of the working fluid that flows in the cooling circuit of the CPV/T system under several operating conditions. The temperatures of the triple junction (TJ) cells, experimentally evaluated referring to different solar radiation and atmospheric conditions, were considered as the input data for the model. The values of the fluid temperature, theoretically and experimentally determined, were thus compared with good agreement. The electrical production of the CPV/T system depends generally on the TJ cell characteristics and the concentration factor, while the thermal production is above all linked to the system configuration and the direct normal irradiance (DNI) values. Hence, in this paper the electric power obtained by the linear-focus CPV/T system was evaluated referring to the cogeneration applications, and it was verified if the TJ cell and the cooling fluid reach adequate temperature levels in this type of system, in order to match the electrical and the thermal loads of a user.

The Effects of Spraying Parameters on Spray Cooling Heat Transfer Performance in the Non-Boiling Regime

2017 ◽  
Author(s):  
Azzam S. Salman ◽  
Jamil A. Khan
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Target Surface ◽  
Spray Cooling ◽  
Operating Conditions ◽  
Droplet Velocity ◽  
Inlet Pressure ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Spraying Parameters

Experiments were conducted in a closed loop spray cooling system working with deionized water as a working fluid. This study was performed to investigate the effect of the spraying parameters, such as Sauter mean diameter (SMD), the droplet velocity, and the residual velocity on the spray cooling heat transfer in the non-boiling region. Thermal effects on plain and modified surfaces with circular grooves were examined under different operating conditions. The inlet pressure of the working fluid was varied from 78.6 kPa to 183.515kPa, and the inlet temperature was kept between 21–22 °C. The distance between the nozzle and the target surface 10 mm. The results showed that increasing the coolant inlet pressure increases the droplet velocity and the number of droplets produced while decreasing the droplet size. As a consequence of these changes, increasing inlet pressure improved the heat transfer characteristics of both surfaces.

The Heat Transfer Performance of Porous Gas Turbine Blades

1968 ◽  
Vol 72 (696) ◽  
pp. 1087-1094 ◽  
Author(s):  
F. J. Bayley ◽  
A. B. Turner
Keyword(s):  
Gas Turbine ◽  
Turbine Blades ◽  
Engine Performance ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Specific Power ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Turbine Inlet ◽  
Compression And Expansion

It is well known that the performance of the practical gas turbine cycle, in which compression and expansion are non-isentropic, is critically dependent upon the maximum temperature of the working fluid. In engines in which shaft-power is produced the thermal efficiency and the specific power output rise steadily as the turbine inlet temperature is increased. In jet engines, in which the gas turbine has so far found its greatest success, similar advantages of high temperature operation accrue, more particularly as aircraft speeds increase to utilise the higher resultant jet velocities. Even in high by-pass ratio engines, designed specifically to reduce jet efflux velocities for application to lower speed aircraft, overall engine performance responds very favourably to increased turbine inlet temperatures, in which, moreover, these more severe operating conditions apply continuously during flight, and not only at maximum power as with more conventional cycles.

Heat Transfer Characteristics of Oscillating Heat Pipe With Ethanol as Working Fluid

2009 ◽  
Author(s):  
Haizhen Xian ◽  
Dengying Liu ◽  
Yongping Yang ◽  
Xiaoze Du
Keyword(s):  
Heat Transfer ◽  
Heat Pipe ◽  
Inclination Angle ◽  
Effective Conductivity ◽  
Heating Temperature ◽  
Operating Conditions ◽  
Working Fluid ◽  
Experimental Investigations ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics

In this paper, experimental investigations on the heat transfer characteristics of OHP with ethanol as working fluid were conducted. The experimental results show that there exists a necessary temperature difference between evaporator and condenser section to keep the heat pipe working. The minimum temperature differences for the optimal operating conditions varied from 1.5 to 2.0°C. The maximum effective conductivity achieved could reach up to 111kW/m•°C. The heat pipe was obviously affected by the filling ratio in some cases but the influence law is irregular and related to inclination angles and heating temperatures. Not all OHPs operated well in the limiting case of a zero inclination angle. In most cases, the optimal value of the inclination angle went up when the heating temperature increased. An appropriate high heating temperature is helpful for the OHP to achieved excellent performances. The startup temperature varied from 40°C to 50°C without considering the horizontal heating mode.

scholarly journals Numerical Performance Investigation of Parabolic Dish Solar-Assisted Cogeneration Plant Using Different Heat Transfer Fluids

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Muhammad Sajid Khan ◽  
Muhammad Abid ◽  
Khuram Pervez Amber ◽  
Hafiz Muhammad Ali ◽  
Mi Yan ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Solar Collector ◽  
Integrated System ◽  
Operating Conditions ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Pressurized Water ◽  
Parabolic Dish ◽  
Process Heating

Parabolic dish solar collectors gain higher solar to thermal conversion efficiency due to their maximum concentration ratio. The present research focuses by integrating the parabolic dish solar collector to the steam cycle producing power and rate of process heating. Pressurized water, therminol VP1, and supercritical carbon dioxide are the examined working fluids in the parabolic dish solar collector. The aim of the current research is to observe the optimal operating conditions for each heat transfer fluid by varying inlet temperature and flow rate of the working fluid in the parabolic dish solar collector, and combination of these parameters is predicted to lead to the maximum energy and exergy efficiencies of the collector. The operating parameters are varied to investigate the overall system efficiencies, work output, and process heating rate. Findings of the study declare that water is an efficient heat transfer fluid at low temperature levels, whereas therminol VP1 is effective for a higher temperature range. The integrated system efficiencies are higher at maximum flow rates and low inlet temperatures. The efficiency map of solar collector is located at the end of study, and it shows that maximum exergy efficiency gains at inlet temperature of 750 K and it is observed to be 37.75%.

Experimental Investigation on the Performance of the Organic Working Fluid Scroll Expander Under the Variable Conditions

2017 ◽  
Author(s):  
Zemin Bo ◽  
Yuping Wang ◽  
Zhenkun Sang ◽  
Xiaojing Lv ◽  
Yiwu Weng
Keyword(s):  
Output Power ◽  
Great Influence ◽  
Operating Conditions ◽  
Inlet Pressure ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Experimental Conditions ◽  
Scroll Expander ◽  
Variation Range ◽  
Variable Operating Conditions

The expander is a key component of the Organic Rankine Cycle (ORC) power generation system, which has great influence on the system performance. Based on an experiment on a ORC system using the dry working fluid R600a, the thermodynamic parameters at the inlet and outlet of the scroll expander, and the output power under the experimental conditions were obtained. The performance of the scroll expander under variable operating conditions was studied. The effect of the superheat amount, inlet temperature, and inlet pressure on the performance of the scroll expander was analyzed. The results show that the scroll expander has good performance under variable operating conditions. The inlet pressure has the greatest influence on the performance of the scroll expander, followed by the inlet temperature, while the working fluid superheat has the least effect. A change in inlet pressure of about 50kPa results in about 20W of output power at the same inlet temperature variation range. While a change in inlet temperature of about 20 ° C can result in about 15W of output power at the same inlet pressure variation range. The results can provide a reference for the design and operation of the scroll expander. (CSPE)

Performance Evaluation of Asymmetric CPC-PVT Collectors Connected in Series

2017 ◽  
Author(s):  
M. T. Nitsas ◽  
I. P. Koronaki
Keyword(s):  
Open Circuit ◽  
Operating Conditions ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Solar Collectors ◽  
In Series ◽  
Reflector Geometry ◽  
Temperature Levels ◽  
Useful Heat ◽  
Fundamental Equations

In this study, a series of thermal-photovoltaic collectors with hybrid reflector geometry and flat plate receiver is investigated experimentally and analytically through fundamental equations regarding solar collectors. The series of five compound parabolic thermophotovoltaic collectors are located in Athens, Greece and the experiments took place in June at open circuit state, i.e. the collectors were not electrically connected. The developed model combines optical and thermal analysis. The main objective of this study is to determine the thermal and the exergetic performance of the collectors under various operating conditions. For these reasons, the developed model is validated with the respective experimental data and afterwards, the solar collector model is examined parametrically for different tilt angles. The experiments are performed with water as heat transfer fluid and for low temperature levels up to 60°C. The final results proved that the investigated solar collectors are able to produce about 2.8 kW useful heat for low working fluid mass flow rates exhibiting at the same time an exergetic efficiency of nearly 1.4%. Also, the results of the developed model showed that the maximization of the produced thermal energy during summer occurs at a tilt angle of 10°.

scholarly journals Turbulence Modeling in Side-Entry Stirred Tank Mixing Time Determination

2021 ◽  
Vol 333 ◽  
pp. 02003
Author(s):  
Suci Madhania ◽  
Ni’am Nisbatul Fathonah ◽  
Kusdianto ◽  
Tantular Nurtono ◽  
Sugeng Winardi
Keyword(s):  
Turbulence Model ◽  
Turbulence Modeling ◽  
Mixing Time ◽  
Paper Industry ◽  
Turbulence Models ◽  
Computational Prediction ◽  
Operating Conditions ◽  
Stirred Tank ◽  
Critical Parameters ◽  
Working Fluid

Mixing is one of the critical processes in the industry. The stirred tank is one of the operating units commonly used in the mixing process. Several factors greatly influence the efficiency of the stirred tank, including the stirred-tank design, operating conditions, and working fluid properties. The side-entry stirred tank is widely applied in industry, among others; the processing of crude oil in the refinery industry, water-molasses mixing in the bioethanol industry, pulp stock chest in the pulp and paper industry, and anaerobic digester for biogas reactors. Mixing time is one of the critical parameters used in the design of the stirred tank. This research will model mixing time in a flat bottomed-cylindrical side-entry stirred tank with dimensions D = 40 cm and T = 40 cm using CFD ANSYS 18.2 by applying the Standard κ − ε (SKE) and Realizable κ − ε (RKE) turbulence models. The stirrer used is a three-blade marine propeller d = 4 cm which is an axial type impeller. The phenomenon of mixing in the side-entry stirred tank, qualitatively described through computational prediction results in the form of flow profiles and tracer density change contours locally. Moreover, quantitatively indicated by mixing time validated using experimental data carried out by the conductometry method. The computational prediction shows that the mixing time modeled using the SKE turbulence model shows a similarity level of 68.16%, while the RKE turbulence model shows 31.94%.

scholarly journals Experimental study of Organic Rankine cycle system by using R141b as working fluid

2020 ◽  
Vol 8 (1) ◽  
pp. 21-30
Author(s):  
Aya H.A .Kareem Kareem ◽  
Ali A. F. Al-Hamadan
Keyword(s):  
Experimental Study ◽  
Heat Source ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Operating Conditions ◽  
Hot Water ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Cycle System ◽  
Energy And Exergy Analysis

Organic Rankine cycle (ORC) is one of the renewable energy to generate power at low temperatures; however, the thermal and physical properties data of the working fluid in this system are limited. In this regards, the experimental study by using R-141b as the working fluid and hot water (i.e. 50°C and 90°C) on the ORC system was conducted in order to evaluate the ORC performance via changing temperatures. Further, the air compressor was modified to act as a multi-vane expander in the ORC system. Energy and exergy analysis of ORC system was done by using Engineering Equation Solver (EES) program. It was found that the performance of the expander is acceptable and suitable for operating conditions. In addition, the heat source temperature has a direct effect on expander performance. The higher temperatures of the heat source led to an increase the expander inlet temperature. This system satisfied maximum thermal and exergy efficiency and they found equal to 1.8 % and 21%, respectively. Moreover, the rotation speed and power of expander are equal to 1200 RPM and 2.331 kW respectively. It was concluded that the working fluid R-141b is suitable for ORC system due to consider the working fluid that do not need high temperatures to evaporate.

scholarly journals Investigation of a Novel CO2 Transcritical Organic Rankine Cycle Driven by Parabolic Trough Solar Collectors

2021 ◽  
Vol 4 (3) ◽  
pp. 53
Author(s):  
Evangelos Bellos ◽  
Christos Tzivanidis
Keyword(s):  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Solar Irradiation ◽  
Electricity Production ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Present System ◽  
Secondary Circuit ◽  
Parabolic Trough ◽  
Turbine Inlet

The objective of the present study is the detailed investigation and optimization of a transcritical organic Rankine cycle operating with CO2. The novelty of the present system is that the CO2 is warmed up inside a solar parabolic trough collector and there is not a secondary circuit between the solar collector and the CO2. Therefore, the examined configuration presents increased performance due to the higher operating temperatures of the working fluid in the turbine inlet. The system is studied parametrically and it is optimized by investigating different pressure and temperature level in the turbine inlet. The simulation is performed with a validated mathematical model that has been developed in Engineering Equation Solver software. According to the results, the optimum turbine inlet temperature is ranged from 713 up to 847 K, while the higher pressure in the turbine inlet enhances electricity production. In the default scenario (turbine inlet at 800 K and turbine pressure at 200 bar), the system efficiency is found 24.27% with solar irradiation at 800 W/m2. A dynamic investigation of the system for Athens (Greece) climate proved that the yearly efficiency of the unit is 19.80%, the simple payback period of the investment is 7.88 years, and the yearly CO2 emissions avoidance is 48.7 tones.

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