Second law analysis and multi-criteria optimization of turbulent heat transfer in a tube with inserted single and double twisted tape
Present paper deals with numerical modeling of heat transfer in a tube with two types of twisted tape inserted in a circular tube. Single twisted tape and double twisted (coaxial) tape as two enhancing elements are added to the circular tube. A numerical investigation conducted to explore the effects of these elements on the pressure drop (ΔP), convective heat transfer coefficient (h) and entropy generation (S). The results demonstrate that increasing the Reynolds number has a positive effect on the convective heat transfer coefficient in all cases due to enhance the flow swirling which improves the heat transfer on the tube wall. The results represent that the coaxial tape in the lower twisted ratio (TR) has a better performance than single tape while the opposite is true for a high twisted ratio. The results of pressure drop for two studied cases reveal that pressure drop in the coaxial tape is higher than single tape in all …
Thermodynamic and economic analyses and multi-objective optimization of harvesting waste heat from a biomass gasifier integrated system by thermoelectric generator
Thermoelectric waste heat recovery systems (WHRSs) can be used appropriately to recover wasted heat from various industrial processes. In the current work, new thermodynamic modeling was developed to harvesting waste heat from an integrated system includes an externally fired gas turbine and a biomass gasifier by three thermoelectric WHRSs. The biomass system consisted a gas turbine cycle, an organic Rankine cycle (ORC) and a domestic water heater were first thermodynamically modeled, and then effects of adding thermoelectric WHRSs to different locations of the system were investigated. It is observed that first law efficiency of the system (η 1) will become 17.11%(an increase of 0.35%) if the total output heat from the stack enters W H R S s. The efficiencies of the system can be increased from 16.76% to 17.93% by placing a WHRS on the condenser of ORC. Moreover, the operating parameters have …
Thermodynamic modeling and analysis of a novel heat recovery system in a natural gas city gate station
In the present study, five configurations of integrated system are introduced and comprehensive thermodynamic modeling and analysis for different arrangements are carried out. An organic Rankine flash cycle (ORFC) and a thermoelectric generator (TEG) are integrated with a real city gate station (CGS) to recover the thermal energy of exhaust gas at 400° C in an indirect water bath heater (IWBH). The new aspect of the present research is proposal the novel arrangements of the TEG modules, ORFC and IWBH to improve the thermal performance of the CGS integrated system. Energy and exergy analyses employed to evaluate different arrangements of integrated systems. Comparative analysis of different suggested systems revealed that integrated system including IWBH, ORFC and TEG modules with placing the TEG modules after ORFC (Case V) shows better performance. Due to the better performance, Case …
Feasibility study of using solar energy as a renewable source in office buildings in different climatic regions
Present research focus on using solar energy as a renewable option for office buildings in different climatic conditions in Iran. To seeking a way to use clean solar energy and reduce current expense in buildings an investigation carried out. Nine office buildings in various climatic regions selected as case studies. Through a precise examination, buildings specifications, energy demand and climate information carried out. In the first step based on the buildings type and hot water demand, solar water heater systems designed for each case. In the second step, a cost-benefit analysis is done to detriment the economic aspects of implement aforementioned type of solar system. A cost-benefit analysis is done from saving energy and return time of investment point of view. Results indicate that solar water heater with low investment about US $500 and payback time between 2 and 5 years can be noticed as a …
Thermodynamic and economic assessment of an integrated thermoelectric generator and the liquefied natural gas production process
The current research deals with the thermodynamic and economic assessments of an integrated thermoelectric generator system with the liquefied natural gas production process. The main aim of the present work is investigation the influence of the thermoelectric generators modules location, in a liquefied natural gas production cycle, on the thermodynamic and economic criteria. A Matlab code has been developed to assess the integrated system performance. Suggested integrated systems include adding the thermoelectric generators between the condensers and evaporators (Case I) and adding the thermoelectric generators between the condensers and ambient air (Case II). The results show that the position of the thermoelectric generators considerably influences the system performance. The results indicates that in Case I (with adding thermoelectric generators between condenser and evaporator) the system …
Performance enhancement of an integrated system with solar flat plate collector for hydrogen production using waste heat recovery
The current research presents the thermodynamic modeling and assessment of the solar-based integrated energy systems (IES) for hydrogen production with and without thermoelectric generators (TEGs) waste heat recovery system (WHRS). The results show that the net output power of the conventional system is 66.9 kW and 14 k W more power can be generated by using the TEGs WHRS in the IES. The net output power of the proposed system reaches 78.7 kW, indicating an enhancement by 17.6%. Also, increasing output power leads to an increase in the efficiency of IES from 6.9% to 8.1%. It means that, with the use of WHRS the efficiency is increased by 1.2%. However, more increase in efficiency is observed in the proposed system, and the variations of efficiency relative to the mass flow rate of the collector are extremely slight in the conventional system. Moreover, modeling results demonstrate that the …
A novel comprehensive experimental study concerned synthesizes and prepare liquid paraffin-Fe3O4 mixture to develop models for both thermal conductivity & viscosity: A new approach of GMDH type of neural network
This research aims to understand the impacts of volume concentration of Fe 3 O 4 nanoparticles and temperature on the viscosity & thermal conductivity of liquid paraffin based nanofluid. Several experiments are conducted in the Fe 3 O 4 concentration range of 0.5–3% and temperature range of 20–90° C. Oleic acid is utilized as a surfactant for the improved dispersibility and stability of nanofluids. It was found that the nanofluid behaves as a shear thinning fluid. Additionally, it was revealed that both the thermal conductivity and viscosity boost with increasing the nanoparticle concentration, whereas when the temperature increases the viscosity reduces and the thermal conductivity rises. Moreover, the Artificial Neural Network (ANN) was utilized to model the thermal conductivity and viscosity of the nanofluid using experimental data. The accuracy of the models was assessed based on four known statistical indices …
Energy and exergy analysis and multi-criteria optimization of an integrated city gate station with organic Rankine flash cycle and thermoelectric generator
The current study deals with the thermodynamic modeling, and multi-objective optimization of a pressure reduction station integrated with an organic Rankine flash cycle (ORFC) and a thermoelectric generator (TEG) waste heat recovery system (WHRS). Using the real operating data of a city gate station (CGS), a thermodynamic simulation was developed using EES (Engineering Equation Solver). The exergy analysis as a rigorous method was applied to find the exergy destructive components of the integrated system. Computations indicate that the exergy efficiencies of the indirect water bath heater (IWBH), ORFC condenser and TEG modules are 1.41%, 30.45%, and 16.34%, respectively, which are the lowest asset values among all components. Five main decision variables were defined as objective functions by the parametric study of the integrated system. Results of multi-objective optimization offer a set of …
Experimental investigation and develop ANNs by introducing the suitable architectures and training algorithms supported by sensitivity analysis: Measure thermal conductivity and viscosity for liquid paraffin based nanofluid containing Al2O3 nanoparticles
The objective of this experimental investigation is to assess the variations of thermal conductivity and viscosity of liquid paraffin-Al2O3 nanofluid containing oleic acid surfactant against temperature, nanoparticle mass concentration and surfactant concentration. The experiments are performed in the temperature range of 20–50 °C, nanoparticle mass concentration range of 1–5%, and surfactant/nanoparticle mass ratio of 1:3, 2:3 and 3:3. The results showed that the nanofluid behaves as a shear thinning fluid. Besides, it was found that boosting the nanoparticle concentration causes an increase in the thermal conductivity and viscosity, while augmenting the temperature results in a decrease in the viscosity and an increase in the thermal conductivity. Moreover, it was observed that the viscosity increases with surfactant concentration, while the thermal conductivity initially rises with surfactant concentration and then …
Feasibility of a hybrid BIPV/T and thermal wheel system for exhaust air heat recovery: Energy and exergy assessment and multi-objective optimization
In this paper, a numerical study is conducted to examine the energy and exergy performance and multi-objective optimization of a novel exhaust air heat recovery system made up of a building integrated photovoltaic/thermal (BIPV/T) collector and a thermal wheel (TW) system. The innovative BIPV/T-TW system is capable of pre-heating/pre-cooling the ambient fresh air in winter/summer and also producing electricity. Comparisons are carried out on the basis of energy and exergy by considering three different exhaust air heat recovery systems including the BIPV/T-TW system, the conventional BIPV/T collector, and the convectional TW system. It is observed that the BIPV/T-TW system has the best energy performance among the considered systems in all months of the year, while its exergy performance is lower than the BIPV/T system. Then, the multi-objective optimization technique is utilized to obtain the optimal …