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The main purpose of this paper is to study the thermodynamic, economic, and environmental aspects of a integrated system combined cooling, heating, and power generation system empowered by biomass and natural gas. Eco-Indicator 99 method is utilized to quantify the environmental impact. The proposed system consists of four main subsystems producing power, heating, and cooling. Natural gas is mixed with the syngas to enhance its heating value. The results indicate that the exergy efficiency of system is 39.45%, the products cost per exergy unit is 9.71 $ h−1, and the products environmental impact per exergy unit is 4422 mpt GJ−1. Also, when the natural gas mass flow rate-to-syngas mass flow rate ratio increases from 0 to 0.5, the exergy efficiency is found to improve by 71.97%, whereas the products cost per exergy unit and environmental impact per exergy unit of total products are seen to decline by 70.75 and 64.09%, correspondingly. Additionally, the exergy efficiency enhances by 19.48%, while the cost and environmental impact per exergy unit of the total products drop by 13.39 and 13.02%, respectively, as the splitter separation ratio increases from 0 to1. [ABSTRACT FROM AUTHOR]

Industrial surplus heat is a great available source and because of potential for external use can create benefits for society and industry. Utilizing surplus heat can deliver a way to decrease the use of primary energy and to play a part in global CO2 mitigation. The potential of using excess heat in the main industrial CO2 capture and utilization plant of Iran is investigated. A CO2 liquefaction cycle i.e., ammonia-water absorption system is developed using the heat waste of the flue gas. Process modeling is developed in Aspen Hysys™ v.10 software with the aid of Peng-Robinson equation of state. Energy, exergy, economic and exergoeconomic analyses are then employed to evaluate the developed CO2 liquefaction cycle integrated into the carbon capture and utilization plant. Results of process design and simulation show that the developed CO2 liquefaction system can liquify CO2 with the capacity of 54.5 tons per day using the flue gas enthalpy. The developed CO2 liquefaction system has the COP of 0.28, and overall exergy efficiency of 69.7%. The highest amount of exergy is destructed in ammonia reboiler with the amount of 281.92 kW. Exergoeconomic results reveal that the compressors in CO2 compression unit along with ammonia absorber and stripper have the highest importance among equipment. [ABSTRACT FROM AUTHOR]

Viscosity can be mentioned as one of the most crucial properties of nanofluids due to its ability to describe the fluid resistance to flow, and as the result it affects other phenomena. The effects of nanofluids' viscosity on different parameters can be enumerated as pressure drop, pumping power, feasibility of the nanofluid, and its convective heat transfer coefficient. In this investigation, the viscosity of TiO2/water nanofluid was compared and analyzed with experimental data. The primary goal of this investigation was to introduce a combination of experimental and modeling approaches to predict viscosity values using four different neural networks. Between MLP-ANN, ANFIS, LSSVM, and RBF-ANN methods, it was found that the LSSVM produced better results with the lowest deviation factor and reflected the most accurate responses between the proposed models. The regression diagram of experimental and estimated values shows an R2 coefficient of 0.995 and 0.993 for training and testing sections of the ANFIS model. These values for MLP-ANN, RBF-ANN, and LSSVM models were 0.998 and 0.999, 0.996 and 0.997, and 0.997 and 1.000 for their training and testing parts, respectively. Furthermore, the effect of different parameters was investigated using a sensitivity analysis which demonstrates that the average diameter can be considered as the most affecting parameter on the viscosity TiO2–water nanofluid with a relevancy factor of 0.992123. [ABSTRACT FROM AUTHOR]

The thermodynamic and economic analysis of a transcritical carbon dioxide power cycle is coupled with solar thermal subsystem and LNG subsystem. Solar thermal subsystem consists of parabolic trough collectors and a thermal storage tank, and the Copper-Therminol VP1 nanofluid is used in this subsystem. In most hours of the day, the solar subsystem based on Copper-Therminol VP1 nanofluid has a better thermal performance, which includes the output temperature of the collector and temperature of the storage tank, compared to the solar subsystem based on Therminol VP1. LNG subsystem is employed as a heat sink of the transcritical CO2 power subsystem, as well as the power generation by LNG turbine. The exergoeconomic analysis is performed to evaluate the effects of the key parameters, including turbine inlet temperatures and pressures, condensate pressure, CO2 mass flow rate and LNG pressure, on the exergy efficiency and product cost rate. In addition, parameter optimization is conducted via genetic algorithm. TOPSIS decision making technique is employed to select optimum point. System is capable of producing power with exergy efficiency of 8.53%, and product cost rate is equal to 2.09 million dollars per year, under optimum conditions. The values of exergoeconomic variables for each component of the system are calculated. The results represent that solar collector, evaporator, condenser, CO2 turbine and LNG turbine have the highest total cost rate of exergy destruction and investment (C ˙ d + Z ˙) , respectively. The highest amount of investment cost rate Z ˙ occurs in solar collector. The condenser has the lowest value of exergoeconomic factor which indicates that the costs associated with condenser come from exergy destruction rate. [ABSTRACT FROM AUTHOR]

The thermophysical specifications of working fluid play a key role in thermal performance of various types of heat pipes. Fluids with high thermal conductivity, low viscosity and surface tension are more favorable to be applied in heat pipes. In order to have fluids with higher thermal conductivity, adding nanoparticles can be an acceptable idea. In the present study, the effects of using nanofluids in several types of heat pipes are reviewed. The nanofluids are categorized based on the types of particles (as carbonic, metallic, etc.). Based on the results of the literature review, applying nanostructures in the base fluid can significantly reduce the thermal resistance of heat pipes compared with utilizing pure as operating fluid. For instance, it is observed that using graphene oxide/water nanofluid in pulsating heat pipe reduces the thermal resistance up to 42% in comparison with the water-filled heat pipe. In addition, reviewed studies revealed that the type of nanoparticle, concentration and their stability are among the most important parameters affecting thermal performance. The enhancement in thermal performance of heat pipes by using nanofluid is mainly attributed to higher thermal conductivity of the nanofluids and increase in nucleation sites. [ABSTRACT FROM AUTHOR]

In this study, a mixture of nano-encapsulated phase change materials in water has been used as the working fluid in a pulsating heat pipe in order to investigate its thermal performance. The results of the experiments showed that using the nano-encapsulated paraffin dispersed in water as working fluid improves heat transfer and decreases the thermal resistance of the pulsating heat pipe. On the other hand, among the tested concentrations for nano-encapsulated paraffin, there is an optimal value in which increasing the concentration causes an increase in the thermal resistance of the pulsating heat pipe due to the increased dynamic viscosity of the fluid. Enhancement in the thermal performance of the pulsating heat pipe by adding paraffin nanocapsules is attributed to the increase in effective specific heat of the fluid mixture as a result of the latent heat of paraffin nanocapsules. Higher effective sensible heat leads to an augmentation of convective heat transfer which has the main role in heat transfer of heat pipes. Moreover, the existence of nano-encapsulated paraffin can result in more mixing which is another reason for heat transfer enhancement. In addition, the use of nano-encapsulated phase change paraffin at high concentrations causes a cessation in the dry-out phenomenon at higher heat input compared with water or, in other words, increases the operating range of the pulsating heat pipe, which is due to an increase in the heat capacity of the fluid. In addition, the effect of inclination angle (30°, 60°, and 90°) on the thermal performance of the PHP at an optimum concentration among tested concentrations of nano-encapsulated paraffin was investigated, which was equal to 6.25 g L−1. It was observed that the PHP had its best thermal performance at the vertical position. The lowest measured thermal resistance of the PHP was 0.86 K W−1 in a vertical orientation and 50 W heat input. Moreover, at 30°, the thermal resistance of the PHP sharply increased, which can be attributed to the reduced effect of gravity in fluid return from the condenser to the evaporator. The maximum thermal resistance of the PHP observed in the case of inclination angle equal to 30° and 10 W heat input was 5.38 K W−1. [ABSTRACT FROM AUTHOR]

In this study, a model is proposed by applying the least squares support vector machine (LSSVM). In addition, genetic algorithm is used for selection and optimization of hyperparameters that are embedded in the LSSVM model. In addition to temperature and concentration of nanoparticles, the parameters which are used in most of the modeling procedures for thermal conductivity, the effect of particle size is considered. By considering the size of nanoparticles as one of the input variables, a more comprehensive model is obtained which is applicable for wider ranges of influential factor on the thermal conductivity of the nanofluid. The coefficient of determination (R2) for the introduced model is equal to 0.9902, and the mean squared error is 8.64 × 10−4 for the thermal conductivity ratio of Al2O3/EG. [ABSTRACT FROM AUTHOR]