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In the present work, a novel parabolic trough solar collector model has been developed and validated. The validation has been carried out through a comparison with results of previous studies conducted in the worldwide most renowned laboratories, i.e., Sandia National Laboratory (SNL) and National Renewable Energy Laboratory (NERL). The comparison with experimental data collected by SNL, during LS-2 tests at AZTRAK platform, has shown good agreement, particularly for the case of receivers with Cermet coating. When compared with the Engineering Equation Solver (EES) code developed by NREL, the novel model offers improvements in the accuracy of thermal performance prediction. It has been found that the proposed model in the present study predicts more accurately the thermal efficiency than EES; with an average uncertainty of 0.64% compared to 1.11% for ESS, in the case of Cermet coating. Nevertheless, minor inaccuracy in the estimation of heat losses at higher operation temperatures has been found due to the error propagation in the model. The present work also includes a survey of the design and manufacturing processes of the parabolic trough collector that are of a particular interest for developing this promising technology.

In the present work, a novel parabolic trough solar collector model has been developed and validated. The validation has been carried out through a comparison with results of previous studies conducted in the worldwide most renowned laboratories, i.e., Sandia National Laboratory (SNL) and National Renewable Energy Laboratory (NERL). The comparison with experimental data collected by SNL, during LS-2 tests at AZTRAK platform, has shown good agreement, particularly for the case of receivers with Cermet coating. When compared with the Engineering Equation Solver (EES) code developed by NREL, the novel model offers improvements in the accuracy of thermal performance prediction. It has been found that the proposed model in the present study predicts more accurately the thermal efficiency than EES; with an average uncertainty of 0.64% compared to 1.11% for ESS, in the case of Cermet coating. Nevertheless, minor inaccuracy in the estimation of heat losses at higher operation temperatures has been found due to the error propagation in the model. The present work also includes a survey of the design and manufacturing processes of the parabolic trough collector that are of a particular interest for developing this promising technology.

Abstract A mathematical model that describes a trailer scale biomass steam gasification system coupled with a solar collector heat source and a micro gas turbine is reported in this paper. This combined heat and power system is set to a prescribed output of 20 kW e and several system conditions have been optimized in a parametric study to minimize resource consumption rates. Biomass feeding rates under optimal conditions were found to range between 23 and 63 kg/h depending on the types of feedstock and other parameters. Water consumption is reduced through a condensation and recirculation process that is part of a heat recovery unit. Also, solar energy requirements have been reduced by means of a recuperator that extracts heat out of the combustion products. The overall system performance has been evaluated by a utilization factor which was found to range between 30% and 43%. The system has been compared to a baseline case of an air breathing gasification system of a similar scale. It was found that steam gasification produces the syngas with heating values over twice as high as those obtained by air gasification. Steam gasification also led to a 25% and 50% reduction in emission rates of contaminants like CO 2 and nitrogen oxides respectively relative to the baseline case.

Abstract A mathematical model that describes a trailer scale biomass steam gasification system coupled with a solar collector heat source and a micro gas turbine is reported in this paper. This combined heat and power system is set to a prescribed output of 20 kW e and several system conditions have been optimized in a parametric study to minimize resource consumption rates. Biomass feeding rates under optimal conditions were found to range between 23 and 63 kg/h depending on the types of feedstock and other parameters. Water consumption is reduced through a condensation and recirculation process that is part of a heat recovery unit. Also, solar energy requirements have been reduced by means of a recuperator that extracts heat out of the combustion products. The overall system performance has been evaluated by a utilization factor which was found to range between 30% and 43%. The system has been compared to a baseline case of an air breathing gasification system of a similar scale. It was found that steam gasification produces the syngas with heating values over twice as high as those obtained by air gasification. Steam gasification also led to a 25% and 50% reduction in emission rates of contaminants like CO 2 and nitrogen oxides respectively relative to the baseline case.

Abstract Organic Rankine cycle (ORC) is a promising thermal-to-power technology that uses low-temperature heat from various sources including renewable energy and waste heat. A zeotropic fluid ORC offers thermodynamic-performance advantages over pure fluid ORC because of the relatively low irreversibility during the heat transfer process. Nonetheless, zeotropic fluid ORC may incur higher cost than pure fluid ORC because the former has high mass transfer resistance and small temperature difference in the heat exchanger. Limited research has been carried out to enhance thermo-economic performance of zeotropic ORC. In the present study, an ORC that uses zeotropic fluids and undergoes liquid–vapor separation during condensation is proposed. A thermo-economic analysis is developed based on a new optimization model for the proposed ORC. The objective function of the optimization model is the minimization of the specific investment cost. A genetic algorithm is used to solve the optimization model. A case study is then solved to illustrate the advantages of the proposed ORC and validate the proposed thermo-economic optimization method. The results of the thermodynamic analysis show that the condenser area of the proposed ORC is 17.6% lower than that of the conventional ORC under the same working conditions. Thermo-economic optimization results show that the specific investment cost of the proposed ORC is 13.3–18.4% lower than that of the basic ORC. Meanwhile, the second law efficiency of the proposed ORC is 4.2% higher than that of the conventional ORC. A sensitivity analysis is carried out to assess the dependence of the ORC performance on the temperatures of the heat source and the surrounding environment.

Abstract Organic Rankine cycle (ORC) is a promising thermal-to-power technology that uses low-temperature heat from various sources including renewable energy and waste heat. A zeotropic fluid ORC offers thermodynamic-performance advantages over pure fluid ORC because of the relatively low irreversibility during the heat transfer process. Nonetheless, zeotropic fluid ORC may incur higher cost than pure fluid ORC because the former has high mass transfer resistance and small temperature difference in the heat exchanger. Limited research has been carried out to enhance thermo-economic performance of zeotropic ORC. In the present study, an ORC that uses zeotropic fluids and undergoes liquid–vapor separation during condensation is proposed. A thermo-economic analysis is developed based on a new optimization model for the proposed ORC. The objective function of the optimization model is the minimization of the specific investment cost. A genetic algorithm is used to solve the optimization model. A case study is then solved to illustrate the advantages of the proposed ORC and validate the proposed thermo-economic optimization method. The results of the thermodynamic analysis show that the condenser area of the proposed ORC is 17.6% lower than that of the conventional ORC under the same working conditions. Thermo-economic optimization results show that the specific investment cost of the proposed ORC is 13.3–18.4% lower than that of the basic ORC. Meanwhile, the second law efficiency of the proposed ORC is 4.2% higher than that of the conventional ORC. A sensitivity analysis is carried out to assess the dependence of the ORC performance on the temperatures of the heat source and the surrounding environment.

Because some physicists continue to defend the nonexistent theory of finite time thermodynamics, additional incontrovertible experimental and theoretical evidence is provided about its irrationality and nonreality.

Because some physicists continue to defend the nonexistent theory of finite time thermodynamics, additional incontrovertible experimental and theoretical evidence is provided about its irrationality and nonreality.

A detailed numerical simulation of the performance of household refrigerator having a top-mount configuration is made in this study, and an experiment is carried out with a real refrigerator for verification. The results indicate the temperature distributions from the numerical simulation are qualitatively in line with the experimental measurements. Cyclic temperature variations occur amid freezer, refrigerating, and vegetable compartments due to on/off control strategy. However, it is found that the temperature variation for freezer and refrigerating compartment are in phase with each other while the temperature variation in vegetable compartment is roughly out-of-phase with the other two compartments. The simulations show that the design of air duct and its locations may impose a detrimental role on the temperature uniformity within the refrigerator, yet the airflow is strongly influenced by gravity. It is also found that the refrigerating compartment possesses the worst temperature non-uniformity. For improving the temperature non-uniformity, a modified design incorporating the air duct design with appropriate locations of the inlet openings in the freezer and refrigerating compartment is proposed. Though these modifications the maximum temperature difference and the root mean-square of temperature variation in refrigerating compartment, had been reduced from 7.17 °C to 3.57 °C and from 3.17 °C to 1.55 °C, respectively.