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Research Papers

J. Energy Resour. Technol. 2017;140(2):020901-020901-13. doi:10.1115/1.4036544.

The most critical component of an absorption heat transformer (AHT) is the absorber, by which the exothermic reaction is carried out, resulting in a useful thermal energy. This article proposed a model based on improving the performance of energy for an absorber with disks of graphite during the exothermic reaction, through an optimal strategy. Two models of artificial neural networks (ANN) were developed to predict the thermal energy, through two important factors: internal heat in the absorber (QAB) and the temperature of the working solution of the absorber outlet (TAB). Confronting the simulated and real data, a satisfactory agreement was appreciated, obtaining a mean absolute percentage error (MAPE) value of 0.24% to calculate QAB and of 0.17% to calculate TAB. Furthermore, from these ANN models, the inverse neural network (ANNi) allowed improves the thermal efficiency of the absorber (QAB and TAB). To find the optimal values, it was necessary to propose an objective function, where the genetic algorithms (GAs) were indicated. Finally, by applying the ANNi–GAs model, the optimized network configuration was to find an optimal value of concentrated solution of LiBr–H2O and the vapor inlet temperature to the absorber. The results obtained from the optimization allowed to reach a value of QAB from 1.77 kW to 2.44 kW, when a concentrated solution of LiBr–H2O at 59% was used and increased the value of TAB from 104.66 °C to 109.2 °C when a vapor inlet temperature of 73 °C was used.

Commentary by Dr. Valentin Fuster

Research Papers: Energy Systems Analysis

J. Energy Resour. Technol. 2017;140(2):020902-020902-10. doi:10.1115/1.4037900.

The economical and clean environment issues for a sustainable energy source at low temperature (LT) were considered and compared to natural gas technology as a fossil fuel source. The friendly environment refrigerants R410A, R407C, R717, R134a, and R600a were analyzed in an approximately 500 kW heating load output cascade heat pump. The heat pump was investigated at an intermediate temperature of 35 °C, high temperature (HT) cycle condenser at 70 °C, and compressors isentropic efficiency of 70%. All analyzed refrigerant pairs exhibited high heating season performance factor (HSPF), and it was ranged between 7 and 8.5. The thermal performance comparison revealed that the HSPF for R717/R600a showed the highest values among other refrigerant pairs. The results showed that at LT cycle evaporator temperature range of −10 to −2 °C, the natural gas technology revealed a higher season heating cost values than that of the heat pump plant by up to 10%. On the contrary at lower LT evaporator temperature, the heat pump plant technology exhibited a higher season heating cost lied in the range of 4–13.6% than that of the natural gas system. At compressors isentropic efficiency of 90%, the seasonal heating cost of the heat pump plant was lower than that of the natural gas technology by the range of 9–25% at test conditions. The mean seasonal CO2 amount released by the natural gas firing technology from all tested refrigerant pairs ranged between 2.1 and 2.5 times that of the heat pump plant technology for the investigated LT evaporator temperature range.

Commentary by Dr. Valentin Fuster
J. Energy Resour. Technol. 2017;140(2):020903-020903-7. doi:10.1115/1.4038118.

Air pollution can have detrimental effects on gas turbine performance leading to blade fouling, which reduces power output and requires frequent cleanings. This issue is a fairly well-known phenomenon in the power industry. However, site selection for gas turbine installation on the basis of air quality is rarely part of the decision-making process, mainly due to lack of geographical options especially in an urban environment or perhaps due to a simple assumption that air quality at a local micro-level has no impact on the performance of the engine. In this paper, we perform a computational fluid dynamics (CFD) study on an area surrounding a combined heat and power (CHP) facility to assess the impact of local wind distribution on air quality and the performance of a gas turbine engine. Several aerodynamic properties are suggested as possible indicators of air quality and/or high airborne particulate concentration. These indicators are then compared to data collected at various points in and around the site. The results suggest that through post-processing of a simplified CFD simulation analyzing the adjacent terrain, a continuous map of field variables can be obtained and help designers locate future CHP or gas turbine power plants in regions of lower particulate concentrations. This, in turn, would greatly increase efficiency and cost-effectiveness of the proposed power plant.

Commentary by Dr. Valentin Fuster

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