Search

• Refrigerant maldistribution does not have always the same influence in evaporator performance. • The penalty of the maldistribution depends on the relation between superheat and water temperature drop. • Two parameters are used to characterize refrigerant maldistribution. • The conditions with 0 superheat do not show any degradation in the performance. • Higher qualities produces a better refrigerant distribution in the evaporator. The maldistribution of the refrigerant mass flowrate among the different channels of a brazed plate heat exchanger evaporator with distributor, has been studied with a thermographic camera working under different conditions of inlet vapor quality, superheat, and water temperature drop. Part A of this work includes the description of the experimental campaign and a full discussion of the obtained results. This paper (part B) presents, first an evaluation of the penalty caused by the refrigerant maldistribution on the evaporator performance, and the effect of the operation conditions on that penalty; second, a data reduction methodology, which allows the quantification of the maldistribution based on a series of simple assumptions and the flow conservation equations. Finally, given that it has been found that the water temperature drop across the evaporator has a strong influence on the performance penalty due to refrigerant maldistribution, the water temperature evolution is analyzed in detailed and the reasons for its great influence are explained and commented. On this regard, it is concluded that the penalty of the maldistribution on the evaporation performance strongly depends on the availability of the secondary fluid in the channels where most of the refrigerant liquid is concentrated. The described data reduction methodology, based on the analysis of the thermographies and the measured evaporator performance, is suitable to give an estimate of the maldistribution which seems reasonable and consistent with the observed data. [ABSTRACT FROM AUTHOR]

• Thermography is a reliable technic to evaluate refrigerant maldistribution in Brazed Plate evaporators. • Evaluation of refrigerant maldistribution at different evaporator working conditions. • Conditions with 0 superheat show a uniform thermal map. • The rest of the conditions have shown some degree of thermal maldistribution. • The effect of the maldistribution on the evaporator performance depends on the working conditions. The refrigerant distribution in a brazed plate heat exchanger evaporator with distributor has been studied with a thermographic camera working under different conditions of inlet vapor quality, superheat, and water temperature drop. The thermographies have shown a clear uneven thermal distribution except when superheat is null. In most of the cases, they show that a great part of the liquid accumulates at the end channels of the evaporator. The degradation of the evaporator performance is higher when the water temperature drop has a similar or higher value than the superheat. On the other hand, when the superheat is significantly higher than the water temperature drop, the evaporator performance is very similar to situations in which there is an even distribution of the refrigerant. The registered evaporation temperatures are much lower for the case of 13 K of water temperature drop, highlighting the importance of the influence of this parameter on the evaporator performance. This research is described in two parts, Part A (present paper) including the description of the experimental campaign, the obtained experimental results and the results discussion and Part B including an analysis of the degradation of the evaporation temperature due to the refrigerant maldistribution as well as a deeper analysis of the registered temperatures and of the causes for the great degradation observed when the water temperature drop is increased. [ABSTRACT FROM AUTHOR]

This paper investigates the challenges isolated islands face in transitioning from fossil fuel-based electricity generation to renewable energy sources. The Canary Islands serve as a case study, where photovoltaic and wind power are the primary renewables, but their variability requires a deep techno-economic analysis. The island's energy demand is predicted to rise by 100% due to economic growth, electrification and electric vehicles. However, implementing renewable systems encounters obstacles, such as limited suitable sites and protected areas. The study uses Wilks' methodology and Monte Carlo sampling to explore 59 combinations of randomly selected inputs of the uncertain variables, aiming for a 95/95% coverage and confidence level in the results. In most cases, they experience energy shortages, failing to meet electric demand. Even though a new generation mix appears to cover demand under all circumstances, the uncertainty unveils a different reality, leading to an approximate 25% increase in system costs. Surpluses in energy generation, while seemingly positive, can pose challenges. The new system's Levelized Cost of Energy increases from around 14 to 17c€/kWh. These cost increases are contingent upon future performance and the variability of uncertain parameters, leading to excesses ranging from slightly below 25% to over 40%. • Demand coverage scenario designed to meet electric demand through renewable sources. • Uncertainty analysis of a scenario for the complete electrification of the economy. • Best Estimate Plus Uncertainty analysis implementing the Wilks' methodology. • Resizing the system to cover the demand with 95% coverage and confidence levels. • Differences in using deterministic and stochastic methods for electric demand coverage. [ABSTRACT FROM AUTHOR]