Andrés Sarmiento

Owing to the need for continuous improvement in building energy performance standards (BEPSs), facilities must adhere to benchmark performances in their quest to achieve net-zero performance. This research explores machine learning models that leverage historical energy data from a cluster of buildings, along with relevant ambient weather data and building characteristics, with the objective of predicting the buildings’ energy performance through the year 2040. Using the forecasted emission results, the portfolio of buildings is analyzed for the incurred carbon non-compliance fees based on their on-site fossil fuel CO_2e emissions to assess and pinpoint facilities with poor energy performance that need to be prioritized for decarbonization. The forecasts from the machine learning algorithms predicted that the portfolio of buildings would incur an annual average penalty of $31.7 million ($1.09/sq. ft.) and ~$348.7 million ($12.03/sq. ft.) over 11 years. To comply with these regulations, the building portfolio would need to reduce on-site fossil fuel CO_2e emissions by an average of 58,246 metric tons (22.10 kg/sq. ft.) annually, totaling 640,708 metric tons (22.10 kg/sq. ft.) over a period of 11 years. This study demonstrates the potential for robust machine learning models to generate accurate forecasts to evaluate carbon compliance and guide prompt action in decarbonizing the built environment.

Frost is an undesirable problem in energy conversion and engineering applications because it negatively affects the operating system performance by reducing the heat transfer for energy conversion systems and the coefficient of performance (COP) for refrigeration and air conditioning (HVAC) equipment. Among the various frost prevention or removal techniques, electrohydrodynamics (EHD) is an active frost prevention and removal technique that has been studied since the 1970s. This review paper clarifies the fundamentals of EHD, while offering a comprehensive review of the works published in the literature regarding both the influence of EHD on frost growth control and its effectiveness on frost removal. It is observed that while individual research works have drawn conclusions on the specifics of EHD for frost control and removal, there is no consensus in the literature on the specific effects of some of the critical parameters associated with EHD phenomena, such as the influence of electric field intensity and the use of AC and DC voltage, which can both affect frost growth. In addition, no baseline for comparison has been established, making it difficult to compare the results of various investigators. Finally, prospects and conclusions are discussed. This article is part of the theme issue ‘Heat and mass transfer in frost and ice’.

Compared to state-of-the-art heat exchangers, manifold-microchannel heat exchangers have shown superior heat removal density (kW/kg) at moderate pressure drops. However, manifold-microchannel heat exchangers made of Ni-based superalloys or other tough-to-machine materials can be a challenge to fabricate using conventional fabrication methods. This is mainly because of the inherently complex manifold microchannel geometry, as well as the required small feature sizes (e.g., fin thickness) that should be comparable, or smaller than state-of-the-art high-performance metallic-based heat exchangers (∼150 μm or smaller). In this study, a direct metal laser sintering (DMLS) additive manufacturing technique was used to fabricate the compact high-temperature manifold-microchannel heat exchanger reported here. The additively manufactured manifold-microchannel heat exchanger was fabricated as a single object, which significantly simplifies the fabrication process. In this work, three different additive manufacturing machines were used to study the effect of laser power, powder size, and layer thickness on the fin and channel sizes of the fabricated microchannel heat exchangers. To evaluate the minimum wall thickness for holding the required design pressures, pressure containment tests were performed. As a result, a wall thickness of 0.3 mm was shown to withstand 340 kPa and be leakage-free. A detailed analysis of different printing orientations and their effect on the manifold-microchannel heat exchanger's design was also performed. Finally, a 76 × 76 × 76 mm3 manifold microchannel heat exchanger was successfully fabricated with a fin thickness of 0.13 mm out of maraging steel. A second unit with dimensions of 94 × 87.6 × 94.4 mm3 was successfully fabricated with a fin thickness of 0.22 mm out of Inconel 718. Details of the fabrication process and key take-away results are discussed in this paper.

El bore (Alocasia macrorrhiza) es una planta que puede alcanzar hasta 3 metros de altura y sus hojas hasta un metro de largo, es una planta vista como maleza y una de sus características principales es acumular almidón en tallos subterráneos llamados cornos. Existe un poco aprovechamiento de esta planta, ya que solo se suelen utilizar sus hojas para concentrado de ganado y se pierde todo el potencial agroindustrial de los tallos. Con el fin de aprovechar la biomolécula de almidón, la presente investigación utilizó el tallo de Bore para extraer esta biomolécula y, posteriormente, la elaboración y evaluación del rendimiento de un biopolímero a través del método Casting, utilizando tres concentraciones diferentes de almidón y ácido acético durante el proceso de elaboración. Para cada una de estas concentraciones se realizaron 6 repeticiones. Por último, para evaluar el rendimiento se comparó con un biopolímero obtenido a partir de otro tipo de almidón (maíz) bajo la misma metodología y concentraciones. En los resultados se observó como para las pruebas con concentración de 18 g y 24 g el rendimiento fue mayor en el almidón de Bore, mientras que la concentración de 12 g el mayor rendimiento se evidenció en el almidón de maíz.