Browsing by Author "Cacabelos, Antón"

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    Assessing the energy demand reduction in a surgical suite by optimizing the HVAC operation during off-use periods
    (Applied Sciences (Switzerland), 2020-03-25) Cacabelos, Antón; López-González, José Luis; González-Gil, Arturo; Febrero-Garrido, Lara; Eguía-Oller, Pablo; Granada-Álvarez, Enrique
    Hospital surgical suites are high consumers of energy due to the strict indoor air quality (IAQ) conditions. However, by varying the ventilation strategies, the potential for energy savings is great, particularly during periods without activity. In addition, there is no international consensus on the ventilation and hygrothermal requirements for surgical areas. In this work, a dynamic energy model of a surgical suite of a Spanish hospital is developed. This energy model is calibrated and validated with experimental data collected during real operation. The model is used to simulate the yearly energy performance of the surgical suite under different ventilation scenarios. The common issue in the studied ventilation strategies is that the hygrothermal conditions ranges are extended during off-use hours. The maximum savings obtained are around 70% of the energy demand without compromising the safety and health of patients and medical staff, as the study complies with current heating, ventilation and air conditioning (HVAC) regulations.
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    Development of an improved dynamic model of a Stirling engine and a performance analysis of a cogeneration plant
    (Applied Thermal Engineering, 2014-08-13) Cacabelos, Antón; Eguía, Pablo; Míguez, José Luis; Rey, Guillermo; Arce, Elena
    In this paper, the authors develop a dynamic model of a commercial micro-combined heat and power (mCHP) unit and analyse its dynamic behaviour when the engine is running at different mass flow inputs. The simulation predicts with a low root mean bias error (RMSE) the most important outputs from the cogeneration unit during the starting, steady-state and stopping periods. Furthermore, the presentedc transient model reproduces the behaviour of the cogeneration unit when the fuel and air mass flows are changing. The obtained results are discussed, and the different possibilities for the variation of the thermal to power ratio are analysed. These combinations include the variation of the flow distribution inside the machine and the position of the exhaust heat exchanger. The power to thermal ratio can be modified between 0.15 and 0.26 for these combinations. The performance of the engine and the variation of the heat source temperature are also analysed theoretically. The simulation results conclude that an important saving could be obtained when the electrical to thermal ratio (ETTR) is tracked for the power or thermal demands from a dwelling.
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    Influence of crystal structure on the thermophysical properties and figures-of-merit of propylene glycol: water-based SiC nanofluids
    (Powder Technology, 2024) Vallejo, Javier P.; Febrero-Garrido, Lara; Cacabelos, Antón; González-Gil, Arturo; Lugo, Luis
    Silicon carbide is a material with a promising thermal conductivity. However, no literature has been found on SiC nanofluids based on propylene glycol:water mixtures (widely used in renewable installations). Likewise, the contribution of α-SiC and β-SiC to the thermophysical properties of nanofluids has scarcely been explored. In this work, dispersions of α-SiC and β-SiC on propylene glycol:water 30:70 wt% at 1 and 2% wt% concentration are designed. Densities, thermal conductivities, dynamic viscosities, and isobaric heat capacities from 293.15 to 313.15 K are obtained by vibrating tube densimetry, transient-hot-wire technique, rotational rheometry and differential scanning calorimetry, respectively. Convective heat transfer performance is also assessed using figures-of-merit. Thermal conductivity and viscosity show a greater dependence on the crystal structure. The β-SiC nanofluids present the highest increases of thermal conductivity (12%) and dynamic viscosity (17%). The least complex crystal structure (β-SiC) exhibits better prospects for convection applications both for laminar and turbulent flow.