• Energy Research

Abstract This paper reports on an experimental and numerical investigation of a modifiable Tesla turbine driven by compressed air. To study the impact of geometrical parameters like the rotor’s diameter and space between the rotor and the housing, two Tesla turbine prototypes with diameters of 11.25 and 15 cm were designed and built. For both, a 3 mm space between rotor and housing is considered. In particular, for each turbine the effect of disc spacing and pressure flow in the range of real operating conditions is analyzed. Experimental characterization based on a thermodynamic analysis allows estimating optimum values of 0.9 mm and 103.89 kPa for the disc spacing and pressure flow, respectively. Additionally, values for the efficiency and the stall torque are calculated when the pressure flow is varied in the range of 50 to 327 kPa and of 59.34 to 272.46 kPa, maximum efficiencies of 33% and 50% are obtained, and stall torque measurements reach up to 0.304 N · m and 0.448 N · m, for the turbines with small and large diameters, respectively. 3D simulations performed with the open source CFD library OpenFOAM ®, well reproduced the stall torque measurements. Numerical results show that the loss of isentropic power in the space between the rotor and the housing is up to 36.17% and that the largest wall shear stress values are located on the periphery of the rotor’s disc.

ABSTRACTThis investigation aims to develop a device that meets the specific requirements of energy‐intensive household cooking tasks, such as the nixtamalization process. In particular, a pot‐type biomass stove is designed and built. A computer‐aided design (CAD) model of the stove was created, followed by a metal prototype. Thermal performance was evaluated by means of numerical simulations as well as experimental thermographic images. The numerical and experimental results were compared, and the quantitative correlation was found to be in good agreement. The results show that this stove can handle energy‐intensive cooking tasks like nixtamalization of maize. The development of this stove resulted in significant improvements in thermal efficiency and fuel consumption when compared to conventional stoves.

Abstract In this work, the fluid flow, heat transfer, and combustion processes for a plancha-type biomass cookstove are numerically studied. This approach takes into account the numerical solution of mass, momentum, thermal energy, and chemical species conservation equations by using ANSYS Fluent™. Besides the fluid domain, a solid one representing the metallic comal is also considered for the simulations. In particular, numerical results for the CO2 mass flow rate emissions, unburned volatile combustion efficiency (UVE), and thermal efficiency are compared with experimental Water Boiling Tests (WBT) data. For different firepower values, a good comparison is observed. Differences between numerical and experimental results are in the ranges of 2–9% and 1–2% for the CO2 mass flow rates and combustion efficiencies, respectively. Results indicate that the thermal efficiency is higher for the low firepower cases, which is in agreement with experiments.

AbstractThis study investigates the flow dynamics and energy losses of Tesla turbines using Computational Fluid Dynamics with OpenFOAM. Our goal is to identify the main sources of energy loss. Four main sources of energy loss were identified. The most significant loss occurred during the conversion of pressure energy to kinetic energy, estimated to range from to of the total energy. Energy losses due to leaks between the rotor and the casing were also quantified, ranging from to of the kinetic energy at peak efficiency points. Design modifications, such as incorporating a nozzle at the entrance of the turbine, can improve efficiency. These findings highlight specific areas for efficiency improvement, offering opportunities for improved turbine design and integration into energy‐generation systems.

The authors would like to make the following corrections about the published paper [...]

AbstractImproved cookstoves are used to reduce carbon emissions into the atmosphere and the impact of deforestation, thus improving the quality of life of their users. The main objective of this work is to evaluate three combustion chamber geometries for biomass plancha-type cookstoves, in the range of 9.5–12.5 kW, which corresponds to real operating conditions. The first geometry corresponds to a traditional rocket elbow section that is widely used in this kind of device. The other two geometries are new modified designs. They make use of three and four chamfers above the rocket elbow. Additionally, for all the geometries, the effect of a baffle close to the exit of the chimney is evaluated. Numerical simulations for fluid flow, heat transfer, and gas-phase chemical reactions for the three-dimensional internal volume of the geometries are conducted using ANSYS Fluent 2019 R3. Results for the average temperature on the comal and total mass flow rate at the exit of the chimney are validated with experimental measurements and a theoretical model, respectively. The main findings are that the use of a baffle in all geometries increases the flow recirculation below the comal; as a result, the average temperature of the comal and hence the thermal efficiency reach higher values. Based upon numerical predictions, the cookstove with three chamfers and a baffle provided a more temperature homogeneous distribution on the comal.

This paper introduces a new methodology for the development of appropriate technology that allows satisfying energy needs in rural communities. The methodology integrates the technological development, taking particularly into account the assessment of environmental impacts as well as evaluation of the functionality of the technology. Therefore, it is implemented as a case study in the development of a solar wood-dryer in an artisan community in Mexico. Relevant issues were identified for the success of the methodology, which includes identifying key participants in the community, as well as the use of specialized simulation- and computer-based design tools, and a prior evaluation of the potential environmental impacts through Life-Cycle Assessment (LCA) of the solar wood-dryer. Three geometries of a solar wood-dryer prototype were proposed and analyzed with computer-based simulations, which showed better interior heat transfer than the traditional wood brick-dryer. LCA revealed that the new solar wood-dryer prototype has environmental impacts in all analyzed categories that are 5% or smaller than those of the traditional dryer. Therefore, it was demonstrated that the solar wood-dryer developed with our introduced methodology leads to less environmental impacts compared to those of the traditional wood brick-dryer previously used by the rural community.