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In the present work, a methodology that allows optimizing the permanent magnet synchronous generator (PMSG) design by establishing limit values of magnet radius and length that maximize efficiency for the nominal parameters of the wind turbine is developed. The methodology consists of two fundamental models. One model calculates the generator parameters from the radius of the magnet base, and the other optimization model determines two optimum generators according to the optimization criteria of maximum efficiency and maximum efficiency with minimum weight starting from the axial length and the radius of the magnet base. For the optimization, the numerical method of the golden section was used. The model was validated from a 10 kW PMSG and the results of two optimum generators are presented according to the optimization criteria. In addition, when the obtained results are compared with the reference electric generator, an increase in efficiency of 1.15% and 0.81% and a reduction in weight of 30.79% and 39.15% of the optimized generators are obtained for maximum efficiency and minimum weight, respectively. Intermediate options between the maximum efficiency generator and the minimum weight generator allows for the selection of the optimum dimensioning for the electric generator as a function of the parameters from the wind turbine design.

Se reporta el diseño, construcción y evaluación de un secador solar para mango Ataulfo cosechado en la región del Soconusco en el estado de Chiapas. En esta región se pierde 15% del mango ya sea por súper producción y por no tener un método de conservación poscosecha. Para el diseño se utilizaron las especificaciones del producto a secar, el registro de las condiciones climáticas del lugar y los ensayos experimentales de secado realizados en la UNICACH. La metodología propuesta se basa en la sistemática combinación de la aplicación de los conceptos básicos de diseño y reglas generales de la transferencia de calor y masa, presentándose los resultados de dichos cálculos en un cuadro. Se obtuvieron de la evaluación en vacío del secador valores promedios de humedad y temperatura del aire en la cámara de secado de 5. (%) y 45 °C respectivamente. La temperatura promedio del aire ambiente fue de 25 °C y la radiación solar promedio de 500 W m-2. El tiempo de secado fue de 8 horas sol, secándose hasta 8.4% desde una humedad inicial de 80%. Se presentan las curvas la evaluación en vacío; además de la variación del peso, humedad y la humedad libre del mango respecto al tiempo. Se demostró que es posible dar tratamiento poscosecha del mango Ataulfo y aprovechar el que se pierde en los campos. Este diseño de secador solar es muy flexible en su funcionamiento.

The radial flow between two parallel circular disks is investigated with the aim to determine the optimum convective heat transfer conditions at the external disk surfaces in order to minimize the intrinsic irreversibilities. A general situation is considered where the fluid is electrically conducting and may be under the influence of a transversal magnetic field. The velocity and electric current density fields are obtained analytically and used to solve the heat transfer equation under boundary conditions of the third kind. The analysis is in the absence of fluid inertia, under creeping flow conditions (Reynolds number « 1). A perturbation approach in order to include the convective heat transfer effects in the flow is used. The Peclet number is assumed to be small. The analytic expressions for the velocity, electric current density and temperature fields are used to calculate explicitly the global entropy generation rate. When the convective heat transfer coefficients for each wall are different, this function displays a minimum for specific heat exchange conditions. The results are shown for both the hydrodynamic and the magnetohydrodynamic cases. It is also found that the mean Nusselt number at the upper wall shows a maximum value for a given value of the Hartman number, when the dimensionless heat transfer coefficients for each disk and the Peclet number are fixed. This mean Nusselt number for maximum heat transfer is near its value for minimum entropy generation conditions.