In this work, a numerical model is presented that describes the transfer of heat and mass inside a cylindrical regenerator of a solar adsorption refrigerator that uses the methanol/activated-carbon refrigerant pair. This model is based on the equations of mass conservation, energy conservation, Darcy's law and the balance model between sorbate and sorbent given by the Dubinin-Astakhov's equation. On the other hand, the linear driving force (LDF) model is used to describe the rate of desorption. In the developed model, the spatial variation of methanol vapor pressure within the activated carbon bed is taken into account and, as one of the boundary conditions, the temperature is used at the external surface of the absorber measured experimentally along the day. Using the developed model, the temperature, pressure and concentration of methanol were calculated; both inside the grains of carbon and in the space between the grains, as a function of time. The algorithm was validated comparing the numerical results with the experimental data, obtaining a satisfactory concordance.

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(Measurement of the solar radiation in Santo Domingo) RESUMEN Se instaló en el edificio del INTEC de Santo Domingo un solarímetro diseñado y construido por nuestro equipo. Se muestran algunas mediciones utilizando la recta de calibración estimada en Buenos Aires, República Argentina. Por otro lado, se comprueban los parámetros que mejor ajustan para el método de Hottel de día claro en esta región geográfica. Finalmente se exponen los resultados de las mediciones luego de realizar una nueva calibración en Santo Domingo. PALABRAS CLAVESRadiación horaria, método de Hottel, Solarímetro. ABSTRACTWe installed a solar gauge, designed and built by our team, in a building of INTEC University, in Santo Domigo, Dominican Republic. Some measurements were made using the calibration curve estimated in Buenos Aires, Argentina. On the other hand, * Área de Ciencias Básicas, Instituto Tecnológico Santo Domingo. República Dominicana.

We determine the flow structure in an axisymmetric diffuser or expansion region connecting two cylindrical pipes when the inlet flow is a solid body rotation with a uniform axial flow of speeds Omega and U, respectively. A quasi-cylindrical approximation is made in order to solve the steady Euler equation, mainly the Bragg-Hawthorne equation. As in our previous work on the cylindrical region downstream [R González et al., Phys. Fluids 20, 24106 (2008); R. González et al., Phys. Fluids 22, 74102 (2010), R González et al., J. Phys.: Conf. Ser. 296, 012024 (2011)], the steady flow in the transition region shows a Beltrami flow structure. The Beltrami flow is defined as a field v_B that satisfies omega_B=nabla v_B= gamma v_B, with gamma = constant. We say that the flow has a Beltrami flow structure when it can be put in the form v = U e_z + Omega r e_theta + v_B, being U and Omega constants, i.e it is the superposition of a solid body rotation and translation with a Beltrami one. Therefore, those findings about flow stability hold. The quasi-cylindrical solutions do not branch off and the results do not depend on the chosen transition profile in view of the boundary conditions considered. By comparing this with our earliest work, we relate the critical Rossby number vartheta_cs$ (stagnation) to the corresponding one at the fold vartheta_cf [J. D. Buntine et al., Proc. R. Soc. Lond. A 449, 139 (1995)].

Received: 29 August 2011, Accepted: 29 February 2012; Edited by: J-P. Hulin; DOI: http://dx.doi.org/10.4279/PIP.040002

Cite as: R González, R Page, A S Sartarelli, Papers in Physics 4, 040002 (2012)

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