Transversal Temperature Profiles of Two-Phase Stratified Flow in the Receiver Tube of a Solar Linear Concentrator. Simplified Analysis
Abstract
A steady-state analytical-numerical heat conduction model has been developed for the peripheral temperature profile in the wall of a straight receiver tube applicable to either parabolic trough or Fresnel solar collectors using innovative counterflow two-phase flow. It uses the slender 1D fin model of heat conduction along the tube wall periphery, which gives an analytical solution to be coordinated with boundary conditions. Constant heat transfer and solar incident irradiance are assumed on finite angle sectors of the tube periphery. This allows consideration for irradiance inhomogeneities and/or two-phase internal flows. The model has been applied using parameters representative of medium temperature collectors of innovative design. Inside them, a sliding liquid film is established under the effect of gravity vertically stratifying a liquid/vapor two-phase flow. This flow configuration is considered for direct vapor generators/separators for advanced solar driven absorption machines and power plants. The results show that for a circular tube with wall thicknesses large enough for withstanding typical pressures the peripheral temperature inhomogeneity is reduced. The inhomogeneity increases in the non- central hours of the day above the inhomogeneity found in the central hours of the day. This is so especially if the liquid film is shallow and for parabolic trough solar collectors.
Keywords
Solar cooling, Receiver tube wall, Parabolic trough, Fresnel, Medium temperature solar collector