Linear Tube Solar Receiver as Stratified Flow Vapor Generator/separator for Absorption Machines Using NH3/LiNO3
Abstract
Straight receiver tubes of either parabolic trough or Fresnel solar collectors can substitute the vapor generator and the solution separator of an absorption machine for producing cold/heat/power, so that no intermediate thermal fluid is required for transporting heat from the collector field to the machine. This way more compact and simpler layouts are possible. Medium temperature solar collectors are attractive for activating innovative cycle absorption machines for producing cold, pumping heat or producing electricity either single or combined. Solar heat is absorbed directly by the solution that internally slides in the lower segment of an inclined tube by the effect of gravity yielding refrigerant vapor and concentrated solution in a stratified two-phase flow configuration. The paper in his first part offers an introduction to this innovative technology and I its second part presents a numerical model for the performance evaluation of the concept, highlighting heat transfer issues. Integral 1D steady-state balances are used to establish equations in a simplified form to accelerate pre-design duties and capture main influencing parameters. Results indicate that this concept is attractive and offers the potential for reducing the cost and burden of nowadays solar facilities in the small and intermediate size range.
Keywords
Solar cooling, Two-phase flow, Receiver tube, Parabolic trough, Fresnel, Medium temperature solar collector, Stratified flow, Direct vapor production.