Direct steam generation for process heat applications in compound parabolic collector (CPC)

摘要

In recent years, CPC (Compound Parabolic Collector) is gaining its acceptance for temperature range higherrnthan non-concentrating stationery solar collectors like flat plate collectors but lower end of temperature rangernof concentrating solar collectors like PTC (parabolic trough concentrators). Generally, pressurized hot waterrnor thermal oil is used as a working fluid in the CPC. The elimination of solar tracking in CPC providesrnflexibility for installation and lower price point compared to other concentrating technologies with tracking.rnSteam is one of the universally accepted working fluid for process heat applications due to availability, nontoxicrnand high heat carrying capacity. Many industrial sectors such as food and beverages, textile, chemicalrnprocesses etc utilize steam as a working fluid for process heat applications. Direct steam generation as arnworking fluid through a CPC has various operational, integration and cost advantages. The use of CPC forrndirect steam generation at saturation steam temperature range 105-145 °C (equivalent saturation pressure 0.5-rn3 bar (g)) can cater for low temperature process heat demand. Solar radiation intensity changes with the timernof the day leading to change in heat flux for steam generation. There are challenges for handling two phasernflow (steam generation) in ‘U’ shaped metal tubes due to pressure drop, flow instabilities and control ofrnsteam dryness fraction under varying solar heat flux.rnThe focus of the present research work is to analyze a CPC system for direct steam generation. This paperrndiscusses an experimental setup and challenges for direct steam generation. The experimental measurementsrnwill be focused on behavior of the thermal flow pattern inside the inclined metal tube at various heat fluxrnconditions throughout the day, measurement of local heat transfer coefficients and corresponding vaporrnquality. Experimental data analysis and understanding will be useful to develop direct steam generationrnengineering schemes and its integration approach with various end-use applications.