Modelling and Simulation of the Freezing Systems and Heat Pumps Using Unisim ® Design C
Abstract—The paper describes the modeling and simulation of the heat pumps domain processes. The main objective of the study is the use of the heat pump in propene–propane distillation processes. The modeling and simulation instrument is the Unisim® Design simulator. The paper is structured in three parts: An overview of the compressing gases, the modeling and simulation of the freezing systems, and the modeling and simulation of the heat pumps. For each of these systems, there are presented the Unisim® Design simulation diagrams, the input–output system structure and the numerical results. Future studies will consider modeling and simulation of the propene–propane distillation process with heat pump.
A COMPRESSOR SURGE CONTROL SYSTEM: COMBINATION ACTIVE SURGE CONTROL SYSTEM AND SURGE AVOIDANCE SYSTEM
A novel method for combining active surge control system (ASCS) and surge avoidance system (SAS) for a centrifugal compressor is presented. ASCS is a promising method to improve compressor operating area by stabilizing surge. However, this method is not applied yet in industrial compressors. Safety issue is considered in implementing the ASCS. A failure in ASCS may endanger the compressor by entering deep surge as the compressor is allowed to operate in the stabilized surge area. Combination of ASCS and SAS is proposed to improve the safety by utilizing the SAS as a back-up system. SAS is a reliable method in surge control and widely applied in industrial compressors. However, the compressor operating area is reduced by applying the SAS. An ASCS by using piston actuation is used as a case study and performance evaluations of the combined system are done by simulations.
Wiki, a New Way to Produce Accessible Documents
Adapting complex documents to make them accessible for print disabled persons is an iterative process which involves various skills and requires the intervention of several people. Collaborative approaches are well suited, especially those based on Wikis which are now widely used to edit contents on the Web. A Wiki offers useful features to overcome some of the difficulties encountered when using word-processors. MediaWiki is a popular Wiki software which can be extended to allow users to import, edit and export contents using XML DTBook, the format designed by the DAISY Consortium for structuring text in an accessible way.