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.
COMPRESSION RESORPTION CYCLES IN DISTILLATION COLUMNS
Distillation columns are generally operated very inefficiently from an energetic point of view. At the bottom, a boiler is required to vaporize the mixture while at the top heat is rejected to the environment. Vapor recompression heat pumps have been very successful in the realization of extremely large energy savings. For larger temperature lifts between top and bottom, the temperature glide in the absorber and desorber of compression-resorption heat pumps reduce the thermodynamic temperature lift and make these heat pumps a competitive solution. In this paper the performance of a diabatic column with the resorber of an ammonia-water compression-resorption heat pump integrated in the stripping section of the column and the desorber in the rectification section will be compared with the performance of an adiabatic column. The conventional boiler / condenser option and a vapor recompression option will both be investigated. The impact of ammonia-water concentration on performance and operating conditions will also be discussed.
AN INTRACORPOREAL (ABDOMINAL) LEFT VENTRICULAR ASSIST DEVICE, XXII: Précis and State of the Art.
Under NHLI auspices, our laboratories have concentrated on the development, modification, evaluation and validation of an intracorporeal left ventricular assist device,*t which has the potential of reducing these mortalities.3' '3'18'32'4' Its use may also broaden the criteria for operability in high risk patients. This left ventricular assist device is conservatively five to six times as effective as the intra-aortic balloon (Table 1) .1,11,12,19,23,24,25,26 Unlike the intra-aortic balloon, which is a volume displacement device that augments existing circulation and is dependent upon a regular ECG signal, this intracorporeal left ventricular assist device is a definitive blood pump which can capture the entire cardiac output with the biologic heart in situ and can be actuated either synchronously or asynchronously.28'30'34'35'36'46