Carbon Dioxide Refrigeration System Dynamic Simulation And Research

The subject of this thesis is a co2-based, transcritical refrigeration system. The components of this system are a cross-flow finned-tube evaporator, cross-flow finned-tube gascooler, a reciprocation compressor, a gas-liquid seperator, a double pipe internal heat exchanger and a throttling valve. Actual refrigerating process is a complex process in which the heat and mass transfer take place simultaneously and the parameters are the function of the time and the locations. With the viewpoint of dynamic and distributed parameters and parameters qualitatively coupled, computing modules of evaporator, gascooler, internal exchanger are programmed. In addition throttling valve and compressor are programmed. Following are the main points of this thesis.1. Analysis is made on structure characteristics of the finned-tube, and analysis has been made on the special heat and mass transfer principle of every micro-unit under both dry and wet conditions. Appropriate hypothesis is made and based on the energy, mass and momentum equivalent, the evaporator models of dynamic distributed parameters are set up. In addition, the gascooler and internal exchanger models of dynamic and distributed parameters, the throttling valve models and the compressor models are set up, too.2. Modules for dynamic simulation of refrigerant and air are programmed. With these modules, refrigerant and air's thermodynamic and transport property data can be computed quickly and accurately in a wide range. Based on components' model, software for simulating co2-based refrigeration system is made.3. Simulation of co2-based refrigeration system after compressor started up or is turned off, throttle opening diminished or increased, decreasing of coming airflow velocity on both gascooler and evaperator sides is made seperativly.4. Main performance parameters of co2-based refrigeration system are also simulated and studed after parameters of airflow changed.5. Joined in design and construction of test bench of co2 system previous to and during this thesis, and experimental investigation has been carried out.The comparison between experiment results and simulation has shown that a good conformity of tendency.