The Mathematical Simulation And Economic Benefit Evaluation On Central And Separated Refrigeration Mode Of Refrigerated Storage

Cooling distribution mode in refrigerated storage system is a main factor impacting the cost of refrigerated storage. According to the mode of cooling distribution, refrigeration system can be divided into central refrigeration system and separated refrigeration system. So far as the quantitative comparison between both modes in system design of refrigerated storage is concerned, there are hardly reports at home and abroad. This paper researched the overall cost of central refrigeration system and separated refrigeration system in refrigerated storage and got a practical approach to choosing different cooling distribution mode in refrigeration sytem design of refrigerated storage. By means of computer simulation for the refrigeration system, the paper presented a general method to calculate overall cost of refrigerated storage with different cooling distribution modes.The main contents of the paper are as follows:1. Formulating the mathematical models of four major segments in the refrigeration system. Compressor modeling is based on a stable state model. And the distribution parameter method is applied to the refrigerant two-phase flow in the tube of evaporator and condenser. Therein the attention is focused on the system internal coupling in heat exchanger modeling, which avoids the entanglement from the configuration of heat exchanger. And the electronic expansion valve is selected as the throttle in the models.According to the known structure of the electronic expansion valve, the refrigerant flux is simulated and adjusted further to be equal with the refrigerant flux of compressor. Thus, the simulation is more close to the practice.2. Building up the simulation models of central refrigeration system and separated refrigeration system. Both central refrigeration system model and separated refrigeration system model are based on the parameter coupling connection of different segments in the refrigerated storage system. And the capacities of compressor could be selected by on-off switch along with the change of burthen of evaporator, which is a main characteristic of the central refrigeration system model. While the separated refrigeration system model responds to the multi-small independent refrigeration system.3.Conducting the simulation of refrigerated storage system and the experimental verification of the system models. On the basis of each segment simulation, the different refrigerated storage systems are simulated and the results are accordant with the experimental data.4. Analyzing the overall economical efficiency of refrigerated storage system. The overall cost per unit of refrigerating capacity during the average lifetime is used as an index for the economic analysis of the refrigerated storage system, which incarnates a comparable character among the different refrigerating systems. According to this arithmetic an analysis of different refrigerating system of refrigerated storage is carried out. Under the common conditions of refrigerated storage: evaporated temperature of -18℃, condensered temperature of 35 ℃, superheat ing temperature of 9℃ andsubcooling temperature of 10℃, and considering only the machine power cost, the results indicate that the separated refrigeration system is better than the central refrigeration system in economic benefit, and that the economic benefit is more prominent in the early years of the lifetime.5. Programming the simulation software with Visual Basic 6.0. A set of visual software of central refrigeration system and separated refrigeration system of refrigerated storage is developed with the programming language for cost analysis of different system of refrigerated storage.