Research On An Ice Harvester System

The ice-storage air conditioning which had been fully developed in many developed countries including USA and Japan is a practical comprehensive technology realizing the electrical network "peak-shifting". Since ice-storage air conditioning accorded with the 21^st century's basic national policy of our country and it has be encouraged by interrelated policies, this technology has a wide developing space. As a new kind of ice-storage system, the dynamic ice-storage system conquered many disadvantages of the traditional static ice-storage system, which has a wider developmental space.This thesis used the ice harvester system in Donghua University as the experimental object. The emphases of this thesis are as follows: (1) the economic analysis of the ice harvest system (2) analyzing of the running strategy of the ice harvest system (3) the relationship between ice-making period and ice capacity. At last, the thesis demonstrated that future trend of ice-storage system is to combine with cold air distribution system. It also provided many advantages of this trend. The author wishes that the thesis could make some contribution to air-conditioning industry and the ice harvester system could more and more popular in China.After a series of theoretic analysis and experimental validation, the author elicited the following conclusions:(1) The refrigerating machinery and the ice storage tank of the dynamic ice storage system are separate. When the system needs more ice capacity, we should only increase the period when the refrigerating machine makes pieces of ice and the capacity of the ice-storage tank. It doesn't necessary for us to increase the cooling capacity of refrigerating machine. Since the ice-storage tank is quite cheap, so the elemental investment of dynamic ice-storage system could be no more than theelemental investment of traditional center air-conditioning system under certain conditions. The weekly circular running strategy increase the period in which the charge of electricity is comparatively low in a week. Taking an ice harvester system as an example, although weekly circular running strategy increases the ice-making period, it should only increase the capacity of the ice-storage tank, the investment of which is quite cheap. Therefore, it is quite economic for us to combine the ice harvester system with weekly circular running strategy.(2) According to the ice harvest machine, wet bulb temperature influences the condensing temperature and the instantaneous cooling load influences the evaporating temperature in summer. After doing some detail research on these two factors, we got some running strategy of this system: if the cold accumulation in the storage-tank can not satisfy the cooling load next day and the system needs the ice harvester machine to supply cooling capacity with the storage tank together, we should consider turning on the machine between 14:00 to 17:00 first. If it still cannot satisfy the cooling load, we should avoid opening the machine in the mid-day (12:00-14:00) and evening (19:00-22:00) as possible.(3) Ice-making period and ice-desquamating period is the most significant factor for ice harvester machine to make pieces of ice. If the ice-making period is too short, it will cause too much times for ice-desquamating which may cause huge energy loss. In contrast, if the ice-making period is too long, the machine may make less and less ice in an ice-making period because resistance of heat conduction will be more and more big with the growth of thickness of ice. How to success resolving the problem is the most significant and difficult point in the thesis. After establishing a heat transfer model and using interrelated knowledge of phase-changing and heat-conducting, the author finally got a series of relationship between the temperature of chilled water and ice-making period. According to this relationship, we got an optimizing project of the ice harvester system.Finally, the author used the software of Fluent to simulate a room's flow organization that used cold air distribution system. The result of the simulating shows that cold air distribution system not only could save the elemental investment and therunning cost, but also could keep people in the room in comfortable condition. Therefore, the cold air distribution system is a good air distribution system which may be more and more popular in the future.