Characteristics Of A Novel Physical Separated Chilled Water Storage With Large Temperature Difference At Low Temperatures

The intermittent electricity consumption of air-conditioning is the main reason of the huge peak-valley difference of load in summer in China.As an effective measure to balance the power grid,cold water storage has developed rapidly in recent years with the widening gap of peak-valley electricity price.And the type of natural stratified cold water storage is a common way to cut peak and fill valley in air conditioning system as a result of its simple structure and low cost.However,the existence of inclined temperature layer has its own drawbacks in spite of its simplification.It reduces the effective utilization of cold storage tank,and the mixing of cold water and warm water reduces the efficiency of cold discharge.In addition,the restrictions on the inlet and outlet water flow,the temperature difference in cold storage and the ratio of height to diameter of the storage tank are in a higher degree.This also increases the cost of cool storage to a certain extent.In view of the problems existing in the above-mentioned natural stratified water storage,a new type of bag-shaped composite water storage tank was proposed with the support of Guangzhou Science and Technology Project.The use of physical interlayer eliminated the limitation of 4 ? density on the temperature difference of natural stratified cold storage,and made up for the defects such as low cold storage density and large space occupation,which facilitated the realization of large temperature difference in water storage.Based on this experimental device,the static storage and dynamic operation characteristics of low temperature cool storage with large temperature difference under different temperature conditions were studied.The thermal conductivity and the distribution of water temperature field of flexible interlayer under different temperature differences were tested.Compared with conventional cold storage,the ratio of effective static cooling storage increment under low temperature condition was significantly increased(> 80%).Increasing the temperature difference in cold storage was beneficial to reduce the proportion of cold loss caused by heat transfer in the tank.There were nodes in the static temperature rise rate of the water body in different height layers under low temperature condition,and the temperature rise rate before and after the node was different.The influence of diverse temperature differences during charging and discharging process on the stability of outlet temperature and cold storage performance of cold storage tank was analyzed.The results showed that under the condition of low-temperature cold storage,the temperature change of outlet in discharging was less than that in charging,while the relationship under the conventional working conditions was different.Compared with changing the load reflux,reducing the storage temperature would cause more fluctuation of outlet temperature in charging.In addition,the semi-circulation quality factor,the recovery rate of cooling capacity and the comprehensive energy efficiency ratio of large temperature difference were obviously improved compared with those of conventional temperature difference.And the feasibility of the bag-shaped interlayer cold storage for low temperature with large temperature difference cold storage was evaluated by economic calculation.Its annual cost-saving ratio was obviously increased,and the storage volume decreased greatly under the same cooling demand.