Study On Centralized And Distributed District Cooling System Based On The Existing Heating Pipe Networ

The actual operation data from a centralized district cooling system in Yantai based on the existing heating network is analyzed as an example in this paper.Two schemes of district cooling system based on the existing heating network are compared,namely distributed district cooling system and centralized district cooling system.The cooling station energy consumption,the pipe network energy loss,the influences of the temperature rise of chilled water caused by chilled water pump,the power consumption and the cooling load density which is suitable for the latter of both are analyzed,in order to provide guidances for the expansion of this existing district cooling system and the other district cooling system based on existing heating system.The equipments of the designed distributed district cooling system are selected and the power consumption of the equipments is calculated using the measured data from Qingquan centralized district cooling system in this paper.The result is that we can find that in the present cooling scale,the distributed district cooling system consumes 35.7% more power than the the centralized district cooling system.This paper take the measured average cooling demand during the cooling season as the basis of calculation and use the heat transfer theory to establish the mathematical model of the cooling station energy consumption and the pipe network energy loss between the water supply flow and the cooling distance.Meanwhile,the accuracy of the model is verified by measured temperature rise of the supp ly water.The cooling station energy consumption and the pipe network energy loss aspect of the distributed district cooling system during the cooling season are calculated using this model,and then the influence of pipeline insulation on this project is analyzed.And the result is that we can find that in the present cooling scale,the cooling station energy consumption and the pipe network energy loss of the distributed district cooling system increase 94.6% and 236.6% in comparison with the centralized district cooling system.This paper use above mathematical model based on the Qingquan existing heating network to calculate by changing the size of the pipe diameter,the water supply flow,the cooling distance and the pipeline insulation.We can find that whether the pipe network is in the state of full load during the transportation of chilled water is the determining factor which influence the proportion of energy loss caused by chilled water pump in the total pipe network energy loss.The ratio is less affected by the cooling distance but more affected by the cooling load.This ratio is as high as 81.7% when the centralized district cooling system based on Qingquan system is in the state of full load by increasing the water supply flow,and then the income of the system will be greatly affectedThe influence of user-side comprehensive performance coefficient on energy efficiency ratio of two cooling distance systems is analyzed,the result shows that for the performance of the existing hot water lithium bromide absorption chiller,even the the pipe network energy loss of the distributed district cooling system is lower than the centralized district cooling system under certain conditions,but in any cooling load density,the cooling station energy consumption of the distributed district cooling system is higher than the centralized district cooling system.The energy efficiency ratio of the distributed district cooling system can be improved if it is combined with temperature and humidity independent control air conditioning.This combined system is better than the centralized district cooling system in the cooling station energy consumption and the pipe network energy loss.