Optimal Design Of Hot Water Supply System In Residential District

With the rapid development of urbanization,the residential model has gradually entered the community model,and its supporting facilities are more perfect and reasonable.The water supply and drainage technology must be continuously developed and improved to meet people's living needs in water supply and hot water supply.As an important symbol of the improvement of people's living standards,the status of hot water supply systems in people's lives should be continuously promoted and valued.As more and more residential communities in China have entered the full-time hot water supply system,the safety and reliability of the water supply is an important indicator to evaluate the quality of people's lives,which is worth studying.At present,there are still some controversies about the terminology of the “reversed return hot water systern”,basic design ideas,and the design ideas of the small circulation pump in the backwater system in the residential communities hot water supply system,which lead to the safety and reliability of water supply for the designers is in the execution of the standard.Therefore,it is necessary to optimize the design of the hot water supply system.This article systematically describes the classification,composition and water supply methods of hot water supply systems,the basic characteristics of residential communities,heat sources,heat medium,and circulation methods,etc,the design theory and optimization methods for hot water supply systems.For the term “reversed return hot water systern” put forward in “Code for Design of Building Water Supply and Drainage”(GB50015-2003)(2009 edition),a new viewpoint is put forward through theoretical analysis:That is,for the whole hot water supply system,the hot water pipe network can be regarded as a large parallel pipe system.According to the principle that there is only one pressure at each node,the head pressure difference between the start point and the end point is constant.Regardless of the branch path chosen,the head loss is equal for each branch,and the head loss is determined not only by the length of the segment but also by the head loss per unit length.Therefore,it is not possible to use only equal lengths as a criterion for judging whether or not the system is the reversed return,change the length of the pipeline,and adjust the head loss per unit length is also the reversed return design category.Based on this,we further complement and perfect the statement that the length of the water supply and return water pipeline is basically equal to each water distribution point defined in the specification.Based on the basic concept of ' reversed return ',a research method for optimal design of pipe network for residential hot water systems is proposed for hot water supply systems.For the whole community hot water system,the key to the whole project is that the return system can return to the heat exchange station in accordance with a certain hydraulic gradient safely and unobstructed under the premise of ensuring the most unfavorable water pressure.The pressure of the branch pipe connected to any part of the middle pipe can not disturb the basic hydraulic gradient of the backwater.When the return water pressure of the branch pipe is too high,the system return water can be ensured by reducing the pipe diameter of the water distribution pipe or setting pressure relief valve or digital pressure relief valve at the water supply branch pipe insert the main pipe to ensure the smooth return of the system,then the whole system is optimized.In order to ensure that the hot water supply system and the residential hot water circulation system can operate normally at work,the method of setting up a small circulation pump in the return water system proposed in the "GB50015-2003"(2009 Edition)is theoretically analyzed.It is pointed out that the method can only solve the return water pressure of this branch pipe,and adding the pump to increase the pressure will cause the problem of return water pressure to be high,which makes the whole system disorderly.Therefore,this method can only improve the local return water and can not improve the return water situation of the whole system.The object studied in this paper is a residential area with a certain terrain height difference.The starting point is the optimal design of the hot water pipe network.In order to ensure the normal and effective operation of the system,the water head loss of each pipe section is calculated by hydraulic calculation of hot water pipe network,and the Bernoulli equation is established to calculate the water supply pressure and backwater pressure at each node.Then choose the most unfavorable point of water supply and return water,with the principle of having only one most unfavorable point for each project,and the values of the water supply and water return pressure at the most unfavorable point are equal for the concept of unit treatment of residential building.The water pressure curve is used as the control line to install a pressure reducing valve at the water supply branch pipe insert the main pipe,so that the water return system can return water according to the return water pressure curve to ensure the reliable water supply and unobstructed water return of the entire system.The decompression value is the pressure provided by the water supply system minus the actual pressure required by the water supply branch pipe.