Research On Characteristics Of Hot Water Tank Exchange In Solar Heating System

With the rapid development of my country’s economy,energy consumption is increasing.Building energy consumption accounts for a large proportion of total energy consumption.Renewable energy has the advantage of being clean,environmentally friendly and pollution-free.Instead of traditional energy sources for building energy,it is to achieve"carbon neutrality"."One of the effective ways,among them,solar energy,as a widely distributed renewable energy,is widely used in the northern regions where the solar energy resources are rich in three or more categories.On the other hand,"near-zero energy-consumption buildings" have been vigorously promoted in my country in recent years,and related technologies have become increasingly mature.This type of building adopts fresh air heat recovery technology due to its high thermal insulation performance and high air tightness It can effectively reduce the energy consumption of buildings.This paper combines solar energy utilization technology and near-zero energy building technology,and mainly explores the heat transfer characteristics and heat storage characteristics of hot water tanks in solar heating systems under low load scenarios.The main research contents and results of this article are:(1)Take a two-story ultra-low energy house in the cold area of Dalian as an example,use the multi-regional building load model TRNBuild of TRNSYS software,and set the interior design parameters and envelope structure parameters according to relevant specifications to the building’s heat load Time-by-hour simulation was performed to compare the heating energy consumption before and after the addition of the fresh air heat recovery device,and it was concluded that the addition of the heat recovery device can reduce energy consumption by about 33%.(2)Based on the building,a set of solar-electric energy(auxiliary energy)combined heating system was designed,and TRNSYS simulation software was used to establish a solar-electric composite heating system simulation model,and the first year of the heating season was studied from November 16 th to the following year 3.According to the operating characteristics of the system on the 27 th,the solar energy utilization rate was 89% after the system had been running for one year.The guarantee rate of solar heating for heating is 49%,which has good applicability.(3)Based on the heating system to optimize the heat transfer characteristics of the hot water exchange tank,the method of combining single factor sensitivity analysis and orthogonal simulation is used to obtain the significance degree of the factors affecting the heat transfer coefficient of the spiral coil heat exchanger.From the largest to the smallest,they are the area of the spiral coil heat exchanger,the mass flow rate in the coil and the volume of the hot water exchange tank;at the same time,the significance degree of the factors affecting the heat transfer of the spiral coil heat exchanger is obtained,and from the largest to the smallest,the spiral The area of the coil heat exchanger,the volume of the hot water exchange tank and the mass flow rate in the tube;the significance of the factors affecting the solar energy guarantee rate is also obtained.The area of the spiral coil heat exchanger,the area of the collector and the heat exchange rate in descending order are The volume of the hot water tank.(4)Maintaining good thermal stratification in the water tank can increase the heat storage rate of the water tank.For this reason,in the heat storage process of the hot water exchange tank,the CFD simulation software is used to calculate and simulate the temperature field in the water tank.Using ANSYS ICEM software to generate a calculation grid for the solution area,set boundary conditions for three-dimensional non-steady-state numerical simulation analysis,analyze the influence of coil bending diameter and tube mass flow on the thermal stratification of the water tank,and get the following conclusions: heat exchanger There is no obvious thermal stratification inside;the indirect hot water exchange tank presents a similar "piston flow" temperature migration compared to the direct hot storage tank,and the thermal stratification effect is better;the thickness of the thermocline layer of the water tank increases with the storage during the heat storage process.The heating time increases and gradually becomes larger;the water tank with the ratio of the coil bending radius to the water tank radius of 2/5 and 4/5 has a good thermal stratification effect.Five baffle angles are also designed,and the center opening is 15 upwards.°The design of thermal stratification has the best effect.