| The energy issue is a common concern of the international community today.How to solve this problem has become an important problem in today's social development.At present,new energy sources with development potential include solar energy,geothermal energy,wind energy,ocean energy,nuclear energy,etc.Ground source heat pump technology has become an effective way to solve this problem due to energy conservation and environmental protection.The Dashiqiao Municipal Government of Liaoning Province proposed to adjust the local energy structure based on the concept of environmental pollution control and sustainable economic development,and strongly supported and encouraged the use of ground source heat pump technology in the local area.Therefore,the government urgently needs to understand the Dashiqiao area.Shallow ground temperature resource potential,and plan and design how to develop and apply local ground source heat pump.This research is based on the newly-built office building of the Dashiqiao Public Security Bureau.Through research on thermal response tests,heat exchangers and backfill materials,it provides a reference for the design of local buried ground source heat pump projects.The theoretical basis of the heat transfer efficiency of the ground source heat pump is provided to provide theoretical guidance for the design of ground source heat pump engineering.The specific research contents are as follows:(1)Study on the potential of shallow ground temperature resources in Dashiqiao area.In this paper,the shallow ground temperature capacity QR=591.84×1012KJ/? is calculated by measuring the local shallow ground temperature parameters,and the heat content is equivalent to the heat value of the 20.2 million tons of standard coal,which can provide energy structure adjustment for the area.The basis of material conditions.At the same time,through the evaluation of the potential of shallow geothermal energy resources,the potential zoning of the area is carried out,and the potential zoning map is drawn.The newly built office building of Dashiqiao Public Security Bureau is in the high potential area.The shallow geothermal energy capacity of the site can be heated to heat load 1278kw.And cooling requires a cold load of 1052kw.(2)Geothermal response testThis test is based on the infinite long-term heat source model combined with the least squares method to test the geothermal response of the Dashiqiao project.The soil thermal properties of the project are obtained through experiments.The original temperature of the rock is T0=12.3?,and the thermal conductivity of the rock and soil.The coefficient?=2.17 w/(m·?),the thermal diffusivity a=1.065×10-6(m2/s),and the specific heat capacity C=1.915×106J/(m3 k).(3)Indoor preparation test of backfill materialsBased on the relevant research results,this paper considers the ratio of water-cement ratio and sand-ash ratio,and uses scrap steel slag instead of some quartz sand,graphite,water reducing agent and expansion agent as additives for high-performance backfill materials.Test the thermal conductivity,fluidity,compressive strength and other related performance indicators,select a reasonable optimal additive ratio;at the same time,obtain a more economical and practical backfill material with good performance,that is,the backfill material in the scrap steel slag replacement rate of 15%The comprehensive performance of the backfill material is best when the water-cement ratio is 0.55,the sand-cement ratio is 2,the amount of the expansion agent is 6%,the amount of the water reducing agent is 1%,and the addition amount of graphite is 8%.The ratio of thermal conductivity of the backfill material to the ratio is 2.55 W/(m k),the fluidity is 264.3 mm,the expansion is 0.05%,and the pressure strength is 31.56 MPa.(4)Study on the influence of thermal properties of backfill materials on heat transfer performance of buried pipesBased on the constructed geometric model,a mathematical model was established.The heat transfer process of the buried pipe is studied by CFD numerical simulation.The heat transfer effect of the backfill material on the ground heat exchanger is theoretically studied.The temperature of the buried pipe wall,the heat transfer radius and the shaft thermal resistance are studied.To explain the effect of backfill materials with different thermal conductivity on the heat transfer performance of the buried tube heat exchanger.At the same time,the influence of the choice of backfill materials of ground source heat pump system on the heat transfer performance of buried heat exchangers in several different geology is studied.According to the thermal conductivity of the rock in the field is 2.17W/(m K),it is most economically feasible to obtain the thermal conductivity of the backfill material of 2.55W/(m·K)after comprehensively considering the relevant performance.(5)Design of underground tube heat exchangerAccording to the data of thermal response test and backfill material laboratory test,the heat exchanger of the new office building of Dashiqiao Public Security Bureau was designed to calculate the water flow of the system side,the water flow of the buried pipe and the thermal resistance of the buried pipe.The length of the buried tube heat exchanger,the number of shafts,and the heat exchange power of the buried tube heat exchanger.Using the measured data of the buried heat exchanger of the new office building of Shiqiao City Public Security Bureau,the calculation formula of the length of the buried heat exchanger given by the Code was revised,and the formula for calculating the length of the buried heat exchanger was proposed.(6)Study on soil heat balance of ground source heat pump with buried pipeThe mathematical model of the ground source heat pump system for the newly built office building of the Dashiqiao City Public Security Bureau was established.The heat transfer model of the U-type buried tube heat exchanger and the surrounding soil of the 4×4 vertical shaft group was simulated to simulate the system in winter and summer.The soil temperature change around the heat exchanger under different working conditions;the soil temperature change during a hydrological year and the temperature change trend of the soil during the 10-year period of the system were simulated respectively,and the thermal balance of the soil in the newly built office building area of the Dashiqiao City Public Security Bureau was evaluated.Under the joint action of two working conditions in one year,the soil can maintain a basic heat balance.After 10 years of operation,the soil temperature of the shaft group changed,and the system soil temperature dropped by 1.2?,which became 11.1?.At this temperature,the water temperature of 9? was still guaranteed.It shows that the design of the ground source heat pump system of the newly built office building of Dashiqiao City Public Security Bureau can ensure the reliable operation of the project. |
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