垂直双U型埋管换热器换热性能研究

发布时间：2018-05-07 20:01

本文选题：地源热泵系统 + 双U型埋地管换热器　；参考：《长沙理工大学》2013年硕士论文

【摘要】：随生产力水平的提高和人民生活资料的丰富，人们在享受着物质资料飞速发展带来的更为优越生活的同时，能源不足的矛盾也越来越尖锐化。地源热泵系统作为利用浅层地表储存的地热资源来对人居环境进行供热、供冷的新型绿色节能环保的空调系统，受到了国内外的政府、专家、设备制造商等广泛人群的关注及推广。对地源热泵系统关键在于其埋地管换热器，其换热性能将直接影响整个系统的运行和工作效率。目前，国内对土壤源热泵的研究主要通过对地下换热器用性能实验和数值模拟的方式来了解和模拟地下单U型埋管换热器的换热能力和换热机理并由此进行影响换热器换热的因素的分析。换热器换热性能与埋管方式、土壤温度场分布、土壤导热物性等情况有关，双U型埋地管作为传统垂直单孔单U型地源热泵系统的变型和发展尝试，理论和研究和在工程实际应用上较单U型滞后，且由于没有大量的数据和实例的支撑双U型埋地管换热器在推广应用方面并不普遍。且因换热系统的复杂性，国内各地区气候差异过大，所得的可参考经验数据的参考范围过大，设计中的上下限选取不明。综上所述，对地源热泵双U型埋管换热器的换热情况缺乏相对应的基础资料，设计、施工技术不成熟，双U型地源热泵系统的推广应用存在诸多问题亟待解决。本文主要研究垂直单孔双U型埋地管换热器的换热机理和换热能力，对位于夏热冬冷地区的一套垂直单孔双U型地源热泵系统进行了夏、冬季连续工况测试，实时采集双U型管的进、出口的水温、流量等数据。通过对所采集的实验数据进行整理，以单位井深热流q h为标准，对埋地管换热器进、出口温差及单位井深换热量进行分析，得出不同工况下双U型埋管的换热效果。再利用fluent等软件建立与实验相似的模拟模型，利用CFD计算传热效果并进行简单理论分析。本文通过实验和数值模拟的方法，研究了单孔双U型埋管换热器的周围温度场分布规律及埋管换热特性，主要研究结果如下：(1)据传热原理建立垂直单孔双U型埋管的三维非稳态传热模型，提出了相应的数值求解的方法；(2)在理论分析基础上搭建了实验台，对夏热冬冷地区原始地温的情况进行分析，并设计不同工况对双U管换热器在实际的工程运行时的地温场的温度变化进行分析研究；(3)模拟不同回填材料、循环液入口流量、温度对换热器换热特性的影响情况。经实验、模拟结果研究表明，，当单管流量不变时，对于夏热冬冷地区在夏季工况下双U型埋地管换热器的q h为单U型的1.5~1.7倍。夏热冬冷地区，据实测结果，双U管在冬、夏季的q h均大于60W/m。单管流量达1.6m~3/h时，长时运行的q h可达到100W/m，而流量为0.9m~3/h，双U型埋地管换热器在长时运行下q h达70W/m。一定流量范围，双U型埋地管换热器换热性能随管内循环液的流量增加而增加，但存在最佳流量，通过模拟分析最佳流量为1.01m3/h。地源热泵机组越接近满状态运行，机组EER和系统EER越大，分区控制埋地管的运行有益于提高其换热效果，也利于地温恢复。在夏季运行的工况下，双U型埋地管换热器的q h随进口水温的增加而提高，利于换热。每升高1℃，增加1.5~4.5%，达到近35℃时，q h的增速度变缓。
[Abstract]:With the improvement of productivity and the rich people ' s living data , the contradiction of energy shortage is becoming more and more acute while enjoying the better life brought by the rapid development of material data . The source heat pump system is a new green energy - saving and environment - friendly air - conditioning system for heating and cooling the human settlement environment by using the geothermal resources stored in the shallow surface .

The key to ground source heat pump system is that its heat transfer performance will directly influence the operation and working efficiency of the whole system .

In this paper , the heat transfer mechanism and heat transfer capacity of a vertical single - hole double U - type buried pipe heat exchanger are studied in this paper . In summer and winter continuous working conditions , a set of vertical single - hole double U - type ground source heat pump system located in the cold area of summer is analyzed . The heat transfer effect of the double U - shaped buried pipe under different working conditions is obtained . A simulation model similar to the experiment is established by using software such as the heat exchanger , and the heat transfer effect is calculated by CFD and the simple theoretical analysis is carried out .

Based on the experimental and numerical simulation methods , the distribution law of the surrounding temperature field and the heat transfer characteristics of the buried pipe are studied . The main results are as follows : ( 1 ) The three - dimensional unsteady heat transfer model of the vertical single - hole double U - type buried pipe is established according to the heat transfer principle , and the corresponding numerical solution method is proposed .
( 2 ) Based on the theoretical analysis , the experiment table was built to analyze the original geothermal temperature in the cold region of summer and winter , and the temperature change of the geothermal field of the double U - tube heat exchanger in the actual engineering operation was analyzed under different working conditions .
( 3 ) The effect of different backfill materials , inlet flow and temperature on heat transfer characteristics of heat exchanger is simulated . The results show that the q h of double U - type buried pipe heat exchanger is 1.5 - 1.7 times of the single U shape when the flow rate of single tube is constant .

【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU83

【参考文献】