重庆某土壤源热泵项目双U竖直地埋管最佳埋管深度研究

发布时间：2018-01-03 03:38

本文关键词：重庆某土壤源热泵项目双U竖直地埋管最佳埋管深度研究　出处：《重庆大学》2014年硕士论文　论文类型：学位论文

【摘要】：竖直埋管式土壤源热泵其地埋管埋设深度直接影响到地埋管换热系统的换热性能和工程造价，也对整个冷热源系统的可靠性和经济性有重要影响。本文基于某实际土壤源热泵项目，建立出可分层设置土壤初始温度及物性参数的地埋管群换热模型，并采用在双U型垂直地埋管上预埋热电偶温度传感器的方式，对该项目地下埋管换热情况进行长期监测，通过模拟及实测相结合的方式研究出该项目的最佳地下换热器埋管深度范围。本文首先分析了U型地埋管与周围土壤的换热过程，并建立出三维竖直双U型地埋管群与周围土壤的换热模型，该模型可以分层设置土壤的初始温度及物性参数，更加符合项目实际情况，并对模型求解所需参数进行了详细阐述。其次，依托该实际项目搭建实验平台，以实测的方式获取土壤初始温度分布，监测并采集系统运行时地埋管换热器进、出水温，流量及地下土壤温度逐时变化数据，为模拟提供必要参数。随后，以实测获取的地下土壤初始温度分布、地埋管进水温度和流量参数做为模拟边界和初始条件，利用fluent软件对系统在排热及取热工况下，，地埋管周围土壤温度随运行时间的变化情况进行模拟，并与实测数据进行对比，验证模型的可靠性。利用验证后的换热模型，对排热及取热工况下，地埋管内水温变化情况及不同深度管段的单位面积换热量进行分析，发现该工程地下土壤在竖直方向上物性参数的变化造成竖直地埋管换热器在供水管前70m单位面积换热量最大，70m以下管段单位面积换热量出现较大降幅。由此选取6种埋管深度方案：60m，70m，80m，90m，100m及110m，分别建立出相应的地埋管管群模型，并模拟分析不同埋深方案地埋管管内最佳流速以及不同进水温度条件下地埋管的换热效果。最后，对最佳埋管深度的确定方法进行了介绍。计算出各埋深方案所需的钻井数量及对应的地源侧水泵参数，进而计算出各自的初投资费用，对埋深方案在定流量、变温差及定温差、变流量运行方式下的年运行费用分别进行了计算，通过对比得出系统较合理的运行方式，并最终通过计算并对比各埋深方案对应的动态费用年值得出该土壤源热泵系统最佳埋管深度为80m。
[Abstract]:The depth of buried pipe directly affects the heat transfer performance and engineering cost of the buried pipe heat transfer system in vertical buried pipe type ground source heat pump (GSHP). It also has an important impact on the reliability and economy of the whole cold and heat source system. Based on a practical project of ground-source heat pump, the heat transfer model of buried pipe group can be set up in layers to set the initial soil temperature and physical property parameters. The heat transfer of underground buried pipes in this project is monitored for a long time by using the temperature sensor of embedded thermocouple on the double U vertical buried pipe. The optimum depth range of buried tube of underground heat exchanger is obtained by combining simulation and measurement. In this paper, the heat transfer process between U-type buried pipe and surrounding soil is analyzed, and a three-dimensional vertical double-U-type buried pipe group and surrounding soil heat transfer model is established. The model can set the initial temperature and physical parameters of the soil layer, which is more in line with the actual situation of the project, and the parameters needed to solve the model are described in detail. Secondly, based on the actual project to build an experimental platform to obtain the initial temperature distribution of the soil in a measured way, monitoring and collecting the temperature of the ground buried tube heat exchanger in and out of the water while the system is running. The data of flow rate and soil temperature change time by time provide necessary parameters for simulation. Then, the initial temperature distribution of underground soil, the inlet water temperature and flow parameters of underground pipe are taken as the simulation boundary and initial conditions, and the system is simulated under the condition of heat removal and heat recovery by using fluent software. The variation of soil temperature around the buried pipe with running time was simulated and compared with the measured data to verify the reliability of the model. Using the verified heat transfer model, the variation of water temperature in buried pipe and the heat transfer per unit area of different depth pipe sections are analyzed under the condition of heat discharge and heat removal. It is found that the variation of physical properties of underground soil in vertical direction results in the largest heat transfer in 70m unit area of vertical buried pipe heat exchanger. The heat exchange per unit area of the pipe section below 70 m decreased greatly. From this, six kinds of buried pipe depth schemes: 60m ~ 70m ~ 80m ~ 90m ~ 100m and 110m are selected respectively, and the corresponding models of buried pipe group are established respectively. The heat transfer efficiency of the buried pipe was simulated under the conditions of different inlet temperature and the optimum velocity of flow in the buried pipe with different buried depth. Finally, the method of determining the optimum depth of buried pipe is introduced. The drilling quantity and the corresponding parameters of the source side pump for each buried depth scheme are calculated, and the respective initial investment costs are calculated. The annual operating cost of the buried depth scheme under constant discharge, temperature difference, constant temperature difference and variable flow operation mode is calculated respectively, and the more reasonable operation mode of the system is obtained by comparison. Finally, the optimal buried depth of the GSHP system is 80 m by calculating and comparing the dynamic cost year corresponding to each buried depth scheme.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU831

【参考文献】