某桩基埋管式地源热泵中桩基埋管部分换热性能的数值模拟
发布时间：2018-08-04 11:03
【摘要】：地下埋管换热器的性能严重影响着地埋管地源热泵系统的初投资,所以,努力提高地下埋管换热器的换热性能是我们追求的重要目标。节能效果明显是地源热泵系统的主要优点之一。但同时也存在着一些问题如：热泵长时间运行可能导致蒸发或冷凝温度受地温影响而发生波动。因此强化地下埋管换热器的传热会受到一定的限制。地埋管分为水平管和垂直管两种形式。垂直埋管由于其占地面积小而被应用广泛。随着先进技术的不断发展，出现了桩基埋管，该埋管充分利用了桩基埋设换热管从而减少了钻孔费用而被广泛应用。 地埋管换热器有多种形式可供选择,且很多不同形式的地埋管换热器已经投入使用,目前比较常见且使用较多的有以下三种:套管式、单U型、双U型。已经有一部分研究者对这些形式的地埋管换热器换热问题进行了模拟研究,但其物理模型大部分都采用等效管法的方式,即将U型管两根支管简化为一根等效管[62]~[64]。本文主要对影响双U型换热器换热过程的因素进行分析,利用Gambit软件建立双U型管与土壤换热的几何模型,并使用Fluent来进行换热数值模拟计算。分析各种因素(如换热器进口水温及流速大小、下桩深度和管腿中心距等)对换热的影响程度，得到换热较优值，在实际工程中起到一定的指导作用。 通过模拟试验本文得出以下结论： (1)双U型埋管水流速度取0.6m/s较适宜； (2)夏季双U型埋管进水温度为36℃较适宜； (3)冬季双U型埋管进水温度为6℃较适宜； (4)当回填土的导热系数等于或大于土壤的导热系数时，增加回填土的导热系数对桩基埋管的换热量基本没有影响，所以不能盲目追求导热系数高的回填土，应根据土壤实际情况选择回填土； (5)管材的导热系数对桩基埋管的换热影响较小，所以应根据管材适用性及其价格等进行选择；增加井深对桩基埋管换热的影响不明显，所以应根据当地地质条件、地下阻挡物等选择适宜的井深； (6)增加U型管的管腿中心距会使其换热量增加，在实际选择时，，还应考虑桩基的管径等其他影响因素。
[Abstract]:The performance of underground tube heat exchanger seriously affects the initial investment of ground source heat pump system. Therefore, it is an important goal that we pursue to improve the heat transfer performance of underground buried tube heat exchanger. Energy saving effect is one of the main advantages of ground source heat pump system. But at the same time, there are some problems such as heat pump running for a long time may lead to evaporation or condensation temperature affected by the ground temperature fluctuations. Therefore, the enhancement of the heat transfer of underground tube heat exchanger will be limited to a certain extent. Buried pipe can be divided into horizontal pipe and vertical pipe. Vertical buried pipe is widely used because of its small area. With the development of advanced technology, pile-foundation buried pipes have emerged, which make full use of the heat transfer pipes embedded in pile foundations and thus reduce the drilling cost and are widely used. There are many kinds of underground tube heat exchangers available for selection, and many different types of ground heat exchangers have been put into use. At present, there are three types of underground tube heat exchangers: casing type, single U type and double U type. Some researchers have simulated the heat transfer problems of these types of buried tube heat exchangers, but most of their physical models are based on the equivalent tube method, which simplifies the U-tube two branch tubes to one equivalent tube [62] ~ [64]. In this paper, the factors affecting the heat transfer process of double U type heat exchanger are analyzed. The geometric model of heat transfer between double U tube and soil is established by using Gambit software, and the numerical simulation of heat transfer is carried out by Fluent. The influence of various factors (such as the inlet water temperature and velocity of heat exchanger, the depth of the pile under the pile and the center distance of the pipe leg etc.) on the heat transfer is analyzed, and the optimum heat transfer value is obtained, which plays a certain guiding role in the actual engineering. The conclusions are as follows: (1) 0.6m/s is suitable for the flow velocity of double U-shaped buried pipes, (2) the inlet water temperature is 36 鈩
本文编号：2163756
[Abstract]:The performance of underground tube heat exchanger seriously affects the initial investment of ground source heat pump system. Therefore, it is an important goal that we pursue to improve the heat transfer performance of underground buried tube heat exchanger. Energy saving effect is one of the main advantages of ground source heat pump system. But at the same time, there are some problems such as heat pump running for a long time may lead to evaporation or condensation temperature affected by the ground temperature fluctuations. Therefore, the enhancement of the heat transfer of underground tube heat exchanger will be limited to a certain extent. Buried pipe can be divided into horizontal pipe and vertical pipe. Vertical buried pipe is widely used because of its small area. With the development of advanced technology, pile-foundation buried pipes have emerged, which make full use of the heat transfer pipes embedded in pile foundations and thus reduce the drilling cost and are widely used. There are many kinds of underground tube heat exchangers available for selection, and many different types of ground heat exchangers have been put into use. At present, there are three types of underground tube heat exchangers: casing type, single U type and double U type. Some researchers have simulated the heat transfer problems of these types of buried tube heat exchangers, but most of their physical models are based on the equivalent tube method, which simplifies the U-tube two branch tubes to one equivalent tube [62] ~ [64]. In this paper, the factors affecting the heat transfer process of double U type heat exchanger are analyzed. The geometric model of heat transfer between double U tube and soil is established by using Gambit software, and the numerical simulation of heat transfer is carried out by Fluent. The influence of various factors (such as the inlet water temperature and velocity of heat exchanger, the depth of the pile under the pile and the center distance of the pipe leg etc.) on the heat transfer is analyzed, and the optimum heat transfer value is obtained, which plays a certain guiding role in the actual engineering. The conclusions are as follows: (1) 0.6m/s is suitable for the flow velocity of double U-shaped buried pipes, (2) the inlet water temperature is 36 鈩
本文编号：2163756
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