Analysis of Temperature Field and Stress Field around Vertical U-Tube Exchange Used in Ground Source Heat Pump

2014 ◽  
Vol 1008-1009 ◽  
pp. 1097-1100 ◽  
Author(s):  
Pei Sheng Xi ◽  
Xing Wang
Keyword(s):  
Thermal Conductivity ◽  
Thermal Expansion ◽  
Temperature Field ◽  
Stress Field ◽  
Thermal Conduction ◽  
Ground Source Heat Pump ◽  
Radius Of Influence ◽  
Ground Source ◽  
Tube Exchange ◽  
Advection Velocity

Basing on coupled thermal conduction and groundwater advection conduction, this paper analyzed the effects to the temperature field and the stress field caused by the Vertical U-tube exchange used in ground source heat pump. And then this paper analyzed the relationship between heat influence radius and thermal conductivity and groundwater advection velocity. Also, we obtained the simple formula which can estimate the heat radius of influence. Basing on coupled thermal conduction and solid mechanics analyzed the stress field caused by thermal expansion. The results show that: without groundwater advection, the heat radius of influence linear correlate to the thermal conductivity; the radius will obviously expand when the groundwater advection velocity is not too small; the stress field caused by thermal expansion near the U-tube is much larger than the farther region and it will trends to balance with the distance increasing.

The experimental study on thermal conductivity of backfill material of ground source heat pump based on iron tailings

2018 ◽  
Vol 174 ◽  
pp. 1-12 ◽  
Author(s):  
Rong Wan ◽  
Dequan Kong ◽  
Jiayuan Kang ◽  
Tianyu Yin ◽  
Jiangfeng Ning ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Experimental Study ◽  
Heat Pump ◽  
Ground Source Heat Pump ◽  
Backfill Material ◽  
Ground Source

Experimental Study on Determining Thermal Conductivity of Soil

2012 ◽  
Vol 170-173 ◽  
pp. 516-519
Author(s):  
Dai Yong Jia ◽  
Lu Yan Sui ◽  
Liang Kai Fan ◽  
Jin Sheng Wang
Keyword(s):  
Thermal Conductivity ◽  
Energy Saving ◽  
Air Conditioning ◽  
Critical Parameter ◽  
Operating Performance ◽  
Ground Source Heat Pump ◽  
Soil Thermal Conductivity ◽  
Ground Source ◽  
Energy Saving Technology ◽  
Water Contents

Ground source heat pump (GSHP) is an effective energy saving technology for heating and air conditioning. Thermal conductivity of soil is a critical parameter for designing a GSHP system, as the parameter is indispensable in analyzing and determining initial investment, energy saving effects, and operating performance of the system. In this study, the major influencing factors of soil thermal conductivity were analyzed. With different compositions and water contents of soil, the values of conductivity were determined experimentally, which can provide essential data for designing a GSHP system. This template explains and demonstrates how to prepare your camera-ready paper for Trans Tech Publications. The best is to read these instructions and follow the outline of this text

scholarly journals Ground-Source Heat Pump Systems: The Effects of Variable Trench Separations and Pipe Configurations in Horizontal Ground Heat Exchangers

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3919
Author(s):  
Yu Zhou ◽  
Asal Bidarmaghz ◽  
Nikolas Makasis ◽  
Guillermo Narsilio
Keyword(s):  
Thermal Conductivity ◽  
Effective Thermal Conductivity ◽  
Heat Pump ◽  
Heat Exchangers ◽  
Element Model ◽  
Fluid Temperature ◽  
Ground Source Heat Pump ◽  
Carrier Fluid ◽  
Ground Heat Exchangers ◽  
Ground Source

Ground-source heat pump systems are renewable and highly efficient HVAC systems that utilise the ground to exchange heat via ground heat exchangers (GHEs). This study developed a detailed 3D finite element model for horizontal GHEs by using COMSOL Multiphysics and validated it against a fully instrumented system under the loading conditions of rural industries in NSW, Australia. First, the yearly performance evaluation of the horizontal straight GHEs showed an adequate initial design under the unique loads. This study then evaluated the effects of variable trench separations, GHE configurations, and effective thermal conductivity. Different trench separations that varied between 1.2 and 3.5 m were selected and analysed while considering three different horizontal loop configurations, i.e., the horizontal straight, slinky, and dense slinky loop configurations. These configurations had the same length of pipe in one trench, and the first two had the same trench length as well. The results revealed that when the trench separation became smaller, there was a minor increasing trend (0.5 °C) in the carrier fluid temperature. As for the configuration, the dense slinky loop showed an average that was 1.5 °C lower than those of the horizontal straight and slinky loop (which were about the same). This indicates that, when land is limited, compromises on the trench separation should be made first in lieu of changes in the loop configuration. Lastly, the results showed that although the effective thermal conductivity had an impact on the carrier fluid temperature, this impact was much lower compared to that for the GHE configurations and trench separations.

Determination of Optimum Design Parameters of Horizontal Parallel Pipe and Vertical U-Tube Ground Heat Exchangers

2009 ◽  
Author(s):  
Hakan Demir ◽  
Ahmet Koyun ◽  
S¸. O¨zgu¨r Atayılmaz
Keyword(s):  
Thermal Conductivity ◽  
Energy Consumption ◽  
Heat Exchanger ◽  
Objective Function ◽  
Heat Exchangers ◽  
Ground Heat Exchanger ◽  
Ground Source Heat Pump ◽  
Soil Thermal Conductivity ◽  
Ground Heat Exchangers ◽  
Ground Source

The most important part of a ground source heat pump (GSHP) is the ground heat exchanger (GHE) that consists of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger of the ground source heat pump. Soil composition, thermal properties and water content affect the length of ground heat exchanger. Another parameter affects the size of the ground heat exchanger is the shape. There are two basic ground heat exchanger configurations: vertical U-tube and horizontal parallel pipe. There are plenty of works on ground source heat pumps and ground heat exchangers in the literature. Most of the works on ground heat exchangers are based on the heat transfer in the soil and temperature distribution around the coil. Some of the works for thermo-economic optimization of thermal systems are based on thermodynamic cycles. This study covers comparative thermo-economical analysis of horizontal parallel pipe and vertical u-tube ground heat exchangers. An objective function has been defined based on heating capacity, investment and energy consumption costs of ground heat exchanger. Investment and energy consumption costs were taken into account as total cost in the objective function. The effects of the soil thermal conductivity, number of pipes, thermal capacity of ground heat exchanger, pipe diameter and the burial depth on the objective function were examined. The main disadvantage of U-tube ground heat exchanger is higher borehole cost that makes installation cost higher than parallel pipe ground heat exchanger. To make reference functions equal for both type of ground heat exchangers, the borehole cost must be under 20 $/m (now 55 $/m) for a given heating or cooling capacity. The performance of ground heat exchangers depends on the soil characteristics especially the soil thermal conductivity.

A Study on the Calculation Model of Rock Soil Thermal Conductivity in the Design of the Ground Source Heat Pump System

2014 ◽  
Vol 889-890 ◽  
pp. 1347-1352
Author(s):  
Hong Wen Jin ◽  
Qing Shen Fang
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Pump ◽  
Soil Layer ◽  
Heat Extraction ◽  
Ground Source Heat Pump ◽  
Soil Thermal Conductivity ◽  
Pump System ◽  
Heat Pump System ◽  
Ground Source

The rock soil thermal conductivity is the most important design parameter for the ground source heat pump system. Based on the equation applied for the heat transfer between the geothermal heat exchanger and its surrounding rock soil, a quasi-three dimensional heat conduction model showing the heat transfer inside the borehole of the U-tube was established to determine the thermal conductivity of the deep-layer rock soil. The results obtained show that the average thermal conductivity got through calculation and actual determination in a tube-embedding region of the ground source heat pump engineering were 1.895 and 1.955W/(m·°C), respectively. The soil layer, which has a great thermal conductivity and a strong integrated heat transfer capability, is suitable for the use of the ground source heat pump system with the tubes embedded underground. The soil layer, with a body temperature of 19 °C and a higher initial temperature, is suitable for the heat extraction from underground in winter. The deviation between the calculation and the determination of the average thermal conductivity in the abovementioned region was 0.06, which could meet the required precision, indicating that the results from the calculation could be used for design.

The Effects of Groundwater Flow on Vertical-Borehole Ground Source Heat Pump Systems

2014 ◽  
Author(s):  
Ayako Funabiki ◽  
Masahito Oguma ◽  
Taisei Yabuki ◽  
Takao Kakizaki
Keyword(s):  
Thermal Conductivity ◽  
Heat Flux ◽  
Groundwater Flow ◽  
Flow Velocity ◽  
Heat Pump ◽  
High Thermal Conductivity ◽  
Ground Source Heat Pump ◽  
Ground Heat Exchangers ◽  
Ground Source ◽  
Gravel Size

Heat advection by groundwater flow is known to improve the performance of ground heat exchangers (GHEs), but the effect of groundwater advection on performance is not yet fully understood. This study examined how parameters related to groundwater flow, such as aquifer thickness, porosity, lithology, and groundwater flow velocity, affect the performance of a borehole GHE. Under the thin-aquifer condition (10 m, or 10% of the entire GHE length in this study), groundwater flow velocity had the greatest effect on heat flux. With a groundwater flow velocity of at least 10−4 m/s through a low-porosity aquifer filled with gravel with high thermal conductivity, the heat flux of a GHE was as much as 60% higher than that of a non-aquifer GHE. If the aquifer is as thick as 50 m (50% of the entire GHE length), the high thermal conductivity of gravel doubled the heat flux of the GHE with a groundwater flow velocity of at least 10−5 m/s. Thus, not only groundwater flow velocity, but also aquifer thickness and thermal conductivity were important factors. However, groundwater seldom flows at such high velocities, and porosity, gravel size, and aquifer thickness vary regionally. Thus, in the design of ground source heat pump systems, it is not appropriate to assume a large groundwater effect.

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