scholarly journals Investigation of pipe materials and thermal conductivity of soil on the performance of ground heat exchanger operating under Malaysia climate

2021 ◽  
Vol 1078 (1) ◽  
pp. 012030
Author(s):  
A M Aizzuddin ◽  
T M Yusof ◽  
W H Azmi
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Ground Heat Exchanger ◽  
Pipe Materials

An Experimental Study on the Thermal Performance Evaluation of SCW Ground Heat Exchanger

2017 ◽  
Vol 25 (01) ◽  
pp. 1750006 ◽  
Author(s):  
Keun Sun Chang ◽  
Min Jun Kim ◽  
Young Jae Kim
Keyword(s):  
Thermal Conductivity ◽  
Performance Evaluation ◽  
Heat Exchanger ◽  
Effective Thermal Conductivity ◽  
Thermal Performance ◽  
Thermal Response ◽  
High Heat ◽  
Injection Rate ◽  
Operating Parameters ◽  
Ground Heat Exchanger

In recent years, application of the standing column well (SCW) ground heat exchanger (GHX) has been noticeably increased as a heat transfer mechanism of ground source heat pump (GSHP) systems with its high heat capacity and efficiency. Determination of the ground thermal properties is an important task for sizing and estimating cost of the GHX. In this study, an in situ thermal response test (TRT) is applied to the thermal performance evaluation of SCW. Two SCWs with different design configurations are installed in sequence to evaluate their effects on the thermal performance of SCW using a single borehole. A line source method is used to derive the effective thermal conductivity and borehole thermal resistance. Effects of operating parameters are also investigated including bleed, heat injection rate, flow rate and filler height. Results show that the effective thermal conductivity of top drawn SCW (Type A) is 11.7% higher than that of bottom drawn SCW (Type B) and of operating parameters tested bleed is the most significant one for the improvement of the thermal performance (40.4% enhanced in thermal conductivity with 10.9% bleed).

Thermal Conductivity Estimation of Soils Using Coil Shaped Ground Heat Exchanger

2012 ◽  
Vol 32 (5C) ◽  
pp. 177-183 ◽  
Author(s):  
Seok Yoon ◽  
Seung-Rae Lee ◽  
Hyunku Park ◽  
Skhan Park
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Ground Heat Exchanger

Thermal Foundation Benefits and Efficiency

2017 ◽  
Author(s):  
Youssef Aoun ◽  
Maya Kadi ◽  
Charbel Bou-Mosleh
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Residential Building ◽  
Basic Operation ◽  
Ground Heat Exchanger ◽  
Current Application ◽  
Circulating Water ◽  
Cost Efficient ◽  
The Cost

In this paper, a novel type of ground heat exchanger for geothermal applications is introduced. This heat exchanger is installed in the foundations of a commercial and residential building that has piles and diaphragm walls. This dramatically reduces the cost of the ground heat exchanger and makes the application more cost efficient with a payback period of 1–2 years compared to 10 years with the conventional vertical loops. The system will be detailed and its basic operation will be explained. In addition, test results of an in-situ thermal test response of a loop that is already installed in a foundation of a building in Beirut, Lebanon will also be presented. This test allows the approximation of the thermal conductivity of the ground and the amount of heat that is absorbed and extracted from and to the ground. The preliminary tests have given very promising results, since the ground is water dense and has a high thermal conductivity which increases the heat transfer between our heat exchanger installed in the foundation and the ground. In addition, in the current application, and around the foundation, there exists a lot of circulating water. This renders the application more and more efficient since the ground temperature will not fluctuate in the next 10 years.

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.

scholarly journals Analysis on Thermal Performance of Ground Heat Exchanger According to Design Type Based on Thermal Response Test

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 651 ◽  
Author(s):  
Sang Bae ◽  
Yujin Nam ◽  
Jong Choi ◽  
Kwang Lee ◽  
Jae Choi
Keyword(s):  
Thermal Conductivity ◽  
Heat Exchanger ◽  
Heat Exchange ◽  
Thermal Resistance ◽  
Heat Pump ◽  
Thermal Performance ◽  
Thermal Response ◽  
Ground Heat Exchanger ◽  
Thermal Response Test ◽  
Borehole Thermal Resistance

A ground source heat pump (GSHP) system has higher performance than air source heat pump system due to the use of more efficient ground heat source. However, the GSHP system performance depends on ground thermal properties and groundwater conditions. There are many studies on the improvement of GSHP system by developing ground heat exchanger (GHX) and heat exchange method. Several studies have suggested methods to improve heat exchange rate for the development of GHX. However, few real-scale experimental studies have quantitatively analyzed their performance using the same ground conditions. Therefore, the objective of this study was to evaluate the thermal performance of various pipe types of GHX by the thermal response test (TRT) under the same field and test conditions. Four kinds of GHX (HDPE type, HDPE-nano type, spiral fin type, and coaxial type) were constructed in the same site. Inlet and outlet temperatures of GHXs and effective thermal conductivity were measured through the TRT. In addition, the borehole thermal resistance was calculated to comparatively analyze the correlation of the heat exchange performance with each GHX. Result of the TRT revealed that averages effective thermal conductivities of HDPE type, HDPE-nano, spiral fin type, and coaxial type GHX were 2.25 W/m·K, 2.34 W/m·K, 2.55 W/m·K, and 2.16 W/m·K, respectively. In the result, it was found that the average borehole thermal resistance can be an important factor in TRT, but the effect of increased thermal conductivity of pipe material itself was not significant.

Development of a Tool to Calibrate Vertical Ground Heat Exchanger Model Using Optimization

2013 ◽  
Author(s):  
Junghyon Mun ◽  
Yong Tao
Keyword(s):  
Thermal Conductivity ◽  
Thermal Properties ◽  
Heat Exchanger ◽  
Field Measurement ◽  
Input Data ◽  
Measurement Data ◽  
Ground Heat Exchanger ◽  
Optimization Scheme ◽  
Vertical Ground ◽  
Ground Loop

This paper presents a calibration process and its tool of the vertical ground heat exchanger model used in a building energy simulation program, Energyplus. To adequately analyze the performance of the system, calibration of the system model is crucial. The calibration procedure is to estimate input data of the simulation that match the results of the simulation with measured data by an inverse method. The vertical ground loop heat exchanger consists of ground and borehole systems. The thermal properties of the borehole system usually can be found from manufacturer’s data. However, the thermal property of the ground is hard to evaluate. In this paper, an evaluation tool of the thermal properties of the ground around the borehole is developed using Matlab. This tool consists of three submodels. The first one is a G-function curve fit model which represents the relationship between variation of thermal conductivity and g-function values. The second model is the vertical ground loop heat exchanger model which predicts the return water temperature from a ground loop heat exchanger using the short time response factor method. The vertical ground loop heat exchanger model in Energyplus is converted to Matlab code and integrated into the calibration model for this research. The last sub-model is the optimization model that uses the Nelder and Mead simplex optimization scheme to find parameters which minimize the difference between the simulation results and the field measurement data. This tool estimates the ground thermal propertiesusing an optimization scheme based on data collected from field measurement. Far field ground temperature and the ground thermal conductivity are estimated to be used as input data of the vertical ground loop heat exchanger model in Energyplus. This program is validated using a case study which is performed for an actual building, ZOE which is located in the University of North Texas and its system. 2 weeks’ measurement data were compared with the simulation result. The average deviation between the simulation result and measurement data for 2 weeks is 0.27 °C.

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