Comparison of Borehole Thermal Resistance Values of Ground Heat Exchanger Obtained by Several Methods

2013 ◽  
Vol 732-733 ◽  
pp. 103-108 ◽  
Author(s):  
Han Byul Kang ◽  
Seok Yoon ◽  
Gyu Hyun Go ◽  
Seung Rae Lee
Keyword(s):  
Heat Exchanger ◽  
Thermal Resistance ◽  
Heat Pump ◽  
Heating System ◽  
Geothermal System ◽  
Ground Heat Exchanger ◽  
Ubiquitous System ◽  
Borehole Thermal Resistance ◽  
Quantity Of Heat ◽  
Emission Of Greenhouse Gases

The Ground-Coupled or Source Heat Pump (GCHP/GSHP) system is increasingly being considered as an alternative to traditional cooling/heating system because it can reduce the emission of greenhouse gases. The GCHP/GSHP system uses sustainable ground temperature to emit heat during the summer and to extract heat during the winter. It is a ubiquitous system because it can be used at any time or place and semi-permanent energy. The geothermal system is composed of Ground Heat Exchanger (GHE), heat pump and load facilities. The GHE is embedded in a borehole, which is made up of GHE and grout. The borehole thermal resistance is the most important parameter in designing the geothermal system because it shows the quantity of heat transfer in the borehole. There are many methods to estimate the borehole thermal resistance. Thermal Performance Tests (TPTs) were conducted to directly measure the borehole thermal resistance of several kinds of GHEs. Then the experiment results and analytical results were compared in order to select the most accurate methods to evaluate the borehole thermal resistance.

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.

scholarly journals Borehole Thermal Analysis for a Closed Loop Vertical U-Tube DX Ground Heat Exchanger

2021 ◽  
Vol 8 (4) ◽  
pp. 501-509
Author(s):  
Ali H. Tarrad
Keyword(s):  
Heat Exchanger ◽  
Thermal Resistance ◽  
Thermal Design ◽  
Ground Heat Exchanger ◽  
Total Thermal Resistance ◽  
Steady State Condition ◽  
Tube Heat Exchanger ◽  
Cooling Unit ◽  
Geometry Configuration ◽  
Borehole Thermal Resistance

The borehole geometry configuration and its sizing represent great challenges to the thermal equipment designer in the field of geothermal energy source. The present work represents a piece in that direction to avoid elaborate mathematical and computation schemes constraints for the preliminary design of the U-tube ground heat exchanger operates under a steady-state condition. A correlation was built for the prediction of the borehole thermal resistance. The U-tube diameter, leg spacing, borehole diameter, and the offset configuration with respect to the center of the borehole were introduced in the present correlation. An equivalent tube formula and borehole configuration were postulated to possess the same grout volume as the original loop. A variety of geometrical configurations were tested at different U-tube and borehole sizes. The predicted total thermal resistance of the borehole was implemented into the thermal design of the (DX) ground condenser to sizing the borehole U-tube heat exchanger. A hypothetical cooling unit of (1) ton of refrigeration that circulates R410A refrigerant was chosen for the verification of the present model outcomes. The predicted thermal resistance revealed an excellent agreement with other previously published work in this category.

scholarly journals Evaluation of Borehole Thermal Resistance in Ground Heat Exchanger

2013 ◽  
Vol 29 (10) ◽  
pp. 49-56 ◽  
Author(s):  
Seok Yoon ◽  
Seung-Rae Lee ◽  
Han-Byul Kang ◽  
Gyu-Hyun Go ◽  
Min-Jun Kim ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Thermal Resistance ◽  
Ground Heat Exchanger ◽  
Borehole Thermal Resistance

scholarly journals Heating system with vapour compressor heat pump and vertical U-tube ground heat exchanger

2010 ◽  
Vol 31 (4) ◽  
pp. 93-110 ◽  
Author(s):  
Małgorzata Hanuszkiewicz-Drapała ◽  
Jan Składzień
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Mutual Influence ◽  
Heating System ◽  
Calculation Model ◽  
Ground Heat Exchanger ◽  
Heating Season ◽  
Residential House ◽  
Time Parameters ◽  
Heated Object

Heating system with vapour compressor heat pump and vertical U-tube ground heat exchangerIn the paper a heating system with a vapour compressor heat pump and vertical U-tube ground heat exchanger for small residential house is considered. A mathematical model of the system: heated object - vapour compressor heat pump - ground heat exchanger is presented shortly. The system investigated is equipped, apart from the heat pump, with the additional conventional source of heat. The processes taking place in the analyzed system are of unsteady character. The model consists of three elements; the first containing the calculation model of the space to be heated, the second - the vertical U-tube ground heat exchanger with the adjoining area of the ground. The equations for the elements of vapour compressor heat pump form the third element of the general model. The period of one heating season is taken into consideration. The results of calculations for two variants of the ground heat exchanger are presented and compared. These results concern variable in time parameters at particular points of the system and energy consumption during the heating season. This paper presents the mutual influence of the ground heat exchanger subsystem, elements of vapour compressor heat pump and heated space.

scholarly journals Heating of external surfaces by means of heat pumps

2018 ◽  
Vol 44 ◽  
pp. 00128
Author(s):  
Krzysztof Nowak
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Financial Analysis ◽  
Negative Impact ◽  
Heating System ◽  
Heat Pumps ◽  
Ground Heat Exchanger ◽  
Heating Installation ◽  
Manual Methods ◽  
Snow And Ice

In winter we are forced to eliminate or mitigate the disadvantages associated with the accumulation of snow and ice on sidewalks, steps, driveways, roofs, squares, sports fields. There are many ways to remove snow and ice from the considered surfaces, including chemical, mechanical or use of a heating installation. Mechanical or manual methods do not always allow to completely remove snow and ice, while chemicals often have a negative impact on the environment. The most effective is the use of an electric or liquid heating installation. The article presents the results of technical analysis for a maneuver area heating system for driving training lesson using a heat pump with a ground heat exchanger, as well as financial analysis of its application in the established conditions. The literature lacks information on this subject, so it was interesting to investigate whether the proposed installation is technically and economically feasible.

scholarly journals Borehole Resistance and Heat Conduction Around Vertical Ground Heat Exchangers

2012 ◽  
Vol 6 (1) ◽  
pp. 32-40 ◽  
Author(s):  
Zoi Sagia ◽  
Athina Stegou ◽  
Constantinos Rakopoulos
Keyword(s):  
Heat Conduction ◽  
Heat Exchanger ◽  
Thermal Resistance ◽  
Heat Exchangers ◽  
Borehole Diameter ◽  
Working Fluid ◽  
Geometrical Parameters ◽  
Conductive Heat ◽  
Ground Heat Exchanger ◽  
Borehole Thermal Resistance

Borehole thermal resistance in Ground Heat Exchanger (GHE) installations is affected by several parameters such as geometrical attributes of heat exchanger in the borehole, pipes' characteristics and grout’s thermal conductivity. A study is carried out to compare the values computed by Ground Loop Design (GLD) Software, GLD 2009, with three ana-lytical solutions for U-shaped tubes. The analysis is focused on dimensionless ratios of borehole geometrical parameters (borehole diameter to outside pipe diameter and shank spacing to borehole diameter) and pipes according to Standard Di-mension Ratio (SDR) and on eight common grouts. Finally, the effect of heat conduction in the borehole is examined by means of finite element analysis by Heat Transfer Module of COMSOL Multiphysics. A two-dimensional (2-D) steady-state simulation is done assuming working fluid temperatures for winter and summer conditions and typical Greek undis-turbed ground temperature in a field of four ground vertical U-tube heat exchangers surrounded by infinite ground. The temperature profile is presented and the total conductive heat flux from the pipe to the borehole wall per meter of length of ground heat exchanger is computed for pipes SDR11 (the outside diameter of the pipe is 11 times the thickness of its wall), SDR9 and SDR17 for summer working conditions and three different configurations. It is attempted to reach to comparative results for borehole thermal resistance value through different types of analysis, having considered the major factors that affect it and giving trends for the influence of each factor to the magnitude of its value.

scholarly journals OPTIMAL WORKING CONDITIONS OF THE GROUND SOURCE HEAT PUMP FOR HEAT SUPPLY

2017 ◽  
pp. 19-26
Author(s):  
M.K. Bezrodnyi ◽  
N.A. Prytula ◽  
M.A. Gobova
Keyword(s):  
Heat Exchanger ◽  
Heat Pump ◽  
Working Conditions ◽  
Heat Carrier ◽  
Heating System ◽  
Ground Heat Exchanger ◽  
Heat Exchanger Tube ◽  
Vertical Ground ◽  
Optimum Velocity ◽  
Exchanger Tube

The method of determination of optimal working conditions of vertical ground heat exchanger for heat pump low temperature water heating system, providing minimum energy cost for heat production is presented in this article. It was determined that there is an optimum speed of a heat carrier to which minimum total cost of electricity for heating system in a whole corresponds when using vertical probes for heat pump heating system. The correlation between the characteristics of vertical ground heat exchanger (depth of the well, the intensity of selection of heat from the soil pipe diameter, the velocity of a heat carrier) in its optimal working conditions was found. It is shown that the optimum velocity of a heat carrier in the lower circuit depends on the depth of the well, the heat exchanger tube diameter, and is almost independent of temperature conditions works of heat pump systems. It is found that the higher velocity observed at the beginning of the heating period in view of energy storage in the ground. Optimum coolant velocity should decrease until the end of the heating season to ensure minimum specific energy expenditure at HPS. Also noted that an optimum velocity increases with increasing depth of the well and with decreasing diameter of the heat exchanger tube. The established correlation may be used when determining the optimum operating conditions of the vertical ground heat pump heat exchanger low-temperature heating systems with a plan to maximize their energy efficiency. Bibl. 8, Fig. 7.

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