Thermosyphon Models for Downhole Heat Exchanger Applications in Shallow Geothermal Systems

1978 ◽  
Vol 100 (4) ◽  
pp. 713-719 ◽  
Author(s):  
D. B. Kreitlow ◽  
G. M. Reistad ◽  
C. R. Miles ◽  
G. G. Culver
Keyword(s):  
Heat Exchanger ◽  
Analytical Models ◽  
Geothermal Systems ◽  
Flow Rates ◽  
Estimated Parameters ◽  
Design Variables ◽  
Circulation Mechanism ◽  
Geothermal Wells ◽  
Experimental Values ◽  
Theoretical Results

The analysis of downhole heat exchangers used to extract energy from relatively shallow geothermal wells leads to the consideration of several interesting problems of buoyancy-driven heat transfer in enclosures. This paper considers thermosyphoning through and around the wellbore casing which is perforated at two or more depths. Analytical models are developed for thermosyphoning in the cased well both with and without a heat exchanger installed. Theoretical results are compared with experimental values. These comparisons show that the observed energy extraction rates and flow rates through the well casing are possible with thermosyphoning as the only circulation mechanism within the well bore. The model with a heat exchanger installed is parametrically evaluated to illustrate the sensitivity of the model to estimated parameters and the effect of changes in design variables or constraints.

scholarly journals Modelling an unconventional closed-loop deep borehole heat exchanger (DBHE): Sensitivity Analysis on the Newberry Volcanic Setting

2020 ◽  
Author(s):  
Hannah Rose Doran ◽  
Theo Renaud ◽  
Gioia Falcone ◽  
Lehua Pan ◽  
Patrick Verdin
Keyword(s):  
Sensitivity Analysis ◽  
Heat Exchanger ◽  
Closed Loop ◽  
Critical Conditions ◽  
Working Fluid ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Low Carbon ◽  
Deep Borehole ◽  
Geothermal Wells

Abstract Geothermal energy is a baseload resource that has the potential to contribute significantly to the transition to a low-carbon future. Alternative (unconventional) deep geothermal designs are thus needed to provide a secure and efficient energy supply. Current Enhanced Geothermal Systems (EGS) are under technical review as a result of the associated low recovery factors and risk of induced seismicity in connection with reservoir stimulation operations, and Supercritical EGS (SEGS) concepts are still under early research and development. The Newberry and Icelandic Deep Drilling Projects (NDDP and IDDP) aid these developments to drill deeper into very hot temperature zones. An in-depth sensitivity analysis was investigated considering a deep borehole closed-loop heat exchanger (DBHE) to overcome the current limitations of deep EGS. Using the DBHE, cold working fluid is pumped down in the outer annulus and rises to the surface via natural convection or is pumped up via an inner tubing. A T2Well/EOS1 model previously calibrated on an experimental DBHE in Hawaii was adapted to the current NWG 55-29 well at the Newberry volcano site in Central Oregon. A sensitivity analysis was carried out, including parameters such as: the working fluid mass flow rate, the casing and cement thermal properties and the wellbore radii dimensions. The results allow an assessment of key thermodynamics within the wellbore and provide an insight into how heat is lost/gained throughout the system. This analysis was performed under the assumption of sub-critical conditions. Requirements for further software development are briefly discussed, which would facilitate the modelling of unconventional geothermal wells in supercritical systems.

Analysis of Stress Concentrations in Thick Cylinders With Sideholes and Crossholes

1972 ◽  
Vol 94 (3) ◽  
pp. 815-824 ◽  
Author(s):  
J. C. Gerdeen
Keyword(s):  
Stress Concentration ◽  
Stress Concentrations ◽  
Concentration Factors ◽  
Stress Concentration Factors ◽  
Experimental Values ◽  
Pressure Stress ◽  
Shrink Fit ◽  
Outside Diameter ◽  
Theoretical Results

An approximate theoretical analysis is presented for the determination of stress concentration factors in thick walled cylinders with sideholes and crossholes. The cylinders are subjected to both internal pressure and external shrink-fit pressure. Stress concentration factors are plotted as functions of the geometrical ratios of outside diameter-to-bore diameter, and bore diameter-to-sidehole diameter. Theoretical results are compared to experimental values available in the literature and results of experiments described in a separate paper.

scholarly journals Theoretical and experimental comparative studies of nonlinear optical properties for selected melaminium compounds

2010 ◽  
Vol 8 (6) ◽  
pp. 1192-1202 ◽  
Author(s):  
Marek Drozd ◽  
Mariusz Marchewka
Keyword(s):  
Optical Properties ◽  
Acetic Acid ◽  
Nonlinear Optical ◽  
Time Dependent ◽  
X Ray ◽  
Hartree Fock ◽  
Optical Applications ◽  
Experimental Values ◽  
Nonlinear Optical Applications ◽  
Theoretical Results

AbstractThe bis(melaminium) sulphate dihydrate, 2,4,6-triamine-1,3,5-triazin-1,3-ium tartrate monohydrate, 2,4,6-triamine-1,3,5-triazin-1-ium hydrogenphthalate, 2,4,6-triamine-1,3,5-triazin-1-ium acetate acetic acid solvate monohydrate, 2,4,6-triamine-1,3,5-triazin-1-ium bis(selenate) trihydrate, melaminium diperchlorate hydrate, melaminium bis(trichloroacetate) monohydrate and melaminium bis(4-hydroxybenzenesulphonate) dihydrate were discovered recently as perspective materials for nonlinear optical applications. On the basis of X-ray structures for eight melaminium compounds the time dependent Hartree Fock (TDHF) method was used for calculation of the polarizability, and first and second hyperpolarizability. Detailed directional studies of calculated hyperpolarizability for all investigated melaminium compounds are shown. The theoretical results are compared with experimental values of β.

scholarly journals A Nonlinear Inverse Design Problem for a Pipe Type Heat Exchanger Equipped with Internal Z-Shape Lateral Fins and Ribs

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6424
Author(s):  
Cheng-Hung Huang ◽  
Chih-Yang Kuo
Keyword(s):  
Heat Exchanger ◽  
Thermal Performance ◽  
Design Problem ◽  
Direct Problem ◽  
Numerical Solutions ◽  
Three Dimensional ◽  
Design Variables ◽  
Non Linear ◽  
Inverse Design Problem ◽  
Η Value

A non-linear three-dimensional inverse shape design problem was investigated for a pipe type heat exchanger to estimate the design variables of continuous lateral ribs on internal Z-shape lateral fins for maximum thermal performance factor η. The design variables were considered as the positions, heights, and number of ribs while the physical properties of air were considered as a polynomial function of temperature; this makes the problem non-linear. The direct problem was solved using software package CFD-ACE+, and the Levenberg–Marquardt method (LMM) was utilized as the optimization tool because it has been proven to be a powerful algorithm for solving inverse problems. Z-shape lateral fins were found to be the best thermal performance among Z-shape, S-shape, and V-shape lateral fins. The objective of this study was to include continuous lateral ribs to Z-shape lateral fins to further improve η. Firstly, the numerical solutions of direct problem were solved using both polynomial and constant air properties and then compared with the corrected solutions to verify the necessity for using polynomial air properties. Then, four design cases, A, B, C and D, based on various design variables were conducted numerically, and the resultant η values were computed and compared. The results revealed that considering continuous lateral ribs on the surface of Z-shape lateral fins can indeed improve η value at the design working condition Re = 5000. η values of designs A, B and C were approximately 13% higher than that for Z-shape lateral fins, however, when the rib numbers were increased, i.e., design D, the value of η became only 11.5 % higher. This implies that more ribs will not guarantee higher η value.

A Numerical Study on the Sensitivity of the Discrete Element Method for Hopper Discharge

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
H. Kruggel-Emden ◽  
S. Rickelt ◽  
S. Wirtz ◽  
V. Scherer
Keyword(s):  
Discrete Element Method ◽  
Numerical Study ◽  
Discrete Element ◽  
Tangential Direction ◽  
Flow Properties ◽  
Friction Coefficients ◽  
Flow Rates ◽  
Design Variables ◽  
Side Walls ◽  
Element Method

Based on the time-driven discrete element method, granular flow within a hopper is investigated. The main focus is thereby set on hopper vessel design variables such as discharge rates and applied wall pressures. Within the used model contacts are assumed as linear viscoelastic in normal and frictional-elastic in tangential direction. The hopper geometry is chosen according to Yang and Hsiau (2001, “The Simulation and Experimental Study of Granular Materials Discharged From a Silo With the Placement of Inserts,” Powder Technol., 120(3), pp. 244–255), who performed both experimental and numerical investigations. The considered setup is attractive because it involves only a small number of particles enabling fast modeling. However, the results on the experimental flow rates reported are contradictory and are afflicted with errors. By an analysis of the hopper fill levels at different points of time, the correct average discharge times and flow rates are obtained. Own simulation results are in good agreement with the experimental flow rates and discharge times determined. Based on the thereby defined set of simulation parameters, a sensitivity analysis of parameters such as friction coefficients, stiffnesses, and time steps is performed. As flow properties, besides the overall discharge times, the discharge time averaged axial and radial velocity distributions within the hopper and the normal stresses on the side walls during the first seconds of discharge are considered. The results show a strong connection of the friction coefficients with the discharge times, the velocity distributions, and the stresses on the side walls. Other parameters only reveal a weak often indifferent influence on the studied flow properties.

scholarly journals Influence of coolant flow rates on the heat exchanger parameter at variable operation modes

Vestnik MGSU ◽  
2019 ◽  
pp. 621-633 ◽  
Author(s):  
Tatyana A. Rafalskaya ◽  
Valery Ya. Rudyak
Keyword(s):  
Heat Exchanger ◽  
Heat Exchangers ◽  
Operation Mode ◽  
Coolant Flow ◽  
Flow Rates ◽  
Variable Heat ◽  
Operation Modes ◽  
Mathcad Software ◽  
The Given ◽  
Supply Systems

Introduction. Being used in various industries, heat exchangers most often work under conditions of variable coolant flows and temperatures. At the same time, the existing theories of calculating the heat exchanger operation modes are based on the use of constant unitless parameters at any operation mode. Taking into account the effect of coolant rates on the heat transfer coefficient of the heat exchangers, the given relations are bound to specific types of heat exchangers and can only be used at constant coolant temperatures. The purpose of this study is to obtain expressions for determining the effect of coolant flow rates on the variable heat exchanger parameter. Materials and methods. The main variable operation modes for water-to-water heat exchangers used in heat supply systems are determined. Using simulation in the PTC Mathcad software, dependencies describing the change in the heat exchanger parameter for all the considered variable operation modes are defined. This made it possible to obtain a general formula for the change in the heat exchanger parameter for varying coolant flow rates. Coefficients in this formula take into consideration the effect of coolant temperatures, which cannot be known when calculating variable conditions, especially when the interconnected heat exchangers are operating. Results. To test applicability of the existing relations describing the change in the heat exchanger parameter and of obtained formula, a large number of heat exchangers is calculated at variable operation modes. Comparison with the simulation results shows that the correlations of heat exchanger theories work well at the mode with constant coolant temperatures only, while their use at other operation modes can lead to large calculation errors. Conclusions. The obtained formula allows finding the effect of coolant flow rates on the variable heat exchanger parameter. The formula can be used to predict the operation modes of large systems including a large number of various-type heat exchangers.

scholarly journals Methodology Applied for Thickness Selection and Stored Heat Evaluation in Non-producer Geothermal Wells in Order to Its Investment Rescue

2020 ◽  
pp. 91-111
Author(s):  
Alfonso Aragon- Aguilar ◽  
Georgina Izquierdo- Montalvo ◽  
Dominic A. Becerra- Serrato ◽  
Victor M. Monrroy- Mar
Keyword(s):  
Electric Energy ◽  
Geothermal Field ◽  
Geothermal Systems ◽  
Drainage Radius ◽  
Heterogeneous Behavior ◽  
Water Recharge ◽  
Geothermal Wells ◽  
Using Data ◽  
Heat Calculation ◽  
Heat Store

An assessment methodology of stored heat in rock formation surrounding to wellbore in geothermal systems is shown. Due to geothermal systems generally are nested in volcanic rock, it is characteristic its heterogeneous behavior. Proposed methodology starts since zone selection with possibilities of heat store. This methodology is focused to be applied in geothermal reservoirs with tendency to production decline, due to low permeability and unbalance between exploitation and water recharge. Because the high costs of drilling geothermal wells, methodology shown in this work is proposed to be applied in those with production decline or non-producers, in order to rescue its investment. The objective is to select the thickness with heat, evaluate its storage, design the appropriate instrumentation for its recovery, its energy conversion and rescue its investment done. The different designs for energy recovery using non-conventional methods to those, used habitually are reviewed. Each one of the variables for stored heat calculation was determined using technical tools of reservoir engineering. A parametric analysis about variables sensitivity (porosity and drainage radius) for determining thermal energy and corresponding electric energy of analyzed rock volume is done. Practical application of this methodology was carried out using data of one of wells of Los Humeros Mexican geothermal field.

Enhanced Geothermal Systems Projects and its Potential for Carbon Storage

2013 ◽  
Vol 732-733 ◽  
pp. 109-115 ◽  
Author(s):  
Chao Yin Feng
Keyword(s):  
Carbon Dioxide ◽  
Power Plants ◽  
Subsurface Water ◽  
Working Fluid ◽  
Low Permeability ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Geothermal Fields ◽  
Geological Conditions ◽  
Geothermal Wells

Enhanced Geothermal Systems represent a series of technology, which use engineering methods to improve the performance of geothermal power plant. In some geothermal fields, the rocks are in high temperature but a low permeability, or the subsurface water is scarce. In these geological conditions, cool water was injected into the geothermal wells to fracture the tight rock and create man-made reservoir for thermal exploitation. Furthermore, these engineering methods can be utilized to improve the productivity of pre-existing hydrothermal power plants. To save water and treat the global warming, using carbon dioxide instead of water as working fluid was proposed. Numerical simulation reveals that the carbon dioxide has numerous advantages over water as working fluid in the heat mining process. The precipitation caused by carbon dioxide will restore part of carbon dioxide in the rock and reduce the micro-seismicity risk.

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