| | MODELING OF VERTICAL GROUND LOOP HEAT EXCHANGERS FOR |
| | 1,71 | | MB | GROUND SOURCE HEAT PUMP SYSTEMS |
| | 251 | | stron |
| | 6386 | | ID | Oklahoma State University |
| | 2000 | | rok |
| | TABLE OF CONTENTS |
| | Chapter Page |
| | 1. INTRODUCTION .1 |
| | 2. BACKGROUND AND LITERATURE REVIEW .8 |
| | 2.1 Existing Design and Simulation Tools for Ground Loop Heat Exchangers-Analytical.8 |
| | 2.1.1. Ingersoll’s Approach10 |
| | 2.1.2. Hart and Couvillion Approach.13 |
| | 2.1.3. IGSHPA Approach 17 |
| | 2.1.4. Kavanaugh’s Approach21 |
| | 2.2. Existing Design and Simulation Tools for Ground Loop Heat Exchangers-Numerical.26 |
| | 2.2.1. Eskilson’s Model .27 |
| | 2.2.2. Hellstrom’s Model .29 |
| | 2.2.3. Thornton et al. Implementation of Hellstrom’s Model31 |
| | 2.2.4. Mei and Emerson Model31 |
| | 2.2.5. Muraya’s Model.32 |
| | 2.2.6. Rottmayer, Beckman and Mitchell Model.32 |
| | 2.2.7. Shonder and Beck Model.33 |
| | 2.3. Currently Available Methods for the Determination of Thermal Conductivity of Ground |
| | Formation .34 |
| | 2.3.1. Steady State Methods.36 |
| | 2.3.2. Transient Methods .36 |
| | 3. DEFINITION OF THE PROBLEM AND OBJECTIVES 38 |
| | 4. TRANSIENT, TWO-DIMENSIONAL NUMERICAL MODEL OF THE VERTICAL GROUND HEAT |
| | EXCHANGER.42 |
| | 4.1. Finite Volume Approach.43 |
| | 4.2. Parametric Grid Generation46 |
| | 4.3. Pie-Sector Approximation 47 |
| | 4.4. Boundary Conditions 49 |
| | 4.5. Convective Resistance Adjustment .51 |
| | 4.6. Model Validation and Error Analysis .53 |
| | 4.6.1. Validation Test Cases 55 |
| | 4.6.1. Sensitivity to Grid Resolution and Time Step .57 |
| | 4.7. Discussion of the Results 63 |
| | 5. SHORT TIME-STEP RESPONSE FACTOR MODEL 66 |
| | 5.1. Eskilson’s Long Time-Step Temperature Response Factors Model.66 |
| | 5.2. Short Time-Step Temperature Response Factors .70 |
| | 5.2.1. Development of Short Time-Step g-Functions 70 |
| | 5.2.2. Aggregation of Ground Loads .74 |
| | 5.3. Component Model for TRNSYS 82 |
| | 5.4. Example Application for the Component Model85 |
| | 5.5. Discussion of the Model Results.89 |
| | 6. SHORT TIME-STEP RESPONSE FACTOR MODEL VALIDATION90 |
| | 6.1. Description of the Maxey Elementary School Ground Source Heat Pump System90 |
| | 6.2. Monitored Field Data 91 |
| | 6.3. Comparison of Model Predictions and Field Data94 |
| | 6.3.1. Adjustments to Field Data .94 |
| | 6.3.2. Adjustments to the Short Time Step Component Model.95 |
| | 6.3.3. Short Time Step Model Predictions .98 |
| | 6.4. Sensitivity Analysis 102 |
| | 6.4.1. Power Consumption Sensitivity Analysis based on Maximum Power Consumption103 |
| | 6.4.2. Power Consumption Sensitivity Analysis based on Total Error in Power Consumption for the |
| | Best and Worst Prediction Months .105 |
| | 6.5. Discussion of Model Validation .106 |
| | 7. EXAMPLE APPLICATION USING A HYBRID GROUND SOURCE SYSTEM 109 |
| | 7.1. Background on Hybrid Ground Source Heat Pump Systems .109 |
| | 7.2. Review of Literature .112 |
| | 7.3. Supplemental Heat Rejection117 |
| | 7.4. Hybrid System Operation Using the Short Time-Step Simulation Model .118 |
| | 7.4.1. Example Hybrid System Description.118 |
| | 7.4.2. Climatic Considerations-Building Loads.119 |
| | 7.4.3. Hybrid System Component Configuration 121 |
| | 7.4.4. Ground Loop Heat Exchanger and Cooling Tower Sizing 122 |
| | 7.4.5. Operating and Control Strategies .124 |
| | 7.4.5.1. Base Case-Optimum Design of the Borefield without Supplemental Heat Rejection.127 |
| | 4.1. Input Data Varied for Model Validation Test Cases 56 |
| | 4.2. Input Data common to all Validation Test Cases .56 |
| | 4.3. Relative Error (%) between the Analytical and Numerical Results for each Test Case at 1 and |
| | 192 hours Simulated Time (3- min. time steps) 58 |
| | 6.1 Comparison of Total Error on Maxey Elementary School Power Consumption for the Months |
| | August and December 1996106 |
| | 7.1. System Simulation Summary for Base Case 130 |
| | 7.2. System Simulation Summary for Case 2 133 |
| | 7.3. Hybrid System Simulation Summary for Control Strategy 3a .135 |
| | 7.4. Hybrid System Simulation Summary for Control Strategy 3b .136 |
| | 7.5. Hybrid System Simulation Summary for Control Strategy 4a .140 |
| | 7.6. Hybrid System Simulation Summary for Control Strategy 4b .141 |
| | 7.7. Hybrid System Simulation Summary for Control Strategy 4c .142 |
| | 7.8. Hybrid System Simulation Summary for Control Strategy 5a .145 |
| | 7.9. Hybrid System Simulation Summary for Control Strategy 5b .148 |
| | 7.10. Hybrid System Simulation Summary for Control Strategy 5c .149 |
| | 7.11.Cost Analysis Summary for each Control Strategy for Houston, TX153 |
| | 7.12. Cost Analysis Summary for each Control Strategy for Tulsa, OK.154 |
| | 8.1. Thermal Conductivity Estimation for the Cored Borehole and the Simulated Borehole |
| | Configuration179 |
| | 8.2. Thermal Conductivity Estimations and Associated Errors from the Converged Value for the |
| | Okla. State University Site A#1, #1 and Chickasha Test Boreholes186 |
| | 8.3. Change in Ground Thermal Conductivity BTU/hr-ft-°F (W/m-K) Estimations Based on Changes |
| | in Power Input and Temperature Measurements .196 |
| | 8.4. Summary of Primary Sources of Uncertainties in the Estimation of Thermal Conductivity of |
| | the Ground .200 |