1、Shaping Tomorrows Built Environment Today 2012 ASHRAE www.ashrae.org. This material may not be copied nor distributed in either paper or digital form without ASHRAEs permission. Requests for this report should be directed to the ASHRAE Manager of Research and Technical Services.Investigation of Meth
2、ods for Determining Soil and Rock Formation Thermal Properties From Short-Term Field Tests ASHRAE1118-TRP Stephen P. Kavanaugh, Professor Lan Xie, Graduate Research Associate And Chad Martin, Graduate Research Associate The University of Alabama Department of Mechanical Engineering 290 Hardaway Tusc
3、aloosa, AL 35487-0276 Final Report for the period of September 1999 - September 2000 May 2001 American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. 1791 Tullie Circle NE Atlanta, GA 30329-2305 COPYRIGHT MFRiCAN SOCIETY QPMEATING. REFRIGERATING AND AIR-CONDITIONING ENGINEER?
4、 INC 791 TULLIE CIRCLE. ATLANTA, GA 30329 EXECUTIVE SUMMARY A critical need in the design procedure of closed-loop GSHPs, or ground-coupled heat pumps (GCHPs), is an accurate knowledge of soil/rock formation thermal properties. These properties can be estimated in the field by installing a loop of a
5、pproximately the same size and depth as the heat exchangers planned for the site. Heat is added in a water loop at a constant rate and data is collected. From this information the thermal conductivity of the soil and/or rock formation can be estimated ASHRAE has supported this project to investigate
6、 details associated with these tests by collecting and added scientific information to items currently being debated in this industry. These issues include the length of test, required heat input level and quality, analysis procedures, specifications of test methods, equipment and instrumentation, c
7、orrections for deviations from fundamental assumptions, and validation of results. Objective The objective of this project is to evaluate the validity of the models, estimate the accuracy and costs of the test methods, and propose a set of recommended practices to be used for field tests to determin
8、e soil and rock formation thermal properties at ground-coupled heat pump installation sites. Project Scope The project began with a traditional search in the technical literature followed by written and oral communication with experienced thermal conductivity testers and their clients. An abundant s
9、et of test data was provided with some information regarding costs and methods. A series of tests were also conducted at a controlled site to supplement the information. Thermal properties were computed using publicly available software and methods developed specifically for this project. This has p
10、ermitted comparative analysis, impact of uncertainty resulting from measurement error, variations from fundamental assumptions, test procedures, and unavoidable disturbances to the natural formations. Summary Conclusions and Recommendations Test durations of 36 to 48 hours are recommended. In some c
11、ases shorter periods were adequate. However, the recommendation is due to the high frequency of data sets that required longer tests for convergence. Information collected during the project indicates that longer tests do no significantly impact total cost. When test data were good there was agreeme
12、nt among several line source methods, the cylindrical heat source method, and numerical methods. The recommendation is to apply multiple analysis methods. Higher levels of confidence will result if agreement is good and further testing and analysis is warranted if agreement is poor. Acceptable power
13、 quality can be obtained when the standard deviation 34 gal. $1.45 $49.00 The following is a breakdown of the costs associated with building the experimental test apparatus. It should be noted that these costs are approximate, and that some of the supplies (heater tank, thermistors, data acquisition
14、 system) were donated or used from previous projects. Table 3.3 Summary of Costs for Construction of Experimental Test Unit Does not Include Labor and Data Acquisition System UNIT COSTS Piping and Insulation Instrumentation 5 kW Generator Miscellaneous (circulator pump and boxes) TOTAL: $450 $360 $1
15、000 $400 $2210 12 4. FIELD TEST DATA 4.1 Data of Thermal Conductivity Testers A great amount of test data and analytical results were provided by the five organizations that perform formation thermal property testing. A letter requesting information (See Appendix C) was circulated to all the known t
16、hermal conductivity testers and several of their clients. Fifty-three sets of test results were provided. Most of 53 data sets had the information of test location, except the data from OSU/Spitler-Yavuzturk. Some of the data had the bore completion information, from which the volumetric specific he
17、at of soil can be estimated by the weighted average approach. Most of the data did not include well log information but did contain information of bore depth, bore size, U-tube size, grout material and far field temperature. The data from OSU/Spitler-Yavuzturk provided the thermal conductivity of th
18、e grout material. The information of bore size, U-tube size and far field temperature for five sets data from Ewbank were unknown but assumed to be the same as the other data from the same data site. There were 26 sets of data sets from GRTI/Remund. Most of these data had test durations longer than
19、40 hours and were considered as long-term tests. The sampling rate was once every five minutes for all of these data sets. There were 16 sets of data from Ewbanks and Smith. Most of these tests were 12-hour or less and considered as short-term tests, except 5 tests performed at OSU. These five sets
20、of data were long-term tests and were conducted to show the advantage of the geo-clips, which are used to push the tubes closer to the outer bore wall. The data sampling rate for these tests was one minute. There were four sets of data from OPPD, five sets of data from OSU/Spitler-Yavuzturk, and two
21、 sets of data from ORNL/Shonder-Beck. These sets of data were long-term tests. The data sets from OPPD were recorded once every 10 minutes. The sampling rate of 30 minutes was used for data sets from OPPD, since only the printed-out data files was provided. The data sets from OSU/Spitler-Yavuzturk w
22、ere recorded once every 2.5 minutes. And the data sets from ORNL/Shonder-Beck were recorded once very 5 minutes. Values for thermal diffusivity, a secondary parameter, were not provided with the line source method results. However, a procedure for calculating this value is provided in appendix B. Th
23、e cylindrical heat source and numerical methods also provide estimated values for the density-specific heat product, which is used to compute diffusivity (a = k * pCp). 4.2 Analysis Procedure for Different Methods 4.2.1 Line-Source Method In the literature review section, the equations for the Line
24、Source Model were introduced. Because of the simplicity of this method, most firms adopted it to analyze in-situ test data. The methods differ with regard to the selection of which portions of data to analyze. 13 With the information of constant heat flux rate, thermal conductivity of the soil and g
25、eometric dimensions of the borehole, the temperature difference between the initial ground temperature (tg) and the location under consideration can be evaluated by Equation 2.1 and tabulated values of exponential functions. In order to determine the thermal conductivity of the soil, the inverse met
26、hod has been used to analyze field test data by applying Equation 2.1 or 2.2. At = Slope * ln(r) + B a 342*P Where Slope = -, thus, k = AnkL 4nL * Slope (4.1) Normally, a power transducer is used to record the heat flux (P) into the ground and the unit is watts, which must be converted to Btu/h if E
27、nglish units are used. Several time periods were analyzed with the line source method. The power used is the average power over the time period in question. For example, if the time period in question is 5-48 hours, then the power used is the average over that period. Any data before the fifth hour
28、is not used. Knowing the slope of the average loop temperature (tioop) versus time (T) curve, the thermal conductivity of the soil can be computed using Equation 4.1. The basic procedure to analyze field test data is given as the following steps (Using Test #32 as example, other details are shown in
29、 Table 4.1. Line Source Model-Slope Method 80.0 cn70.0 o = * re * E 60.0 - 500 400 0.0 -Exp. Temp. 10.0 20.0 30.0 40.0 Elapsed Time (Hour) 50.0 Figure 4.1. Linear Time Plot Temperature Line Source Model-Slope Method 80.0 ii 70.0 O) = * Tk Ainsworth NE Camp Lejeune NC, NC1 Camp Lejeune NC. NC2 Camp L
30、ejeune NC. NC3 Camp Lejeune NC. NC4 Colubus NE Ft. Necessity, PA Lexington KY clay, sand gravel.silt sandstone * * -clay, shale sandstone coal clay limestone sandstone Type of grout Bore description Dia of bore in u-tube Len. dia of SDR bore in ft Len. of test hr 111 w Jw/ft) Power Far varia. field
31、temp. % 30% Bentonite Thermal Grout 85 Thermal Grout 85 Benseal EZ-Mud Benseal EZ-Mud natural cuttings 30% Bentonite 30% Bentonite 30% Bentonite 6“ 6“ 4.75“ 5.25“ 5.75“ 5“ 4.75“ 4.75“ 4.75“ .75“m .75711 .75711 1711 1711 1711 .75711 .75711 .75711 200 2001 20ff 225 13C 245 200 160 200 50 43 48 42 47 4
32、0 43 42 36 3061 15.3 3086 15.4 3161 15.8 3071 13.6 2942 22.6 2148 8.8 2928 14.6 2903 18.1 3105 15.5 1.4% -2.3% 1.7% -1.3% 1.6% -2.2% 4.6% -29% 0.1% -0.3% 3.8% -2.7% 1.4% -1.7% 9.7% -5.3% 1.6% 2.0% Highsolid Bentonite 20% Bariods Quick Grout Bariods Quick Grout Bariods Quick Grout Bariods Quick Grout
33、 Benseal EZMud CETCOs grout, 65% solid natural cuttings 5.5“ 4.75“ 4.75“ 4.75“ 4.75“ 6“ 6“ 6.5“ .75“/11 1711 1711 1711 1711 .75711 1711 1711 200 185 203 2041 197 155 20CT 3001 42 96 44 43 45 44 49 42 2906 14.5 3163 17.1 3391 16.7 3316 16.3 3062 15.5 3033 19.6 3214 16.1 4037 13.5 3.1% -2.2% 3.1% -5.2
34、% 2.6% -2.7% 2.7% -3.9% 2.2% -2.7% 2.3% -2.7% 2.5% -2.3% 2.6% -4.0% L F 55.2 52.7 47 60.3 60.3 63.5 50.0 48 50.5 56 63 62 64 62 53 45.7 52 Report results K 0.98 0.94 0.96 1.02 0.71 0.78 6.58 1.55 1.17 0.96 1.12 1.26 1.54 1.48 1.13 2.50 1.13 A in -,r Results of analysis Line Source 1 X, X. X, X, X, c
35、y1-Results ORNL LS k Numerical k t Btu/hr*ft*F 0.80 0.85 0.96 1.08 1.20 1.35 0.90 0.99 0.73 0.72 0.66 0.61 4.94 13.9 1.46 1.48 1.05 1.21 0.82 0.88 0.98 0.90 1.20 1.18 0.95 1.05 0.74 0.77 0.69 0.74 8.52 -257 1.43 1.94 1.07 1.15 0.87 0.96 k.i 0.96 0.95 1*47.4 1.12 1.03 1*42.4 0.98 1.04 0.73 0.74 0.71
36、0.77 X, 8.43 10.5 1.38 1.57 1*36.3 1.11 1.19 0.85 .212 0.91 .178 1.18 .313 1.05 .222 0.70 .215 0.70 .289 8.4 .361 1.25 .234 1 14 .220 0.93 0.96 1.08 1.07 0.72 0.77 9.62 1.20 1.17 0.92 .317 0.98 .231 1.23 .340 1.13 .273 0.70 .363 0.86 .469 3.76 .352 1.3 .294 1.2 .292 034 .035 184 055 044 220 2.43 297
37、 102 0.77 0.93 1.10 0.94 1.26 1.08 1.60 1.29 1.43 1.76 0.83 0.84 1.25 1.73 0.74 0.83 0.82 0.87 1.08 1.04 1.23 1.00 1.56 1.46 1.49 1.57 0.88 1.00 1.50 2.23 0.82 0.99 1*41.1 0.85 0.94 1.11 1.13 l*44J 1.35 1.08 1.64 1.73 X* 1.43 1.39 X* 0.93 1.05 1.75 2.36 1*41.5 0.9 1.03 0.85 .250 1.18 .140 1.40 .150
38、1.68 .120 1.54 .170 0.96 .260 1.78 .240 0.90 .360 0.93 1.27 1.41 1.65 1.43 1.01 2.10 1.02 0.95 .401 1.29 .190 1.44 .173 1.69 .130 1.45 .177 1.16 .401 1.88 .308 1.29 .461 169 12 247 118 149 022 342 018 Results-OSUNum k 0.98 0.266 1.02 0.237 1.01 0.298 1.24 0.297 0.91 0.428 1.28 0.279 1.24 0.382 0.93
39、0.312 1.35 0.227 1.505 0.227 1.71 0.164 1.392 0.195 ki2 is the result of 12 hrs test data that is being ignored first 0.08hr test data, k(unit): Btu/hr*ft*F 2 The subscripts of k refer to the total length of test hours used in analysis, e.g. ki2 is the result of 12 hrs test data that is being ignore
40、d first 5hrtest data, k(unit): Btu/hr*ft*F 3 The result of k occurs at the minimum SSE between temperature results from Cylindrical Model and temperatures from field test data. 4 Rb-thermal resistance of borehole (unit): hr-ft-F/Btu 24 Table 4.1. Conductivity Test Sites and Comparative Analysis Resu
41、lts (Continued) Test # Location Type of soil Type of grout Bore description Dia of bore in u-tube dia SDR in Len. of bore ft Len. of test hr Avg. Power avgJL w w/ft Power varia. + % Far field temp. F Source - Skouby (contd) 18 19 20 21 22 23 24 25 26 Rochester MN Stromsber NE Mason City lA San Anton
42、io TX Ciarksville #1 Ciarksville #2 Ciarksville #3 Sylacauga AL Knoxville TN clay, sand limestone clay, sand limestone clay.shale sandstone “ “ “ Benseal EZ Mud Benseal EZMud CETCOs Volcay Granular Bariods Benseal EZMud “ “ “ “ 4.75“ 6“ 4.75“ 4.25“ 4.5“ 6.5“ 4.5“ 8“ 4.75“ .75711 .75711 .75711 1711 1
43、711 1711 1711 1711 .2571 180 1961 200 2941 346“ 300 346“ 240 300 44 45 42 48 47 47 29 42 40 3732 20.7 2971 15.2 3015 15.1 4337 14.8 4398 12.7 4358 14.5 4243 12.3 4403 18.3 4340 14.5 2.0% -2.1% 0.9% -1.4% 2.7% -3.2% 4.4% -1.2% 2.5% -1.9% 2.7% -1.8% 1.9% -2.6% 2.2% -3.0% 2.5% -1.7% 50 52 48 71.5 54.4
44、54.4 54.4 66.2 58.2 Source - Spitler - Yavuzturk 27 28 29 30 31 A B C D E -3.5“ 4.88“ 3.5“ 4.26“ 4.75“ .75711 .75711 .75711 1711 .75711 250 256“ 252 245 248 50 50 50 50 50 2526 10.1 2466 9.6 3222 12.8 2598 10.6 2551 10.3 4.4% -3.3% 7.5% -4.4% 3.6% -3.4% 3.4% -4.1% 4.4% -3.5% 63.5 63 63 54.4 63.2 Sou
45、rce - Shonder - Beck 32 33 Campbell Lincoln, NE, #2 Campbell Lincoln, NE, #1 -Fine sand Soil cuttings 4.25“ 4.25“ 1711 1711 244 245 50 50 2614 10.7 2599 10.6 4.1% -3.5% 3.4% -4.1% 55.6 54.8 Source - OPPD 34 35 Omaha, NE Bellevue, NE clay.shale sandstone sand.rock limestone clay, sand rock Thermal Gr
46、out 85 20% Bentonite EZ-Mud Benseal 15%soli. 5.5“ 6.5“ 0.757 0.75“/ 168 200 65 50 2425 14.4 4850 24.3 6.9% -7.4% 3.3% -3.8% 54 53 Report results k Results of analysis Line Source 2k c.v-Jk fX Results-ORNL LS k Numerical k Btu/hr-ffF 1.40 1.12 1.76 0.97 1.57 1.60 1.57 0.92 1.53 0.77 0.86 1.15 1.40 0.
47、70 0.93 1.21 1.18 1.40 1.37 1.33 1.70 2.19 2.77 1.48 1.88 1.07 1.49 0.82 0.92 1.25 1.50 0.76 0.95 1.26 1.38 1.44 1.49 K2.2 1.44 1.70 233 2.62 1.77 277 1.17 1.44 1*44.7 0.88 1.02 1.38 1.71 0.83 0.97 l47.1 1.34 1.49 48.8 1.49 1.56 -1*41 .t 2.42 2.62 1k 1.99 2.84 1.32 .320 0.89 .28 1.37 .20 0.90 .24 1.
48、37 .18 1.49 .21 1.64 .28 2.64 .14 2.80 .19 1.37 1.01 1.54 0.96 1.43 1.54 1.62 2.54 2.60 1.61 .429 1.26 .396 1.50 .285 0.97 .293 1.49 .229 1.61 .229 1.54 .378 2.38 .174 1.84 .243 093 .362 .069 .096 .032 .026 091 .115 250 -1.34 1.21 1.07 2.76 1.13 1.15 1.30 1.19 1.27 1.36 1.33 1.33 1.22 1.87 1.21 1.38 1.28 1.30 1.44 2.05 1.33 1.34 1.28 1.50 1.32 1.51 1.25 1.24 1.60 2.03 1.37 .16 1.22 .26 1.43 .19 1.20 .20 1.46 .16 1.30 -1.45 1.24 1.81 1.35 .214 1.35 .327 1.54 .237 1.15 .197 1.59 .197 076 045 081 030 033 1.19 .158 1.20 226 1.14 1.11 1.24 1.20 1.16 1.20 1.2
