2017 2nd International Conference on Sustainable Energy and Environment Protection (ICSEEP 2017) ISBN: 978-1-60595-464-6
Design and Performance Test of Cement Grout Cooling Device Jun Xu1,a, Liangchun Wang2,b, Lunchao Zhang1,3,c, Yu Nie1, Hao Shen2 and Jikai Zhou1 1
College of Civil and Transportation Engineering, Hohai University, Nanjing 210098, China
2
State Grid Xinyuan Company LTD., Beijing 100761, China; East China Tianhuangping Pumped Storage Power Co. LTD., Anji 313302, China 3
Department of Civil Engineering, Chuzhou Vocational and Technical College, Chuzhou 239000, China a
[email protected],
[email protected],
[email protected]
Keywords: Cement Grouting; Cooling device; paste; performance testing
Abstract. The grouting effect will be affected when the cement grout temperature exceeds 40°C. In order to solve the problem, this paper designs a cement grout cooling device and carries out experimental tests of the device’s performance. The cooling experiments are conducted respectively on room-temperature static water (full-water condition and semi-full water condition), flowing hot water and flowing cement grout. The experimental results indicate that the cooling device realizes the function of cooling cement grout and provides reference for design, application and technological optimization of the equipment. Introduction Since the Frenchman Charles Bellini successfully applied the technology of clay-lime mixed paste into the strata for the reinforcement of the gate in 1802, after two hundred years of development, grouting has become an essential means in the field of hydro-power projects, tunnels and mines. Not only grouting progress and equipment but also grouting materials determine the effect of grouting [1-3]. Cement is the main grouting material [4,5]. The temperature of the cement paste increases after the hydration reaction occurs when the cement comes into contact with water. Meanwhile, mechanical friction and the friction of the paste in the grouting pipeline result in a quick rise in the temperature of the cement paste during the pressure grouting process. Studies have shown that when the temperature of the cement-based material exceeds 40°C, it will have unfavorable effect on the growth of its stone strength and irrigation [6-9]. Therefore, in the specific construction, it is necessary to take effective measures to control the temperature of the paste. This paper will design a cooling device for the cement paste and carry out a cooling performance test. Design of cement paste cooling device In order to solve the problem that the temperature of the cement grouting paste is too high during the stirring, this test decreases the temperature of the paste during agitation to control the temperature below the set value. The design of the temperature control device is shown in Figure 1.
218
10
11 5 6 7 9
1
1-thermostat, 2-compressor, 3-condenser, 4-copper tube, 5-stainless steel inner-tube, 6- stainless steel box surface, 7-evaporator, 8-frame (two layers), 9-paste outlet, 10-paste inlet, 11-top cover of inner box
8
4 3
2
Figure 1.Temperature control device.
The device uses a set of single-stage steam compression refrigeration system which consists of four components compressor, evaporator, condenser and throttle to cool the paste. The evaporator (copper tube) is wound around the lower half of the outer wall of the inner box in the inter-layer. The inter-layer is filled with refrigerating fluid, which can evenly reduce the temperature of the inner-tube. The refrigerating fluid, whose freezing point is -10°C, is composed of water mixed with 20% ethylene glycol. Ethylene glycol aqueous solution has the advantages of non-toxic, non-corrosive, good thermal conductivity, long service life and cheaper price. The copper tube is wound around the outer wall of the stainless-steel box in the inter-layer, and the tube is connected with the compressor, and the cooling system is filled with the refrigerant. Fill the refrigerant into the system. The thermostat is installed in this unit, and a specific temperature T can be set. When the temperature is higher than T, the compressor will start to work. The cement paste flowing through the stainless-steel box can be cooled by the present invention. The working principle of this single stage steam compression type refrigeration system: The liquid refrigerant absorbing heat in the evaporator will be vaporized into low temperature and low-pressure steam. The compressor draws the steam and compresses it into high temperature steam, and discharge the high temperature into the condenser to compress the steam into high-pressure liquid. The high-pressure liquid can be converted by the throttle to low pressure and low temperature refrigerant. The refrigerant will re-enter the evaporator to achieve the cycle of refrigeration. The refrigeration cycle consists of four basic processes evaporation, compression, condensation and throttling. The operation steps of the cooling device are as follows: (1) Turn on the power, set the probe of the thermostat in the refrigerating fluid and then set the designed temperature. The thermostat has a delay function that after one minute the compressor begins to work, which ensures the compressor does not switch frequently. (2) When the freezing fluid drops to the set temperature, the compressor stops working. Then, inject the cement grouting paste into the stainless-steel box through the inlet port and the paste will flow out of the paste outlet. Performance test of cooling device Performance test methods Fill the device with full water and half water at room temperature to conduct static cooling test. The Portland cement paste with 1:1 water/cement ratio is used to carry out the test for getting the cooling efficiency of the device. The temperature can be measured with electronic thermometers and the electric energy as well as the power can be tested with the electric energy meter. The cooling efficiency is calculated as follows: 1 Q = Cm ∆ T η =
Q W
219
（） （ 2）
Where, Q is the heat that the paste absorbs or emits, C is the specific heat of the paste, m is quality, ∆ T is temperature difference before and after the test, W is electric energy and η is the cooling efficiency of the device. Cooling test of static water Full-water cooling test at room temperature During the full-water cooling test at room temperature, 12 temperature test points are set in the inner box, namely: the top, middle and bottom of the long side center line; the top, middle and bottom of the short side center line; the top, middle and bottom points of the inner box corner; the top, middle, bottom of the upper and lower center axis of the inner box. In addition, three temperature test points are set in the inter-layer, namely the top, middle, bottom of the upper part of the refrigerating fluid in the irrigation mouth position of the inter-layer. The test is shown in Figure 2.
Figure 2. Full-water cooling test at room temperature.
The specific steps are as follows: (1) Seal the inlet and outlet; (2) Fill the inner tube with room temperature water, cover the lid, record the reading of the thermometer after the temperature is stable; (3) Turn on the power, place the probe of the thermostat into the refrigerating fluid and set the temperature to 0 °C; (4) When the compressor starts to work, use a stopwatch to count. Record the temperature once every 5 minutes for 1 hour; (5) Ultimately, read the electricity consumption on the meter. The test results are shown in Figures 3 to 5 and Table 1. 16
16
14
14
12
12
℃10
Temperature/
Temperature/
℃10 8
Long side Short side Corner Center axis
6 4 2
8
Long side Short side Corner Center axis
6 4 2
Refrigerating fluid
Refrigerating fluid
0
0 0
10
20
30
40
50
0
60
10
20
30
40
50
60
Time/min
Time/min
Figure 3. Temperature changes in the upper points of the full-water cooling test.
Figure 4. Temperature changes in the middle points of the full-water cooling test.
220
16 14 12
Temperature/
℃10 8 6
Long side Short side Corner Center axis
4 2
Refrigerating fluid
0 0
10
20
30
40
50
60
Time/min
Figure 5. Temperature changes in the bottom points of the full-water cooling test. Table 1. Full-water cooling test at room temperature. Station 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Specific heat C J/(k• )
℃
Quality m kg 117
℃
14.3
4185
3757
Temperature T1
50.25
Temperature T2
℃
14.4 14.0 13.9 14.5 14.1 13.9 14.6 14.1 14.2 14.2 14.1 13.8 14.2 14.5 14.3
Q kJ
Qave kJ
-50.22 13.9 9.8 14.6 14.0 9.2 14.8 14.1 10.9 14.2 13.8 10.4 10.9 11.1 1.3
652.86 50.22 2059.02 -50.22 50.22 2360.34 -100.44 0 1657.26 0 150.66 1707.48 576.88 594.36 2272.57
Electric energy W kJ
η
1584
0.41
1147.94
It can be seen from Figure 3 to Figure 5 and Table 2 that the temperature of the water in the inner box is very uneven. The temperature of the upper and middle part of the water is substantially the same at each time, and the temperature of the bottom water is low. It follows that the cooling effect of the device on the bottom of the water is obvious. The temperature of the upper and middle water basically does not change, while the bottom of the water cools down quickly. The temperature difference between the bottom points before and after cooling is respectively 4.1 , 4.7 , 3.3 and 3.4 . The cooling efficiency of the cooling device is 0.41 during the full-water cooling test at room temperature. Semi-water cooling test at room temperature During the semi-water cooling test at room temperature, 9 temperature test points are set in the inner box, namely: 2 points close to the top of the liquid surface and the bottom of the inner box in the midline of the long side; 2 points close to the top of the liquid surface and the bottom of the inner box in the midline of the short side; 2 points close to the top of the liquid surface and the bottom of the inner box in the corner of the inner box; the top, middle, bottom of the upper and lower center axis of the inner box. Just as full-water cooling test, three temperature test points are set in the inter-layer. The test results are shown in Figure 9, Figure 10 and Table 3.
℃ ℃ ℃
℃
221
12
12
10
10
8
8
℃6
4
Temperature/
Temperature/
℃6 Long side Short side Corner Centre axis Refrigerating fluid
2 0
4 2
Long side Short side Corner Center axis
0
-2
-2
Refrigerating fluid -4
-4
0
0
5
10
20
30
40
50
60
Time/min
10 15 20 25 30 35 40 45 50 55 60 65
Time/min
Figure 6. Temperature changes in the upper points Figure 7. Temperature changes in the bottom points of the semi-water cooling test. of the semi-water cooling test. Table 2. Semi-water cooling test at room temperature. Station
Specific heat C J/(k•°C)
1 2 3 4 5 6 7 8 9 10 11
Quality m kg
4185
63
3757
50.25
Temperature T1
℃
11.7 10.8 11.8 10.9 11.8 11.6 11.6 11.1 12.6 10.6 7.3
Temperature T2 °C 10.3 5.9 10.9 6.3 10.8 7.4 9.4 7.2 8.5 7.4 -2.7
Q kJ 369.12 1291.91 237.29 1212.81 263.66 1107.35 580.04 1028.25 716.73 559.40 1748.13
Qave kJ
Electric energy W kJ 1404
η 0.54
761.30
1008.09
It can be seen from Figure 9, Figure 10 and Table 3 that the temperature of the water in the inner box is very uneven. The temperature of the upper and middle part of the water is substantially the same at each time, and the temperature of the bottom water is low. It follows that the cooling effect of the device on the bottom of the water is obvious. The temperature of the upper and middle water basically does not change, while the bottom of the water cools down quickly. The temperature difference between the bottom points before and after cooling is respectively 4 .9 , 4.6 , 4.2 and 3.9 . The cooling efficiency of the cooling device is 0.54 during the full-water cooling test at room temperature. From the full-water test and semi-water test at room temperature, it can be drawn that no matter what kind of test, the cooling effect of the bottom of the cooling device is very obvious. In addition, the cooling efficiency of the semi-water test is higher than that of the full-water test. It is also found that the greater the initial temperature difference is between the refrigerating fluid and water, the faster the cooling rate is. So, in the actual application process, cool the refrigerating fluid to a certain temperature first, and then cool the cement paste. Cooling test of flowing hot water In actual engineering, the temperature of the fresh mixing paste does not exceed 50 . In the test, the hot water stored in the inner box was stored with the insulation barrel to reduce the influence of the ambient temperature on the hot water temperature. The test procedure is as follows: (1) Turn on the power, place the probe of the thermostat into the refrigerating fluid and set the temperature to 5 ; (2) When the compressor starts to work, record the boundary temperature T at once, which is the temperature of the bottom refrigerating fluid; it is necessary to record the boundary temperature before pouring hot water when continuing to test after pouring out the previous test water; (3) Pour the hot water of a certain temperature T into the inner box from the water inlet. When the liquid surface reaches a certain height, open the valve to the corresponding gear and start timing;
℃
℃
℃
℃
℃
222
℃
(4) Close the valve as soon as the thermos bottle is filled with hot water at the outlet. Record the temperature of the hot water in the thermos bottle at this time.
（ ） （ ） （ ） （ ） （ ）
Flow rate ml/s Boundary temperature °C Initial temperature °C Initial temperature °C Temperature difference °C
Table 3. The cooling test of flowing hot water. 39 11.4 61.3 48.5 12.8
34 14.6 50 42.6 7.4
33 14.6 47 41 6
38 11.2 43 39.1 3.9
36 11.3 40.2 36.1 3.9
31 13.6 35 32 3
It can be seen from Table 3 that the higher the initial temperature of hot water is under the same boundary temperature conditions or the larger the initial temperature difference is between the refrigerating fluid and hot water, the greater the temperature difference is before and after the cooling test. When the initial temperature difference between refrigerating fluid and hot water is around 40 ° C, hot water around 50 ° C can be reduced by approximately 7 °C to 8 °C. Compared to this test process taking insulation measures, the final temperature of the liquid will be lower in the practical application process. Cooling test of flowing cement paste The Portland cement paste with 1:1 water/cement ratio is used to carry out the test. The procedure for the test is as follows: (1) Mix the ordinary Portland cement paste with 1:1 water/cement ratio. Monitor the temperature of the paste during the production process. (2) Turn on the power, put the probe of the thermostat into the refrigerating fluid and set the temperature to 0 °C. Record the boundary temperature and room temperature at this time. Record the boundary temperature before pouring hot water when continuing to test after pouring out the previous test water; (3) Pour the hot water of a certain temperature T into the inner box from the water inlet after the compressor starts working. Until the liquid surface reaches a certain height, open the valve to the corresponding gear; (4) Close the valve as soon as the thermos bottle is filled with hot water at the outlet. Record the temperature of the hot water in the thermos bottle at this time.
（ ） （ ） （ ） （ ） （ ）
Flow rate ml/s Boundary temperature °C Initial temperature °C Final temperature °C Temperature difference °C
Table 4. Cooling test of flowing cement paste. 74 9.0 17.0 16.4 0.6
74 7.3 16.1 15.4 0.7
74 5.9 16.8 15.3 1.5
74 3 15.9 13.2 2.7
It can be seen from Table 4 that the initial temperature of the refrigerating fluid subject to the device has a certain effect on the cooling effect of the paste in the inner box. Especially, when the initial temperature of the refrigerating fluid is low, the cooling effect will be better. During the test, the paste warms up slowly. The temperature of the paste is related to the amount of the paste, and the greater the volume is, the faster the temperature will rise. Conclusions In order to effectively decrease the temperature of the grouting cement paste, this paper develops a cooling device. By using this device, cooling tests at room temperature are respectively conducted in the case of static water, in the case of flowing hot water and in the case of flowing cement paste. Based on the experimental results, the following conclusions can be drawn: (1) The cooling device apparently achieves the cooling function of the cement paste. (2) The cooling efficiency of the cooling device for full-water test is 0.41and for semi-water is 0.54 at room temperature. (3) Before cooling the paste, first open the cooling device to pre-cool, and then the cooling effect will be better. 223
Acknowledgements The authors are grateful to the National Electric Net Ltd Technology Project (No. 52572414005Z) and the Key Project of Natural Science Research of Anhui Provincial Department of Education (No. KJ2017A725) for the financial support. References [1]. Deng JS. In-situ chemical grouting reinforcement technology China Water & Power Press. 2011: 1-5. [2]. Kang PH, Feng ZQ. Status and Development Tendency of Roadway Grunting Reinforcement Technology in Coal Mine. Coal mining Technology. 2013, 18(3): 1-7. [3]. Sun L. Grouting material and application. China Electric Power Press. 2013:1-3. [4]. Liu HB, Kang WQ, Xiao KL, et al. Research progress of cement-based grouting materials. Concrete. 2016(3): 71-75. [5]. Chen MX, Chen YB. Development Tendency and Application of Superfine Cement Grouting Material. Journal of Yangtze River Scientific Research Institute. 1999, 16(5): 37-39. [6]. Jiang CX, Hu XD, Pan RS. The Impact of Fly Ash and Mineral Power on Heat of Hydration of Cement. Water Resources Development & Management. 2011, 31(7):76-78. [7]. Xie XM, Yu QS. Optimization of Heat Release Process of Cement Hydration and Its Role in Concrete Temperature Control. Guangdong Water Resources and Hydropower. 2012(6):32-35. [8]. Zhang BL, Wang JW, Ma BG. The Impact of Mineral Power, Silica fume, Fortifier and Temperature of the Steam Curing on Heat of Hydration and Volume Stability of Cement Mortar. Journal of Wuhan University of Technology. 2015, 37(4):17-21. [9]. Ge CC. Experimental Study of Additive Components Evolution of Cement. Hefei University of Technology. 2015.
224
