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120kw冷水机组设计（蒸发器和冷凝器设计）,120,kw,冷水机组,设计,蒸发器,冷凝器

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Field experimental study on the cooling effect of mine cooling system acquiring coldsource from return airGuo Pingye, Chen ChenState Key Laboratory of Geomechanic and Deep Underground Engineering, Beijing 100083, ChinaSchool of Mechanics & Civil Engineering, China University of Mining & Technology, Beijing 100083, Chinaa r t i c l ei n f oArticle history:Received 5 September 2012Received in revised form 5 October 2012Accepted 12 November 2012Available online 12 June 2013Keywords:Heat disasterCold sourceReturn airCooling systema b s t r a c tWith the increase of mining depth, more and deeper coal mines are limited by heat disaster. The coolingenergy in deep mine cooling system comes from mine water inrush or ground cooling tower, but we can-not adopt the two methods because mine water inrush in many old coal mines in China is limited. Whatis more, the cooling pipelines cannot be put in narrow pit-shaft. To settle the problem above, according tothe characteristics of Zhangxiaolou Coal Mine, this paper adopts the deep mine return air as the coolingenergy for deep mine cooling system. In addition, we carried out cite test to extract cold energy fromreturn air. Through monitoring the water quantity, water temperature of cooling system and air temper-ature, we got the thermodynamic equilibrium parameters during the cooling energy acquisition analysisand the effect of cooling system that the temperature and humidity on working face are respectivelyreduced to 812 ?C and 815% through cooling. This research offers experimental reference for deep minecooling which lacks cooling energy.? 2013 Published by Elsevier B.V. on behalf of China University of Mining & Technology.1. IntroductionWith the exhaustion of shallow coal resources, more andmore coal mines are changing into deep mining, and the rocktemperature is becoming hotter and hotter 1,2. And the envi-ronment on working face is daily deteriorating, so we shouldtake measures for deep mine cooling 3. At present, ice-cooled,water-cooled and air-cooled cooling systems are the main deepmine cooling methods 4,5. There are two cold energy acquisi-tion methods including water mine inrush in deep mine andground cooling tower 69. As for cooling system using minewater inrush as the source of cooling energy, there must beenough mine water inrush; while for ground cooling tower weshould lay pipelines from ground to underground. But in manyold coal mines, the shafts are so narrow that there is no enoughspace to put the cooling water pipe 1014. For many old coalmines in the east of China, the two cooling energy sources arelimited, so we have to adopt other sources 1518. In thispaper, I chose the typical heat hazard coal mine in the eastChina to carry out site test to analyze the feasibility of takingdeep mine return air as cooling energy source.2. Introduction of site test2.1. Introduction of Zhangxiaolou Coal MineZhangxiaolou Coal Mine is located in Liuxin and Liuji town inTongshan county in the northwest of Xuzhou city, and its min-ing depth is about 1200 m. Zhangxiaolou Coal Mine is one ofthe high temperature mines, with average rock temperaturesof34.2,37.2and44.8 ?Catdepthsof?800,?1000and?1200 level respectively, and it belongs to Grade II heat hazard mines. In summer, the air temperature in roadway at ?750 level is 28 ? C, and the highest temperature may reach 32 ? C; the air temperature in roadway at ?1000 level is about 31 ? C, with the highest temperature on working face of about 40 ?C. The heat hazard is very serious. 2.2. Regional meteorological dataIn this area, the mean annual precipitation is 841.9 mm,while the maximum precipitation is 1297 mm (in 1958). Theminimal precipitation is 500.6 mm (in 1988). In this area, theaverage annual temperature is 18 ?C with the lowest and high-est temperatures appearing in January and July at averages ofabout ?0.6 and 27.4 ?C. The East wind prevails all over the yeararound, with average wind speed of 3.2 m/s, and the maximumwind speed of 24.3 m/s (in 1959). The annual evaporation is1440 mm.2095-2686/$ - see front matter ? 2013 Published by Elsevier B.V. on behalf of China University of Mining & Technology./10.1016/j.ijmst.2013.05.008Corresponding author. Tel.: +86 18610841876.E-mail address: guopingye (P. Guo).International Journal of Mining Science and Technology 23 (2013) 453456Contents lists available at SciVerse ScienceDirectInternational Journal of Mining Science and Technologyjournal homepage: /locate/ijmst2.3. Cooling energy source analysis in Zhangxiaolou Coal MineThere is no natural cooling energy source in Zhangxiaolou CoalMine, so we cannot adopt water mine inrush as cooling source. Ifwe build cooling tower, we should lay cooling water pipeline inthe shaft. The shaft in Zhangxiaolou Coal Mine is so narrow thatusing cooling tower as cooling energy source is infeasible. There-fore, according to the site conditions, we adopt return air inclinedlane to cool water by spraying and spreading.3. Experiment designWe adopted 95206 working face to carry out the experiment.95206 Working face is located on ?1225 level with rock tempera-ture 43 ?C. The total power consumption for all electrical equip-ments on the working face is 2000 kW with the coal miningoutput of 3000 t/d and sustained exploitation time of 18 h/d. Theair flow on the working face is 1600 m3/min with air temperatureat the beginning of the working face of 33 ?C. The air temperatureon the working face is between 33.5 and 40 ?C, and the air temper-ature of key points is shown in Fig. 1.The technology flow diagram of the experiment is shown inFig. 2. The detailed tentative design is as follows:(1) Firstly, the working face is set the air-cooler to cool theintake wind. The heat exchange capability of the air cooleris 2000 kW. The temperature of inlet water is 4 ?C; the tem-perature of outlet water is 17 ?C; the temperature of inlet airis 31 ?C; the temperature of outlet air is 18 ?C.(2) The designed refrigerating effect of refrigeration machine inthe experiment is 2200 kW with lowest temperature of out-let chilled water of 3 ?C and return water temperature of18 ?C. However, the highest temperature of outlet coolingwater is 45 ?C, whereas that of return water temperature is36 ?C.(3) The water mine inrush is collected and cooled by spray inthe return air roadway, after which is used as cooling water.The many impurities existing in the mine water easily blockthe condenser of refrigerating machine. In order to improvestability of the system, in this test system, we put a heatexchanger in front of the condenser to separate the minewater and compressor unit.(4) Instead of the ground cooling water, we used a spray andwater spreader to cool the water in underground return air-way. The designed length of the spray is 20 m, and thelength of water spreader is 350 m. The elevation differenceof water spreading is 110 m. We set 550 steps to increasethe heat exchanging area between the return air and coolingwater with step size of 550 m high, 200 mm wide and 7.3 mlong. The section of roadway is 18 m2with a total blast vol-ume of 4000 m3/min, wind speed of 3.7 m/s and wind tem-perature of 33 ?C. The circulating water flow of spray is530 m3/h.(5) A test monitoring system is employed to monitor the waterflow, temperature and pressure of all subsystems. The mon-itoring instruments for water flow and temperature areshown in Fig. 3.4. Analysis of test resultsThe manufacturing of site test system was completed on August16th, 2011, and begun the tests on August 17th, 2011. The refrig-eration equipments in machinery room of site test are shown inFig. 4, whereas the positions of monitoring points in this systemare shown in Fig. 5. The detailed information about the points isas follows:(1) Monitoring parameters at one side of the system: T1inairisthe air temperature before spreading of water; T2inairtheair temperature after spreading of water; Toutairthe air tem-perature after spraying; Qinairthe air volume cooling thewater; T1pwthe water supply temperature at one side ofthe system; T2pwthe outlet water temperature at one sideof the system; T3pwthe water temperature after cooling byspray; and Qpwthe volume of water at one side of thesystem.(2) Monitoring parameters of cooling water: T1cowis the inlettemperature of cooling water; T2cowthe outlet temperatureof cooling water; and Qcowthe cooling water flow.F2 30D23695206Working faceB 33.5A 33D 40C 37D1 36400 m174 mFig. 1. Air temperature of key points on 95206 working face.Cold water sumpSpray and sheetfloodWater consumption 20 m3/hWater discharge into mine550 m3/h530 m3/h4000 m3/minInlet airOutlet air550 m3/h155 m3/hInlet air20 m3/h3118faceAir coolerRefrigeratorHeat exchangerWorking Fig. 2. Technology system of experiment.454P. Guo, C. Chen/International Journal of Mining Science and Technology 23 (2013) 453456(3) Chilled water system: T1chwis the inlet temperature ofchilled water; T2chwthe outlet temperature of chilled water;Qchwthe chilled water flow; Qairthe air volume; TF1the inletair temperature; and TF2the outlet air temperature.4.1. Analysis of cooling system test resultsThe temperature monitoring curve of cooling system is shownin Fig. 6. In this system, the outlet water temperature T2pwat oneside of the system was 38.2 ?C; after spraying, water temperatureT3pwat one side of the system is 36.2 ?C, resulting in water temper-ature reduction of 2 ?C. The spray water flow is 530 m3/h, while theair volume used for cooling is 4000 m3/min. Before spraying, airtemperature T2inairwas 35.5 ?C; after spraying, the air temperatureToutairchanged to 38.0 ?C, resulting in temperature rise of 2.5 ?C.From Fig. 6, we can also know the cooling effect after waterspreading. Before water spreading, water temperature T3pwat oneside of the system was 36.2 ?C, while after water spreading, the fi-nal water temperature T1pwbecame 34.2 ?C resulting in a coolingeffect of 2 ?C. The water flow of spreading is 530 m3/h, and theair volume used for water spreading is 4000 m3/min. Before waterspreading, the air temperature T1inairwas 33.2 ?C, however, afterwater spreading the air temperature T2inairbecame 35.5 ?C givinga temperature rise of 3 ?C.(1) Allowable total energyThe allowable total energy can be calculated from the tempera-ture changes at one side of the heat exchanger:EREFG cmDT cmT1pm? T2pm1Substituting T1pm, T2pmand Qpmin Fig. 6 into Eq. (1), through calcu-lation, EREFGis 2466 kW. This cold energy includes two parts, onepart is from spray cooling, whereas the other is from waterspreading.(1) Cold energy acquisition analysis by sprayEspray cmDT cmT1pm? T3pm2Substituting T1pm, T3pmand Qpmin Fig. 6 in Eq. (2), through calcula-tion, Esprayis 1233 kW.Eair spray Gioutair? i2inair3From Fig. 6, we know that: before spraying the return air tempera-ture T2inairwas 35.7 ?C, after spraying the air temperature Toutairbe-came 38.0 ?C. As for two situations, the relative humidity is thesame, which is 100%, based on the data above, we then calculateioutairas 152 kJ/kg, i2inairas 135 kJ/kg and Eair spraya 1360 kW.From the calculation results of Eqs. (2) and (3), we can know:Eair spray Espray.The reason is that the return air speed reaches 3.7 m/s, whenspray is about 20 m3/h of water needed. This water absorbs partof heat which causes release of cooling energy by return air duringspray more than the heat absorbed by water at one side of thesystem.(1) Cooling energy acquisition analysis by water spreadingEsheetflood cmDT cmT3pm? T2pm4Substituting T2pm, T3pmand Qpmin Fig. 6 into Eq. (4), through calcu-lation, Esheetfloodis 1233 kW.Eair spray Gi2inair? i1inair5From Fig. 6, we know that: after water spreading, the return airtemperature T2inairis 35.7 ?C, but before water spreading theair temperature Toutairis 33.2 ?C. As for the two situations above,the relative humidity is the same, which is 100%. Based on the dataabove, we calculate i1inairas119 kJ/kg, i2inair135 kJ/kg andEair sheetflood1280 kW.Fig. 3. Field monitoring instruments.Fig. 4. Refrigeration equipments in machinery room at test site.TF1Air coolerRefrigeratorHeat exchangerT2chwQchwT1chwQcowT2cowT1cowTFCTFATF2SprayWater sumpToutairT2PWT1pwSheetfloodT3PWT2inairTPWSQPWST1inairWater discharge into mineWorking faceFig. 5. Position of monitoring points in this test.00:0004:0008:0012:0016:0020:0024:0033.033.534.034.535.035.536.036.537.037.538.038.5QPW: 530 m3/hTemperature (C)Time (h)T1inairT2inairToutairT1pwT2pwT3pwCooling air quality: 4000 m3/minFig. 6. Temperature monitoring curves of cooling system.P. Guo, C. Chen/International Journal of Mining Science and Technology 23 (2013) 4534564554.2. Analysis of cooling system test resultsFrom the operation curve of cooling system shown in Fig. 7, wecan see that the cooling water flow Qcowis 530 m3/h, and the tem-perature of water supply T1cowis 39 ?C, while temperature of waterleaving T2cowis 43 ?C. From Eq. (6), we can calculate the acquiredcooling energy Ecowby cooling water is 2466 kW.Ecow cmDT cQcowT2cow? T1cow:6The flow of chilled water Qchwis 155 m3/h; the temperature ofwater inlet T1chwis 7 ?C, and the temperature of water leavingT2chwis 17 ?C. Therefore, the calculated cooling energy acquiredEchwby chilled water is 1803 kW. Echwis 663 kW less than Ecow,so the wasted energy includes two parts including work done bycompressor in refrigeration and energy loss by chilled water inthe pipeline.The air flow in air cooler Qairis 1600 m3/min, the temperature ofinlet air in the cooler TF1is 31 ?C, while the temperature of outletair in the cooler TF2is 18 ?C. Therefore, the total cooling energyused for cooling the working face is 1757 kW, while the total en-ergy loss by the entire cooling system is 600 kW. So the final en-ergy efficiency ratio of the system is about 3.After starting the test, the temperature changes curve in 72 h on95206 working face is shown in Fig. 8. The temperature on 95206working face is between 18 and 29 ?C after cooling, compared withthe temperature (3137 ?C) before cooling resulting a temperaturereduction on 95206 working face of 812 ?C.5. ConclusionsIn this paper, we propose using the return air in deep mine toget cold energy for cooling in deep coal mines cooling processwhich lacks cooling energy. Based on the results analyses of sitetests carried out in Zhangxiaolou Coal Mine, we got the main con-clusions as follows:(1) For deep coal mines, cooling process which lacks coolingenergy, we propose using the return air in deep mine toget cooling energy for cooling process, which perfects thetheory and technical system of heat hazard control.(2) Through site tests, we got thermodynamic equilibriumparameters for water spray and water spreading whichoffered testing foundation for the research and developmentof deep mine cooling process which lacks cooling energy.(3) The deep mine cooling system was successfully applied inZhangxiaolou Coal Mine, and the temperature on workingface was reduced by 812 ?C through cooling; while humid-ity was reduced by 815%. This greatly improved the coolingsystem of working environment on the working face whichhad been a major problem for a long time, and created acomfortable working environment for the miners workingunderground.AcknowledgmentsFinancial supports for this project, provided by the key programsupported by the National Natural Science Foundation of China(No. 51134005) and the Doctoral Scientific Fund Project of the Min-istry of Education of China (No. 20120023120004), are gratefullyacknowledged.References1 He MC, Xie HP, Peng SP. Study on rock mechanics in deep mining engineering.Chin J Rock Mech Eng 2005;24(16):280313.2 Yang SQ, Ou XY, Cheng JW, Wang TJ, Yu BH. Micro-climate evaluation systemin thermal mines. J China Univ Min Technol 2006;16(1):14.3 Zhang RX, Yu DF, Li XW, Yao XG, Liu Y. Surface mine system simulation andsafety risk management. J China Univ Min Technol 2006;16(4):4135.4 Qi YD, Cheng WM, Pan G, Wang G. 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