| Data center air conditioning system energy consumption in the data center total energy consumption accounted for 30%—45%ratio,mechanical refrigeration compressor energy consumption occupy a considerable share?about 50%?,in order to reduce the data center cooling system energy It is the trend of energy-saving practice in data center cooling system to reduce the operating time of mechanical refrigeration in the cooling system by free cooling instead of using natural cold source instead of the artificial cold source of the steam compressor cycle.However,most data center operators prefer to adopt indirect natural cooling in air-conditioning systems to indirectly cool the circulating air in the equipment room by means of heat exchangers using external natural cold sources so as to avoid or significantly reduce external ambient air pollutants and Impact of humidity on IT equipment reliability in data centers.In order to strengthen the cooling effect of the heat exchange equipment in the indirect natural cooling system,it is possible to combine the dry cooling area with the evaporative cooling technology so as to further extend the natural cooling operation time in the data center cooling system.The air conditioning system in the data center is mainly composed of a cooling medium circulation,a cooling medium circulation and a cooling medium circulation.According to different medium circulation,the corresponding energy-saving ideas and the best energy-saving practices are discussed.According to the type of natural cold source in the data center,free cooling can be divided into free cooling of the air cooling source and free cooling of the water body?including lake water,seawater,etc.?;free cooling can be based on the cooling medium to be handled by the natural cold source Divided into the wind side of the free cooling and water side of the free cooling.Air-cooled sources based on dry-bulb temperature Indirect air-side free cooling uses three main types of core heat exchangers:plate-fin heat exchangers,rotor heat exchangers and heat pipe heat exchangers.The cooling performance of the cross-flow plate-fin indirect air heat exchanger was tested and the cooling efficiency was generally 60%—75%.However,the cooling efficiency of the rotary heat exchanger and the heat pipe heat exchanger are usually 75%—85%and 50%—70%,respectively.For the air-cooled indirect air-side free cooling system based on dry-bulb temperature,the data center cooling system can be switched to the fully-free cooling mode when the ambient air temperature is lower than 21?.When ambient air temperature is between 21?—31?,you can switch to the part of the free cooling mode of operation;when the ambient air temperature is higher than 31?,you need to switch to full mechanical cooling mode of operation.Indirect evaporative cooling heat exchangers are usually used for the indirect air-side free cooling of the air source based on the wet-bulb temperature.They have three types of heat exchangers:internal cooling,external cooling and hybrid.Through the test of plate-fin indirect evaporative cooling heat exchanger cooling performance can be drawn,heat exchanger maximum heat transfer temperature difference in the range of 10.8?—15.3?,the internal cooling plate-fin indirect evaporative cooling heat exchanger The wet bulb efficiency is maintained at about75.0%.Compared with the cooling efficiency of the cross-flow plate-fin indirect heat exchanger,the wet-bulb efficiency of the internally cooled plate-fin indirect evaporative cooling heat exchanger increases by 10%-20%.In the indirect air-side free cooling system based on the wet-bulb temperature air source adopting the internal cooling indirect cooling evaporative heat exchanger,when the ambient air temperature is lower than 15?,the data center cooling system can be switched to dry When the dry-bulb temperature of ambient air is higher than 15?,and the wet-bulb temperature is lower than 20?,it can switch to wet-type free cooling mode.When the ambient temperature of the ambient air is higher than20?,you need to switch to the part of the free cooling operation mode.A typical city based on the dry northwest region was used for statistical analysis in the data center cooling system based on the dry-bulb temperature or the hours of energy-saving operation of the indirect wind-side free cooling system based on the wet-bulb temperature air source.Urumqi,Xinjiang,Xining,Qinghai,Gansu,Lanzhou,Gansu,Yinchuan,Ningxia,and Xi'an,Xi'an,Shaanxi Provinces Wet-bulb-based air-cooled indirect air-side natural cooling systems operate at full natural cooling mode for the whole year compared with dry-bulb-based natural cooling systems.They were 25.5%?1777 h?,6.5%?532 h?,20.8%?1504 h?,19.7%?1404 h?,and 18.1%?1104 h?,respectively.According to whether the external ambient air is directly contacted with the circulating water being cooled,the evaporative cooling chillers can be divided into direct evaporative cooling chillers?ie,open cooling towers?and indirect evaporative cooling chillers?ie,closed cooling towers?;according to the external environment Whether the air and the water film within the unit is in contact with the precooling treatment before evaporative cooling chillers can be divided into air directly into the type of evaporative cooling chillers and air precooling evaporative cooling chillers.Through the direct evaporative cooling chiller?open cooling tower?in the data center field test and analysis of the relevant simulation data obtained that the degree of approximation will increase with the supply and return water temperature increases,and in the same for In the case of backwater temperature difference,the degree of approximation will decrease as the temperature of the inflow wet bulb increases.When the temperature difference between supply and return water is 5?,the data fitting function between the approximation degree and the inlet wet-bulb temperature is A=10.56-0.34twb,o.In the data center direct evaporative cooling chiller?open cooling tower?indirect water side of the free cooling parallel system,when the ambient air wet ball temperature is below 11?,the data center cooling system can switch to fully free cooling mode of operation;And when the ambient air wet bulb temperature is higher than 11?,you need to switch to fully mechanical cooling mode of operation.According to the air indirect evaporative cooling heat exchanger,air precooling direct evaporative cooling chillers can be divided into internal cooling,external cooling and hybrid.The air pre-cooling type direct evaporative cooling chillers in the air precooling section is indirect pre-cooling for standpipe riser,indirect wetting and direct evaporative precooling of standpipe+wet membrane,precooling of coil indirect evaporation,indirect evaporation of coil+Cold and the wet bulb temperature efficiency of coiled+standpipe+wet membrane indirect and direct evaporative precooling were 43.8%,36.4%,28.5%,52.1%and 48.0%,respectively.The wet bulb temperature efficiency decreases as the maximum possible wet bulb temperature drop increases.The predicted feed water temperature of the spill filling of the unit is expressed as tG,pre=1-?/??(twb,o-tdp,o+tdp,o.When the wet-bulb temperature of external ambient air is lower than 15?,the data center cooling system can be switched to the non-precooled fully-free-cooling operation mode;When the ambient air wet ball temperature is higher than 15?,but after the evaporative cooling chiller pre-chilled air pre-chilled air wet ball temperature is below 15?,you can switch to the pre-cooling completely free cooling operation Mode;and when the external ambient air is cooled by the air precooling section of the chiller,the temperature of the wet bulb of the precooled air is higher than 15?it is necessary to switch to the full mechanical cooling mode of operation.Aimed at the typical cities in northwest dry areas,the direct air cooling and air precooling indirect evaporative cooling water chilling units are used in the data center cooling system.Energy-saving hours of operation were analyzed.Indirect water-side natural cooling systems for air-cooled direct evaporative cooling chillers in Urumqi,Xinjiang,Qinghai,Xining,Qinghai,Gansu,Lanzhou,Ningxia,Yinchuan,Xi'an and Xi'an,Xi'an have full-year operating hours in direct cooling compared to air direct-evaporative cooling.The indirect waterside natural cooling system of the unit is40.8%?2508 h?,20.5%?1467 h?,38.0%?2195 h?,25.3%?1473 h?,and 38.1%?1576 h?,respectively. |
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