Analysis Of The Effects Of Large Temperature Difference Cooling Water On Chiller’s Performance

On the time of rising global energy crisis and deteriorating of living environment,China build an energy-efficient and environment-friendly society as a basic national policy,and increase the dynamics of promotion and support to energy-saving products. In aircondition system, cooling water system is very important while easy to ignore its energyconsumption. At present, the cooling water system usually use the mode of cooling waterpump and cooling tower, to take advantage of cooling tower to lower the temperature ofcirculating cooling water. But under the hygrothermal condition in the south, the coolingeffect of cooling tower is limited which always lead to the lesser temperature difference,even effect the operation of air conditioning unit. In actual projects, Its always increase thecirculating cooling water to reduce bad influence. Under such background, this paperanalysis the central air conditioning system which use large temperature difference coolingwater, such cooling water is coming from nature.The paper analysis the main performances of cooling water pump、shell and tubecondenser、screw chiller under the condition of large temperature difference cooling water.Take the follow conditions as example to theoretical calculate the heat transfer coefficientof tube and shell condenser and the refrigeration coefficient of screw chiller. The airconditioning cooling load is300kW, the inlet cooling water temperature is22～28℃andits temperature difference is5～15℃. The analysis and calculation results shows that：1、The heat transfer coefficient of condenser decrease slightly when the inlet and outlettemperature difference increase and the flue decrease, while the refrigeration coefficient ofscrew chiller is still in the high level——higher than4.209;2、When the reduce the flues the cooling water pump’s power sharp fall; When thetemperature difference is6℃, its power will reduce42.2%. If put the energy consumption of cooling water pump and screw chiller into account, the system still have some energysaving effect.Based on theoretical calculation, this paper hold an experimental measurement in largetemperature difference cooling water technology. Measure and compare the operating datafrom different cooling water sources——deep phreatic water and river water. The datashows that:1、In summer, deep phreatic water temperature is about22.4℃, river water temperatureis about26.7℃, both temperature are lower than32℃which usually supplied from coolingwater tower.2、Deep phreatic water temperature is stable. It coefficient of performance is5.2whichhigher than the recommended value4.209when use deep phreatic water as cooling water;3、River water temperature is change with the outside air temperature，when use riverwater as cooling water,its COP’s value is among3.9～7.0,which is also higher than therecommended value, the lower the river water temperature, the higher the COP is.Through the analysis from regional applicability and economic applicability aboutlarge temperature difference cooling water system. The results shows that the use ofcooling water system is feasible and without the limit of region,the region which near theriver is better. The longer the system used, the economic efficiency will be more obviously.