Study On Evaporative Cooling Air Conditioning Chiller And Its Performance

The prosperity and development of the country cannot be separated from the consumption of energy.Under the background of reaching the peak of carbon and carbon neutrality,how to rationally use energy and reduce carbon emissions are the main problems facing our country at this stage.Air conditioning energy consumption accounts for the largest proportion of building energy consumption,accounting for a quarter of the entire building energy consumption,how to reduce air conditioning energy consumption,to achieve refrigeration effect,is one of the current hot issues,but also one of the main directions of energy conservation and emission reduction.At present,the traditional air conditioner is mostly used in domestic air conditioners,reaching more than 80%,and the traditional air conditioners have problems such as high operating costs and energy and environmental crises.Most of the northwest region belongs to arid and semi-arid areas,the air is hot and dry,the temperature difference between dry and wet spheres is large,and the evaporation capacity is strong,which is suitable for the use of evaporative cooling air conditioning system.Moreover,evaporative cooling air conditioning uses water as refrigerant,does not consume compression work,environmental protection,energy saving and economy,so this topic chooses evaporative cooling air conditioning to replace traditional household air conditioning.Through evaporative cooling technology,cold water below the wet-bulb temperature is generated from dry air.Use it as a cold source to supply dry fan coils or radiant refrigeration terminals.This will make indirect evaporative cooling technology have a larger application field.In this paper,evaporation cooling technology is used to design a small household evaporative cooling air conditioner chiller which can meet the requirements of air conditioning rooms in Lanzhou in summer according to outdoor meteorological parameters and indoor design parameters of air conditioning rooms in Lanzhou in summer and integrates energy saving,environmental protection and economy.It is used as the cold source of radiant floor refrigeration or dry fan coil.Instead of using mechanical refrigeration,it directly uses the natural cooling of evaporative cooling air conditioning chiller for cooling,which reduces the power consumption of refrigeration,saves energy,and also reduces the emissions of greenhouse gases and CFC,providing theoretical basis and data support for the use of evaporative cooling air conditioning chiller as a cold source in Lanzhou households.This topic intends to use the method of theoretical calculation for the design and selection of various parts of evaporative cooling air conditioning chiller,including the heat exchanger part,spray water system,axial fan and sleeve ventilation tube design.The heat and mass transfer mechanism of household evaporative cooling air conditioning chiller is analyzed,and the heat and mass transfer mathematical model of heat exchanger is constructed.The influence of operating conditions and structural conditions on the performance of the chiller was studied and analyzed by numerical calculation method,and the optimum operating conditions and structural parameters of the chiller were obtained,so as to achieve the best operating effect.The influence of cold water flow direction on the performance of the chiller is also analyzed numerically.For the household evaporative cooling air conditioning chiller designed in this paper,the length of heat exchange coil is 1.25m.φ10 smooth copper tubes are used in 4 rows with 8 tubes in each row,and the relative tube spacing is 0.03m.The total pressure P of axial fan is 35Pa,and the motor power N is 7.97×10^-5k W.PVC pipe ofφ100 is used for the inlet pipe of the jacket ventilation pipe,PVC pipe ofφ90 is used for the exhaust pipe.Spray pipe isφ10 PPR material water pipe,each pipe contains 3 nozzles,nozzle spacing 0.08m,a total of 5 spray pipes,each pipe spacing 0.3m.The water tank is made of iron sheet material,and the size of the water tank is 1.25×0.205×0.019m.The flow Q of the submersible spray pump is 0.004m³/h,and the head H is 0.45m.For the household evaporative cooling air conditioning chiller studied in this subject,the relatively reasonable structural conditions are as follows:hydraulic diameter is 0.01m,the relative pipe spacing is 0.03m;Relatively reasonable operating conditions are as follows:the air flow rate is 2m/s,the cold water flow rate is 1.4m/s,the ambient dry bulb temperature is28℃,the relative humidity is 45%RH,the spray water density is 14 m3/（m2·h）,and the gas-water ratio is 1.2.Under these conditions,the water supply temperature,cooling efficiency,cooling capacity per unit area,resistance loss per unit length,comprehensive heat transfer coefficient and COP are 18.8℃,66%,52W/m2,1470N/m2,1000W/（m·s）and 16,respectively.At this point,the water supply temperature is slightly higher than the wet bulb temperature of the ambient air.The water supply temperature of the home evaporative cooling air conditioning chiller studied in this subject is slightly higher than that of the downstream type under the same conditions,but only 0.1～0.2℃higher,and its cooling efficiency is also slightly lower.It can be seen that the reverse flow of cold water has little influence on the performance of the home evaporative cooling air conditioning chiller,and the cooling performance of the chiller under the same conditions is slightly better than that under the reverse flow.