Performance Research On Direct Evaporation Air Dehumidification And Dry-coil Air Conditioning System

Conventional fan coil central air conditioning systems existed energy waste and lowthermal comfort problems, which could be solved by adopting Direct evaporation airdehumidification and Dry-coil air conditioning system. The outdoor fresh air independentlydehumidificated by a direct evaporative, then mixed with dry fan coil handling return airinto the air conditioning room, eliminating indoor by-product heat and wet, achieving thegoal of temperature and humidity independent control on air conditioning room.The airconditioning system had the certain energy-saving effect and provides good indoor airquality.In this paper, the performance researching on Direct evaporation air dehumidificationand Dry-coil air conditioning system was presented. By the method of simulation andexperiment, providing the application theoretical and experimental basis of the system, atthe same time technical reference for the practical application. First of all, for an officebuilding in tianjin area for the model, using EnergyPlus software on the building loadsimulation and energy consumption simulation, geting the distribution regularity of energyconsumption for air conditioning system equipment.The simulation conclusion was asfollows:(1) the peak cooling load on the summer design day was74.1W/m2, including sensibleheat load68.8W/m2, latent heat load5.3W/m2.(2) the time accounted for71%of the whole running time of air conditioning coldoutput rate was25%~75%, better than that of the tandem type independent fresh air plusdry fan coil air conditioning system. In Direct evaporation system system, the energyconsumption of fan energy consumption for air conditioning system energy consumptionwas the largest energy consumption; Followed by fresh air units and water chillers, eachaccounted for25%,23%, and the energy consumption was lower than the sum of the seriessystem energy consumption of chiller. In the entire cooling season, the Direct evaporationsystem saved12.1%than tandem system energy.(3) the air conditioning during the cooling season was most of indoor temperature atthe set value of25℃, fluctuating less than1.5℃, and the relative humidity, between40~55%, range15%, showing that the temperature and humidity air-conditioning system hadgood control ability and provide better comfort.By establishing Direct evaporation air dehumidification and Dry-coil air conditioningsystem test bench, experimenting on factors affecting the system respectively, analysisingthe influence factors in the fresh air, dry fan coil unit and operation performance of the system, and the system under various influencing factors of indoor temperature andhumidity change rule. The experiment research was as follows:(1) the air handling unit fresh air temperature was directly affected by the windparameters. With the increase of outdoor dry bulb temperature and relative humidity, thfresh air load increased, as also as the supply air temperature and air unit unit capacity, butthe amount and undertake indoor latent heat reduced.(2) with the increase of the new air volume, fresh air temperature, the watercondensation rate, undertake indoor latent heat quantity and air load increased.(3) the fan coil refrigerating capacity dropped as the higher water temperature, and thewater supply when the wind plate in dry operation temperature could be lower than theindoor air dew point temperature.(4) the dry fan coil coiling capacity increased with the increase of return air, and whenthe temperature of the water supply was low, increasing the back air flow could make thedry fan coil in dry operation.(5) the dry fan coil coiling capacity increased with the increase of frozen water, andwhen the water temperature was higher, increasing the chilled water flow could make thedry fan coil units with larger refrigerating capacity.(6) the system providing indoor sensible heat load was more noticeable than change asoutdoor dry bulb temperature and relative humidity increased, which was because theoutdoor parameters affect the ability of air unit dealing with fresh air fresh, and the higherthe outdoor dry bulb temperature and relative humidity, the lower fresh air to the indoorlatent heat load. As the change of outdoor parameters, the system as a whole had a goodtemperature and humidity control.(7) the system providing the total load and fresh air units bear the cold quantity reducewith the increase of new return air ratio by changing the new air volume and air and returnair ratio. The reason was with the increase of the new air volume, the effect of temperaturewas greater than the increase of the fresh air volume, resulted in the decrease of fresh airunit for the indoor load, and changing with the new air volume of fan coil unitsrefrigerating capacity.(8) with the increase of indoor sensible heat load ratio, the system providing indoorsensible heat load was bigger than change.When indoor sensible heat load was low, the fancoil units was in wet condition of operation, increasing the new air volume could reduce thesystem providing indoor sensible heat load ratio, in order to meet the requirements of theindoor load.With changing indoor sensible heat load ratio, the change of indoor temperatureand humidity was bigger, we could adjust the system flow and the new air volume setting toachieve the room temperature and humidity range.