The Optimization Research On Control Strategy Of Ground Source Direct Cooling System With Radiant Floor

The technology of coupling displacement ventilation system of floor radiant cooling air conditioning has matured in our country,but in the domestic very successful application example is uncommon.The biggest advantage of this system is that it realized sharing the same set of terminal devices both in winter and summer,which save investment cost.Secondly,the comfort level of the system is better also,in winter it can achieve "cold head and warm feet",in summer,displacement ventilation will mix the indoor temperature evenly,so it decrease the temperature stratification in vertical direction to maintain indoor air quality is good.But this kind of combined air-conditioning system requires accurate control program,real-time monitoring about indoor temperature and humidity,avoiding air condensation on the surface of floor.The thermal inertia and temperature lag phenomenon of floor also should be considered.The ultimate goal of this study is to improve the comfort of the air-conditioning system as much as possible on the basis of minimizing energy consumption.This paper takes the floor radiant cooling air conditioning system as the research object,on the condition of buried tube(U-tube)deliver cold water directly.Take the Antaeus energy-saving demonstration building's air conditioning system as prototype,using the software of TRNSYS to some energy consumption simulation.By means of combining experiment and simulation,this paper analyzed the operation strategy of the air conditioning system and the indoor environment.The indoor temperature data of fifth floor were stored up in the real-time monitor.Through the analysis of a large number of experimental data,the indoor temperature distribution are obtained.Under the condition of radiant cooling combining with displacement ventilation,the phenomenon of indoor temperature stratification is extremely significant.This conclusion has a great help to research the trend of room temperature change in vertical direction by further analysis.For floor radiation,when the water flow rate reach the engineering experience value 20000 kg/h,water segregator will evenly distributed total water to each layer,but the floors temperature exists obvious difference,not all of the room temperature can meet the design requirements of air conditioning,occasionally room temperature is more than 27 ?.In this paper,an idea was proposed that the water flow can be adjustment proportionally according to room temperature feedback,this control scheme can effectively alleviate the above problem.Floor radiant cooling system often appear to harden phenomenon on the surface of floor,and the influence factors are very complicated,including people's behavior such as opening the door or window,as a result high temperature air flow into the indoor,when it encounter the low temperature floor surface condensation generated;If the floor surface temperature below the dew point temperature of indoor air,condensation can occur.There are usually two solutions to this phenomenon,one is to keep the basis of the relative humidity,lower air temperature makes its dew point temperature is less than the floor surface temperature;Second,under the condition of the same supply air temperature,reduce the air humidity,that is,reduce indoor air relative humidity.In this experiment system,reducing the air relative humidity of displacement ventilation is the most effective method.Though analysis the change regulation of indoor temperature,this paper proposes a new control strategy in view of the extreme weather,then the simulation study was carried out: by predicting outdoor temperature,the total water supply can be controlled ahead of schedule.While the program is possible to have the effect of buffer room temperature significantly lift,but due to the thermal inertia of the floor radiant refrigerating capacity is not proportional to the water flow change,and it also will increase the energy consumption of the unit and pump.Forecasting scheme although did not solve unusual weather influence on room temperature,but also confirmed the advantages of floor radiation thermal inertia in the application of this kind of composite system.From the proposing of experiment scheme to validating its deficiencies,the process explained a myth in control strategy of the hybrid air conditioning system,it will have great significance for the next step to optimize control strategy.