Indoor Thermal Environment Analysis Of A Building Heating With Solar Air Collector In Kunming Area

In recent years,solar space heating is considered to be an effective and environmentally friendly way to reduce space heating energy consumption.Among them,the method of using solar energy to heat air to warm indoor air temperature has been paid more attention because of its simple system structure and low cost.The western temperate region represented by Kunming is rich in solar radiation resources in winter,but the temperature difference between day and night is large,which is very suitable for solar heating.With the improvement of living standard,the heat demanding in winter is increasing and it has become a hot topic to seek a healthy living environment that combines low energy consumption solar space heating with higher indoor comfort degree.In this paper,by combining theoretical analysis,experimental test and CFD numerical simulation,the experimental study was carried out on an experimental room heated by solar air collector under winter weather conditions in Kunming.The experimental data were used as the boundary condition to optimize the design of the space heating for experimental room through CFD numerical simulation.In addition,the simulation study about solar air collector area was carried out on Urumqi,a cold region in the west of China,which has the same amount of total solar radiation as Kunming area.The main research contents are as follow:(1)On the basis of heat transfer theory,the heat transfer principle of the space heating for experimental room was analyzed,and two indexes of indoor thermal comfort,the predicted mean vote PMV and the predicted percent dissatisfied PPD,were introduced.(2)The experimental room which was built in Kunming city was taken as the research object,its area was 24m~2.And the measuring places were arranged for five experimental cases under different test conditions of heating.The indoor and outdoor air temperature,relative humidity,wind speed,surface temperature of the envelope and indoor vertical height temperature under different working conditions were measured.The PMV and PPD values under each working condition were calculated.The experiment results show that space heating with solar air collector is feasible in Kunming area,and it can obviously improve indoor thermal comfort degree during the day under sunny weather although it cannot meet the whole night comfort requirements,and it can extend the comfort time due to the role of envelope structure and indoor air heat capacity.The highest comfort level is?for most of the time while the solar collector area is 2m~2.In order to meet the comfort requirement of the whole night,an auxiliary energy air source heat pump was added and a low-temperature floor radiant heating system was combined.The indoor air temperature increased at night,and the indoor air temperature fluctuated within a small range,At night,indoor comfort has been significantly improved,which could meet the heating demand of Kunming in winter night.Because of the effect of air heat capacity in the daytime,the use time of heat pump is reduced and the energy saving effect is obvious.(3)The physical model for numerical simulation was established according to the experimental room by using Airpak simulation software.The experimental condition with a solar air heater with area of 2m~2 was simulated.The simulated results of the same test point were consistent with the change trend of the measured value,and the high consistency between the two verified the reliability of the model.Temperature,velocity,PMV and PPD cloud images of the horizontal section of human body sitting height Y=1.1m were analyzed.The vertical section Z=2.63m section parallel to the center of the heated air inlet was selected,and the temperature and velocity cloud images were analyzed respectively with the contrast section Z=1.0m.(4)The verified model was used to simulate the thermal environment in the room under different outlet locations(east wall,south wall,west wall)and different air supply temperatures(60?,65?).The section of analysis is the same as that of simulation experiment.In addition,in the middle of the vertical section of the room(Z=2.04m),near the west wall(X=0.85m),in the middle of the room(X=2.85m)and near the east wall(X=4.85m)were selected to form a cross section in the vertical direction of the room.Section data were derived to analyze the variation trend of indoor air temperature,PMV and PPD under each case.The transient model was used to analyze the variation trend of indoor air temperature under different air supply temperatures(50?,55?,60?,65?)in a day with the change of outdoor air temperature.Through the analysis and comparison at different sections and for a whole room,it is concluded that the optimal outlet location is located in the west wall,and the optimal air supply temperature is 60?.The optimal model was used to analyze different area of solar air collector(2m~2,4m~2,6m~2)at the lower outdoor air temperature of -10?.The simulation results show that the area of solar collector is 6m~2 can meet the room comfort requirements.