| Impinging jet ventilation(IJV)is considered to be a new type of ventilation that can create a good indoor thermal environment,improve indoor air quality,and reduce energy consumption.It has been successfully applied in the large-height space.However,there have been few studies on the application of the IJV system in small spaces such as family bathroom.Some studies have preliminarily discussed the feasibility of applying IJV to bathroom heating.The results show that the indoor temperature is suitable,the vertical temperature gradient is small,the draught risk near the ground is small,and so the indoor thermal comfort is good.The IJV system in a standard bathroom with the dimensions of 1.80m × 1.80m × 2.80m(length × width X height)is taken as the research object.Firstly,the thermal environment of the bathroom is simulated by Airpak software under the typical conditions of supply inlet where the supply standpipe is laid along the corner of the bathroom and the return air vent is located on the ceiling at the diagonal.The influences of some factors including the shape,height,velocity and angle of the supply inlet on the airflow field,temperature field and thermal comfort level in the bathroom are discussed.Owing to the low height and small space of the family bathroom,the confluence field near the return air vent may have a significant impact on the air flow and thermal environment in the bathroom.In view of the better supply conditions,this paper discusses the influences of some factors including the position of return air vent on the ceiling,the installation height of the return air vent,and the return air velocity on the indoor thermal environment.Therefore,the feasibility of reducing heating power is analyzed for the case of better heating performance.The results show that,among the IJV system with circular,triangular or square supply inlet,the warm jet from the circular supply inlet has the best diffusion performance along the ground,the longest diffusion distance.As for the IJV system with circular supply inlet,the degree of overheating near the supply inlet is light,the thermal comfort index is evenly distributed on the vertical section near the human body,and the energy utilization effectiveness and air distribution characteristics are also better than the IJV system with the other two supply inlets.For the IJV system with the air supply height of 0.2m～0.6m and the supply velocity of 2.51 m/s～3.51m/s,the higher the jet discharge height,the higher the indoor temperature,the better the heating performance,the greater the average efficiency of energy utilization in the occupied area.But if the jet discharge height is high,the air velocity at ankle height is great and the risk of overheating cannot be ignored.Therefore,under the condition of low supply velocity,higher jet discharge height can be adopted to improve the whole room heating effect;In case of high supply velocity,the supply inlet should be set at a lower place to prevent overheating near the ground.The air supply angles of 90°,75°,60° and 45° are discussed when the discharge height of the circular supply air vent is 0.2 m and the supply velocity is 3.78m/s.The results show that when the air supply angles are 45° and 60°,the velocity and temperature near the ground are high and the indoor vertical temperature difference is large,so it should not be adopted.For the case of 90° supply angle,the PMV distribution on the section near the human body is the most uniform,and the average energy utilization efficiency and ADPI are relatively high,so the comprehensive performance is the best among the four casesThe location of return air vent on the ceiling has no significant effect on indoor air distribution,but it will affect the temperature and PMV near human body.If the return air vent is located at the center of the indoor ceiling,the temperature around the human body below the vent is the highest;If the return air vent is located at the ceiling corner opposite to the air supply standpipe,the energy utilization efficiency is the highest.If the return air standpipe is set along the corner which is located at the diagonal of the supply air standpipe,a slight decrease in the height of the return air vent has no significant effect on the indoor thermal environment,but if the return air vent is lowered to 1.0m,it will be beneficial to improve the indoor temperature and thermal comfort level.If the return air standpipe is located at the middle of the wall opposite to the air supply standpipe,the research on different return air velocities shows that the return airflow velocity has little influence on indoor thermal environment,but with the continuous operation of the IJV system,the influence of return airflow velocity on thermal environment parameters near the human body gradually appears,and the return air velocity of 2.75m/s is slightly better than the other two casesLowering heating power will reduce indoor airflow velocity,air temperature and PMV indices,and then significantly affect indoor thermal environment.If the return air standpipe is located at the middle of the wall and the heating power is 1.5kW,1.3kW or 1.1kW,the indoor thermal comfort corresponding to 1.3kW is the best. |
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