A Numerical Investigation For Indoor Air Distribution Under Jet Ventilation

As it is shown in survey that people spend over80%of their time indoor. To createhealthy and comfortable indoor environment, it is necessary to make researches abouthigh-efficiency ventilation mode. Displacement ventilation although improves theventilation efficiency,it has many technical problems like its limited usage in winter.However, jet ventilation can not only create air distribution effectiveness the same asdisplacement ventilation, but also can run the whole season. It especially suits formechanical ventilation in office building. Based on impinging jet ventilation anddownward directed vertical wall jets, characteristics and influencing factors formulti-operating conditions of the indoor air distribution were studied by numericalanalysis in this paper.Firstly, mathematics model of numerical investigation suitable for indoor jetventilation was built through analyzing on nine different definite conditions fornumerical simulation of turbulence model selection, pressure difference format and wallcondition processing method. Secondly, compared with displacement ventilation, the airdistribution features of impinging jet ventilation and downward directed vertical walljets were studied in numerical experimental investigation for two working cases. Theindoor temperature field, velocity field, air age, air distribution non-uniform coefficient,energy utilization factor and air diffusion performance index were compared andanalyzed at two levels, distribution features of the indoor air distribution and ventilationefficiency. Thirdly, through the studying of key factors that mainly influenced jetventilation and downward directed vertical wall jets, and discussing about the effect ofdifferent air supply outlet and return air inlet to ventilation, the best layout plan wasworked out.It was verified that RNG k-εturbulence model, standard wall function method,and the Body-force-weighted pressure difference format can obtain better numericalsimulation results for indoor air distribution.It was researched that the indoor temperature had an obvious stratification whencold air was supplied to the interior, the room “air lake” temperature was2℃higherthan displacement ventilation for impacting jet ventilation while the temperature was3℃higher than displacement ventilation for downward directed vertical wall jets. Theair age of jet ventilation was similar to displacement ventilation below z=1.2m while it was100~200s lower than displacement ventilation above z=1.2m.When hot air wassupplied to the interior, it was1~2℃temperature variations between z=0.1m planeand the upper with no obvious stratification in air age distributions.It was also found that the energy utilization factors of impinging jet ventilationwere2.021and downward directed vertical wall jets1.609under summer condition,while they were1.08and1.21under winter condition. Jet ventilation had greatenergy-conscious spaces with the energy utilization factors more than1. The indoor airdistribution under jet ventilation was closely related to the arrangement of air supplyoutlet and return air inlet.