Numerical Simulation And Analysis Of Energy Consumption On Displacement Ventilation With Conjugate Heat Transfer

Compared with the traditional mixing ventilation, displacement ventilation, a new concept in air-conditioning system, has showed remarkable advantages in many aspects,and has been studied largely around the world,but the study of displacement ventilation with conjugate heat transfer is few.This paper mainly study three aspects of displacement ventilation with CFD means as follows:The conjugate heat transfer for steady flow is simulated. In this aspect, the infection on indoor temperature distribution and flow distribution is studied when change the surface temperature of the heat sources, the supply air speed, the hight of room, the thickness of wall, the material of wall.The result is:when the outside of the wall is looked as the boundary ,the vertical temperature gradient and the thermal stratification height are affected by both the upflow from the heat sources and the upflow on the inner surface of the wall.The conjugate heat transfer for unsteady flow is simulated. In this aspect, the response of indoor to the outdoor disturb and the change of the displacement ventilation load are studied mainly.the result indicate: When the heat inertia index D increase, the extent of outdoor disturb attenuatin is larger,the delay time is longer,the change of vertical temperature gradient decrease, the heat stability is better,people feel more comfort;When the heat inertia index D increase,the load of the lower room dealed with by the air-conditioning set decrease,the saving energy is larger;when D reachs a fixed value,the change of the indoor temperature and the load of the lower room is not a rule of sine wave like outdoor temperature,this is the result of the conjunct effect of outdoor disturb and indoor disturb.The energy consumption and the infection on the displacement ventilation system are studied for the displacement ventilation system with a exhaust outlet on the ceiling and a backwind vent on the wall.The result indicate:Compared with whether the displacement ventilation system with a exhaust(or backwind) outlet on the ceiling or the mixingventilation, the effect of saving energy of the displacement ventilation system with a exhaust outlet on the ceiling and a backwind vent on the wall is better. The quantity of the saving energy is related to the height of the backwind vent, when height of the backwind vent hoist,the infection of the air distribution change on the occupied zone decrease,ventilation efficiency become larger,comfort is improved,but the saving energy is become small,this is a interrestrict relation,need to be balanced in practice.