The displacement ventilation system (DVS) is one of the mechanical ventilation systems which blow the air with lower temperature than indoor air from the lower part of a room and cause upward moving of indoor air by buoyant force to exhaust it at the ceiling.
As DVS is aimed at meeting only the requirements of workplaces, the thermal and concentration stratification is formed between lower and upper parts. DVS makes the quality of the air better and exhausts the polluted air effectively, and therefore the saving efficiency of energy is remarkable. In the designing of DVS, the height of thermodynamic stratification has to be controlled to be higher than that of the workplace for people, but it should not be too high. This is because being too high might cause an increment in the amount of air blast, which results in waste. Thus, the determination of the height of thermodynamic stratification is one of the vital problems in the application of DVS.
Paek Myong Chol, a section head at the Faculty of Thermal Engineering, analyzed the characteristics of indoor airflow and temperature distribution in the hybrid displacement ventilation system (HDVS) where a vertical supply duct was installed at the middle height of a building by computational fluid dynamics (CFD). Then, he investigated the specific influence of the velocity of air inflow and the length of the supply duct on the air temperature.
The results show that the proposed system saves 35kw of energy compared to the mixing ventilation system, which leads to the annual energy saving of about 80 000kW·h.
If more information is needed, you can refer to his paper “Energy Saving Characteristics of Hybrid Displacement Ventilation System with Vertical Supply Duct” in “GAS Journal of Engineering and Technology” (SCI).