MODELING OF DOUBLE-SKIN FAÇADE SYSTEM USING NEWHASP AND VENTILATION NETWORK PROGRAM FOR PRACTICAL THERMAL LOAD SIMULATION

A ventilation network approach to double-skin cavities, blind circulation airflow and blind operation performance

Abstract

 A multi-space model of a double-skin façade system is proposed using the practical thermal load simulation program NewHASP and the ventilation network program employed in mechanical design practice. Using this model, thermal performance evaluation of various venetian blind controls including the newly proposed blind control system is performed. The conclusions of this paper are shown below.

 1) A method called Meta_simulation was developed to directly replace the airflow rate between zones and infiltration airflow rate in the NewHASP program with the results of the ventilation network program. Using this method, the airflow of the double-skin cavity and the airflow between the blind slats are obtained, and a thermal load simulation is performed.

 2) Derived the formula of double-skin solar heat gain coefficient for double-skin cavity (hereafter DS), blind and double-skin inner glass air layer (hereafter BS), and office room (hereafter RM). Three-space model using NewHASP multi-space calculation is developed.

 3) As a slat control method of the blind installed inside the double-skin cavity, the author proposed two variation of the avoid direct sunlight control. First is to keep the transmittance constant when the avoid direct sunlight angle becomes negative and second is to keep the slat angle constant. The operation curve of the blind control was proposed, and the thermal performance was compared with the conventional control method.

 4) Blind circulation airflow rate on summer peak day was 30 ~ 60m3 / h.m2 and BS air temperature was up to 2K higher than DS air temperature.

 5) When the slat angle is fixed through the year and the slat angle is sequentially increased in increments of 0° to 75° in increments of 15°, the solar shading performance increases as the slat angle is increased from 0° to 45°, and maximum and annual cooling load decreased. However, at slat angles of 60° and 75°, the gap between the slats became narrow, and the ventilation performance between DS / BS was reduced and the cooling load increased.

 6) In the conventional blind avoid direct sunlight angle control, the case where at the night slats were vertical and the case where they were horizontal were compared. Both horizontal and vertical cooling heat loads were reduced when compared to vertical. It is thought that the ventilation performance between DS / BS is promoted when it is horizontal.

 7) As a variation of the blind avoid direct sunlight angle control, the control to keep the transmittance constant when the avoid direct sunlight angle becomes negative and the control to keep the slat angle constant were compared by changing the transmittance and the slat angle. The effect on the maximum / annual cooling load is small. However, it is expected to affect the effectiveness of daylight harvesting systems.

 8) By using the double-skin multi-space model in this paper, if the combination of double-skin structure, solar shading, glass, etc. is changed, it is only necessary to change the double-skin solar heat gain diagram, solar heat gain formula, solar shading, the incident angle characteristic approximation formula of glazing and the blind characteristics. This change can be dealt with only by changing the Excel files, and so it is a model with extremely high flexibility and applicability.