Numerical analysis on the advantages of evacuated gap insulation of vacuum-water flow window in building energy saving under various climates

A novel triple glazing vacuum-water flow window combining the advantages of water medium window and vacuum glazing is proposed in the current study. Its thermal performance as compared to double glazing water flow window was analyzed numerically under various climates. The application of an evacuated gap is proven quite effective in reducing heat flow through the window. In typical cities with cold, hot summer cold winter, and hot summer warm winter climates, room heat gains through the window can be reduced by 43%, 44% and 42% during cooling operation. The contribution is more significant under stronger solar radiation condition. In heating operation, warm water supply is beneficial in reducing room heat loss through the window. Heat loss to ambient from the warm water layer is lessened and heat transfer inward to room space can be enhanced with thermal insulation of the evacuated gap. The benefit of active heating with warm water and evacuated gap insulation is more significant in climate with lower ambient temperature and larger heating demand. Stabilizing the inner glazing temperature and improving the indoor thermal comfort level is another advantage of the evacuated gap insulation.