Experimental and numerical analysis of solar-absorbing metallic facade panel with embedded heat-pipe-array

The integrative performance of advanced building facade is important for sustainable building development. This paper introduces two solar-absorbing curtain-wall panels with embedded straight-heat-pipe and heat-pipe-ring respectively. Taking advantage of the high thermal conductance of heat pipe, the proposed solar-absorbing aluminum panels can preheat cold water, like for the domestic hot water supply. They also reduce the solar transmission to the indoor space. In hot summer, the dual effect leads to considerable energy saving in both the hot-water and the air-conditioning systems. Comparing with the water-tubing collector panel, the heat-pipe type has wider application by eliminating the water-freezing problem. The conceptual design, prototype construction and computer-model development of these two panels are discussed in this paper. Measurements were taken with the two prototypes installed at an outdoor environmental chamber. Dynamic simulation models were then developed through the control volume finite difference method, and validated with the measured data. The simulation models can be used in advanced building simulation tools for transient thermal performance analysis. Further numerical analysis with these models showed that comparatively, the innovative heat-pipe-ring is the more promising design because of the effective increase in solar absorbing surface area. In the studied warm climate scenarios from summer to winter and from sunny to cloudy conditions, the water heat gain efficiency was estimated from 62.5% to 94.9% in all cases with the glazed panel. The estimated room heat gain/loss as well as the electricity saving performance are also attractive.