PMC

Relative contribution of normalized heat transfer coefficients to the total leaf heat transfer coefficient in response to wind speed of light-adapted leaves. Heat transfer coefficient for evapotranspiration heat (h_λE) in dark grez, heat transfer coefficient for convective heat (h_H) in light grey, and heat transfer coefficient for long-wave radiative heat (h_LW) in white. (A) Spring barley (Hordeum vulgare) and (B) common bean (Phaseouls vulgaris). Areas represent mean values of n = 9 single leaves for barley and n = 10 single leaves for bean.

Heat transfer measurement. (a) Heat flux and (b) heat transfer coefficient as a function of logarithmic mean temperature difference. The slope in (a) is the heat transfer coefficient (). The heat transfer coefficient for DWC and IOC are nearly identical at ≈ 80 kW/m² K; a sevenfold increase from FWC (≈ 12 kW/m² K). The heat transfer coefficient increased further by ≈ 30% to ≈ 103 kW/m² K when the silica pores were impregnated with oil (SLIPS condensation). The classical Nusselt model for laminar film condensation is used to validate our heat transfer measurements.

5R1C model, with five temperatures (ϑ) and four heat flows (ϕ), according to ISO 13790. Abbreviations and symbols: ϕ_hc (heat flow for heating and cooling), ϕ_conv (convective heat flow), ϕ_rad,s (radiative heat flow to the surfaces) and ϕ_rad,m (radiative heat flow to the thermal building mass; ϑ_f (air temperature close to the façade, ϑ_e (outside temperature) ϑ_i (room air temperature), ϑ_s (surface temperature) and ϑ_m (thermal mass temperature); H_V (heat transfer coefficient due to ventilation), H_T (heat transfer coefficient due to transmission), H_T,em (heat transfer coefficient due to transmission between ambient air and thermally heavy, opaque components), H_T,es (heat transfer coefficient due to transmission between ambient air and massless, transparent components), H_T,is (heat transfer coefficient room air and interior surface) and H_T,ms (heat transfer coefficient due to transmission between interior surface and building mass); C (storage capacity).

Experimental results for (a) heat flux and (b) heat transfer coefficient as a function of wall superheat temperature. Increased performance is seen for five of the six bi-conductive surfaces, corresponding to those with wavelengths of P = 1.2–3.7 mm. A decrease in performance is seen for the P = 0.96 mm design.