Transpiring artificial leaves

Morrison, John E.; Barfield, B. J.

doi:10.1016/0002-1571(81)90047-9

Cited by 16 publications

(15 citation statements)

References 8 publications

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“…The convective heat transfer coefficient for green wall in the energy balance model (Susorova et al, 2013) is approximated with the same correlation as for bare wall case (h vw ≈ h bw = 10.79 + 4.192V , where V is the air speed at the bare façade). In this work, we intend to explore the other relevant correlations (Deardorff, 1978;Stanghellini, 1987;Morrison Jr and Barfield, 1981;Ayata et al, 2011;Campbell and Norman, 2012;ASHRAE, 2020) as mentioned in the recent work of Convertino et al (Convertino et al, 2019b). The expressions of convective heat transfer coefficients are summarized in Appendix B.…”

Section: Impact Of Convective Heat Transfer Coefficientmentioning

confidence: 99%

Numerical analysis of the performance of green façades

Poupart¹,

Martine²,

Christiansen³

et al. 2021

Linköping Electronic Conference Proceedings

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This study reports a numerical analysis of the performance of green façades in different geographical locations and seasonal conditions. A mathematical model from a previous study is implemented and combined with the modified convective heat transfer coefficients from a recent study of the literature to simulate the transient heat transfer through bare walls and green facades with climbing vegetation. An implicit Finite Difference Method (FDM) based solver is used to perform the numerical simulations. Climate data are taken from relevant weather stations in Oslo and Rome and typical meteorological year (TMY) values are used for this purpose together with variable thermo-physical properties of air. An energy budget analysis reveals that the shortwave radiation term and convective heat transfer term are predominating compared to the other terms involved in the energy balance equation for summer time. The results show that the green walls are most effective in summer seasons with high levels of solar radiation, as most of the cooling effect is credited to the vegetation blocking the solar radiation. In cooler seasons, the benefit is less prominent. Furthermore, an analysis of the effects of the different models of convective heat transfer coefficients is presented.

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Section: Impact Of Convective Heat Transfer Coefficientmentioning

confidence: 99%

Numerical analysis of the performance of green façades

Poupart¹,

Martine²,

Christiansen³

et al. 2021

Linköping Electronic Conference Proceedings

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“…Many kinds of artificial leaves have been used in physical studies on leaf boundary layers (Parkhurst et al, 1968;Thom, 1968;Grace et al, 1980;Morrison & Barfield, 1981;Dixon «fe Grace, 1983). In this experiment, a cucumber leaf was modelled by using a pair of 0.1-mm-thick brass sheets between which a microheater of 0.1 mm constantan wire was sandwiched.…”

Section: Model Leavesmentioning

confidence: 99%

“…For convective heat and mass transfer between leaf and air, forced convection and free convection hitherto have been examined separately (e.g. Parkhurst et al, 1968;Grace, Fasehun & Dixon, 1980;Morrison & Barfield, 1981;Dixon & Grace, 1983). Forced convection is caused by the inertial force of wind and depends on the Reynolds number (Re) which increases with wind velocity.…”

Section: Introductionmentioning

confidence: 99%

Buoyancy effect on forced convection in the leaf boundary layer

Kitano

Eguchi

1990

Plant Cell & Environment

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Abstract. Mixed convection (forced convection plus free convection) in the leaf boundary layer was examined by air flow visualization and by evaluation of the boundary layer conductance at different leaf‐air temperature differences (TL‐TA) under low wind velocities. The visualized air flow was found to become more unstable and buoyant at higher TL‐TA. An ascending longitudinal plume was induced along the upper surface, and the air flow along the lower surface ascended after passing the trailing leaf edge. The air flow modified by buoyancy was considered to result in an increase in boundary layer conductance (GA) for mixed convection, which became higher with higher TL‐TA as compared with the conductance for pure forced convection without buoyancy. This increase in GA appeared larger at larger Grashof number (Gr) and at smaller Reynolds number (Re). The dependences of buoyancy effect on Gr and Re were related to ‘edge‐effects’.

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“…So far, studies using artificial leaves with dimensions and pore sizes similar to real leaves have not been published. Morrison Jr. and Barfield (1981) presented a thin artificial leaf design of similar shape and size to a tobacco leaf, consisting of teflon membrane disks sandwiching a filter paper and an external water supply consisting of cotton wicks, with a total leaf thickness of 0.42 mm. This could easily be combined with some of the above-mentioned perforated foils in order to obtain a more realistic physical model of a real leaf, but surprisingly, we have not found any such experiments in the literature.…”

Section: Introductionmentioning

confidence: 99%

Technical note: An experimental set-up to measure latent and sensible heat fluxes from (artificial) plant leaves

Schymanski

Breitenstein

2017

Hydrol. Earth Syst. Sci.

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Abstract. Leaf transpiration and energy exchange are coupled processes that operate at small scales yet exert a significant influence on the terrestrial hydrological cycle and climate. Surprisingly, experimental capabilities required to quantify the energy-transpiration coupling at the leaf scale are lacking, challenging our ability to test basic questions of importance for resolving large-scale processes. The present study describes an experimental set-up for the simultaneous observation of transpiration rates and all leaf energy balance components under controlled conditions, using an insulated closed loop miniature wind tunnel and artificial leaves with pre-defined and constant diffusive conductance for water vapour. A range of tests documents the above capabilities of the experimental set-up and points to potential improvements. The tests reveal a conceptual flaw in the assumption that leaf temperature can be characterized by a single value, suggesting that even for thin, planar leaves, a temperature gradient between the irradiated and shaded or transpiring and non-transpiring leaf side can lead to bias when using observed leaf temperatures and fluxes to deduce effective conductances to sensible heat or water vapour transfer. However, comparison of experimental results with an explicit leaf energy balance model revealed only minor effects on simulated leaf energy exchange rates by the neglect of cross-sectional leaf temperature gradients, lending experimental support to our current understanding of leaf gas and energy exchange processes.

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Transpiring artificial leaves

Cited by 16 publications

References 8 publications

Numerical analysis of the performance of green façades

Numerical analysis of the performance of green façades

Buoyancy effect on forced convection in the leaf boundary layer

Technical note: An experimental set-up to measure latent and sensible heat fluxes from (artificial) plant leaves

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