Bidirectional transmittance of transparent windows with external or backside condensation of nonabsorbing cap-shaped droplets

Huang, Yong; Cao, Feng; Hoeniges, Jack; Zhu, Keyong; Pilon, Laurent

doi:10.1016/j.jqsrt.2020.107039

Cited by 9 publications

(14 citation statements)

References 36 publications

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“…Interestingly, both the normal-hemispherical transmittance T nh and the directional-hemispherical transmittance T dh of the droplet-covered window were found to be independent of droplet size distribution and droplet spatial arrangement. Similar results were observed for the bidirectional transmittance T bd [7]. The normal-hemispherical transmittance T nh was nearly independent of contact angle θ c until it reached the critical angle θ cr for total internal reflection at the droplet/air interface, i.e., for θ c < θ cr .…”

Section: Background 21 Light Transfer Through Droplet-covered Pbr Win...supporting

confidence: 80%

“…The interaction between light and droplet-covered windows has been studied both analytically [7,8,[10][11][12] and experimentally [11,[13][14][15][16][17]. Zhu et al [8] simulated visible light transfer through a transparent window covered with non-absorbing cap-shaped water droplets on its back side.…”

Section: Background 21 Light Transfer Through Droplet-covered Pbr Win...mentioning

confidence: 99%

“…Light transfer through the droplet-covered windows was simulated using the Monte Carlo ray-tracing method [7,8,12]. To do so, the following assumptions were made [8]:…”

Section: Assumptionsmentioning

confidence: 99%

“…When the culture is covered by a transparent window, evaporation leads to the formation of water droplets on the interior surface of the PBR cover, as illustrated in Figure 1b. However, the presence of droplets on the back side of a window has been shown to reduce its transmittance and change the direction of the transmitted light [7,8]. Both of these phenomena could impact the PBR biomass productivity [4,9].…”

Section: Introductionmentioning

confidence: 99%

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Impact of Dropwise Condensation on the Biomass Production Rate in Covered Raceway Ponds

et al. 2021

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This study investigates the effect of condensed water droplets on the areal biomass productivity of outdoor culture systems with a free surface, protected by a transparent window or cover to prevent contamination and to control the growth conditions. Under solar radiation, evaporation from the culture causes droplets to condense on the interior surface of the cover. To quantify the effect of droplets on the system’s performance, the bidirectional transmittance of a droplet-covered window was predicted using the Monte Carlo ray-tracing method. It was combined with a growth kinetics model of Chlorella vulgaris to predict the temporal evolution of the biomass concentration on 21 June and 23 September in Los Angeles, CA. A droplet contact angle of 30∘ or 90∘ and a surface area coverage of 50% or 90% were considered. Light scattering by the condensed droplets changed the direction of the incident sunlight while reducing the amount of light reaching the culture by up to 37%. The combined effect decreased the daily areal biomass productivity with increasing droplet contact angle and surface area coverage by as much as 18%. Furthermore, the areal biomass productivity of the system was found to scale with the ratio X0/a of the initial biomass concentration X0 and the specific illuminated area a, as previously established for different photobioreactor geometries, but even in the presence of droplets. Finally, for a given day of the year, the optical thickness of the culture that yielded the maximum productivity was independent of the window condition. Thus, the design and operation of such a system should focus on maintaining a small droplet contact angle and surface area coverage and an optimum optical thickness to maximize productivity.

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Section: Background 21 Light Transfer Through Droplet-covered Pbr Win...supporting

confidence: 80%

Section: Background 21 Light Transfer Through Droplet-covered Pbr Win...mentioning

confidence: 99%

“…Light transfer through the droplet-covered windows was simulated using the Monte Carlo ray-tracing method [7,8,12]. To do so, the following assumptions were made [8]:…”

Section: Assumptionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Impact of Dropwise Condensation on the Biomass Production Rate in Covered Raceway Ponds

et al. 2021

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“…5g), where the incident sunlight can be further reduced due to backscattering by the condensed droplets. 88 Third, the single-stage desalination device based on the back-side evaporator can be easily upgraded to a multistage device using a modular design (discussed in Section 3.3). On the other hand, as mentioned in Section 2.1, a potential drawback of the back-side design is the limited water transport capability due to the water supply from the side of the evaporator.…”

Section: Single-stage Solar Desalination Device Configurationsmentioning

confidence: 99%