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Sunday, July 26, 2020 | History

3 edition of Effect of condensation on performance and design of extended surfaces found in the catalog.

Effect of condensation on performance and design of extended surfaces

Virgil J. Lunardini

Effect of condensation on performance and design of extended surfaces

by Virgil J. Lunardini

  • 396 Want to read
  • 28 Currently reading

Published by US Army Corps of Engineers, Cold Regions Research & Engineering Laboratory, Available from NTIS in [Hanover, N.H.], [Springfield, Va .
Written in English

    Subjects:
  • Condensation,
  • Surfaces (Physics),
  • Heat-transfer media,
  • Heat -- Transmission

  • Edition Notes

    StatementVirgil J. Lunardini and Abdul Aziz ; prepared for Army Research Office.
    SeriesCRREL report -- 95-20.
    ContributionsAziz, Abdul., United States. Army Research Office., Cold Regions Research and Engineering Laboratory (U.S.)
    The Physical Object
    Paginationvii, 49 p. :
    Number of Pages49
    ID Numbers
    Open LibraryOL17604013M
    OCLC/WorldCa34089025

    The higher the relative humidity, the warmer a surface temperature needs to be in order to avoid condensation. To reduce the likelihood of condensation, refer to the chart below for recommended maximum percentage of indoor relative humidity based upon varying outdoor air temperatures with an indoor air temperature of 70°F/20°C. surface texture play a crucial role in stabilizing the lubricant and reducing pinning of the condensate. With properly engineered surfaces to promote dropwise condensation of low-surface tension fluids, we demonstrate a four to eight-fold improvement in the heat transfer coefficient.

    Heat Exchangers 73 individual thermal resistances of the system. Combining each of these resistances in series gives: 1 UA = 1 (ηohA)i 1 Skw 1 (ηohA)o () where η0 is the surface efficiency of inner and outer surfaces, h is the heat transfer coefficients for the inner and outer surfaces, and S is a shape factor for the wall. Condensation happens when moisture in the air (vapor) hits a cool enough surface to convert the vapor into water. The moisture condenses from a gas to a liquid, and then it drips into a puddle. The temperature that triggers condensation is the dew point. It's like the opposite of .

    condensation formation on interior fenestration surfaces. This paper compares the differences between the performance of fenestration products relative to U-factor and condensation resistance and outlines principal design features to improve the latter. The results show that water condensation can be increased by 40% by rationally designing the geometry of the condensation surface. However, the condensation rate in the atmospheric environment is relatively slow due to the presence of non-condensable gas. In order to increase the condensation rate, a relatively pure vapor environment is desired.


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Effect of condensation on performance and design of extended surfaces by Virgil J. Lunardini Download PDF EPUB FB2

Get this from a library. Effect of condensation on performance and design of extended surfaces. [Virgil J Lunardini; Abdul Aziz; United States. Army Research Office.; Cold Regions Research and Engineering Laboratory (U.S.)]. Effect of Condensation on Performance and Design of Extended Surfaces Article (PDF Available) November with Reads How we measure 'reads'.

{{Citation | title=Effect of condensation on performance and design of extended surfaces / Virgil J. Lunardini and Abdul Aziz ; prepared for Army Research Office | author1=Lunardini, Virgil J | author2=Aziz, Abdul | author3=United States.

But the omniphobic surfaces developed so far suffer from a major problem: Condensation can quickly disable their liquid-shedding properties. Now, researchers at MIT have found a way to overcome this effect, producing a surface design that drastically reduces the effects of condensation, although at a slight sacrifice in performance.

A large temperature jump is observed between the liquid and the hydrophobic solid surface, which causes the dropwise condensation to lose its advantage in condensation heat transfer enhancement.

Instead, the hydrophilicity of the solid surface can reduce the interfacial thermal resistance and improve the heat transfer performance by:   Low energy surfaces to promote dropwise condensation are manufactured cheaper than extended surfaces to improve gas side heat transfer in condensers.

Therefore, considerable effort has been put into coatings and other surface treatments of metal heat exchanger surfaces to change the mode of condensation from filmwise to dropwise [13], [ Book January maximum condensation performance can be achieved.

The effect of surface roughness on the cluster growth is relatively insignificant and the experimental. Further, the effect of thin films studied in this report makes a significant contribution as indicated by C. The combined contribution ofB and C reaches a value between times the Nusselt prediction, being a little insignificant for the design of high performance condensation surfaces.

Although oil infusion of structured surfaces has recently been shown to render filmwise condensation dropwise in many cases, challenges remain in the case of extremely low-surface-tension fluids.

This work aims to provide a unified experimental platform and study the impact of mini/micro/nanostructures on condensation heat transfer of low. Surfaces (ISSN ) is a peer-reviewed open access journal covering all aspects of surface and interface science, and it is published online quarterly by MDPI.

Open Access —free for readers, with article processing charges (APC) paid by authors or their institutions.; Rapid Publication: manuscripts are peer-reviewed and a first decision provided to authors approximately days. Condensation affects the performance of buildings, causing problems such as: Mould growth, which can be a cause of respiratory allergies.

geometry of the condensation surface. However, the condensation in the atmospheric rate environment is relatively slow due to the presence of non-condensable gas. In order to increase the condensation rate, a relatively pure vapor environment is desired, in which condensed water will be the major heat transfer barrier.

condensation. In metal building systems, we are concerned with two different areas or locations: visible condensation which occurs on surfaces below dew point temperatures; and concealed condensation which occurs when moisture has passed into interior regions and then condenses on a surface that is below the dew point temperature.

Internal surface condensation can promote mould growth, thus reducing indoor air quality, as well as creating unsightly pattern staining.

Thermal bridges can undermine effective insulation and can contribute to the formation of surface condensation as the heat is drawn out, leaving the inner surface cold.

The third way fin performance can be described is with overall surface efficiency, η o = Q ˙ t h A t θ b, {\displaystyle \eta _{o}={\frac {{\dot {Q}}_{t}}{hA_{t}\theta _{b}}},} where A t {\displaystyle A_{t}} is the total area and Q ˙ t {\displaystyle {\dot {Q}}_{t}} is the sum of the.

When condensation builds up for an extended period of time it can cause corrosion of metal framing, sheeting, foil sarking or any metal components that have not been designed to tolerate such moisture.

The difference between fog and clouds which form above the Earth's surface is that rising air is not required to form fog. Fog develops when air having a relatively high humidity comes in contact with a colder surface, often the Earth's surface, and cools to the dew point.

Additional cooling leads to condensation and the growth of low-level clouds. Closure to “Discussion of ‘Condensation on an Extended Surface’” (, ASME J. Heat Transfer,pp. The most common and best understood case of condensation heat transfer is that of film condensation of a pure quiescent vapor on a solid surface.

The problem of calculating the heat transfer rate for a plane vertical surface and for a horizontal cylinder with uniform surface temperatures, and where the condensate flow is laminar and governed. On the super-hydrophobic surface with β = (θ ≈ °), as shown in Fig. 2a–d, no condensation gh the number of clusters increases after the surface is cooled (), n max.

Shah RK, Zhou SQ, Tagavi KA () The role of surface tension in film condensation in extended surface passages. J Enhanc Heat Transf 6(2–4)– CrossRef Google Scholar Shekriladze IG, Gomelauri VI () Theoretical study of laminar film condensation of flowing vapour.

2. Condensation and Mold In or On Ducts. Condensation occurs when air is humid and surfaces are cold. To be more specific, the temperature of the surface has to be at or below the dew point temperature of the air for condensation to occur.

A .High-performance windows create warmer interior glass surfaces, reducing frost and condensation. High-performance windows with warm edge technology and insulating frames have such a warm interior surface that condensation on any interior surfaces is significantly reduced under all conditions.

Condensation occurs when the interior surface temperature of the glass drops below either the .