The thermal insulating value of air spaces

Robinson, Henry E; Powlitch, F J

doi:10.6028/nbs.rpt.3030

Cited by 27 publications

(41 citation statements)

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“…These models also used the ASHRAE technique for measuring heat loss through a composite wall, and use the given still l air coefficients, which are used on a Housing Research Paper No. 32 [ 11 ] . The aspect ratio of the gap dimension is completely different from an experimental test performed in this paper, and the paper clearly states that the values apply to the air spaces of uniform thickness with reasonably flat surfaces of moderate smoothness.…”

Section: Reduction In R Valuementioning

confidence: 97%

Cause and Effect of Shrin Kage in Urea Based Foams

Timm¹,

Smith²

1980

Journal of Thermal Insulation

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Shrinkage of urea-based foam insulation has been one of the most quoted and least understood properties of this product. Shrinkage appears to be a very simple property to measure, but because of the irregularity and non-uniformity of the shrinkage, it is most difficult to measure it accurately.Methods of measuring shrinkage can lead to new definitions, as maximum, approximate, and average shrinkage. This paper will present field data of shrinkage measurements which will fall under each of these definitions. Comparisons will be made with actual field measurements and carefully measured controlled shrinkage panels. The irregularities of the gap space, and the anticipated error caused by the limited accuracy of the measuring system are also presented.Shrinkage is caused by a number of different effects, starting with the formulation of chemicals and ending with a rate of curing of the final foam.One of the most profound claims has been the derating of the thermal insulating value caused by the various assumed percentages of shrinkage. The models of these studies are discussed and the results of a comprehensive computer study are presented which show the effective shrinkage to be much less than prior reported claims. A new term -quality factor, must be added to any mathematical model, and this factor can reduce the percentage of derating to an insignificant value, as shown in this paper.

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Section: Reduction In R Valuementioning

confidence: 97%

Cause and Effect of Shrin Kage in Urea Based Foams

Timm¹,

Smith²

1980

Journal of Thermal Insulation

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“…The calculation methods are valid for single air spaces with known conditions. Variations from parallel plane surfaces can be accommodated in some cases by using an average value for the distance across the air space [14,17]. The method for calculating RSI for an enclosed reflective air space generally starts with two equations.…”

Section: Evaluation Of Performancementioning

confidence: 99%

“…In this case E is replaced by a "configuration factor, F 12 " that includes the impact of the emittances of the surfaces 1 and 2 and re-radiation from the bounding surfaces [18]. The radiation transport is subtracted from the hot-box measurement of total heat transfer rate to determine the convective-conduction transport across an enclosed region [14].…”

Section: Evaluation Of Performancementioning

confidence: 99%

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Field evaluation of reflective insulation in south east Asia

Teh¹,

Yarbrough²,

Haw³

et al. 2017

Open Engineering

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Abstract:The objective of this research was to obtain thermal performance data for reflective insulations in a South East Asia environment. Thermal resistance data (RSI, m 2 · K/W) for reflective insulations are well established from 1-D steady-state tests, but thermal data for reflective insulation in structures like those found in South East Asia are scarce. Data for reflective insulations in South East Asia will add to the worldwide database for this type of energyconserving material. RSI were obtained from heat flux and temperature data of three identical structures in the same location. One unit did not have insulation above the ceiling, while the second and third units were insulated with reflective insulation with emittance less than 0.05. RSI for the uninsulated test unit varied from 0.37 to 0.40 m 2 ·K/W. RSI for a single-sheet reflective insulation (woven foil) varied from 2.15 to 2.26 m 2 · K/W, while bubble-foil insulation varied from 2.69 to 3.09 m 2 · K/W. The range of RSI values resulted from differences in the spacing between the reflective insulation and the roof. In addition, the reflective insulation below the roof lowered attic temperatures by as much as 9.7 ∘ C. Reductions in ceiling heat flux of 80 to 90% relative to the uninsulated structure, due to the reflective insulation, were observed.

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“…ここに，A, n は空気層の傾斜角と熱流方向によって決まる数値であり中空層が「垂直」で熱流方向が「水平」の場合，A = 0.035, n = 0.38 26) とする。また，Gr はグラスホフ数(式(7) ) ，Pr はプ…”

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Evaluate on the Thermal Insulation Efficiency and Surface Condensation of Air Supply Window System Applied to Dual Double-Glazed Window

Lee¹,

Kato²

2014

Nihon Kenchiku Gakkai Kankyokei Ronbunshu

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It still remains heat loss and high risk of moisture condensation occurrence at glass of window because they have relatively poor insulating qualities and usually contribute the greatest heat loss in residential buildings. To solve these problems, this paper proposed air supply type airflow window system applied to dual double-glazed window combine with a mechanical ventilator and a heat-recovery heat pump system. The aim of this paper is to evaluate the thermal insulation efficiency and probability of moisture condensation in the proposed system using numerical simulation. To verify its thermal insulation efficiency and probability of moisture condensation, the temperature distribution and the dew-point temperature of the surface of window was calculated. The calculated results show the energy saving efficiency of the proposed system is enhanced approximately 113.10% by airflow effect in comparison with the dual double-pane window. It also shows that it is effective to use low emission film to avoid moisture condensation occurrence.

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The thermal insulating value of air spaces

Cited by 27 publications

References 0 publications

Cause and Effect of Shrin Kage in Urea Based Foams

Cause and Effect of Shrin Kage in Urea Based Foams

Field evaluation of reflective insulation in south east Asia

Evaluate on the Thermal Insulation Efficiency and Surface Condensation of Air Supply Window System Applied to Dual Double-Glazed Window

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