Thermal Conductivity Measurements By Means of a New ‘Small Hot-Box’ Apparatus: Manufacturing, Calibration and Preliminary Experimental Tests on Different Materials

Buratti, Cinzia; Belloni, Elisa; Lunghi, Leandro; Barbanera, Marco

doi:10.1007/s10765-016-2052-2

Cited by 38 publications

(31 citation statements)

References 20 publications

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“…where: In the implementation of Equations (5) and (6), the sample transmittance τ (λ) and reflectance ρ(λ) of the whole sample are the ones measured in [18]; the transmittance and reflectance of the glass layers were measured by using the same experimental facility and methodology.…”

Section: Simplified Methodology For the Calculation Of The Solar Heatmentioning

confidence: 99%

“…The solar factor value was finally calculated as the sum of the solar direct transmittance, measured in [18], and the calculated q i .…”

Section: Simplified Methodology For the Calculation Of The Solar Heatmentioning

confidence: 99%

“…The apparatus known as Small Hot Box [18] was used for measuring the thermal properties of the sample ( Figure 2); it was designed, built, and calibrated by preliminary measurements at the University of Perugia (Laboratory of Environmental Control, Department of Engineering). The experimental apparatus consists of a hot chamber with external dimensions of 0.94 × 0.94 × 0.50 m 3 : the walls are made of wood panels (20 mm thick) and of an internal insulation layer of about 200 mm thickness, in order to minimize the heat flux.…”

Section: Thermal Resistance Measurementsmentioning

confidence: 99%

“…Finally, the solar factor (Table 4) was estimated on the basis of the methodology shown in paragraph 2.3, starting from optical data reported in [18] and the results of thermal tests (Table 3). 0.62 [18] 0.19 [18] 0.08 0.70…”

Section: Thermal and Solar Propertiesmentioning

confidence: 99%

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Experimental and Numerical Energy Assessment of a Monolithic Aerogel Glazing Unit for Building Applications

et al. 2019

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In the last few decades, the attention of researchers has been focused on the characterization of aerogels in order to improve the thermal performance of transparent building envelopes. Granular aerogel is already spread in the market thanks to the easy manufacturing system, whereas the difficulty in producing monoliths without defects, cracks, and inhomogeneity limited the diffusion of monolithic aerogel systems. A new production process for the monolithic panels was developed at Union College (Schenectady, NY, USA); it is a rapid supercritical extraction technique which allows a reduction in production time (only a few hours) and results in less solvent waste. Panes with maximum dimensions of about 100 × 100 mm were fabricated and composed in a unique glazing system, with external dimensions 300 × 300 mm. The thermal characterization of the innovative monolithic aerogel glazing system (simple float glazing 4.7-mm-thick monolithic aerogel pane 15-mm-thick simple float glazing 4.7 mm thick), which was carried out by means of a Small Hot Box apparatus, showed a thermal transmittance value of about 1.1 W/(m 2 K). Data was used in dynamic simulations of a typical non-residential building. They showed that the new investigated solution allows a valuable reduction with respect to a low-e double glazing system in terms of heating energy demand (about 5-7% for Helsinki, 8-12% for Paris, and 10-15% for Turin), for different window-to-wall ratios. monolithic form is the difficulty in fabrication of samples without defects, cracks, and inhomogeneity, and their high cost [5]. In the last years, a rapid supercritical extraction method was developed at Union College (Schenectady-NY), allowing a significant reduction in fabrication times (6-8 hours) and in solvent waste. Good optical properties can be obtained (τ v > 80%); when assembled with two glasses (total thickness 22 and 12.7 mm of aerogel), a thermal resistance of 0.86 and 1.55 m 2 K/W is obtained at atmospheric pressure and in evacuated conditions, respectively [6,7].Guoqing Zu et al. evaluated the thermal performance of monolithic alumina aerogel systems, prepared by a sol-gel method combined with the ethanol supercritical drying technique [8]. The thermal conductivities at 30 • C and 400 • C were 0.028 and 0.065 W/mK, respectively [8]. Duer and Svendsen [9] presented the main results of a research project founded by the European Commission. They discussed an aerogel pane prototype of 450×450x15 mm 3 , made under vacuum conditions and sandwiched between two glasses; a conductivity value of about 0.010 W/mK was measured at ambient temperature.Another interesting study presents a detailed investigation of the mechanical microstructural and thermal properties of monolithic aerogels made from polyethoxydisiloxane [10]. The thermal conductivity is highly dependent on the densities of monolithic panes; a minimum value of 0.0135 W/mK was measured for a density of 120 kg/m 3 , a maximum value of 0.024 W/mK for about 300 kg/m 3 . Similar values of thermal conductivity were fo...

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Section: Simplified Methodology For the Calculation Of The Solar Heatmentioning

confidence: 99%

“…The solar factor value was finally calculated as the sum of the solar direct transmittance, measured in [18], and the calculated q i .…”

Section: Simplified Methodology For the Calculation Of The Solar Heatmentioning

confidence: 99%

Section: Thermal Resistance Measurementsmentioning

confidence: 99%

Section: Thermal and Solar Propertiesmentioning

confidence: 99%

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Experimental and Numerical Energy Assessment of a Monolithic Aerogel Glazing Unit for Building Applications

et al. 2019

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“…The test material is placed between two rooms maintained at different temperatures (so-called hot and cold chambers), the external envelops of the chambers should be well insulated to reduce heat loss. The thermal resistance of the test films could be calculated by the power needed to maintain the hot chamber at constant temperature as well as to maintain a temperature difference between the hot and cold chambers (Buratti et al, 2016). There are two methods for the laboratory measurement of overall heat transfer coefficient: guarded and calibrated hot box methods.…”

Section: Introductionmentioning

confidence: 99%

Development of a model to calculate the overall heat transfer coefficient of greenhouse covers

Rasheed

Lee

2018

Span. j. agric. res.

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A Building Energy Simulation (BES) model based on TRNSYS, was developed to investigate the overall heat transfer coefficient (U-value) of greenhouse covers including polyethylene (PE), polycarbonate (PC), polyvinyl chloride (PVC), and horticultural glass (HG). This was used to determine the influences of inside-to-outside temperature difference, wind speed, and night sky radiation on the U-values of these materials. The model was calibrated using published values of the inside and outside convective heat transfer coefficients. Validation of the model was demonstrated by the agreement between the computed and experimental results for a singlelayer PE film. The results from the BES model showed significant changes in U-value in response to variations in weather parameters and the use of single or double layer greenhouse covers. It was found that the U-value of PC, PVC, and HG was 9%, 4%, and 15% lower, respectively, than that for PE. In addition, by using double glazing a 34% reduction in heat loss was noted. For the given temperature U-value increases as wind speed increases. The slopes at the temperature differences of 20, 30, 40, and 50 °C, were approximately 0.3, 0.5, 0.7, and 0.9, respectively. The results agree with those put forward by other researchers. Hence, the presented model is reliable and can play a valuable role in future work on greenhouse energy modelling.

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Thermal Conductivity Characterization of Industrial Small-Sized Building Materials: Experimental and Simulation Study

Charai

Sghiouri

Mezrhab

et al. 2021

Emerging Research in Sustainable Energy and Buildings for a Low-Carbon Future

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Thermal Conductivity Measurements By Means of a New ‘Small Hot-Box’ Apparatus: Manufacturing, Calibration and Preliminary Experimental Tests on Different Materials

Cited by 38 publications

References 20 publications

Experimental and Numerical Energy Assessment of a Monolithic Aerogel Glazing Unit for Building Applications

Experimental and Numerical Energy Assessment of a Monolithic Aerogel Glazing Unit for Building Applications

Development of a model to calculate the overall heat transfer coefficient of greenhouse covers

Thermal Conductivity Characterization of Industrial Small-Sized Building Materials: Experimental and Simulation Study

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