Performance Evaluation of a Guarded Hot Box U-value Measurement Facility under Different Software based Temperature Control Strategies

Ghosh, A.; Ghosh, Sibdas; Neogi, Subhasis

doi:10.1016/j.egypro.2014.07.287

Cited by 20 publications

(11 citation statements)

References 2 publications

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“…Due to the latter feature, no useful guideline was found in literature to support the design process: the only technical standard available [17] deals with guarded (GHB) and calibrated (CHB) hotboxes, which are both designed to investigate steady state properties of conventional building envelope components, likewise in [18][19][20]. In literature, even when Dynamic Insulation walls were involved [10], a basic setup was used, allowing only a partial control of temperature boundary conditions.…”

Section: Methodsmentioning

confidence: 99%

Experimental investigation of the steady state behaviour of Breathing Walls by means of a novel laboratory apparatus

Alongi

Angelotti

Mazzarella

2017

Building and Environment

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Breathing Walls are envelope components, based on porous materials, crossed by a natural or forced airflow. Since they behave both as recovery heat exchangers and active insulation, reducing the conductive heat flux, they represent a promising envelope technology, allowing to reduce energy consumption in buildings.From the modeling point of view, an analytical model can be found in literature, describing heat and mass transfer across Breathing Walls in steady state conditions. However, to the best of the authors' knowledge, the model lacks an exhaustive experimental validation. Therefore, in this paper, the novel laboratory apparatus named Dual Air Vented Thermal Box developed at Politecnico of Milano is presented. The apparatus is used to experimentally investigate the steady state behavior of a 1 m 2 Air Permeable Concrete sample, crossed by an airflow at different velocities up to 12 mm/s.The temperature profile inside the sample, measured in different positions, is compared with the model predictions. While in the central portion of the wall a very good agreement is found, the experimental results at the top and at the bottom of the wall suggest a non-uniform velocity field entering the sample. A qualitative confirmation of this hypothesis is provided by CFD simulations on the apparatus, clearly showing a mixed convection regime on both sides of the wall. The results lead to state the validity of the one-dimensional analytical model in literature, although a careful application should take into account adjusted boundary conditions, consisting in an airflow velocity possibly variable with height.

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Section: Methodsmentioning

confidence: 99%

Experimental investigation of the steady state behaviour of Breathing Walls by means of a novel laboratory apparatus

Alongi

Angelotti

Mazzarella

2017

Building and Environment

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“…In addition to the above-mentioned Standards, for the construction and use of the hot box, useful suggestions were taken in the following studies [19][20][21]. Furthermore, other suggestions were taken in studies on the thermal characterization of the materials carried out in a simplified manner [22][23][24].…”

Section: Standard and Scientific Sourcesmentioning

confidence: 99%

Steady-State Thermal Properties of Rectangular Straw-Bales (RSB) for Building

Conti¹,

Barbari²,

Monti³

2016

Buildings

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Abstract:Straw is an inevitable product of cereal production and is available in huge quantities in the world. In order to use straw-bales as a building material, the characteristic values of the thermal performances should be determined. To not lose the benefits of the cheapness and sustainability of the material, the characteristics must be determined with simple and inexpensive means and procedures. This research aims to implement tools and methods focused at the determination of the thermal properties of straw-bales. For this study, the guidelines dictated by ASTM and ISO were followed. A measurement system consisting of a Metering Chamber (MC) was realized. The MC was placed inside a Climate Chamber (CC). During the test, a known quantity of energy is introduced inside MC. When the steady-state is reached, all the energy put into MC passes through its walls in CC, where it is absorbed by the air-conditioner. A series of thermopiles detect the temperature of the surfaces of the measurement system and of the specimen. Determining the amount of energy transmitted by the various parts of MC and by the specimen, it is possible to apply Fourier's law to calculate the thermal conductivity of the specimen.

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“…Therefore, the literature review shows that the calibrated hot box is the most used [3,4,6,13,17,19,20,[23][24][25][26]28,30,32,33,36,37] followed by the guarded hot box [5,7,14,15,18,21,22,29,31,34,35] and the simple hot box [16,27,38]. The measuring systems always employ analog probes and the thermocouples are more widely used [3][4][5][6][13][14][15][16]18,[21][22][23][24][25][26][27]29,31,[33][34]…”

Section: Common Systems and Literature Backgroundmentioning

confidence: 99%

“…The number of probes installed that, as mentioned, depends on the size of the hot box, is very variable: some cases have less than 20 probes [13,16,19,20,27,28,38], most cases have a number of probes between 20 and 100 [4][5][6]14,15,[23][24][25]33,36], while in three cases there are more than 100 probes [34,35,37]. The measuring and control systems are mainly commercial [3,6,7,16,[19][20][21][23][24][25]27,28,31,33,37] except for one customized system [17].…”

Section: Common Systems and Literature Backgroundmentioning

confidence: 99%

Integrated Measuring and Control System for Thermal Analysis of Buildings Components in Hot Box Experiments

et al. 2019

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In this paper, a novel integrated measuring and control system for hot box experiments is presented. The system, based on a general-purpose microcontroller and on a wireless sensors network, is able to fully control the thermal phenomena inside the chambers, as well as the heat flux that involves the specimen wall. Thanks to the continuous measurements of air and surfaces temperatures and energy input into the hot chamber, the thermal behavior of each hot box component is analyzed. A specific algorithm allows the post-process of the measured data for evaluating the specimen wall thermal quantities and for creating 2D and 3D thermal models of each component. The system reliability is tested on a real case represented by a double insulating X-lam wall. The results of the 72 h experiment show the system’s capability to maintain stable temperature set points inside the chambers and to log the temperatures measured by the 135 probes, allowing to know both the U-value of the sample (equal to 0.216 ± 0.01 W/m2K) and the thermal models of all the hot box components. The U-value obtained via hot box method has been compared with the values gathered through theoretical calculation and heat flow meter measurements, showing differences of less than 20%. Finally, thanks to the data postprocessing, the 2D and 3D thermal models of the specimen wall and of the chambers have been recreated.

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Performance Evaluation of a Guarded Hot Box U-value Measurement Facility under Different Software based Temperature Control Strategies

Cited by 20 publications

References 2 publications

Experimental investigation of the steady state behaviour of Breathing Walls by means of a novel laboratory apparatus

Experimental investigation of the steady state behaviour of Breathing Walls by means of a novel laboratory apparatus

Steady-State Thermal Properties of Rectangular Straw-Bales (RSB) for Building

Integrated Measuring and Control System for Thermal Analysis of Buildings Components in Hot Box Experiments

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