Abstract
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.
Highlights
The building sector, responsible for more than one third of the total energy use and associated greenhouse gas emissions [1], needs continuous and constant energy efficiency improvement
The dispersing elements have a relevant impact on the buildings ‘energy consumption [2] and their thermal characteristics can be experimentally studied by means of hot boxes able to recreate real and repeatable operating conditions [3]
Based on the literature review, the following observations can be made: (1) all the analyzed cases employ analog temperature sensors; (2) except for one case, all the analyzed hot box facilities use commercial and separated measuring and control systems; (3) none of the cases analyzed would appear to show the possibility of real-time monitoring the thermal distributions
Summary
The building sector, responsible for more than one third of the total energy use and associated greenhouse gas emissions [1], needs continuous and constant energy efficiency improvement. Hot box experiments require measuring and control systems able to save temperature values from several (order of hundreds) probes and for long-lasting campaigns, and to maintain imposed boundary conditions by controlling the heating and cooling systems that equip the hot box itself. Add to this that the sizes and features of the hot box components directly influence the number of installed probes and, the control system complexity.
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