Energy Digitalization: Main categories, Applications, Merits and Barriers

Editorial – EFE 2020 Energy Fuels Environment Special Issue

Numerical simulations are widely used to evaluate the thermal comfort and energy savings in the ret-rofit of historic buildings. In most cases, however, no detailed data are available on the materials and stratigraphy of the building envelopes, and on-site measurements can be expensive and time consum-ing. The present work uses as a case study a university building characterized by a high thermal capacity in the city of Rome to verify whether the use of natural ventilation can be a practice of use in order to guarantee energy saving and natural comfort. To this end, in the summer of 2020, an experimental campaign was carried out aimed at acquiring thermofluximetric measurements through the vertical walls, the air temperature inside and outside the analyzed environment and the air velocity. Measurements were conducted under three different usage protocols, including night ventilation and 24-hour continuous ventilation. These measurements made it possible to identify the thermophysical characteristics of a wall considered "equivalent" to the real wall, allowing the real-ization of thermofluidodynamic computational models. In particular, in the study, 3 different stra-tigraphies were considered and compared, corre-sponding in the first case to the equivalent wall, in the second to

Modeling and Measurements in Natural Ventilation of Massive Buildings: A Case Study

We present a method and corresponding experimental setup for estimating thermal diffusivities of insulating materials. The setup consists of a boiling water container placed on a heating plate; the test plate is placed atop the boiling water container. Under this condition, both the steady and transient input-response temperature characteristics are measured. We find that the water in its boiling state causes a nearly stable temperature at one side of the test plate. However, this stable condition is reached only after an initial transient period. Rather than using either steady or transient behavior of the response temperature characteristics exclusively in the analysis, we show the potential of using both by combining the experimental observations with the subsequent theoretical and optimization analyses. The proposed method and experimental setup do not require any prior estimation of other parameters. All the necessary information, including the thermal diffusivity, can be estimated from the input-response temperature characteristics only, as we show here.

https://pubs.aip.org/aip/pof/article-pdf/doi/10.1063/5.0152832/18031701/077102_1_5.0152832.pdf

Measurement of the thermal diffusivities of insulating materials using boiling water

On the equivalent thermo-physical properties for modeling building walls with unknown stratigraphy

In recent years, experimental tests related to building components through laboratory facilities have relatively matured. The techniques are based on one-dimensional heat transfer by creating a permanent temperature difference over a specimen to control heat fluxes. The three main methods are the Guarded Hot Box (GHB) method, the Calibrated Hot Box (CHB) method, and the Heat-Flow Meter method (HFM). The HFM method is the most widely applied technique for measuring on-site U-values of building components and several scientific works stressed the need for high temperature differences between the environments, suggesting 10 °C or 15 °C. However, temperature stability and high temperature gradients are difficult to obtain, especially for Mediterranean climatic conditions. Starting from this, an experimental study was conducted through a GHB apparatus, setting temperature differences from 2 °C to 20 °C between the hot and cold chambers. Heat flow measurements were performed to compute the thermal conductance of a specimen characterized by a known stratigraphy, thus highlighting the effect of the low thermal gradient on data acquired by the heat flow sensor. It was found that, even for low temperature differences (2 °C) maintained by ensuring stable thermal conditions, the experimental results are comparable with those obtained for higher and usual temperature differences (20 °C). 

/pdf/how-do-temperature-differences-and-stable-thermal-conditions-1yl39x0d.pdf

Dekun Yin

Papers

On the equivalent thermo-physical properties for modeling building walls with unknown stratigraphy

On the equivalent thermo-physical properties for modeling building walls with unknown stratigraphy

How Do Temperature Differences and Stable Thermal Conditions Affect the Heat Flux Meter (HFM) Measurements of Walls? Laboratory Experimental Analysis