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In Feerie pour une autre fois II (also titled Normance), Celine recounts the chaos engendered by the Allied bombing of Paris in April 1944, which killed 1,800 people in seven days. The novel, publi...

A Haitian writer who left his island at the age of twenty-one, Jean-Claude Charles was a particular type of exile. As he explains in his concept of “rooting” that he himself created, he did not get...

In this paper, the coupled heat and mass transfer within porous media has been studies. First, the studied materials have been characterized experimentally and than evaluated their thermal properties, namely thermal conductivity and specific heat in different states (dry-wet). The hygroscopic properties, namely water vapour permeability, water vapour sorption. At second time, we present and validate the mathematical model describing heat and mass transfer within bio-based materials, by the confrontation with the experimental results. The materials properties obtained from the characterisation part are used as model?s input parameters. Moreover, a test facility is mounted in the laboratory in order to compare the numerical and experimental data. The founded results show a good concordance between the simulated and measured data. According to this results the mathematical model of Philip and de Vries gives a good prediction of hygrothermal behaviour of bio-based material. This model will allow us to save money and time of the experimental part in the future.

An energy pile equipped with a W-type heat exchange pipe was constructed in reclaimed soft ground, which is fabricated in a large-diameter cast-in-place pile. The diameter of the energy pile is 1.5 m and the drilled depth reaches to a 60 m whilst the heat exchange pipe is inserted to 30 m depth from the ground surface. To evaluate thermal performance of the constructed energy pile, a series of in-situ thermal performance tests was carried out by controlling intermittent cooling and heating loads, in which the inlet and outlet fluid temperatures, flow rate, and temperatures inside the energy pile were recorded. The test results show that a large-diameter cast-in-place energy pile can provide sufficient heat exchange compared with other types of ground heat exchangers. A series of CFD analyses was performed to simulate the thermal performance tests and provide the designer with preliminary estimation of thermal performance of energy piles. The numerical model was verified by comparing with the field measurements. Using the developed numerical model, the thermal behavior of the energy piles was evaluated with various parameters, and effects of the thermal interference and the temperature difference between the fluid and ground formation on the thermal performance were discussed.

International audience; Current environmental concerns have promoted efforts to reduce the consumption of energy. In moving towards improving existing buildings, the study of the thermal behaviour of a wall is not easy because its actual thermophysical properties are not well-known. These parameters are nevertheless fundamental for the economic optimisation of building refurbishment or for the verification of their performance in situ. It is thus important to be able to characterize existing building walls.The objective of our study was to develop a method to thermally characterize a wall adapted to in situ applications based on an active approach. The principle of identification consists of thermally examining an access surface by applying a heat flux and studying the response in terms of the temperature recorded by infrared thermography on the opposite surface. Based on signals of flux and of temperatures measured at the edges of the wall, the thermophysical properties (thermal conductivity and volumetric heat) of the wall are estimated by inverse method.The method was applied first to a homogeneous gypsum-tile panel in laboratory. The results were compared to reference values obtained from a classical procedure. Then, the method has been implemented in situ on a homogeneous reinforced concrete shell.

This article presents a light and easy to use method for simultaneous determination of thermal conductivity and volumetric heat capacity of a construction material without any control of boundary conditions. The material to be characterized is placed between two layers of materials with known thermophysical properties. Thermocouple probes are placed at the different interfaces and record the variations in temperature when the whole multilayer is subjected to stimulation. An inverse method based on a numerical model allows us to simultaneously identify the unknown thermal properties. This method was tested respectively on samples of polyvinyl chloride, expanded polystyrene, plaster and concrete.

This article describes a new thermophysical characterization method for granular materials. It is based on the creation of a cylindrical probe, fitted with peripheral flux and temperature sensors. These sensors record changes in thermal variables in the case of cylindrically symmetrical heat diffusion. A numerical exchange model integrated into an inversion algorithm identifies the thermal effusivity and diffusivity of the material being tested and the sensor/material contact resistance. In this first study, the method was applied to dry sand.

A technique for determining thermophysical properties is proposed and applied to a sample of concrete by taking advantage of pseudo-random signals. Data are treated in the frequency domain. A new approach is developed for estimating the thermal impedance based on the formalism of non-integer order models. An experimental setup consisting of a heat flux and temperature sensor arranged in contact with a material assuming a semi-infinite boundary condition is studied. The theoretical expression for such a thermal impedance takes into account the thermal capacity of the sensor and the contact resistance and emphasizes fractional orders in the behavior model.

Carbon Fiber Reinforced Polymers (CFRPs) have been increasingly employed for structural strengthening, and are attached to structures using bonding adhesives. The aim of this work is to characterize defects in the bond between CFRP and concrete (after they are located by pulse infrared thermography), and assign the defects a “numerical value” (ranging from 0 for a complete air–gap to 1 for a fully glued bond). Quantitative characterization is performed by measuring the thermal impedance, and then identifying the thermophysical parameters of the system through fitting the measured impedance to a theoretical model. An inversion procedure is carried out to estimate the unknown parameters, without prior knowledge of sample properties. In particular, it is possible to estimate more accurately both the amount of glue within a defect and the thermal contact resistance.

The purpose of this article is to present a method for identifying the apparent thermal effusivity of a wet soil. This thermal magnitude is indeed fundamentally important, as it fully characterises the behaviour of the system provided it is possible to make the assumption of a semi-infinite medium. The condition is very frequently encountered while studying heat transfers in soils. The apparent thermal effusivity of a soil is also particularly sensitive to the water content of the material. Because of this property, it is possible to evaluate the instantaneous water content of the medium from a correlation law linking thermal effusivity with water content.

It is proposed to apply a method for identifying thermal effusivity in order to monitor the percolation of water in a soil by means of a noninteger order model. This model is expressed in the form of a linear relation connecting the fractional derivatives of the temperature at a point of the system to the fractional derivatives of the stress applied, namely a flux. These derivatives are replaced by their discrete definitions and the model coefficients are identified from experimental measurements by a method of linear least squares. Flux sensors are used to measure the flux and temperature simultaneously in the access plane to the system, enabling the thermal impedance to be calculated. The study is made up of two parts: The first part consists in establishing in the laboratory a correlation between the effusivity and water content of a sample of ground studied by traditional methods. The second part constitutes the in situ tests, where with the flux sensors and the application of the method, the effusivity of the ground can be estimated and thus the water content deduced.

Thermal characterization of materials, especially civil engineering materials, in the way of non-destructive methods, are more and more widespread. In this article, we show an original point of view to describe the used method, the thermal waves, to obtain the thermal impedance of the studied system, using a specific sensor--a fluxmeter. The identification technique, based on a frequential approach, is optimized by applying a random input to the system. This kind of random heating is shown to provide a frequency range where the thermal effusivity is able to be identified and not correlated to another parameter. The strength of the method is also the determination of the contact resistance of the system, that allows to validate the identification process. Experimental results obtained from a sample with well-known thermal properties (polyvinyl chloride) are used to validate the proposed method.

In numerous fields, especially that of geothermal energy, we need to know about the thermal behaviour of the soil now that the monitoring of renewable forms of energy is an ecological, economic and scientific issue. Thus heat from the soil is widely used for air-conditioning systems in buildings both in Canada and in the Scandinavian countries, and it is spreading. The effectiveness of this technique is based on the soils calorific potential and its thermophysical properties which will define the quality of the exchanges between the soil and a heat transfer fluid. This article puts forward a method to be used for the in situ thermophysical characterisation of a soil. It is based upon measuring the heat exchanges on the surface of the soil and on measuring a temperature a few centimetres below the surface. The system is light, inexpensive, well-suited to the taking of measurements in situ without the sensors used introducing any disturbance into the heat exchanges. Whereas the majority of methods require excitation, the one presented here is passive and exploits natural signals. Based upon a few hours of recording, the natural signals allow us to identify the soils thermophysical properties continuously. The identification is based upon frequency methods the quality of which can be seen when the thermophysical properties are injected into a model with finite elements by means of a comparison of the temperatures modelled and those actually measured on site.

In a period of surging energy prices, resource depletion, and concerns over the use of nuclear power, energy savings are paramount and a major component of ongoing sustainable development. Geothermal energy is the energy stored in the form of heat beneath the surface of the Earth. Related to this, the thermal properties of soils are of great importance, particularly with regard to the modern trends of utilizing the subsurface for transmission of either heated fluids or high power currents. For example, in geothermal hydrology or geotechnical engineering applications, the thermal conductivity must be determined to assess the energy potential of the soil. The presence of water (groundwater, rainfall, natural moisture) improves both the thermal conductivity and thermal capacity fields. We present an original method—based on a thermal study and the use of non-integer order models—to determine the thermophysical parameters of different soils in near-surface layers, and link them to the water content variations...