Novel Dual Walling Cob Building: Dynamic Thermal Performance

This paper emphasizes the experimental and numerical study of new cob mixes used for insulation and load bearing wall elements. The experimental study provides complete datasets of thermal properties of the new walling materials, using cob with density ranging from 1107 kg/m3 to 1583 kg/m3 for structural walls and less than 700 kg m−3 for insulation walls. Various mixes of French soils and fibres (reed, wheat straw, hemp shiv, hemp straw, and flax straw) with different water contents are studied. The lowest average thermal conductivity is obtained for the structural cob mix prepared of 5% wheat straw and 31% of water content. The insulation mix, prepared with 25% reed and 31% water content, has the lowest thermal conductivity. Investigation of diffusivity, density, and heat capacity shows that, when thermal conductivity is lower than 0.4 W m−1 K−1, the decrease in cob density leads to better insulation values and higher heat capacity. Little variation is noticed regarding the density and heat capacity for cob mixes with thermal conductivity higher than 0.4 W m−1 K−1. Furthermore, the non-uniformity of local thermal conductivity and heat losses through the samples is due mainly to the non-uniform distribution of fibres inside the mixes inducing an increase in heat loss up to 50% for structural walls and 25% for insulation walls. Cob thermal properties are used in a comparative simulation case study of a typical house under French and UK climatic conditions. The energy performance of the conventional building is compared to a dual walled cob building, showing remarkable reduction in energy consumption as the cob walls, whilst maintaining comfortable indoor conditions without additional heating.</jats:p

Comparison of the thermal performance between conventional and cob building

The appliance of sustainable development approach in building has urged construction industry to adopt proper measurements to protect environment and reduce residential building energy consumption and CO2 emissions. Thus, an increasing interest in alternative building materials has developed including the use of bio-based materials such as cob which is studied in this paper. In the previous work, many experimental and numerical studies have been carried out to characterize thermal behaviour of earth buildings, reduce its thermal conductivity and water content. In this paper, an experimental study is carried out to determine the thermal properties and energy performance of cob building. Cob samples within different soil and fiber contents are studied using an experimental set up instrumented with flux meters and micro-thermocouples in order to evaluate the local heat flux and thermal conductivity during stationary regime. The results are analysed and compared to deduce the performant mixes in terms of thermal behaviour while respecting the French thermal regulation. A static thermal simulation based on RT 2012 calculation method (the official French calculation method for the energy performance of new residential and commercial buildings according to France thermal regulation) is used to compare energy performance between conventional and cob building using the French climate data base

Realization and thermal characterization of thin-film optothermal microsensor

The aim of this investigation is to study thin-film thermoelectric linear arrays for high spatial temperature measurements and to analyze power laser energy profile. The sensitive area consists of a planar of 16 individual thin-film Au-Pd thermocouple junctions with 8 μm × 8 μm of surface area. This sensor allows 16 temperature measurements per 288 μm. It is processed by means of standard integrated circuit techniques. Thermal simulation of heat conduction in gold and palladium layers has been carried out. The sensor thermoelectric response has been characterized in transient regime and steady state. The time constant of thermocouple response is of the order of 140 μs. A linear relationship between the thermoelectric voltage and the incident power laser has been put in evidence. Using the linear array, a Gaussian profile of the incident laser beam is obtained

Transient Characteristics of a Two-Phase Thermosyphon Loop for Cooling Telecommunication Outdoor Cabinets

International audienceIn this paper, experimental investigations of a two-phase thermosyphon loop are presented in order to keep telecommunication equipments temperature below 55°C. The experimental setup consists of a thermosyphon loop containing an evaporator and a condenser connected by two flexible tubes. Tests are performed firstly in transient state using the thermosyphon loop prototype inside telecommunication cabinet. The n-pentane is used as the working fluid. Firstly, transient thermal characteristics of the thermosyphon loop are measured. In the other way, the thermosyphon loop is tested for different power input up to 450W. Operating temperatures of the telecommunication equipments cooled with forced air convection and two-phase thermosyphon loop are compared

Experimental investigation of thermosyphon loop thermal performance

International audienceThis paper presents the experimental investigation of a two-phase closed loop. The experimental setup consists of an evaporator and a condenser connected by two insulated tubes. Using water as a working fluid, the experiments were conducted to evaluate the performance of a thermosyphon: the effects of fill charge ratio, the condenser jacket coolant inlet temperature and the mass flow rate. Finally, the results show that the optimal fill charge ratio is between 7% and 10%, the cooling system has the optimal performance when controlling the condenser jacket water temperature and flow rate at 5 °C and at 0.7 l/min respectively. System, loop, evaporator, vapor line, condenser, and liquid line thermal resistances analysis is directed additionally to the pressure and temperature evolutions for the better understand of the main parameters affecting the cooling system performance