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Summary: A series of experiments have been conducted to measure the in‐depth heating of laminated bamboo samples subjected to heat fluxes of 5, 10, 30, and 60 kW/m2, either perpendicular or parallel to the grain. These heat fluxes were chosen to induce different phenomena within the material—from inert heating to moisture evaporation, pyrolysis, oxidation, and flaming—so that the effects of these can be isolated and evaluated separately by simple heat‐transfer models. Moisture migration along the fibres becomes a critical factor when bamboo is heated parallel to the grain, resulting in increased convective heat transfer to deeper parts of the material and an accumulation of moisture in depth that accentuates the endothermic plateau in the temperature profiles around 100°C. Average charring rates for 60 minutes of exposure under 60 kW/m2 were 0.74 and 0.70 mm/min for perpendicular and parallel heating, respectively. The thickness of the heated layer was much larger for parallel heating due to moisture migration, which is less significant perpendicular to the grain. Inert heat diffusion is a good approximation at heat fluxes of 5 and 10 kW/m2, but exothermic oxidation reactions become critical above 400°C and must be included in future models. [ABSTRACT FROM AUTHOR]

A series of large-scale experiments has been conducted on under-ventilated mass timber room compartments with kerosene pool fires. To characterise the role of exposed timber walls on the fully-developed phase of the fire, the exposed surface area of mass timber was varied between experiments. Experiments with all timber surfaces protected were compared against compartments with the ceiling and one or two walls exposed. The results show that increasing the surface area of exposed timber alters the flow fields both inside the compartment and at the doorway. The momentum-driven flow fields control the spatial distribution of temperatures, surface heat fluxes, and the neutral plane. Temperatures, heat fluxes and velocities within the compartment are shown to be spatially heterogeneous in both horizontal and vertical planes, highlighting the complexity of the flow fields. This represents a significant divergence from the conventional assumptions for under-ventilated compartments of minimal velocities and homogeneous thermal conditions governed by the opening factor. The results demonstrate that the momentum-driven flow fields created by the burning walls control the compartment fire dynamics. Therefore, typical simplifications of the momentum equation in zone models are not valid for mass timber compartments, and these solutions should only be used in a conservative manner. • Large-scale experimental series on under-ventilated mass timber room compartments. • Exposed CLT walls alter the flow fields and thermal conditions in the compartment. • Momentum-driven flow fields control the spatial distribution of temperatures. • Temperatures, heat fluxes and velocities in the compartment are highly heterogeneous. • Typical assumptions of uniform mixing and hydrostatic flows are invalid at this scale. [ABSTRACT FROM AUTHOR]

Fire safety remains a major challenge for engineered timber buildings. Their combustible nature challenges the design principles of compartmentation and structural integrity beyond burnout, which are inherent to the fire resistance framework. Therefore, self-extinction is critical for the fire-safe design of timber buildings. This paper is the first of a three-part series that seeks to establish the fundamental principles underpinning a design framework for self-extinction of engineered timber. The paper comprises: a literature review introducing the body of work developed at material and compartment scales; and the design of a large-scale testing methodology which isolates the fundamental phenomena to enable the development and validation of the required design framework. Research at the material scale has consolidated engineering principles to quantify self-extinction using external heat flux as a surrogate of the critical mass loss rate, and mass transfer or Damköhler numbers. At the compartment scale, further interdependent, complex phenomena influencing self-extinction occurrence have been demonstrated. Time-dependent phenomena include encapsulation failure, fall-off of charred lamellae and the burning of the movable fuel load, while thermal feedback is time-independent. The design of the testing methodology is described in reference to these fundamental phenomena. • Self-extinction as a critical design consideration for mass timber buildings. • Literature review on solid wood and engineered timber self-extinction. • Primary factors influencing flaming self-extinction of mass timber compartments. • Methodology designed to validate a self-extinction design framework. • Description of the large-scale testing programme. [ABSTRACT FROM AUTHOR]

When a thermocouple is embedded in a material of lower thermal conductivity, under certain heating or cooling conditions, the presence of the thermocouple can distort the surrounding temperature field. As a result, the measured temperatures may be very different to the 'undisturbed' temperatures that would exist without the thermocouple. This study presents the results of a sensitivity analysis of key factors influencing this thermal disturbance. A series of heat transfer models and accompanying experiments are used to demonstrate the effects of thermocouple geometry, contact conditions, thermal properties, and heating regime on the temperature measurement error. These tailored finite element models were validated against experiments on vermiculite insulation board, which confirmed the accuracy of the models in simulating the thermal disturbance for inert heating conditions. Also, a simplified version of the finite element model was used to calculate the thermal disturbance error for a number of conditions, and subsequently to predict a range of corrected temperatures for the experimental measurements. This correction method was found to greatly improve the accuracy of the results for inert heating conditions. Since the method does not account for the effects of moisture in heat transfer, a creep of uncorrected errors could be observed. • Coupled modelling and experiments highlight factors influencing thermocouple errors. • Optimising thermocouple orientation and geometry reduces error. • A simplified correction method was developed and validated for inert heat diffusion. • Correction requires minimal knowledge of boundary conditions or material properties. • Effects of moisture in heat transfer can reduce accuracy of correction. [ABSTRACT FROM AUTHOR]

An investigation has been conducted into measurement errors associated with the thermal disturbance created when a thermocouple is inserted perpendicular to a thermal wave in a charring material of low conductivity. Laminated bamboo was used as the embedding material because in-depth temperature measurements are of practical relevance to the characterisation of this potential building material. A combination of experiments and models have been used to determine the error. Experimental results have shown significant differences between the measurements from thermocouples inserted parallel and perpendicular to the isotherms, in terms of both in-depth temperatures and estimated charring rates. Experimental measurements match well with model predictions that accurately represent the thermal disturbance error. This error has been found to decrease over time following a logarithmic trend, and to increase linearly with increasing distance from the heated surface. Models have been used to 'correct' the experimental temperature measurements, and the corrected temperatures have been found to closely approximate the results from thermocouples inserted parallel to the heat wave for inert conditions. This approach may be applied further to correct temperature measurements up to the depth of the char layer for more severe heating conditions. • Significant under-prediction of temperatures for 'back-inserted' thermocouples. • Thermal disturbance errors negligible for 'side-inserted' thermocouples. • Thermal disturbance errors are accurately represented by a simple model. • Errors decrease over time and increase linearly with distance from heated surface. • A method of correcting experimental measurements using a model is applied. [ABSTRACT FROM AUTHOR]