A Method to Evaluate the Thermal Stress Management of Firefighters' Protective Clothing

Abstract

The clothing worn by firefighters is essential in ensuring their safety. One of the tradeoffs that is made when designing apparel for firefighting is between its ability to protect the individual from high external heat and its ability to manage the thermal stress of the firefighter. More research is required to evaluate the thermal stress management of firefighters’ protective clothing. Some of the methods that have been used in the past to assess the thermal stress management of firefighters’ protective clothing include the sweating hot plate test, the sweating thermal manikin test and the dry manikin test. The planar geometry of the flat plate does not provide a very realistic representation of the human body while the complexity in the design and testing of the thermal manikin makes it more involved than the hot plate and expensive to obtain thermal resistance values for different fabric ensembles. So a testing method that could be simpler than the heated manikin test but provides a better representation of the human body than the hot plate test is required. This led to the development of the heated cylinder method presented in this thesis. The method makes use of a heated cylinder in a wind tunnel. In the present research, a finite-height cylinder with a free end at the top causing a 3D airflow, and an infinitely long cylinder that spanned the height of the wind tunnel to create two-dimensional (2D) flow, were used. The fabric specimens were wrapped around the heated sections of these two cylinder models and the Nusselt number and thermal resistance values for the 2D and three-dimensional (3D) fabric-covered cylinders were obtained by subjecting the fabric and cylinder ensemble to airflow at different speeds in a wind tunnel and measuring the temperatures in the different layers of the ensemble. The results for the Nusselt number and thermal resistance data showed the impact of fabric permeability on the heat transfer from the surface of the fabric-covered cylinder and the thermal stress management of the fabric ensembles. This method was developed as a proof of concept; the results from this thesis research would be used in the development of a more realistic but relatively simple method to test the thermal stress management of firefighters’ protective clothing.