Ming Fu

Quantitative assessment of the relationship between radiant heat exposure and protective performance of multilayer thermal protective clothing during dry and wet conditions

The beneficial effect of clothing on a person is important to the criteria for people exposure to radiant heat flux from fires. The thermal protective performance of multilayer thermal protective clothing exposed to low heat fluxes during dry and wet conditions was studied using two designed bench-scale test apparatus. The protective clothing with four fabric layers (outer shell, moisture barrier, thermal linear and inner layer) was exposed to six levels of thermal radiation (1, 2, 3, 5, 7 and 10kW/m(2)). Two kinds of the moisture barrier (PTFE and GoreTex) with different vapor permeability were compared. The outside and inside surface temperatures of each fabric layer were measured. The fitting analysis was used to quantitatively assess the relationship between the temperature of each layer during thermal exposure and the level of external heat flux. It is indicated that there is a linear correlation between the temperature of each layer and the radiant level. Therefore, a predicted equation is developed to calculate the thermal insulation of the multilayer clothing from the external heat flux. It can also provide some useful information on the beneficial effects of clothing for the exposure criteria of radiant heat flux from fire.

Review on modeling heat transfer and thermoregulatory responses in human body.

Several mathematical models of human thermoregulation have been developed, contributing to a deep understanding of thermal responses in different thermal conditions and applications. In these models, the human body is represented by two interacting systems of thermoregulation: the controlling active system and the controlled passive system. This paper reviews the recent research of human thermoregulation models. The accuracy and scope of the thermal models are improved, for the consideration of individual differences, integration to clothing models, exposure to cold and hot conditions, and the changes of physiological responses for the elders. The experimental validated methods for human subjects and manikin are compared. The coupled method is provided for the manikin, controlled by the thermal model as an active system. Computational Fluid Dynamics (CFD) is also used along with the manikin or/and the thermal model, to evaluate the thermal responses of human body in various applications, such as evaluation of thermal comfort to increase the energy efficiency, prediction of tolerance limits and thermal acceptability exposed to hostile environments, indoor air quality assessment in the car and aerospace industry, and design protective equipment to improve function of the human activities.

Aerodynamic characteristics of human movement behaviours in full-scale environment: Comparison of limbs pendulum and body motion

The aerodynamic effects of human movement can significantly influence the airflow motion and contaminants transmission in enclosed environments such as in aircraft cabins, cinema and conference room, and so it is necessary and important to study the characteristics of these aerodynamic effects. This work focuses on the aerodynamic characteristics of human movement behaviours including limbs pendulum and body motion. A thermal manikin is used in the corresponding environments to simulate these behaviours. The step frequencies of 20, 30, 40, 50 and 60 double steps per minute for limbs pendulum and the moving speeds of 0.5, 0.75, 1.0, 1.25 and 1.5u2009m/s for body motion are investigated in the experiments. In each case, the velocity distribution around the human body is measured by using hot-wire anemometers. The experimental results show that the characteristics of the velocity distribution induced by limbs pendulum depend on pendulum frequency and spatial location, and for body motion, it depends on moving speed, moving distance and spatial location. The analysis results show that body motion has a significant influence on the flow field, and its aerodynamic effects are greater than those due to limbs pendulum. When a human moves, more detailed profile of the human body leads to more complicated flow field in the nearby area.

Effects of fabric thickness and material on apparent ‘wet’ conductive thermal resistance of knitted fabric ‘skin’ on sweating manikins

Currently, no published standard and research work have addressed the basic requirements on knitted fabric skin on sweating manikins. In this study, we performed 252 experiments to investigate the influence of fabric thickness and material on the apparent wet conductive (or effective) thermal resistance of the fabric skin using a Newton manikin. Four types of cotton fabric skin (fabric thickness: 0.38, 0.54, 0.92 and 1.43mm) and three types of polyester fabric skin (fabric thickness: 0.41, 0.54 and 1.0mm) were selected and their wet conductive thermal resistance was determined. Empirical equations were also developed for each fabric skin to predict wet fabric skin surface temperatures. It was found that both fabric thickness and material significantly affected the apparent wet conductive thermal resistance. Clothing total evaporative resistance determined using thin fabric skin (e.g., CO1, CO2) was normally lower than that determined using thick fabric skin (e.g., CO4). Besides, synthetic fabric skin tended to have a larger apparent wet conductive thermal resistance than the cotton fabric skin due to a smaller amount of moisture contained. Hence, there is a great need to standardize the fabric skin to eliminate the influence of fabric skin on the measurement of clothing evaporative resistance by means of a sweating manikin.

Prediction of thermal skin burn based on the combined mathematical model of the skin and clothing

Abstract As the result of exposed to thermal radiation and fire exposure, skin burn or even worse injuries are very common for building occupants and fire fighters. To accurately predict their skin temperature and burn situation, an assessment method of the mathematical model is developed for various thermal radiation conditions. The combined mathematical model includes the heat and moisture transfer within the skin and clothing systems. It is validated with a good agreement with the previous experimental study. The effects of thermal radiation, air gap and moisture transfer on burn prediction were also studied. The results showed that the time to the second degree burn is affected by the heat flux level, gap size and moisture location. It is expected that the developed method can be used to evaluate the thermal protective performance of protective clothing during exposure to thermal hazards and provide appropriate information to clinical observation and decision-making for skin thermal injuries.

The Preparation and Characterization of Ultrafine Fatty Acid Ester/Poly(meta-phenylene isophthalamide) Phase Change Fibers Designed for Thermo-regulating Protective Clothing

Poly(meta-phenylene isophthalamide, PMIA)-based phase change fibers (PCFs) with fatty acid ester (i.e. HPCMEs) as the functional ingredient were successfully fabricated by emulsion electrospinning. Subsequent characterizations by FE-SEM, TEM, DSC and TGA were performed to investigate their morphology, structure, thermal storage and decomposition behavior, respectively. Experimental results reveal that the fabricated PCFs are randomly arranged and show a good cylindrical structure with fiber diameters ranging from tens to hundreds of nanometers. Most of the HPCMEs are well encapsulated by PMIA sheaths and appear as isolated segments or elongated channels inside the fiber. Given their proper phase change span (30-40°C), considerable enthalpies, good shape stability and greatly enhanced thermal resistance, the prepared HPCMEs/PMIA PCFs are expected to have wide prospects in thermo-regulating protective clothing and other fields related to thermal energy storage.

Numerical investigation of airflow, heat transfer and particle deposition for oral breathing in a realistic human upper airway model

Inhalation injury from exposure to fire smoke is one of the causes of burn-related death. In this study, a realistic three-dimensional human upper airway model was built from magnetic resonance imaging (MRI) scanned images, including the nasal, oral, pharynx, larynx, trachea and part of the first generation of the tracheobronchial tree, as well as a tissue region from the pharynx to the upper bronchi. The Transition Shear Stress Transport (SST-transition) turbulence model, Pennes bioheat transfer equation, convective boundary conditions and a Lagrangian frame were applied and verified with experimental measurements to simulate the airflow fields, temperature distributions and particle deposition in the human airway model. The effects of flow rate, inhalation temperature and particle diameter were studied. It showed that the oral cavity is more likely to be affected by the inlet air conditions. The mucosa in the oral, pharynx and larynx are more likely to cause the thermal injury. The inspiration flow rate significantly influences the airflow fields, temperature distributions and particle deposition fraction interior of the human upper airway model, especially in the pharynx-larynx region. The rising flow rate, inhalation air temperature and particle diameter all contribute to boosting the total deposition fraction in the model. The heated particles with a higher temperature are more likely to be deposited in the oral cavity and the influence of the inlet temperature has a minor influence in the case of a bigger particle diameter.