On Demand Thermal Protection (ODTP): A New Approach for Designing Garments Exposed to Flash Flame Incidents

2012 ◽  
Author(s):  
Eduardo Mendoza ◽  
Jean-pierre Cooper ◽  
John W. Evangelista ◽  
Margaret Auerbach ◽  
Özer Arnas
Keyword(s):  
Heat Transfer ◽  
Numerical Model ◽  
Heat Equation ◽  
Thermal Protection ◽  
Experimental Testing ◽  
Sudden Change ◽  
Muscle Layer ◽  
The Body ◽  
On Demand ◽  
Combined Convection

Soldiers, first responders and other high risk occupations such as power line technicians are routinely exposed to dangerous situations where severe burn injuries are possible. Standard flame resistant (FR) fabrics provide minimal burn protection when exposed to a flash flame incident. As a result, improvement in thermal protection is desperately needed and remains an ongoing subject of research and development. A simplified one dimensional physical model composed of a muscle layer, skin/fat layer, air gap(s) and fabric layer(s) is used to model heat transfer entering the body covered by a garment that is exposed to a flash flame. Heat transfer within the skin and muscle layers is modeled by combined conduction, metabolic heat generation and blood perfusion by a recently developed modification to the heat equation termed the bio-heat equation. Boundary conditions include a fixed temperature (core body temperature) at the inside of the muscle layer and combined convection and radiation from the flame on the outside of the fabric. The heat equation is solved by discretizing the domain in one dimension and using a finite volume approach to derive the finite difference equations. This model is an initial step to be used to provide an assessment of common FR garments with respect to both comfort in ambient conditions and protection during a flash flame. It also provides for parametric analysis to determine ideal thermo-physical properties, fabric thicknesses and layering for better protection during flash flame incidents. Estimates for time to burn injury from the numerical model is presented with experimental results using live mannequin flame tests (ASTMF-1930), standard vertical flame tests (ISO-17492) and a non-standard flame test with combined convection and radiation heat fluxes up to 85 kW/m2. The main effort of this study revolves around an initial working design for a dynamic garment termed On Demand Thermal Protection (ODTP). The primary focus of the design is the development of a thermistor circuit embedded in a protective garment to act as an electric sensor for rapidly deploying the necessary thermal protection that is needed as predicted by the numerical model instantaneously in the event of a flash flame incident. An initial prototype is being developed with a focus on designing the thermistor circuit to mechanically actuate protective components in a flash-flame environment. Concepts include rapidly releasing a pressurized flame retardant fluid through vinyl tubing sewn into a garment and deploying a protective barrier around the face and neck when the thermistor circuit detects a sudden change in heat transfer. A summary of the prototype along with experimental testing to date compared to the theoretical predictions from the model described above is presented.

Computational Study on Radiative Aerothermodynamics of a Reentry Space Vehicle

2021 ◽  
Author(s):  
Qi Li ◽  
Sijun Zhang
Keyword(s):  
Heat Transfer ◽  
Thermal Protection ◽  
Computational Study ◽  
Space Vehicle ◽  
The Body ◽  
Stagnation Region ◽  
Convective Flux ◽  
Transit Times ◽  
Key Issues ◽  
Nonequilibrium Flows

Abstract Under hypersonic flight conditions, a vehicle travelling through the atmosphere could excite the air that flows around the body to very high temperatures as the kinetic energy of the vehicle is dissipated to the gas. Depending on the flight velocity, various chemical reactions will be produced behind a shock wave for stagnation region. These reactions greatly change the properties of air and cause considerable deviation from those of a thermally and calorically perfect gas. A vehicle flying through the higher altitude of the atmosphere at high velocities may also experience thermal non-equilibrium since the lower density reduces the collision frequency and the high velocity results in smaller transit times for the air molecules. Under such extremely thermal circumstances, the heat transfer by convection and radiation around a vehicle has been one of key issues for thermal protection system (TPS). In this paper, the computational aerothermodynamics with fully coupled radiative heat transfer is developed. To validate the proposed approach, it is employed to simulate the thermal and chemical nonequilibrium flows over Stardust. The computed results on the reentry space vehicle reveal both of convective flux and radiative flux are in good agreements with other predicted results.

A Procedure to Evaluate the Thermal Response of a Multilayered Thermal Protection System Subjected to Aerodynamic Heating

2009 ◽  
Author(s):  
Michele Ferraiuolo ◽  
Oronzio Manca ◽  
Aniello Riccio
Keyword(s):  
Heat Transfer ◽  
Thermal Protection ◽  
Outer Space ◽  
Thermal Response ◽  
Temperature Limit ◽  
The Body ◽  
Heat Radiation ◽  
Aerodynamic Heating ◽  
Internal Temperature ◽  
Design Activities

Next generation reusable re-entry vehicles must be capable of sustaining consistent repeated aero-thermal loads without damage or deterioration. This means that such structures must tolerate the high temperatures engendered by aero-thermal re-entry fluxes due to the establishment of a hypersonic regime over the body. Thermal Protection Systems (TPS) are used to maintain a reusable launch vehicle’s structural temperature within acceptable limits during re-entry flights; that is, internal temperature should not overcome the temperature limit use of the internal structure. TPS are usually composed by several layers made of different materials. Heat transfer through a multilayer insulation during atmospheric re-entry involves combined modes of heat transfer: heat conduction through the solid, heat radiation to the outer space etc. In the frame of TPS design activities a procedure based on one dimensional analytical solutions of transient nonlinear analyses has been developed in order to estimate the temperature variation with time and space of a multilayered body subjected to aerodynamic heating inside a radiating space. Since internal temperature values of TPSs of re-entry vehicles cannot exceed certain values, that procedure allows to quickly evaluate those temperature values and to preliminary size layer thicknesses before preparing and performing Finite Element analyses.

scholarly journals Heat Transfer with Absorption in Anisotropic Thermal Protection of High-Temperature Products

2019 ◽  
pp. 35-49
Author(s):  
V.F. Formalev ◽  
S.A. Kolesnik ◽  
B.A. Garibyan
Keyword(s):  
Heat Transfer ◽  
Thermal Protection ◽  
Phenol Formaldehyde ◽  
The Body ◽  
Temperature Fields ◽  
Chemical Transformations ◽  
Heat Flows ◽  
Plate Heating ◽  
Heat Shielding ◽  
Physical And Chemical

The purpose of the research was to study the non-stationary heat transfer in anisotropic thermal protection under the action of unsteady heat flows distributed along the body, when there are thermal energy sinks inside the body, the energy being proportional to temperature, due to endothermic physical and chemical transformations. Thermal protection is made of anisotropic material, such as phenol-formaldehyde fiberglass, asboplastics, carbon-carbon plastics, etc. A new analytical solution has been obtained for the problem of plate heating under the action of unsteady heat flows distributed along the body. Using this solution, we studied the temperature fields when the components and orientation angles of the main axes of the thermal conductivity tensors of anisotropic heat-shielding materials were changed. Findings of research show that with increasing time, the temperature field inside the plate is localized and does not extend further than the limiting isotherm.

Experimental and Numerical Study of a Latent Heat Thermal Energy Storage Unit Enhanced by Fins

2020 ◽  
Author(s):  
Addison Hockins ◽  
Samantha Moretti ◽  
Mahboobe Mahdavi ◽  
Saeed Tiari
Keyword(s):  
Heat Transfer ◽  
Energy Storage ◽  
Numerical Model ◽  
Latent Heat ◽  
Thermal Energy ◽  
Thermal Energy Storage ◽  
Experimental Testing ◽  
Storage Unit ◽  
Energy Storage Unit ◽  
Charging Time

Abstract Latent heat thermal energy storage (LHTES) systems are used to store thermal energy and release it for later use by melting or solidifying a phase change material (PCM). One problem associated with latent heat thermal energy storage systems is the low thermal conductivity of most commercially aviable phase change materials. This can have a significant negative effect on the thermal performance of the system by leading to a longer charging or discharging process. Several passive heat transfer enhancement techniques are used to resolve this issue. Common passive heat transfer enhancement techniques include inserting fins and extended surfaces into the PCM, embedding heat pipes or other two-phase heat transfer devices within the PCM, dispersion of highly conductive nanoparticles in the PCM, and impregnation of highly conductive porous media with the PCM. The current study analyzes the effect of a fin-based enhancement technique on the thermal performance of a latent heat thermal energy storage unit. Copper fins are attached annually around the central pipe inside the PCM. A transient two-dimensional numerical model technique is developed using ANSYS FLUENT 19.0 to simulate the operation of the system. Baseline tests have been conducted experimentally for a system without fins to validate the numerical model. The results obtained from the numerical modeling are in good agreement with those of the experimental testing. Based on the experimental testing, the total charging time of the system using hot water at 70°C and flow rate of 7.57 L/min is around 47.9 hours which is very close to the prediction by the numerical model which is 48 hours. Numerical modeling of the system with 10 fins and 20 fins found that the charging time was decreased by 68.9% and 73.7%, respectively. The discharging time was also decreased by 73.2% and 79.1%, respectively.

Development of Calculated Resistances to Heat Transfer of Floors via the Ground Using Modern Methods of Their Thermal Protection

2019 ◽  
Vol 771 (6) ◽  
pp. 44-48 ◽  
Author(s):  
E.G. MALYAVINA ◽  
◽  
E.A. GNEZDILOVA ◽  
Yu.N. LEVINA ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thermal Protection ◽  
Modern Methods

scholarly journals A numerical model and validation of phase change material integrated thermoelectric radiant cooling panel

2019 ◽  
Vol 111 ◽  
pp. 01001
Author(s):  
Hansol Lim ◽  
Hye-Jin Cho ◽  
Seong-Yong Cheon ◽  
Soo-Jin Lee ◽  
Jae-Weon Jeong
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Numerical Model ◽  
Surface Temperature ◽  
Phase Change ◽  
Transfer Coefficient ◽  
Phase Change Material ◽  
Overall Heat Transfer Coefficient ◽  
Radiant Cooling ◽  
Change Material

A phase change material based radiant cooling panel with thermoelectric module (PCM-TERCP) is proposed in this study. It consists of two aluminium panels, and phase change materials (PCMs) sandwiched between the two panels. Thermoelectric modules (TEMs) are attached to one of the aluminium panels, and heat sinks are attached to the top side of TEMs. PCM-TERCP is a thermal energy storage concept equipment, in which TEMs freeze the PCM during the night whose melting temperature is 16○C. Therefore, the radiant cooling panel can maintain a surface temperature of 16◦C without the operation of TEM during the day. Furthermore, it is necessary to design the PCM-TERCP in a way that it can maintain the panel surface temperature during the targeted operating time. Therefore, the numerical model was developed using finite difference method to evaluate the thermal behaviour of PCM-TERCP. Experiments were also conducted to validate the performance of the developed model. Using the developed model, the possible operation time was investigated to determine the overall heat transfer coefficient required between radiant cooling panel and TEM. Consequently, the results showed that a overall heat transfer coefficient of 394 W/m2K is required to maintain the surface temperature between 16○C to 18○C for a 3 hours operation.

scholarly journals A Computational Study on the Role of Parameters for Identification of Thyroid Nodules by Infrared Images (and Comparison with Real Data)

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4459
Author(s):  
José R. González ◽  
Charbel Damião ◽  
Maira Moran ◽  
Cristina A. Pantaleão ◽  
Rubens A. Cruz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thyroid Nodules ◽  
Numerical Study ◽  
Computational Study ◽  
Internal Heat ◽  
Heat Transfer Process ◽  
The Body ◽  
Physical Parameters ◽  
Infrared Sensors ◽  
Wide Range

According to experts and medical literature, healthy thyroids and thyroids containing benign nodules tend to be less inflamed and less active than those with malignant nodules. It seems to be a consensus that malignant nodules have more blood veins and more blood circulation. This may be related to the maintenance of the nodule’s heat at a higher level compared with neighboring tissues. If the internal heat modifies the skin radiation, then it could be detected by infrared sensors. The goal of this work is the investigation of the factors that allow this detection, and the possible relation with any pattern referent to nodule malignancy. We aim to consider a wide range of factors, so a great number of numerical simulations of the heat transfer in the region under analysis, based on the Finite Element method, are performed to study the influence of each nodule and patient characteristics on the infrared sensor acquisition. To do so, the protocol for infrared thyroid examination used in our university’s hospital is simulated in the numerical study. This protocol presents two phases. In the first one, the body under observation is in steady state. In the second one, it is submitted to thermal stress (transient state). Both are simulated in order to verify if it is possible (by infrared sensors) to identify different behavior referent to malignant nodules. Moreover, when the simulation indicates possible important aspects, patients with and without similar characteristics are examined to confirm such influences. The results show that the tissues between skin and thyroid, as well as the nodule size, have an influence on superficial temperatures. Other thermal parameters of thyroid nodules show little influence on surface infrared emissions, for instance, those related to the vascularization of the nodule. All details of the physical parameters used in the simulations, characteristics of the real nodules and thermal examinations are publicly available, allowing these simulations to be compared with other types of heat transfer solutions and infrared examination protocols. Among the main contributions of this work, we highlight the simulation of the possible range of parameters, and definition of the simulation approach for mapping the used infrared protocol, promoting the investigation of a possible relation between the heat transfer process and the data obtained by infrared acquisitions.

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