This paper presents the findings of medium-scale (5-15 kg) cryogenic liquid experiments on a conc... more This paper presents the findings of medium-scale (5-15 kg) cryogenic liquid experiments on a concrete substrate which may represent an industrial grade diking material. The temperature varying thermal characteristics, i.e. the conductivity (k) and heat capacity (Cp) of the concrete substrate were measured in the range of-160°C to 50°C using guarded hot plate and DSC, respectively. Vaporization rate of liquid nitrogen (LN2), liquid oxygen (LO2) and a mixture of 80% LN2 and 20% LO2, (i.e. liquid air) were studied on the same concrete substrate. It was found that conductive heat transfer from the concrete substrate has the greatest contribution in the vaporization of cryogenic liquids. The evidence of phase change from film boiling to nucleate boiling was observed during the pool vaporization of LO2. The effect of preferential boiling on the temperature and heat flux profiles inside the concrete substrate was also observed. The change of heat fluxes due to the preferential boiling after each refill of mixture liquids were found to vary from 3% to 15%. Finally, the recorded heat flux during the early and later stages of pool vaporization were 12.4 kW/m 2 and 3.7 kW/m 2 for LN2 and 12.9 kW/m 2 and 2.96 kW/m 2 for LO2.
Journal of Loss Prevention in the Process Industries, 2017
This paper presents the findings of small-scale experiments (5e15 kg) of cryogenic liquid spills ... more This paper presents the findings of small-scale experiments (5e15 kg) of cryogenic liquid spills on a representative industrial grade diking concrete. Physical properties of the substrate, i.e., the thermal conductivity (k) and heat capacity (Cp) of the concrete were measured in the range of À160 C to 50 C using guarded hot plate and differential scanning calorimeter (DSC), respectively. Vaporization rate of liquid nitrogen (LN 2), liquid oxygen (LO 2) and a mixture of 80% v/v LN 2 and 20% v/v LO 2 , (i.e., liquid air-LAir) were studied on the same concrete. Convective and radiative heat transfers were limited by insulation. The contribution of conductive heat transfer from the concrete substrate for the vaporization of cryogenic liquids was studied. The effect of preferential boiling was observed when the liquid air was spilled.
Heat transfer correlations obtained from the literature were applied to build numerical model of ... more Heat transfer correlations obtained from the literature were applied to build numerical model of boiling cryogenic liquid spilled on a solid. Different combinations of liquid-solid systems were studied utilizing methane, hydrogen, oxygen and nitrogen on the solid substrates: concrete, soil, aluminium and polystyrene. The boiling curves were generated for a given liquid-solid system and the results were analysed to determine the possibility of occurrence and the duration of each regime during the accidental spill. The analyses show how long each boiling regime can theoretically last for each case. The boiling regime model was compared to simple one-dimensional (1D) “ideal” conduction model, which assumes a semi-infinite solid, heat flux in one direction only and perfect thermal contact at the liquid-solid interface (which leads to constant surface temperature for the solid substrate which is equal to the liquid boiling point). Subsequently, the 1D “ideal” conduction model was modifie...
Over the last few years, the importance of establishing and maintaining a positive safety culture... more Over the last few years, the importance of establishing and maintaining a positive safety culture in the process industry and its impact on the safety performances of a company have strongly been emphasized by regulatory institutions, academia and very importantly by the process industry itself. A strong safety culture, when everyone in a company feels responsible for the safety and acts accordingly, is not achieved overnight as it requires changing behaviors and instilling safety values to individuals. The challenge is there for existing employees of a company but also for new recruits. In the particular case of freshly graduated engineers, it is often only when joining a company that the individual discovers the concept of safety culture and has to buy into it. Academia could play a much better role in training engineers who, not only understands the process safety challenges faced by the industry but genuinely join the industry with a pre-established positive safety culture developed during the years of their education. Instilling a process safety culture to future engineers is an area that still requires major efforts from academia. Experimental research at university or college often involves the handling of hazardous substances and processes, with an associated level of risk that need to be minimized. Incidents (major and minor) do happen in university laboratories. It is very common that only major incidents are reported and investigated. Operational deviations, minor incidents, near misses almost never see the light of the discussion, although they are opportunities to instill a process safety culture to students, as they are in the process industry. The objective of this paper is to provide a case study on building process safety culture in a research environment by applying different key aspects of process safety principles. In this study, a series of experiments were analyzed to show how process safety principles starting from inherently safer design and management program can be learned while performing experimental research. The authors have found that investigating the root causes of near misses have multiple benefits. During the actual experiments , no injuries have occurred and even the potential of having injuries was relatively low. However, in the context of this study, selected issues were investigated as accidents, which referred to not being able to successfully perform the experiments and near-miss which referred to the delay of a planned/scheduled experiment. As a matter of fact, all these issues may be treated as time and financial losses. Different types of failures such as human factor, process design or inherently safer design and standard operating procedures were discussed via case studies. It was found that having students discussing and presenting the investigation results to other students has greatly improved not only the safety aspects of research but also the productivity and safety culture of the involved researchers.
This paper presents the findings of medium-scale (5-15 kg) cryogenic liquid experiments on a conc... more This paper presents the findings of medium-scale (5-15 kg) cryogenic liquid experiments on a concrete substrate which may represent an industrial grade diking material. The temperature varying thermal characteristics, i.e. the conductivity (k) and heat capacity (Cp) of the concrete substrate were measured in the range of-160°C to 50°C using guarded hot plate and DSC, respectively. Vaporization rate of liquid nitrogen (LN2), liquid oxygen (LO2) and a mixture of 80% LN2 and 20% LO2, (i.e. liquid air) were studied on the same concrete substrate. It was found that conductive heat transfer from the concrete substrate has the greatest contribution in the vaporization of cryogenic liquids. The evidence of phase change from film boiling to nucleate boiling was observed during the pool vaporization of LO2. The effect of preferential boiling on the temperature and heat flux profiles inside the concrete substrate was also observed. The change of heat fluxes due to the preferential boiling after each refill of mixture liquids were found to vary from 3% to 15%. Finally, the recorded heat flux during the early and later stages of pool vaporization were 12.4 kW/m 2 and 3.7 kW/m 2 for LN2 and 12.9 kW/m 2 and 2.96 kW/m 2 for LO2.
Journal of Loss Prevention in the Process Industries, 2017
This paper presents the findings of small-scale experiments (5e15 kg) of cryogenic liquid spills ... more This paper presents the findings of small-scale experiments (5e15 kg) of cryogenic liquid spills on a representative industrial grade diking concrete. Physical properties of the substrate, i.e., the thermal conductivity (k) and heat capacity (Cp) of the concrete were measured in the range of À160 C to 50 C using guarded hot plate and differential scanning calorimeter (DSC), respectively. Vaporization rate of liquid nitrogen (LN 2), liquid oxygen (LO 2) and a mixture of 80% v/v LN 2 and 20% v/v LO 2 , (i.e., liquid air-LAir) were studied on the same concrete. Convective and radiative heat transfers were limited by insulation. The contribution of conductive heat transfer from the concrete substrate for the vaporization of cryogenic liquids was studied. The effect of preferential boiling was observed when the liquid air was spilled.
Heat transfer correlations obtained from the literature were applied to build numerical model of ... more Heat transfer correlations obtained from the literature were applied to build numerical model of boiling cryogenic liquid spilled on a solid. Different combinations of liquid-solid systems were studied utilizing methane, hydrogen, oxygen and nitrogen on the solid substrates: concrete, soil, aluminium and polystyrene. The boiling curves were generated for a given liquid-solid system and the results were analysed to determine the possibility of occurrence and the duration of each regime during the accidental spill. The analyses show how long each boiling regime can theoretically last for each case. The boiling regime model was compared to simple one-dimensional (1D) “ideal” conduction model, which assumes a semi-infinite solid, heat flux in one direction only and perfect thermal contact at the liquid-solid interface (which leads to constant surface temperature for the solid substrate which is equal to the liquid boiling point). Subsequently, the 1D “ideal” conduction model was modifie...
Over the last few years, the importance of establishing and maintaining a positive safety culture... more Over the last few years, the importance of establishing and maintaining a positive safety culture in the process industry and its impact on the safety performances of a company have strongly been emphasized by regulatory institutions, academia and very importantly by the process industry itself. A strong safety culture, when everyone in a company feels responsible for the safety and acts accordingly, is not achieved overnight as it requires changing behaviors and instilling safety values to individuals. The challenge is there for existing employees of a company but also for new recruits. In the particular case of freshly graduated engineers, it is often only when joining a company that the individual discovers the concept of safety culture and has to buy into it. Academia could play a much better role in training engineers who, not only understands the process safety challenges faced by the industry but genuinely join the industry with a pre-established positive safety culture developed during the years of their education. Instilling a process safety culture to future engineers is an area that still requires major efforts from academia. Experimental research at university or college often involves the handling of hazardous substances and processes, with an associated level of risk that need to be minimized. Incidents (major and minor) do happen in university laboratories. It is very common that only major incidents are reported and investigated. Operational deviations, minor incidents, near misses almost never see the light of the discussion, although they are opportunities to instill a process safety culture to students, as they are in the process industry. The objective of this paper is to provide a case study on building process safety culture in a research environment by applying different key aspects of process safety principles. In this study, a series of experiments were analyzed to show how process safety principles starting from inherently safer design and management program can be learned while performing experimental research. The authors have found that investigating the root causes of near misses have multiple benefits. During the actual experiments , no injuries have occurred and even the potential of having injuries was relatively low. However, in the context of this study, selected issues were investigated as accidents, which referred to not being able to successfully perform the experiments and near-miss which referred to the delay of a planned/scheduled experiment. As a matter of fact, all these issues may be treated as time and financial losses. Different types of failures such as human factor, process design or inherently safer design and standard operating procedures were discussed via case studies. It was found that having students discussing and presenting the investigation results to other students has greatly improved not only the safety aspects of research but also the productivity and safety culture of the involved researchers.
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