Hydrocarbon refrigerant charge limits for quiescent rooms

Concentration measurements and analysis have been used to develop new methodology for estimating the allowable charge limit (ACL) of flammable refrigerants, particularly R290. Attention has been given to the impacts of construction and dimensional characteristics of the RACHP enclosures, in particular the size and position of the openings, on the concentrations exiting the enclosure. Analysis of the data has shown that these are critical aspects that influence floor concentration and/or safe allowable refrigerant charge limits. Formulae have been proposed to estimate layer-volume heights and ultimately ACL. The results illustrate that current standard's ACLs are overly restrictive, especially for certain types of RACHP equipment

Assessment of factors affecting R290 concentrations arising from leaks in room air conditioners.

Currently R290 is used to a small extent in room air conditioners, such as split, portable and window types. Products are limited to relatively small cooling capacities due to refrigerant charge sizes being constrained to around 300 – 400 g, on account of maximum charge formulae within standards IEC 60335-2-40, ISO 5149-1 and EN 378-1. This is especially challenging in warm countries where the cooling load is greater and charge sizes need to be larger. Work is underway to improve maximum charge size determination methods for a given room size. As a contribution to this on going process, further research has been carried out to understand the factors that affect development of flammable concentrations within roomsin event of a leak. Parameters related to the characteristics of room air conditioners and installations have been investigated experimentally by measuring R290 concentrations from releases and selected findings are described

Minimum airflow rates to dilute R290 concentrations arising from leaks in room air conditioners

Currently R290 is used to a limited extent in room air conditioners, such as split, portable and window types. The product standard IEC 60335-2-40 currently specifies requirements to limit the charge of flammable refrigerants in such a way that it obstructs the wider use of R290. This is particularly challenging in warm countries where the heat load is greater and thus charge sizes need to be larger for a given room size, inferring higher concentrations in the event of a leak. Relying on the airflow of an indoor unit can be used to dilute a refrigerant leak and thus prevent flammable concentrations forming, despite the charge quantity being substantially greater than that currently permitted in the current standard. Research has been carried out to determine the minimum airflow rate from an air conditioner necessary to achieve sufficient dilution. A numerical model based on entrainment theory was developed and supported by experimentally analysing the behaviour of releases under various conditions with RACS airflow

Airflow to disperse refrigerant leaks from hydrocarbon refrigeration systems

Whilst R290 is currently used to a limited extent in room air conditioners there is a desire for wider application due to its excellent performance and negligible global warming potential. The product standard IEC 60335–2–40 specifies requirements to limit the allowable refrigerant charge in such a way that it obstructs the wider use of R290. Airflow of an indoor unit can be used to dilute a refrigerant leak, enabling substantially greater charge quantities to be used. A numerical model based on entrainment theory was developed and supported by analysing the behaviour of experimentally simulated releases under various conditions with indoor unit airflow. The work determines the minimum airflow rate necessary to prevent formation of a flammable concentration within the room. Further, the work includes determination of appropriate response time and leak rate to initiate airflow once a leak has begun. The developed methodology can equally be applied to commercial refrigeration units and other flammable refrigerants

Magnetothermodynamics: Measuring equations of state in a relaxed magnetohydrodynamic plasma

We report the first measurements of equations of state of a fully relaxed magnetohydrodynamic (MHD) laboratory plasma. Parcels of magnetized plasma, called Taylor states, are formed in a coaxial magnetized plasma gun, and are allowed to relax and drift into a closed flux conserving volume. Density, ion temperature, and magnetic field are measured as a function of time as the Taylor states compress and heat. The theoretically predicted MHD and double adiabatic equations of state are compared to experimental measurements. We find that the MHD equation of state is inconsistent with our data.Comment: 4 pages, 4 figure

Magnetic-Field-Induced Hybridization of Electron Subbands in a Coupled Double Quantum Well

We employ a magnetocapacitance technique to study the spectrum of the soft two-subband (or double-layer) electron system in a parabolic quantum well with a narrow tunnel barrier in the centre. In this system unbalanced by gate depletion, at temperatures T\agt 30 mK we observe two sets of quantum oscillations: one originates from the upper electron subband in the closer-to-the-gate part of the well and the other indicates the existence of common gaps in the spectrum at integer fillings. For the lowest filling factors $\nu=1$ and $\nu=2$, both the common gap presence down to the point of one- to two-subband transition and their non-trivial magnetic field dependences point to magnetic-field-induced hybridization of electron subbands.Comment: Major changes, added one more figure, the latest version to be published in JETP Let

The Society’s Perspective of Human Trafficking

Human trafficking has been a great concern in Indonesia and around the world, because the impact is devastating for the individual, the family, and later on the society as well. Meanwhile, human trafficking keeps happening because of the vulnerability of the victims, related to the social and economic backgrounds. The aim of this research is to identify society’s perspective on human trafficking and its scope. Our intention is to identify the possible means to decrease the number, and perhaps that will be suitable in other societies as well. This study used the survey method in a number of sub-districts in several districts in East Java, Indonesia, namely Gempol (Pasuruan), Karang Binangun (Lamongan), Papar (Kediri), Nglegok (Blitar), and Donomulyo (Malang). The subjects in this study were representatives of community leaders, village staff, and community organizations, such as PKK cadres, working groups, teachers, youth and dasa wisma, culminating in as many as 141 participants. The data were obtained through questionnaires and focus group discussions (FGD). FGD questionnaires and guidance were based on issues relating to the research objectives, ie.: identifying human trafficking based on society’s perspectives. The data were analyzed using a descriptive analysis of survey results reported in tabulation and percentages. This study showed that in general, most of the society members who participated in this study had good knowledge about human trafficking. They gained insight from a variety of sources and more from television. This showed that the government and private sectors in Indonesia had considerable concern for this phenomenon. However, the number of human trafficking cases in Indonesia has not decreased. There are still some people who do not know the details about human trafficking, for example about the actions to be taken when seeing or experiencing this scenario. If people know about the insights and knowledge of human trafficking, they can have the ability to detect the existence of human trafficking problems in their surroundings, thereby reducing the level of society’s vulnerability to the case. We propose that the number of human trafficking may be decreased by the participation of both the government and the society together, by detecting the signs by the society, close relatives, and close friends of the vulnerable individuals

The Society’s Perspective of Human Trafficking

Human trafficking has been a great concern in Indonesia and around the world, because the impact is devastating for the individual, the family, and later on the society as well. Meanwhile, human trafficking keeps happening because of the vulnerability of the victims, related to the social and economic backgrounds. The aim of this research is to identify society’s perspective on human trafficking and its scope. Our intention is to identify the possible means to decrease the number, and perhaps that will be suitable in other societies as well. This study used the survey method in a number of sub-districts in several districts in East Java, Indonesia, namely Gempol (Pasuruan), Karang Binangun (Lamongan), Papar (Kediri), Nglegok (Blitar), and Donomulyo (Malang). The subjects in this study were representatives of community leaders, village staff, and community organizations, such as PKK cadres, working groups, teachers, youth and dasa wisma, culminating in as many as 141 participants. The data were obtained through questionnaires and focus group discussions (FGD). FGD questionnaires and guidance were based on issues relating to the research objectives, ie.: identifying human trafficking based on society’s perspectives. The data were analyzed using a descriptive analysis of survey results reported in tabulation and percentages. This study showed that in general, most of the society members who participated in this study had good knowledge about human trafficking. They gained insight from a variety of sources and more from television. This showed that the government and private sectors in Indonesia had considerable concern for this phenomenon. However, the number of human trafficking cases in Indonesia has not decreased. There are still some people who do not know the details about human trafficking, for example about the actions to be taken when seeing or experiencing this scenario. If people know about the insights and knowledge of human trafficking, they can have the ability to detect the existence of human trafficking problems in their surroundings, thereby reducing the level of society’s vulnerability to the case. We propose that the number of human trafficking may be decreased by the participation of both the government and the society together, by detecting the signs by the society, close relatives, and close friends of the vulnerable individuals

Topological Phase Transition in the ν=2/3\nu=2/3 Quantum Hall Effect

The double layer $\nu=2/3$ fractional quantum Hall system is studied using the edge state formalism and finite-size diagonalization subject to periodic boundary conditions. Transitions between three different ground states are observed as the separation as well as the tunneling between the two layers is varied. Experimental consequences are discussed.Comment: 11 pages, REVTEX v3.0, 7 figure