Surgical clothing systems in laminar airflow operating room: a numerical assessment

SummaryThis study compared two different laminar airflow distribution strategies – horizontal and vertical – and investigated the effectiveness of both ventilation systems in terms of reducing the sedimentation and distribution of bacteria-carrying particles. Three different staff clothing systems, which resulted in source strengths of 1.5, 4 and 5CFU/s per person, were considered. The exploration was conducted numerically using a computational fluid dynamics technique. Active and passive air sampling methods were simulated in addition to recovery tests, and the results were compared. Model validation was performed through comparisons with measurement data from the published literature. The recovery test yielded a value of 8.1min for the horizontal ventilation scenario and 11.9min for the vertical ventilation system. Fewer particles were captured by the slit sampler and in sedimentation areas with the horizontal ventilation system. The simulated results revealed that under identical conditions in the examined operating room, the horizontal laminar ventilation system performed better than the vertical option. The internal constellation of lamps, the surgical team and objects could have a serious effect on the movement of infectious particles and therefore on postoperative surgical site infections

Приоритетные направления разработки курса дистанционного обучения в высшей медицинской школе

ИНФОРМАЦИОННЫЕ СИСТЕМЫОБРАЗОВАНИЕ ДИСТАНЦИОННОЕДИСТАНЦИОННЫЕ ТЕЛЕКОНСУЛЬТАЦИИОБРАЗОВАНИЕ МЕДИЦИНСКОЕОБРАЗОВАНИЯ ТЕХНОЛОГИЯМУЛЬТИМЕДИ

Experimental study of energy performance in low-temperature hydronic heating systems

Energy consumption, thermal environment and environmental impacts were analytically and experimentally studied for different types of heat emitters. The heat emitters studied were conventional radiator, ventilation radiator, and floor heating with medium-, low-, and very-low-temperature supply, respectively. The ventilation system in the lab room was a mechanical exhaust ventilation system that provided one air change per hour of fresh air through the opening in the external wall with a constant temperature of 5 °C, which is the mean winter temperature in Copenhagen. The parameters studied in the climate chamber were supply and return water temperature from the heat emitters, indoor temperature, and heat emitter surface temperature. Experiments showed that the mean supply water temperature for floor heating was the lowest, i.e. 30 °C, but it was close to the ventilation radiator, i.e. 33 °C. The supply water temperature in all measurements for conventional radiator was significantly higher than ventilation radiator and floor heating; namely, 45 °C. Experimental results indicated that the mean indoor temperature was close to the acceptable level of 22 °C in all cases. For energy calculations, it was assumed that all heat emitters were connected to a ground-source heat pump. Analytical calculations showed that using ventilation radiator and floor heating instead of conventional radiator resulted in a saving of 17% and 22% in heat pump's electricity consumption, respectively. This would reduce the CO2 emission from the building's heating system by 21 % for the floor heating and by 18% for the ventilation radiator compared to the conventional radiator.QC 20160128</p

Laboratory study of subjective perceptions to low temperature heating systems with exhaust ventilation in Nordic countries

Given the global trends of rising energy demand and the increasing utilization of low-grade renewable energy, low-temperature heating systems can play key roles in improving building energy efficiency while providing a comfortable indoor environment. To meet the need to retrofit existing buildings in Nordic countries for greater energy efficiency, this study focused on human subjects’ thermal sensation, thermal comfort, thermal acceptability, draft acceptability, and perceived air quality when three low-temperatureheating systems were used: conventional radiator, ventilation radiator, or floor heating with exhaust ventilation. Human subject tests were carried out in the climate chamber at the Technical University of Denmark. In total, 24 human subjects, 12 females and 12 males, participated in the tests during the winter season. The results show that no significant differences in thermal sensation and thermal comfort between the three heating systems. Ventilation radiator promised a comfortable indoor environment with a decreased watersupply temperature and floor heating with exhaust ventilation can provide a basic thermal comfort level. Thermal acceptability and draft acceptability show variations in different heating systems. Gender has significant influences on thermal sensation, draft acceptability, and preference of clo values. Personal thermal preference is observed between males and females. The males prefer to dress lighter than the females, but both can get the same thermal comfort level. It is concluded that low-temperature heating systems using exhaust air ventilation are a potentially solution when buildings are being retrofitted for improved energy efficiency and comfort of the occupants

Demand-controlled ventilation in new residential buildings : consequences on indoor air quality and energy savings

The consequences on indoor air quality (IAQ) and potential of energy savings when using a variable airvolume (VAV) ventilation system were studied in a newly built Swedish building. Computer simulationswith IDA Indoor Climate and Energy 4 (ICE) and analytical models were used to study the IAQ andenergy savings when switching the ventilation flow from 0.375 ls1m2 to 0.100 ls1m2 duringunoccupancy. To investigate whether decreasing the ventilation rate to 0.1 ls1m2 during unoccupancy,based on Swedish building regulations, BBR, is acceptable and how long the reduction can lastfor an acceptable IAQ, four strategies with different VAV durations were proposed. This study revealedthat decreasing the flow rate to 0.1 ls1m2 for more than 4 h in an unoccupied newly built buildingcreates unacceptable IAQ in terms of volatile organic compounds concentration. Hence, if the durationof unoccupancy in the building is more than 4 h, it is recommended to increase the ventilation rate from0.100 ls1m2 to 0.375 ls1m2 before the home is occupied. The study showed that when the investigatedbuilding was vacant for 10 h during weekdays, increasing the ventilation rate 2 h before occupantsarrive home (low ventilation rate for 8 h) creates acceptable IAQ conditions. In this system, theheating requirements for ventilation air and electricity consumption for the ventilation fan weredecreased by 20% and 30%, respectively.QC 20150429</p

Demand Controlled Ventilation in a Combined Ventilation and Radiator System

With growing concerns for efficient and sustainable energy treatment in buildings there is a need for balanced and intelligent ventilation solutions. This paper presents a strategy for demand controlled ventilation with ventilation radiators, a combined heating and ventilation system. The ventilation rate was decreased from normal requirements (per floor area) of 0.375 l·s-1·m-2 to 0.100 l·s-1·m-2 when the residence building was un-occupied. The energy saving potential due to decreased ventilation and fan power was analyzed by IDA Indoor Climate and Energy 4 (ICE) simulation program. The result showed that 16 % of the original energy consumption for space and ventilation heating could be saved by utilizing ventilation on demand.QC 20130612</p

The impact of air-tightness in the retrofitting practice of low temperature heating

In Sweden, the energy usage in existing residential buildings amounted to 147 TWh in 2012, equivalent to almost 40 % of the final overall national energy usage. Among all the end users in building service sectors, 60 % of the final energy in Sweden is used for space heating and domestic hot water (DHW) production in 2013. In order to reduce the supply temperature for space heating in existing buildings, combined approaches are favorably adopted: to reduce the net energy demand by air-tightness and insulation retrofits; and renovate the conventional high temperature heating to low temperature heating (LTH) systems. As an energy-efficiency alternative, LTH technology has shown promising advantages and shortcuts to improve the coefficient of performance (COP) of heat pump system, which further saves primary energy. However, existing modeling achievements and field testing reveal that the attained application of LTH has a relatively high requirement to the air-tightness in new constructed single-family houses. Moreover, in some leaky multi-family building stock with low envelope surface temperature, LTH may have limited energy saving potentials. How to evaluate the impact of air-tightness for the LTH implementation and energy saving potentials in existing houses are not sufficiently attained so far. This paper presents a modeling approach combining LTH simulation with air-tightness evaluation, aimed to estimate whether the selected existing building types can cope with LTH with upgraded primary energy savings. In addition, the impact of air-tightness retrofits for LTH implementation in selected Swedish residential buildings is of interests. In the simulation Consoli Retro are employed to simulate the energy performance. It is revealed that the combined effect of floor heating/ ventilation radiators and air-tightness retrofits to 1/1.5 ACH can contribute 19 % to 36 % primary energy savings in total. However, different LTH systems and archetypes have varies sensitivities to air-tightness retrofits. Benchmark the impact of air-tightness to different LTH systems needs further investigations among other archetypes and on-site measures for future application of LTH on a larger scope.QC 20140826Nordic Built-Low temperature heating in retrofitting practic

Energy Performance Evaluation of New Residential Buildings with a Low-Temperature Heating System : Results from Site Measurements and Building Energy Simulations

The purpose of this study was to investigate the national energy requirements of a modern, newly built residential development including four semi-detached houses in Stockholm, Sweden. The apartments were equipped with heat pumps utilising exhaust heat, resulting in a hydronic heating system adapted to low supply temperature. Ventilation radiators as combined ventilation and heating systems were installed in the two upper floors. Efficient preheating of incoming ventilation air in the ventilation radiator was an expected advantage. Under-floor heating with traditional air supply above windows was used on the ground floor. Energy consumption was calculated by IDA ICE 4, a building energy simulation (BES) program. In addition site measurements were made for comparison and validation of simulation results. Total energy consumption was monitored in the indoor temperature controlled buildings during the heating season. Our results so far indicate that total energy requirements in the buildings can be met in a satisfactory manner.QC 20130612</p

Energy Performance Evaluation of New Residential Buildings with a Low-Temperature Heating System : Results from Site Measurements and Building Energy Simulations

The purpose of this study was to investigate the national energy requirements of a modern, newly built residential development including four semi-detached houses in Stockholm, Sweden. The apartments were equipped with heat pumps utilising exhaust heat, resulting in a hydronic heating system adapted to low supply temperature. Ventilation radiators as combined ventilation and heating systems were installed in the two upper floors. Efficient preheating of incoming ventilation air in the ventilation radiator was an expected advantage. Under-floor heating with traditional air supply above windows was used on the ground floor. Energy consumption was calculated by IDA ICE 4, a building energy simulation (BES) program. In addition site measurements were made for comparison and validation of simulation results. Total energy consumption was monitored in the indoor temperature controlled buildings during the heating season. Our results so far indicate that total energy requirements in the buildings can be met in a satisfactory manner.QC 20130612</p