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

CFD modeling of heat charging process in a direct-contact container for mobilized thermal energy storage

Thermal energy storage and phase change materials become increasingly important topics during the last 20 years for heating and cooling purpose in buildings. When there is time delay or mismatch between producing energy and energy demand, thermal energy storage provides a great solution. Furthermore, in the case of space differences between supplier and end user, the mobilized thermal energy storage can be introduced. In this solution the waste and excess heat, which is released from a factory, is recycled by storing in the PCM through heat transfer fluid and transported by a mobilized container to a consumer. In charging process the PCM is initially solid; it becomes melt while the heat transfer fluid flows inside the container. In order to achieve the highest efficiency of transferring energy in charging and discharging process, the melting and solidification times should be considered. In this paper the heat transfer behavior of the phase change material during the charging process has been simulated by CFD modeling of the previous work on Mobilized Thermal Energy Storage. Transient two dimensional heat transfer problems are solved by simulating in the Fluent software while heat is stored in PCM. In order to simulate the phase change in PCM, the Volume-Of-Fluid (VOF) method is extended by the energy conservation to solve for the temperature in the material. The validation of the computational model has been conducted by comparison between experimental data and CFD results; the agreements between the results are convincing. The liquid fraction as functions of time is achieved and the total melting time is estimated. Presented results in this paper lay the groundwork for a future investigation to get more accurate prediction of thermal performance of mobilized thermal energy storage system.

CFD modeling of heat charging process in a direct-contact container for mobilized thermal energy storage

Thermal energy storage and phase change materials become increasingly important topics during the last 20 years for heating and cooling purpose in buildings. When there is time delay or mismatch between producing energy and energy demand, thermal energy storage provides a great solution. Furthermore, in the case of space differences between supplier and end user, the mobilized thermal energy storage can be introduced. In this solution the waste and excess heat, which is released from a factory, is recycled by storing in the PCM through heat transfer fluid and transported by a mobilized container to a consumer. In charging process the PCM is initially solid; it becomes melt while the heat transfer fluid flows inside the container. In order to achieve the highest efficiency of transferring energy in charging and discharging process, the melting and solidification times should be considered. In this paper the heat transfer behavior of the phase change material during the charging process has been simulated by CFD modeling of the previous work on Mobilized Thermal Energy Storage. Transient two dimensional heat transfer problems are solved by simulating in the Fluent software while heat is stored in PCM. In order to simulate the phase change in PCM, the Volume-Of-Fluid (VOF) method is extended by the energy conservation to solve for the temperature in the material. The validation of the computational model has been conducted by comparison between experimental data and CFD results; the agreements between the results are convincing. The liquid fraction as functions of time is achieved and the total melting time is estimated. Presented results in this paper lay the groundwork for a future investigation to get more accurate prediction of thermal performance of mobilized thermal energy storage system.

Low-Temperature Heating and Ventilation for Sustainability in Energy Efficient Buildings

In 2013, the building sector consumed approximately 39 % of the total final energy use in Sweden. Energy used for heating and hot water was responsible for approximately 60 % of the total energy consumption in the building sector. Therefore, energy-efficient and renewable-based heating and ventilation systems have high potential for energy savings. The potentials studied in this thesis include the combination of a low-temperature heat emitter (supply temperature below 45 °C) with heat pump and/or seasonal thermal energy storage, and variable air volume ventilation system. The main aim of this thesis was to evaluate energy savings and indoor air quality when those energy-efficient and sustainable heating and ventilation systems were implemented in buildings. For this purpose, on-site measurements, lab tests, analytical models, and building energy simulation tool IDA Indoor Climate and Energy 4 were used. Annual on-site measurements for five new two-family houses with low- and very-low-temperature heat emitters connected to an exhaust air heat pump showed  that  between  45–51 kWh∙m-2 energy was used  to  produce  and transport supply water for space heating and domestic hot water. Statistical data showed that these values are 39–46 % lower compared to the energy requirement for the same usage  which is, 84 kWh∙m-2)  in  an  average Swedish new single- and two-family house. Annual on-site measurements for five new two-family houses with low- and very-low-temperature heat emitters connected to an exhaust air heat pump showed that between 45–51 kWh∙m-2 energy was used to produce and transport supply water for space heating and domestic hot water. Statistical data showed that these values are 39–46 % lower compared to the energy requirement for the same usage (which is, 84 kWh∙m-2) in an average Swedish new single- and two-family house. In order to compare the energy performance of very-low- and low-temperature heat emitters with medium-temperature heat emitters under the same condition, lab tests were conducted in a climate chamber facility at Technical University of Denmark (DTU). To cover the heat demand of 20 W·m-2 by active heating, measurements showed that the required supply water temperatures were 45 ºC for the conventional radiator, 33 ºC in ventilation radiator and 30 ºC in floor heating. This 12–15 ºC temperature reduction with ventilation radiator and floor heating resulted in 17–22 % savings in energy consumption compared to a reference case with conventional radiator. Reducing the supply temperature to the building’s heating system allows using more renewable and low-quality heat sources. In this thesis, the application of seasonal thermal energy storage in combination with heat pump in a building with very-low-, low-, and medium-temperature heat emitters was investigated. Analytical model showed that using a 250 m3 hot water seasonal storage tank connected to a 50 m2 solar collector and a heat pump resulted in 85–92 % of the total heat demand being covered by solar energy. In addition to the heating system, this thesis also looked at ventilation system in terms of implementing variable (low) air volume ventilation instead of a constant (high) flow in new and retrofitted old buildings. The analytical model showed that, for new buildings with high volatile organic compound concentration during initial years of construction, decreasing the ventilation rate to 0.1 L·s-1·m-2 during the entire un-occupancy period (from 8:00–18:00) creates unacceptable indoor air quality when home is occupied at  18:00.  So,  in  order  to  create  acceptable  indoor  air  quality  when  the occupants come home, a return to the normal ventilation requirements was suggested to take place two hours before the home was occupied. This eight- hour ventilation reduction produced savings of 20 % for ventilation heating and 30 % for electricity consumption by ventilation fan. In addition, the influence of different ventilation levels on indoor air quality and energy savings was studied experimentally and analytically in a single- family house occupied by two adults and one infant. Carbon dioxide (CO2) concentration as an indicator of indoor air quality was considered in order to find  appropriate  ventilation  rates.  Measurements  showed  that,  with  an 0.20 L∙s-1∙m-2  ventilation rate, the CO2   level  was always below 950 ppm, which shows that this level is sufficient for the reference building (CO2 lower than 1000 ppm is acceptable). Calculations showed that low ventilation rates of 0.20 L∙s1∙m-2 caused 43 % savings of the combined energy consumption for  ventilation  fan  and  ventilation  heating  compared  to  the  cases  with 0.35 L∙s-1∙m-2  as a normal ventilation rate recommended by BBR (Swedish Building Regulations).  QC 20150626</p

Energy and Indoor Environment in New Buildings with Low-Temperature Heating System

The aim of this thesis was to evaluate new buildings with low-temperature heating systems in terms of energy consumption and thermal comfort, and to pay some attention to energy savings and indoor air quality. To reach this aim, on-site measurements as well as building energy simulations using IDA Indoor Climate and Energy (ICE) 4 were performed. Results show that the investigated buildings with low-temperature heating system could meet the energy requirements of Swedish regulations in BBR (Boverkets byggregler), as well as provide a good level of thermal comfort. Implementing variable air volume ventilation instead of constant flow, i.e. decreasing the ventilation air from 0.35 to 0.10 l·s-1·m-2 during the whole unoccupancy (10 hours), gave up to 23 % energy savings for heating the ventilation air. However, the indoor air quality was not acceptable because VOC (volatile organic compound) concentration was slightly above the acceptable range for one hour after occupants arrive home. So, in order to create acceptable indoor air quality a return back to the normal ventilation requirements was suggested to take place two hours before the home was occupied. This gave 20 % savings for ventilation heating. The results of this study are in line with the European Union 20-20-20 goal to increase the efficiency of buildings by 20 % to the year 2020.QC 20130612</p

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

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 of Ground-source Heat Pump and Photovoltaic/thermal (PV/T) in Retrofitted and New Buildings: Two Case Studies Using Simulation and On-site Measurements

This paper aims to contribute by presenting calculated and measured electricity usage in two single-family case studies during the heating season of 2019-2020 located in Stockholm, Sweden. The electricity usage included consumption by heat pumps’ compressor to cover space heating and domestic hot water, auxiliary energy for fans and pumps, and ventilation system. The first case study was built in 1936 with an oil burner, which was renovated to a ground-source heat pump (GSHP) in 2015, and the second case study was a new building built in 2013 with a GSHP. The application of photovoltaic/thermal (PVT) systems in combination with GSHP was theoretically investigated for both case studies. Buildings were modelled using the energy simulation tool IDA Indoor Climate and Energy (ICE), and the model was validated against the measured electrical energy usage. PVT was designed to balance the maximum heat production with domestic hot water consumption during the summer months. Simulation results revealed that combining GSHP with 5 m2 grid-connected PVT gave 21% and 22% energy savings in case study 1 and case study 2, respectively. Employing a battery storage to store extra electricity production by PVT increased the energy savings to 24 % and 32 % for case study 1 and case study 2, respectively. Moreover, in both cases approximately half of the total annual domestic hot water need was prepared by 5 m2 PVT.publishedVersio

Energy Performance of Ground-source Heat Pump and Photovoltaic/thermal (PV/T) in Retrofitted and New Buildings : Two Case Studies Using Simulation and On-site Measurements

This paper aims to contribute by presenting calculated and measured electricity usage in two single-family case studies during the heating season of 2019-2020 located in Stockholm, Sweden. The electricity usage included consumption by heat pumps’ compressor to cover space heating and domestic hot water, auxiliary energy for fans and pumps, and ventilation system. The first case study was built in 1936 with an oil burner, which was renovated to a ground-source heat pump (GSHP) in 2015, and the second case study was a new building built in 2013 with a GSHP. The application of photovoltaic/thermal (PVT) systems in combination with GSHP was theoretically investigated for both case studies. Buildings were modelled using the energy simulation tool IDA Indoor Climate and Energy (ICE), and the model was validated against the measured electrical energy usage. PVT was designed to balance the maximum heat production with domestic hot water consumption during the summer months. Simulation results revealed that combining GSHP with 5 m2 grid-connected PVT gave 21% and 22% energy savings in case study 1 and case study 2, respectively. Employing a battery storage to store extra electricity production by PVT increased the energy savings to 24 % and 32 % for case study 1 and case study 2, respectively. Moreover, in both cases approximately half of the total annual domestic hot water need was prepared by 5 m2 PVT.QC 20200821</p