Milorad Bojic | University of Kragujevac (original) (raw)
Papers by Milorad Bojic
The light pipes are innovative devices able to transport and distribute natural light without hea... more The light pipes are innovative devices able to transport and distribute natural light without heat transfer in dark rooms. There are a lot of natural lighting applications able to predict the behaviour of light in a room through a traditional opening. Only few of them are able to model complex systems such as daylight guidance systems. Added to this, they seem to provide disparate and inconsistent results with respect to the actual performance of light pipes. The purpose of this publication is to present the approach undertaken and the results obtained to highlight the problem. To do this, a survey of the different programs has been carried out internationally to model tubular devices. Then, an inter-software comparative analysis was implemented for some of the applications listed. In order to assess the accuracy of numerical results, the results of an experiment - 1:1 scale and in real weather conditions - were used as references to evaluate the chosen applications. We saw that the various selected programs tend to overestimate or underestimate the real phenomenon. The use of an experimental database permitted to put forward the most efficient applications. These results support the future goal to develop a new model. Future prospects of our study that can emerge are mainly based on the introduction of a new model for predicting the performance of light pipes and its integration in two software products developed within laboratory: CODYRUN (a multi-zone software integrating thermal building simulation, airflow transfers, lighting and pollutants) and HEMERA (a daylighting analysis software).
Applied Energy, 2015
In Serbia, radiant heating is increasingly used. Also, in Serbia, the largest portion of produced... more In Serbia, radiant heating is increasingly used. Also, in Serbia, the largest portion of produced electricity is from the fossil fuels which results in a high value of primary energy consumption coefficient (R). This situation raises the question of the justification of the use of ground sources heat pump (GHSP) over natural gas boiler and GSHP with PV array. Also, the impact of the embodied energy and embodied carbon was included in this paper. The operation of this house is simulated by software EnergyPlus. The results indicated that the newly-developed floor-ceiling radiant heating system has the best performances and classical ceiling heating has the worst performances. However in future with decrease of R, it is shown that the panel heating powered by GSHP may have lower total energy consumption than that of such a system powered by natural gas. For the wall panel heating, this would happen for the highest value of R, while in the case of the ceiling heating, it would appear for the lowest value of R.
Building and Environment, 2000
The unbalanced distribution of heat in a district-heating system may be caused by the increase of... more The unbalanced distribution of heat in a district-heating system may be caused by the increase of hydraulic resistance of pipe network, decrease of heat transmittance of radiators inside buildings, and increase of heat transmittance of building envelope. This situation yields the overheating of some buildings and underheating of other buildings. A district-heating system is analyzed that consists of heat plant, primary pipe network, substation, secondary pipe network, and three buildings. A steady-state, bottom-up approach and the ...
Energy, 1997
We have used a thermoelectric cooler and a coldness-recovery device (CRD) for summer air conditio... more We have used a thermoelectric cooler and a coldness-recovery device (CRD) for summer air conditioning of a train carriage. The coldness-recovery device is a countercurrent heat exchanger. This air-conditioning system is described in terms of a heat-exchanger network for which we have developed computer software (GOLAM2-R). We have simulated six different control scenarios for the energy system. Use of the coldness-recovery device produces a higher COP than an increase of the Peltier coefficient for the thermoelectric ...
Energy, 1999
Solar energy accumulated in the soil may be utilized with an air-to-earth heat exchanger (ATEHE) ... more Solar energy accumulated in the soil may be utilized with an air-to-earth heat exchanger (ATEHE) which has two pipes buried in the soil, one made of PVC and one of steel. During the winter, air is heated; during the summer, it is cooled and then used in an air-conditioning device. To obtain the mathematical model of the ATEHE, we divided the soil and pipes into elementary volumes, used steady-state energy equations, and applied a time-marching method. We determined how the season, soil thermal conductivity and pipe spacing ...
Energy and Buildings, 2000
Energy and Buildings, 2001
Energy Conversion and Management, 2002
Energy and Buildings, 2002
Energy, 1995
We use a recovery heat exchanger (RHE) in an industrial building to heat incoming air for space h... more We use a recovery heat exchanger (RHE) in an industrial building to heat incoming air for space heating by using the heat contents of some of the refuse hot-air flows (RAF). Several RAFs are often available with different flow rates and temperatures. A proper scenario for use of their heat contents is essential for efficient management of the energy system. Using a steady-state, bottom-up approach, we have obtained a set of equations that we have linearized. Linear programming (LP) is then used and LINE software has been developed. ...
Energy Conversion and Management, 2002
Energy, 1997
An air-to-earth heat exchanger (ATEHE) consists of pipes buried in soil. We have evaluated the te... more An air-to-earth heat exchanger (ATEHE) consists of pipes buried in soil. We have evaluated the technical and economic performance of an ATEHE coupled to the system for heating or cooling of a building that uses 100% fresh air as heating or cooling medium during winter and summer. The soil is divided into elementary layers. The problem solved, is non stationary; however, steady state-energy equations are used for soil layers in each time step. It is found that the use of the ATEHE covers a portion of the daily building needs for space ...
Energy and Buildings, 2002
Building and Environment, 2002
Nowadays, many apartments in residential buildings in Hong Kong are equipped with air-conditioner... more Nowadays, many apartments in residential buildings in Hong Kong are equipped with air-conditioners to provide comfort cooling for the living, dining and bedrooms. Air-conditioners serving the living and dining rooms would be operated mostly in the evenings and sometimes during daytime as well, but those serving the bedrooms could remain operating overnight. Other rooms, such as bathrooms and kitchens, will not normally be air-conditioned. The paper describes a study into the influence of the building envelope ...
Abstract: Due to the current environmental situation, energy saving has become the leading drive ... more Abstract: Due to the current environmental situation, energy saving has become the leading drive in modern research. Although the residential houses in tropical climate do not use air conditioning to maintain thermal comfort in order to avoid use of electricity. As the thermal comfort is maintained by adequate envelope composition and natural ventilation, this paper shows that it is possible to determine the thickness of envelope layers for which the best thermal comfort is obtained.
Solar energy accumulated in the soil may be utilized with an air-to-earth heat exchanger (ATEHE) ... more Solar energy accumulated in the soil may be utilized with an air-to-earth heat exchanger (ATEHE) which has two pipes buried in the soil, one made of PVC and one of steel. During the winter, air is heated; during the summer, it is cooled and then used in an air-conditioning device. To obtain the mathematical model of the ATEHE, we divided the soil and pipes into elementary volumes, used steady-state energy equations, and applied a time-marching method.
SUMMARY Since the global environmental crisis, energy concerns increase in priority, and it is im... more SUMMARY Since the global environmental crisis, energy concerns increase in priority, and it is important to understand house residents' position on energy savings in different countries. This paper presents results of the 2011 public opinion survey in Serbia in city of Kragujevac. The survey examines the awareness of the Serbian public on energy savings in low-rise housing. The investigation found out that about 43% of respondents do care about energy saving when they build the house and 94% when they operate the house.
SUMMARY Low temperature heating panel systems offer distinctive advantages in terms of thermal co... more SUMMARY Low temperature heating panel systems offer distinctive advantages in terms of thermal comfort and energy consumption, allowing work with low exergy sources. The purpose of this paper is to compare floor, wall, ceiling, and floor-ceiling panel heating systems in terms of energy, exergy and CO2 emissions.
At the Faculty of Mechanical Engineering of Kragujevac, a heat pump (water–water) was installed a... more At the Faculty of Mechanical Engineering of Kragujevac, a heat pump (water–water) was installed as a design made by the senior undergraduates within the academic course Heating and Air-conditioning. This project was financed by ASHRAE. Using electrical power on its compressor, the heat pump transfers heat from the heat source (lower temperature) to the cold source (heat sink)(higher temperature), which comprises central heating radiators, floor heating system and technical water heating system.
The light pipes are innovative devices able to transport and distribute natural light without hea... more The light pipes are innovative devices able to transport and distribute natural light without heat transfer in dark rooms. There are a lot of natural lighting applications able to predict the behaviour of light in a room through a traditional opening. Only few of them are able to model complex systems such as daylight guidance systems. Added to this, they seem to provide disparate and inconsistent results with respect to the actual performance of light pipes. The purpose of this publication is to present the approach undertaken and the results obtained to highlight the problem. To do this, a survey of the different programs has been carried out internationally to model tubular devices. Then, an inter-software comparative analysis was implemented for some of the applications listed. In order to assess the accuracy of numerical results, the results of an experiment - 1:1 scale and in real weather conditions - were used as references to evaluate the chosen applications. We saw that the various selected programs tend to overestimate or underestimate the real phenomenon. The use of an experimental database permitted to put forward the most efficient applications. These results support the future goal to develop a new model. Future prospects of our study that can emerge are mainly based on the introduction of a new model for predicting the performance of light pipes and its integration in two software products developed within laboratory: CODYRUN (a multi-zone software integrating thermal building simulation, airflow transfers, lighting and pollutants) and HEMERA (a daylighting analysis software).
Applied Energy, 2015
In Serbia, radiant heating is increasingly used. Also, in Serbia, the largest portion of produced... more In Serbia, radiant heating is increasingly used. Also, in Serbia, the largest portion of produced electricity is from the fossil fuels which results in a high value of primary energy consumption coefficient (R). This situation raises the question of the justification of the use of ground sources heat pump (GHSP) over natural gas boiler and GSHP with PV array. Also, the impact of the embodied energy and embodied carbon was included in this paper. The operation of this house is simulated by software EnergyPlus. The results indicated that the newly-developed floor-ceiling radiant heating system has the best performances and classical ceiling heating has the worst performances. However in future with decrease of R, it is shown that the panel heating powered by GSHP may have lower total energy consumption than that of such a system powered by natural gas. For the wall panel heating, this would happen for the highest value of R, while in the case of the ceiling heating, it would appear for the lowest value of R.
Building and Environment, 2000
The unbalanced distribution of heat in a district-heating system may be caused by the increase of... more The unbalanced distribution of heat in a district-heating system may be caused by the increase of hydraulic resistance of pipe network, decrease of heat transmittance of radiators inside buildings, and increase of heat transmittance of building envelope. This situation yields the overheating of some buildings and underheating of other buildings. A district-heating system is analyzed that consists of heat plant, primary pipe network, substation, secondary pipe network, and three buildings. A steady-state, bottom-up approach and the ...
Energy, 1997
We have used a thermoelectric cooler and a coldness-recovery device (CRD) for summer air conditio... more We have used a thermoelectric cooler and a coldness-recovery device (CRD) for summer air conditioning of a train carriage. The coldness-recovery device is a countercurrent heat exchanger. This air-conditioning system is described in terms of a heat-exchanger network for which we have developed computer software (GOLAM2-R). We have simulated six different control scenarios for the energy system. Use of the coldness-recovery device produces a higher COP than an increase of the Peltier coefficient for the thermoelectric ...
Energy, 1999
Solar energy accumulated in the soil may be utilized with an air-to-earth heat exchanger (ATEHE) ... more Solar energy accumulated in the soil may be utilized with an air-to-earth heat exchanger (ATEHE) which has two pipes buried in the soil, one made of PVC and one of steel. During the winter, air is heated; during the summer, it is cooled and then used in an air-conditioning device. To obtain the mathematical model of the ATEHE, we divided the soil and pipes into elementary volumes, used steady-state energy equations, and applied a time-marching method. We determined how the season, soil thermal conductivity and pipe spacing ...
Energy and Buildings, 2000
Energy and Buildings, 2001
Energy Conversion and Management, 2002
Energy and Buildings, 2002
Energy, 1995
We use a recovery heat exchanger (RHE) in an industrial building to heat incoming air for space h... more We use a recovery heat exchanger (RHE) in an industrial building to heat incoming air for space heating by using the heat contents of some of the refuse hot-air flows (RAF). Several RAFs are often available with different flow rates and temperatures. A proper scenario for use of their heat contents is essential for efficient management of the energy system. Using a steady-state, bottom-up approach, we have obtained a set of equations that we have linearized. Linear programming (LP) is then used and LINE software has been developed. ...
Energy Conversion and Management, 2002
Energy, 1997
An air-to-earth heat exchanger (ATEHE) consists of pipes buried in soil. We have evaluated the te... more An air-to-earth heat exchanger (ATEHE) consists of pipes buried in soil. We have evaluated the technical and economic performance of an ATEHE coupled to the system for heating or cooling of a building that uses 100% fresh air as heating or cooling medium during winter and summer. The soil is divided into elementary layers. The problem solved, is non stationary; however, steady state-energy equations are used for soil layers in each time step. It is found that the use of the ATEHE covers a portion of the daily building needs for space ...
Energy and Buildings, 2002
Building and Environment, 2002
Nowadays, many apartments in residential buildings in Hong Kong are equipped with air-conditioner... more Nowadays, many apartments in residential buildings in Hong Kong are equipped with air-conditioners to provide comfort cooling for the living, dining and bedrooms. Air-conditioners serving the living and dining rooms would be operated mostly in the evenings and sometimes during daytime as well, but those serving the bedrooms could remain operating overnight. Other rooms, such as bathrooms and kitchens, will not normally be air-conditioned. The paper describes a study into the influence of the building envelope ...
Abstract: Due to the current environmental situation, energy saving has become the leading drive ... more Abstract: Due to the current environmental situation, energy saving has become the leading drive in modern research. Although the residential houses in tropical climate do not use air conditioning to maintain thermal comfort in order to avoid use of electricity. As the thermal comfort is maintained by adequate envelope composition and natural ventilation, this paper shows that it is possible to determine the thickness of envelope layers for which the best thermal comfort is obtained.
Solar energy accumulated in the soil may be utilized with an air-to-earth heat exchanger (ATEHE) ... more Solar energy accumulated in the soil may be utilized with an air-to-earth heat exchanger (ATEHE) which has two pipes buried in the soil, one made of PVC and one of steel. During the winter, air is heated; during the summer, it is cooled and then used in an air-conditioning device. To obtain the mathematical model of the ATEHE, we divided the soil and pipes into elementary volumes, used steady-state energy equations, and applied a time-marching method.
SUMMARY Since the global environmental crisis, energy concerns increase in priority, and it is im... more SUMMARY Since the global environmental crisis, energy concerns increase in priority, and it is important to understand house residents' position on energy savings in different countries. This paper presents results of the 2011 public opinion survey in Serbia in city of Kragujevac. The survey examines the awareness of the Serbian public on energy savings in low-rise housing. The investigation found out that about 43% of respondents do care about energy saving when they build the house and 94% when they operate the house.
SUMMARY Low temperature heating panel systems offer distinctive advantages in terms of thermal co... more SUMMARY Low temperature heating panel systems offer distinctive advantages in terms of thermal comfort and energy consumption, allowing work with low exergy sources. The purpose of this paper is to compare floor, wall, ceiling, and floor-ceiling panel heating systems in terms of energy, exergy and CO2 emissions.
At the Faculty of Mechanical Engineering of Kragujevac, a heat pump (water–water) was installed a... more At the Faculty of Mechanical Engineering of Kragujevac, a heat pump (water–water) was installed as a design made by the senior undergraduates within the academic course Heating and Air-conditioning. This project was financed by ASHRAE. Using electrical power on its compressor, the heat pump transfers heat from the heat source (lower temperature) to the cold source (heat sink)(higher temperature), which comprises central heating radiators, floor heating system and technical water heating system.
Poster for ISES Congress (Nov. 2013) at Cancun (Mexico)