Document Type : Original Article
Authors
1
PhD Candidate, Department of Renewable Energies and Environment, University of Tehran, Tehran, Iran
2
PhD Candidate, Faculty of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran
3
Associate Professor, Department of Renewable Energies and Environment, University of Tehran, Tehran, Iran
Abstract
Introduction
Variable refrigerant flow systems are one of the most efficient and widely used air conditioning systems to reduce energy consumption while maintaining the desired level of thermal comfort. Variable refrigerant flow systems as an efficient and flexible solution for various heating/cooling applications are gaining more attention and are widely used in commercial and residential buildings. Variable refrigerant flow systems have many advantages over traditional air conditioning systems such as chillers and fan coils or air conditioning units, including satisfactory partial load performance, individual control capability at arbitrary temperature range, and no loss in duct transmission. Easy installation and maintenance. However, variable refrigerant flow systems require a dedicated outdoor air system with an additional ventilation unit.
Methodology
This section first discusses the design of a variable refrigerant flow system. The next step is to model the building located in Cyprus with the heating system in question. The parts of this modeling include the characteristics of the selected location of the building, modeling of the relevant building, modeling of variable refrigerant air conditioning system and photovoltaic systems in detail.
Variable refrigerant flow system
Variable refrigerant flow systems Among the various air conditioning systems is the DX system, based on the standard Rankin reverse steam compression cycle. Therefore, these systems are thermodynamically similar to conventional DX systems and have similar equipment such as compressor, expansion valve, condenser, and evaporator. Figure (1) shows the inside of the exterior of a variable refrigerant flow system that is installed outside the building.
A 5-storey residential building with an area of 1061 square meters of space has been modeled in Design Builder software (on each floor, there are two residential units with 110 square meters). Each floor consists of two units with an equal area; the north-facing unit has two bedrooms, the south-facing unit has three bedrooms, and the ground floor is uninhabited and without air conditioning. In addition, the corridors between adjacent apartments on each floor are also without air conditioning. This research will focus on the power consumption of the variable refrigerant flow system as an electric charge. Figure (2) shows a schematic of an integrated photovoltaic variable refrigerant flow system.
Results and Discussion
In this section, energy consumption in variable refrigerant air conditioning, power generation of photovoltaic arrays, and carbon dioxide reduction due to photovoltaics are examined according to the results obtained from the design of builder designs.
Conclusion
The intensity of solar radiation in this city equals 1852kWh, and the annual electricity consumption of a refrigerant flow system varies around 18500kWh. The results show that according to the duration of sunlight during the day, the total daily electricity produced by photovoltaics provides only 54% of the daily electricity required for variable refrigerant current, which has a significant impact on reducing electricity consumption from the grid and a significant impact on Reduces carbon dioxide by 14 tons per year.
Figure 1. Internal view of the outer part of the variable refrigerant flow
Figure 2. Schematic of VRF-PV integrated system
Figure 3. DNI radiation status of the sun kW/m2 on July 21
Figure 4. Energy rate status of a building unit on July 21
Figure 5. External and indoor temperature status of a unit (dining room facing south on the 5th floor of the building), on July 21
Figure 6. Status of carbon dioxide emissions on 21 July
Figure 7. DNI and DIF solar radiation conditions kW / m2 in summer and autumn
Figure 8. Electricity status (Kw) required for cooling and photovoltaic power generation in summer and autumn
Figure 9. External temperature and temperature of the dining room facing south on the 5th floor of the building, in summer and autumn
Keywords
)