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Table 4: Air-cooled chiller capacity and efficiency coefficients.

Table 4 Air-cooled chiller capacity and efficiency coefficients.

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where, Mixing Box Model The values of CAPFT, EIRFT and EIRPLR are dimensionless values, which are obtained in the following way:
where, Mixing Box Model The values of CAPFT, EIRFT and EIRPLR are dimensionless values, which are obtained in the following way:
Figure 2: A HVAC primary system configuration. Figure 1: Example of a two zone building edition.
Figure 2: A HVAC primary system configuration. Figure 1: Example of a two zone building edition.
Building Description
Building Description
Figure 4: PowerDomus window used to edit the Air Handling Unit components.
Figure 4: PowerDomus window used to edit the Air Handling Unit components.
Figure 3: A HVAC secondary system configuration.
Figure 3: A HVAC secondary system configuration.
Table 5 shows the nominal parameters pumps obtained from catalog data.
Table 5 shows the nominal parameters pumps obtained from catalog data.
Table 8: Model parameters for the pumps.
Table 8: Model parameters for the pumps.
building geometric characteristics (dimensions) of a six-storey building.
building geometric characteristics (dimensions) of a six-storey building.
Table 6: Water-cooled chiller simulation parameters. Table 7:Waterr-cooled chiller capacity and efficiency coefficients.
Table 6: Water-cooled chiller simulation parameters. Table 7:Waterr-cooled chiller capacity and efficiency coefficients.
Figure 7 presents a comparison in terms of yearly HVAC energy consumption between primary system with air-cooled chiller (SP-AIR) and water-cooled chiller (SP-WATER). For the SP-AIR are presented he air-cooled chiller, cold-water pumps and secondary system fans energy consumption. While for SP-WATER the condensation-water pumps and cooling towers fans energy consumption have been additionally added. The water cooled chiller show a relative difference of 13% less than air cooled chiller consumption energy. While the water cold pumps showing energy consumption relative difference of 6% greater compared to SP-AIR. The equipment total yearly consumption of the system with water- cooled chiller was approximately 1.6% lower than the air-cooled chiller primary system.
Figure 7 presents a comparison in terms of yearly HVAC energy consumption between primary system with air-cooled chiller (SP-AIR) and water-cooled chiller (SP-WATER). For the SP-AIR are presented he air-cooled chiller, cold-water pumps and secondary system fans energy consumption. While for SP-WATER the condensation-water pumps and cooling towers fans energy consumption have been additionally added. The water cooled chiller show a relative difference of 13% less than air cooled chiller consumption energy. While the water cold pumps showing energy consumption relative difference of 6% greater compared to SP-AIR. The equipment total yearly consumption of the system with water- cooled chiller was approximately 1.6% lower than the air-cooled chiller primary system.
Table 9: Cooling towers simulation parameters.
Table 9: Cooling towers simulation parameters.
Table 10: Cooling coil simulation geometric parameters.
Table 10: Cooling coil simulation geometric parameters.
Figure 7: Yearly HVAC energy consumption. The next simu ations results show the building envelope moisture effects on the temperature and humidity ratio consumption. T zone and the HVAC _ energy he interaction between the porous building envelope, room air and HVAC system is presented by contrasting a pure thermal model (no moisture) and a hygrothermal model (with Moisture) to calculate the conduction loads through the envelope. Figure 8 illustrates the zone-6 air temperature and relative humidity evolution, where the HVAC equipment operates between 8 am and 6 pm. It can be observed that the predicted temperatures are lower when the HVAC system is off using the model that considers the moisture interaction with the building envelope. Figure 8 shows also that even when the HVAC system is on the zone relative humidity is greater when moisture is considered as the vapor flow from walls is important on the zone water vapor mass balance. In addition, Figure 8 depicts a better performance for temperature control considering moisture as the system has been sized using the hygrothermal model.
Figure 7: Yearly HVAC energy consumption. The next simu ations results show the building envelope moisture effects on the temperature and humidity ratio consumption. T zone and the HVAC _ energy he interaction between the porous building envelope, room air and HVAC system is presented by contrasting a pure thermal model (no moisture) and a hygrothermal model (with Moisture) to calculate the conduction loads through the envelope. Figure 8 illustrates the zone-6 air temperature and relative humidity evolution, where the HVAC equipment operates between 8 am and 6 pm. It can be observed that the predicted temperatures are lower when the HVAC system is off using the model that considers the moisture interaction with the building envelope. Figure 8 shows also that even when the HVAC system is on the zone relative humidity is greater when moisture is considered as the vapor flow from walls is important on the zone water vapor mass balance. In addition, Figure 8 depicts a better performance for temperature control considering moisture as the system has been sized using the hygrothermal model.
Figure 8: Zone-6 temperature and relative humidity evolution, with and without moisture. Figure 9 presents a comparison in terms of yearly HVAC energy, predicted with both hygrothermal and thermal building models, showing that ignoring moisture underestimates the yearly energy consumption in 4%, especially because the latent conduction load is not added to the sensible one,
Figure 8: Zone-6 temperature and relative humidity evolution, with and without moisture. Figure 9 presents a comparison in terms of yearly HVAC energy, predicted with both hygrothermal and thermal building models, showing that ignoring moisture underestimates the yearly energy consumption in 4%, especially because the latent conduction load is not added to the sensible one,
Figure 9: Yearly HVAC energy consumption In this way, when moisture is disregarded, there is a risk of oversizing HVAC © system and underestimating energy consumption, as already argued in Mendes (1997) and Mendes et al. (2003). CONCLUSION A generic model for HVAC systems integrated to a hygrothermal whole-building simulation model has been presented. Then, to show the model capability, a 6-storey building - composed of an air-cooled chiller, water-cooled chiller and a secondary system with mixing box, cooling coil and supply fan - has been simulated, showing results for the six building zones.
Figure 9: Yearly HVAC energy consumption In this way, when moisture is disregarded, there is a risk of oversizing HVAC © system and underestimating energy consumption, as already argued in Mendes (1997) and Mendes et al. (2003). CONCLUSION A generic model for HVAC systems integrated to a hygrothermal whole-building simulation model has been presented. Then, to show the model capability, a 6-storey building - composed of an air-cooled chiller, water-cooled chiller and a secondary system with mixing box, cooling coil and supply fan - has been simulated, showing results for the six building zones.
Related topics:
EngineeringCooling TowerHvac SystemWater Environment SimulationWater Chiller
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