A novel operating strategy to avoid dew condensation for displacement ventilation and chilled ceiling system

This study aims to investigate the effect of the cooling load ratio covered by the chilled ceiling on the age of air and comfort level in a classroom in a hot and dry climate in Iraq-Hilla city. Air age, air exchange efficiency, and concentrations of pollutants in a classroom are investigated numerically by used AIRPAK software under displacement ventilation combined with a chilled ceiling system. Four cases are studied at different values of the cooling load covered by the chilled ceiling (0%, 25%, 50%, 80%) with respect to total classroom cooling load. Cooling load removes by chilled ceiling varied from (0 to 84.5 W/m2) based on the classroom area, and its temperature varied between (17.5-22.5oC). The displacement ventilation airflow rate was kept at 0.3m3/s, and the air temperature supply varied between (19.5-24.5oC) depend on the amount of cooling load covered by displacement ventilation. The results showed that the mean local air age increasing with height. The room mean air age increase and air exchange efficiency reduce with increasing load portion, which treated by the chilled ceiling. Increasing the portion of the load treated by chilled ceiling tends to improve comfort levels.

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Increasing Energy Efficiency of HVAC Systems of Buildings Using Phase Change Material

ASME 2011 5th International Conference on Energy Sustainability, Parts A, B, and C ◽

10.1115/es2011-54079 ◽

2011 ◽

Author(s):

Lee Chusak ◽

Jared Daiber ◽

Ramesh Agarwal

Keyword(s):

Thermal Comfort ◽

Phase Change ◽

Phase Change Material ◽

Energy Requirements ◽

Exterior Wall ◽

Displacement Ventilation ◽

Cooling Systems ◽

Comfort Levels ◽

Chilled Ceiling ◽

Change Material

Using Computational Fluid Dynamics (CFD), four different cooling systems used in contemporary office environments are modeled to compare energy consumption and thermal comfort levels. Incorporating convection and radiation technologies, full-scale models of an office room compare arrangements for (a) an all-air overhead system (mixing ventilation), (b) a combined air and hydronic radiant system (overhead system with a chilled ceiling), (c) an all-air raised floor system (displacement ventilation), and (d) a combined air and hydronic radiant system (displacement ventilation with a chilled ceiling). The computational domain for each model consists of one temperature varying wall (simulating the temperature of the exterior wall of the building during a 24-hour period) and adiabatic conditions for the remaining walls, floor, and ceiling (simulating interior walls of the room). Two sets of computations are conducted. The first set considers a glass window and plastic shade configuration for the exterior wall to compare the four cooling systems. The second set of computations consider a glass window, a phase change material layer and the plastic shade configuration for the exterior wall to examine the effect of the phase change material (PCM) layer on the cooling energy requirements. Both sets of simulations assumed an external wall that changed temperature as a function of time simulating the temperature changes on the exterior wall of the room during a 24 hour period. Results show superior thermal comfort levels as well as substantial energy savings can be accrued using the displacement ventilation and especially the displacement ventilation with a chilled ceiling over the conventional overhead mixing ventilation system. The results also show that the addition of a PCM layer to the exterior wall can significantly decrease the cooling energy requirements.

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Reducing Energy Demand in Commercial Buildings: Balancing Convection and Radiant Cooling

ASME 2010 4th International Conference on Energy Sustainability, Volume 1 ◽

10.1115/es2010-90370 ◽

2010 ◽

Author(s):

Lee Chusak ◽

Andrew Harris ◽

Ramesh Agarwal

Keyword(s):

Thermal Comfort ◽

Energy Demand ◽

Energy Savings ◽

Ventilation System ◽

Computational Domain ◽

Exterior Wall ◽

Displacement Ventilation ◽

Comfort Levels ◽

Isothermal Wall ◽

Chilled Ceiling

Using Computational Fluid Dynamics (CFD) software, three different cooling systems used in contemporary office environments are modeled to compare energy consumption and thermal comfort levels. Incorporating convection and radiation technologies, full-scale models of an office room compare arrangements for (a) an all-air overhead system (mixing ventilation), (b) an all-air raised floor system (displacement ventilation), and (c) a combined air and hydronic radiant system (displacement ventilation with a chilled ceiling). The computational domain for each model consists of one isothermal wall (simulating an exterior wall of the room) and adiabatic conditions for the remaining walls, floor, and ceiling (simulating interior walls of the room). Two sets of computations were conducted. The first set of computations utilized a constant temperature isothermal exterior wall, while the second set utilized an isothermal wall that changed temperatures as a function of time simulating the temperature changes on the exterior wall of a building throughout a 24 hour period. Results show superior thermal comfort levels as well as substantial energy savings can be accrued using the displacement ventilation, especially the displacement ventilation with a chilled ceiling over the conventional mixing ventilation system.

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