University of Malaya, Faculty of Engineering: An experimental and numerical study of turbulent flow inside studio apartments
Many cities in Malaya are developing rapidly now. The demand for studio type apartments has increased and there is growing interest among building services engineers and building developers in the analyses of internal airflows and thermal comfort. The factors influencing the built environment include air temperature, air humidity, air velocity, turbulence intensity and cleanliness of the air. There is a constant heat exchange occurring between human bodies and both the indoor and outdoor environments. The rate of heat exchange is functions of the metabolic rate, activity and the amount of work. Humans also have a higher sensitivity to temperature. Effective distribution of fresh air within an occupied space is important in providing good thermal comfort and good indoor air quality (IAQ). To respond to these needs, an air-conditioning system must have greater flexibility, provide better thermal comfort and IAQ, and greater energy savings.
Current research is focussed on mechanical ventilation, heating and cooling inside offices. However, less work has been done on mechanical ventilation and cooling inside residential spaces (apartments and condominiums). We had examined the effective air distribution and obtained good thermal comfort in residential living rooms and bedrooms with air-conditioners. Several researchers have studied on the effects of supply location and its impact on thermal comfort. Gan used computational fluid dynamics (CFD) to investigate local thermal discomfort in an office room. He found that thermal discomfort could be prevented by the optimisation of the supply air velocities and temperature. The majority of studio apartments in Malaysia are equipped with up to two or three air-conditioners. They operate daily to provide effective cooling to the occupants. The improper location of the air-conditioner with respect to furniture is a critical issue. It could cause unwanted air re-circulations, resulting in inadequate mixing of cold air with the warm ambient air as well as the buoyant convective currents from the heat sources within the room. The CFD software solves the governing Navier-Stokes equations (i.e. Continuity, Momentum and Energy balance equations). The objective of this research is to determine the indoor thermal environment in the apartment of interest as well as to determine the hot spots both numerically and experimentally. The velocity, temperature, and humidity in the apartment are determined by using the commercial CFD program FloVENT.
The airflow patterns, air velocity and temperature distributions are measured in a full-scale environmental test facility. The test room, 6720 mm wide, 3040 mm high, and 5860 mm long, simulates the typical indoor environment. The test room is cooled by a 2.5 hp air-conditioner, 1714 wide, 240 mm high, and 500 mm long. The three wooden doors and windows are shut and there are no additional sources of cooling other than the air conditioner. Therefore the airflow in the room is the result of convection currents due to buoyancy effects and forced convection from the air-conditioner. The ceiling is insulated with ceiling boards while the floor is made of reinforced concrete covered with tiles. Thus, the room is isolated from any external wind and solar radiation. However, human disturbances are inevitable.
Simulations are performed with the commercial CFD software. This software is used because it provides state of the art grid generation and flow modelling capabilities. Three different representations of the fluid flow in the apartment are used: laminar flow, turbulent flow using the LVEL Algebraic turbulence model, and turbulent flow using LVEL k-å turbulence model. The airflow and heat transfer are governed by the Navier-Stokes equations. FloVENT solvers are based on Finite Volume method. Domain is dicretised into a finite set of control volume or cells.
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