Paper Conference

Proceedings of Building Simulation 2009: 11th Conference of IBPSA



Nestor Fonseca Diaz, Jean Lebrun, Philippe André

Abstract: This paper presents the results of a study performed to develop a computational model of cooling ceiling systems. This one has to be used in situ, as diagnosis tool in commissioning process in order to determine the main operating conditions of the system in cooling mode. The model considers the cooling ceiling as a fin. Only the dry regime is considered. From ceiling and room dimensions, material description of the cooling ceiling and measurement of supply water mass flow rate and air and water temperatures, the model calculates the cooling ceiling capacity, ceiling surface average temperature and water exhaust temperature. Fin efficiency, mixed convection close to the cooling ceiling (generated by the ventilation system) and panel perforations influence are studied. A series of experimental results (Laboratory test conditions) got on four types of cooling ceilings are used in order to validate the model. NOMENCLATURE A Area, [m²] C Factor, [-] c Specific heat, [J kg⁻¹ K⁻¹] D Diameter, [m] h Superficial (convection and/or radiation) heat transfer coefficient, [W m⁻² K⁻¹] k Thermal conductivity, [W m⁻¹ K⁻¹] L Length, [m] M Mass flow rate, [kg s⁻¹] N Number NTU Number of transfer units, [-] P Pressure or Perimeter, [Pa] or [m] Q Heat flow, [W] Q l Heat flow per unit length, [W m⁻¹] q Heat flow density, [W m⁻²] Rˡ Thermal resistance per unit length,[m K W⁻¹] t Temperature, [°C] U Overall heat transfer coefficient, [W m⁻² K⁻¹] w Distance between tubes, [m] W Width Greek symbols ε Effectiveness, [-] δ Thickness, [m] ρ Density or Ceiling panel porosity factor, [kg m⁻³] or [-] Δ T Temperature difference, [K] μ Dynamic viscosity, [Pa. s] Subscripts a Air b Distant between tube axis and ceiling surface c Characteristic or cross-sectional cc Cooling ceiling conv Convective e External ex Exhaust exp Experimental f Fictitious , façade or fin h Convection i Internal meas Measured mr Mean radiant p Panel or panels blocks connected in parallel rad Radiative res Resultant su Supply s Panels connected in series or surface sim Simulated t Tube w Water x Fin distance 0 Fin base
Pages: 1997 - 2004