Energy and Buildings 88 (2015) 229–237 Contents lists available at ScienceDirect Energy and Buildings j ourna l ho me page: www.elsevier.com/locate/enbuild Influence of the optical and geometrical properties of indoor environments for the thermal performances of chilled ceilings Natale Arcuri, Roberto Bruno ∗ , Piero Bevilacqua Mechanical, Energetic and Management Engineering Department, University of Calabria, Ponte P. Bucci 46/C, ZIP 87036 Arcavacata di Rende, Cosenza, Italy a r t i c l e i n f o Article history: Received 5 March 2014 Received in revised form 30 October 2014 Accepted 6 December 2014 Available online 12 December 2014 Keywords: Chilled ceilings Solar heat gains Cooling loads Buildings dynamic simulation a b s t r a c t The sizing of radiant ceilings for cooling applications requires the correct evaluation of the dynamic removal thermal loads in indoor environments. The evaluation of thermal power removed by convection, infrared radiation and direct absorption of solar radiation incident on ceiling surface, called direct water load (DWL), for systems with low thermal inertia (chilled ceilings or ceilings made by capillary pipes) has to be carried out. The latter contribution must be evaluated in an accurate way because it is not a thermal load for indoor environment and strongly modifies the thermal balance in the air-conditioned volume. In order to evaluate DWL, a parametric study developed as a function of the main optical and geometrical characteristics of the cavity has been carried out with TRNSYS code. The development of a case study has highlighted the dynamic aspects of the several contributions involved in the thermal loads removal. The obtained results have allowed the definition of a new calculation methodology to evaluate the effective solar radiation absorbed by the cavity and, subsequently, to determine the fraction of solar radiation incident on ceiling surface and removed by DWL. Its evaluation has allowed estimation of the DWL incidence on the sizing procedure of light radiant ceiling for cooling applications. © 2014 Elsevier B.V. All rights reserved. 1. Introduction Radiant ceiling cooling systems are increasingly used since they give better comfort conditions, owing to their particular ther- mal exchange, and especially provide thermal energy savings [1]. The energy savings can be extended also to the primary energy sources, because the inlet water temperature of radiant ceilings are higher than conventional air-conditioning systems. Additional advantages are the full utilization of spaces and the reduction of vertical indoor air temperature stratification. Andrès-Chicote et al. have recently investigated the cooling capacity of radiant ceiling in cooling applications by experimental results analysis [2]. Imanari et al. investigated the achievable energy savings and comfort condi- tions obtainable by radiant ceilings in an office building, comparing their performances with traditional air-conditioning systems [3]. The economic analysis developed has highlighted that the payback period of radiant ceiling systems may be advantageous in relation to the installation costs. In this context, the use of radiant ceiling with negligible thermal inertia, such as chilled ceilings or capillary pipes radiant systems mounted in the ceiling, is very interesting because ∗ Corresponding author. Tel.: +39 0984 494158; fax: +39 0984 494673. E-mail address: roberto.bruno@unical.it (R. Bruno). their light weight simplifies the installation operations and there- fore allows the system to be less expensive. Moreover, the use of capillary pipes directly drowned in the ceiling plaster coating leads to a more uniform surface temperature with consequent benefits to the radiant thermal exchange and to thermal comfort conditions. Finally, a low thermal inertia permits the use of simpler control systems. A limitation in the use of radiant ceilings in cooling applications is the lack of appropriate sizing procedures and the uncertainty in the determination of their performances when they are cou- pled with other air-conditioning plants. Radiant panels, in fact, can remove only sensible loads, while the control of humidity level and air cleanliness is assigned to conventional air ventilation sys- tems. In terms of achievable energy consumptions and thermal comfort level, Corgnati et al. have confirmed, with numerical and experimental analysis, the good performance of the radiant ceil- ing coupled to primary air ventilation systems in office buildings [4–6]. However the presence of sensible and latent loads delivered by other plants can affect the sizing procedure of radiant ceilings. In this field many calculation methodologies are available, but the majority are steady state models validated for panels with non- negligible thermal mass. Diaz and Cuevas, for instance, developed a procedure to evalu- ate the main thermal performances by modelling the radiant ceiling http://dx.doi.org/10.1016/j.enbuild.2014.12.009 0378-7788/© 2014 Elsevier B.V. All rights reserved.