The Research On Heat Transfer Characteristics Of Concrete Ceiling Radiant Air-conditioning System

With competitive advantages in energy conservation, thermal comfort andenvironmental friendliness, ceiling radiant heating and refrigeration system isattracting more and more attention and research. Restricted by its structure andcharacteristics, ceiling radiant heating and refrigeration system is different from thetraditional fan coil air conditioning system in the engineering design and theaffecting factors on its properties. This system can maintain a stabilized indoorthermal environment all year around. The current study is mainly concentrated onanalyses of the cooling operating condition in summer, but little research has beendone on the heating operating condition in winter. Based on the concrete of ceilingradiant heating and refrigeration system, heat dissipating capacity and the affectingfactors on the heat transfer characteristic of the system were analyzed in the paper.First, the fundamental structure and characteristics of the concrete ceilingradiant heating and refrigeration system were introduced in the paper. Amathematical calculation model for the heat transfer process of the ceiling radiantpanel was established. Combined with structure characteristics of the radiant panel,a relatively simple composite-fin model was presented for the calculation of ceilingsurface heat transfer. In order to improve the precision of the calculation, thetemperature of composite-fin base and the ratio of heat dissipating capacity throughthe top and the bottom of the ceiling surface was corrected. And then based on aexperimental model of a typical residential building in Changsha, the composite-finmodel was verified by the analysis of the experimental data. The research showedthat the indoor air temperature and relative humidity with the ceiling radiant panelwere less affected by outdoor environment, and the indoor vertical temperaturedifference of the room was relatively small. At last, the heat transfer process withinthe ceiling structure was studied using the FLUENT software. The temperaturedistributions and the change rules of heat dissipating capacity on the ceiling surfacewere analyzed with the change of condition parameters, such as supply and returnwater temperature, indoor air temperature, spacing and depth of buried tube, pipediameter and velocity, and so on. The study suggested that the radiant was the mainway of the heat transfer in this system, which could account for above80%of thetotal heat transfer during the heating condition in winter, The top and the bottom of the ceiling surface were both radiation surface with a heat transfer radio of1:3.Except depth of buried tube and flow velocity, other affecting factors had greaterinfluence on the heat transfer characteristics of the ceiling radiant system.