STUDY ON OPERATION METHOD OF CEILING RADIATION AIR-CONDITIONING SYSTEM WITH HEAT CAPACITY OF SKELETON

Abstract

 The building in our study features a green façade, a heat source system with renewable energy, natural ventilation, and a thermo-active building system (TABS). The floor plan of the building has an open hallway along the windows as a "perimeter aisle, ” and the combination of this open hallway and the green façade functions as a thermal buffer zone. Two air-conditioning systems are installed in this building— a ceiling radiation air-conditioning system, and a whole-floor blow-off air-conditioning system. The ceiling radiation air-conditioning system employs a reverse slab structure. In this system, ceiling radiation is performed by allowing cold or hot water to flow through a pipe buried in a ceiling slab. The ceiling radiation air-conditioning system employs a ceiling consisting of a concrete slab with a large thermal capacity; this raises the comfort and stability of the indoor thermal environment. This building also features TABS. Since the late 1990s, many buildings in Europe have installed TABS. However, only a few buildings in Japan have installed TABS. The authors surveyed the heat flux of the ceiling surface and indoor thermal environment of the building from 2017 through 2018. The ceiling utilizes the heat storage of concrete, and maintained a constant temperature in the workplace when the air conditioning system was switched off on a holiday. In that regard, making use of the thermal behavior of the skeleton improves the operation of the ceiling radiation air-conditioning system. The thermal environment of the perimeter is stabilized by the autonomous thermal behavior of the skeleton in an operating ceiling radiation air conditioning system. A time lag in the heat flux occurs because of the heat behavior of the skeleton in a building with TABS. The heat flow of the ceiling surface after office hours was reduced by advancing the operative schedule by two hours, and the ceiling radiation air conditioning system operated efficiently, thereby suppressing energy waste. In addition, it was confirmed that the coefficient of performance (COP) of the air-source heat pump (HP) increased with a peak shift of the heat source load, because of cool early morning outdoor air.