Thermal and flow resistance characteristics of a parallel-pipe type natural heat transfer air-conditioning terminal device for nearly zero energy buildings

A nearly zero energy building (NZEB) can achieve significant energy saving by reducing its air-conditioning load greatly. At the same time, an NZEB should also achieve a comfortable thermal environment. In this paper, a parallel-pipe type natural heat transfer air-conditioning terminal device is proposed and studied for use in NZEB. The terminal device is able to provide both heating and cooling (including sensible and latent cooling) for a building without noise or air disturbance. The advantages of the terminal device have been demonstrated by comparing with other air-conditioning terminals. Experimental data of the heating and cooling performance of the device under different operation conditions were collected and analysed. The calculation models for the heating and cooling capacities of the device were obtained through data regression analysis, and the flow resistance curve of the device was obtained by means of experimental measurement under various flow rates. In addition, comparison was made on the heating and cooling capacities between the device and a radiant floor that also features little noise or air disturbance. Results show that the heating and cooling capacities of the device were 41.5% and 46.8% higher than the maximum capacities of the radiant floor, respectively. This research laid a foundation for the engineering application of the air-conditioning terminal device.