Energy conservation and thermal environment analysis of room air conditioner with intermittent supply airflow

In a zero energy house, heating load would be reduced sharply during winter, as its building envelope is highly insulated with a highly thermal resistant material. The compressor could be triggered by a low load operation leading to more frequent on-off cycling. This paper presents a novel control algorithm, a fan intermittent operation (FIO) for an indoor unit of a room air conditioner, introduced to remove the compressor on-off cycling under low load condition and to provide stable warm air in heating mode to satisfy the task of local domain with extremely low compressor frequency. Against the conventional on-off cycling, FIO control algorithm would keep the compressor operating at limited low frequency consecutively and apply fan cycles on and off immediately in the indoor unit for establishing the reliable refrigerant condensing temperature (CT). This algorithm details the interrelationship between the control of CT and task zone temperature. The algorithm is capable to provide a dynamically adaptable indoor environment to raise thermal comfort of human occupants. Through qualitative full scale experiments and dynamic simulation, the energy saving effect and indoor thermal environment were investigated. Results show that, FIO control algorithm can provide a better well-being for building occupants and a more comfortable environment for the task zone compared to the conventional thermal on-off control algorithm. Based on interrogating control of condensing temperature, a 5% energy saving rate can be established under the winter condition.