An experimental study on variable air volume operation of ducted air-conditioning with digital scroll compressor and conventional scroll compressor
Introduction
Household central air-conditioning mainly includes household multi-connected air-conditioning, mini-type air-source heat pump/chiller with fan coil unit, ducted air-conditioning (heat pump) unit and so on. Ducted AC (heat pump) unit is characterized of high efficiency, convenient installation, supply of fresh air, less initial investment, etc. It has been widely used in restaurant, supermarket and factory workshop. Ducted AC units mostly adopt constant speed compressor and operate with constant air volume currently, but users often need to adjust the air supply, which requires that the unit operation performance is suitable for the variable air volume. It should be made sure that the unit is operating with high efficiency and reliable status when the main characteristics such as discharge temperature, discharge pressure, suction pressure, and outlet air temperature change in a certain range. AC unit with digital scroll compressor is one which running at variable air volume in high efficiency. So this type of unit has been paid more attention by scientists and engineers. The application of digital scroll compressor in multi-type air conditioning system was introduced by Hu and Yang [1]. Jiang et al. [2] discussed the control of digital compressor applied in multi-type air conditioning system. Kan et al. [3] analyzed the application of digital scroll compressor in cold storage container. Zhou and Zhang [4] studied the energy saving of digital scroll compressor. Qiu and Qiu [5] discussed the application of digital scroll compressor in high accuracy constant temperature and humidity air conditioning. The application of heat pump with digital scroll compressor under low ambient was addressed by He et al. [6]. Analysis and comparison between digital scroll and inverter technology was performed by Shi and Ma et al. [7], [8]. Ye and Chen [9] analyzed the energy saving factors of digital scroll compressor in VRV air-conditioning system. Wu and Wu [10] discussed the problem about how to make digital scroll compressor matching the heat load of a building air conditioning. Up to now, seldom researches have been conducted on variable air volume operation characteristics of ducted AC unit. There is also seldom comparative study on the application of air-conditioning system with digital scroll compressor and conventional scroll compressor. In order to study the operation characteristics, an experimental study on the variable air volume of ducted AC units with digital scroll compressor and conventional scroll compressor is performed under refrigerating and heating condition in this paper. The effects of air volume on refrigerating (heating) capacity, input power, EER (COP), outlet temperature, discharge pressure, discharge temperature and suction pressure will be analyzed. The characteristic of ducted AC unit with digital scroll compressor will be also compared with that of ducted air-conditioning unit with conventional scroll compressor.
Section snippets
Experimental system
The experimental system on variable air volume operation of ducted air-conditioning unit with digital scroll compressor and conventional scroll compressor is shown in Fig. 1. It is certificated by the National Quality Supervision and Inspection Center for Compressor and Refrigeration Equipment Products. As shown, the system consists of outdoor environment room, indoor environment room, units supporting the environment and measuring equipments. The dry-bulb temperature control range of the
Experimental procedure and results analysis
The experimental study on performance characteristics of variable air volume between ducted AC unit with digital scroll compressor and the unit with conventional scroll compressor under the refrigerating and heating condition is performed. In refrigerating running experiments, inlet air dry-bulb temperature and wet-bulb temperature of indoor side are 27 °C and 19 °C, respectively, inlet air dry-bulb temperature and inlet air wet-bulb temperature of outdoor side to be 35 °C and 24 °C, respectively.
Conclusions
The comparative experimental study on operation characteristics with variable air volume under refrigerating and heating condition of ducted air-conditioning (heat pump) unit with digital scroll compressor and the unit with conventional scroll compressor is performed. For a unit with conventional scroll compressor, when air volume decreases, its energy output changes passively in a narrow scope. From the effects of air volume on the unit capacity, efficiency, outlet temperature, especially
Acknowledgements
We are grateful to Nanjing TICA Air-conditioning Co., Ltd. for providing the sampling unit, and we acknowledge Professor Zhenqian Chen for kindly giving revising suggestions.
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