Investigation On Dual-Temperature Heat Source Heat Pump Air Conditioner

China is largest producer and application of heat pump air conditioners,and large-scale use of heat pumps consumes considerable energy in the world.Improving heat pump technology and system energy efficiency is of great significance to China,where resources are scarce.At present,the heat pump uses a single temperature cooling and heating source to handle the air,and the sensible heat and latent heat are combined in the air conditioning process.In the progress,the air is first cooled to a low dew point temperature for dehumidification,and then heated to the supply air temperature.Due to the excessively cooling and reheating,not only is the system less energy efficient,but the indoor comfort is poor.In this paper,theoretical and simulation studies are carried out to solve the above problems.In the first part,aiming at the problems of cold and heat offset caused by the hot and humid coupling treatment of air conditioning systems,the indoor environment control strategy is proposed,and the humidity and temperature control of the new air conditioning system are summarized.For the humidity control system,the full-heat exchanger,the high-temperature cold source,and the low-temperature cold source are used to perform step-down cooling and dehumidification of the fresh air;for the temperature control system,the calculation is for a linear dry fan coil.It is concluded that the new dry air fan coil has the advantages of small differential pressure,low noise and low energy consumption compared with the long pipe length,large flow and small temperature difference of the conventional wind fan coil.In the second part,this paper analysis a dual-temperature heat source heat pump system and establishes a thermodynamic model.The dual-temperature heat source includes the lowtemperature cold source and the high-temperature cold source realized under the cooling condition;Low temperature heat source and high temperature heat source realized under the heating condition.The heat pump system was simulated by modeling and numerical calculation,the cycle parameters such as the temperature of the dual-temperature heat source were determined,the system load was distributed,and the thermodynamic model of the system was optimized.In the third part,the simulation and numerical calculations of the proposed temperature and humidity control equipment are carried out:Firstly,for the linear dry fan coil,based on CFD simulation software and indoor sensible heat load grading processing theory,the modified wind fan coil is simulated,and the influence of simulation calculation on indoor airflow organization including temperature field and velocity field is realized.Optimized design of the equipment placement position and air supply parameters.Then,for a new type of step dehumidification full heat recovery group,the thermodynamic analysis of the energy saving measures to be adopted by the unit is carried out,including: 1.Using different condensation heat reheating mode,the heat exchange efficiency and unit energy efficiency are optimized and selected;2.The change of condensed water and the energy saving effect under the rated working condition and the annual working condition are calculated,and suggestions for efficient evaporation of condensed water are provided;3.The effect of doubletemperature step dehumidification on the energy efficiency of the system is adopted;4.The energy-saving effect of exhaust heat recovery under rated working conditions and variable working conditions is calculated.The fourth part is based on the operating principle and characteristics of the heat source and temperature and humidity control equipment of the dual-temperature heat source heat pump air conditioner.The new air supply control strategy of the dual-temperature heat source airconditioning system is given in this paper.And the indoor humidity control model is established to develop an anti-condensation control strategy.At the same time,based on the annual hourly meteorological parameters of Hangzhou,where is the typical summer hot and cold winter area of China,a year-to-day energy consumption simulation and energy-saving analysis were carried out with an office building.The research in this paper proposes new ideas and methods for structural optimization,performance evaluation and optimization of dual-heat source heat pump air conditioners.It also provides theoretical guidance for optimization design,system transformation,development and improvement of deep dehumidification and full heat recovery air blower units.