Experimental Research And Performance Analysis Of Small Temperature Difference Fan Coil Unit

In recent years,with the increasing demand for winter heating in the hot summer and cold winter zone of South China,air source heat pump system has become an efficient way to solve the winter heating problem.At present,during the application and popularization of air source heat pump,problems like poor operation condition in winter,frequent defrosting and poor indoor air distribution have been found.In order to solve these problems,the concept of small temperature difference fan coil is proposed in this paper,which means the heat transfer temperature difference of the terminal is smaller than that of the traditional fan coil.When satisfying the heating load in winter,the energy efficiency of the heat pump unit is improved by reducing the outlet water temperature of the air source heat pump unit.In order to achieve the goal of small temperature difference heat transfer,a higher requirement is needed for the design and manufacture process of small temperature difference fan coil.On one hand,the heat and mass transfer performance are optimized by heat transfer enhancement method.On the other hand,through the optimization of product structure and industrial design,the function of small temperature difference fan coil can be transferred from commercial use to household use.Based on conditions above,this paper focuses on the concept,simulation,construction,testing,application and optimization of the heat exchanger end of small temperature difference fan coil unit.After the introduction of the concept of small temperature difference fan coil,a simulation model of small temperature difference fan coil unit is built,the average error between simulation value and experimental value is 7.5%.The influence of different structural parameters on the performance of small temperature difference fan coil unit is studied and analyzed.Meanwhile,the part selection of small temperature difference fan coil unit is completed.The design process of the small temperature difference fan coil is clarified and a three-dimensional model is also established in 3D modeling software.According to the engineering drawings,a prototype of small temperature difference fan coil unit is built.In the enthalpy laboratory,the rated cooling and heating condition,small temperature difference working condition have been tested and analyzed.Results show that the heating capacity is 3.22 kW and cooling capacity is 1.92 kW under rated condition.The performance of small temperature difference fan coil and traditional fan coil is compared as well.Finally,the genetic algorithm is applied in the optimization of the single-objective and multi-objectives function,which provides a new direction for further optimization and improvement.