| Temperature and Humidity Independent Control System provides a new research direction for improving the energy efficiency of HVAC system and the comfort of residential environment,and the application of radiation cooling technology to the independent control mode of temperature and humidity has attracted much attention.This paper expounds the advantages and disadvantages and some progresses in the independent control technology of temperature and humidity and radiation supply cooling.Based on the“double evaporating temperature chiller”,a double cooling source refrigeration unit used in radiation induced air conditioning system is put forward,which is able to produce double temperature of chilled water and two modes.Besides,the environment-friendly mixed refrigerant is applied to the refrigeration unit.The research process uses the theoretical analysis and experimental method verifies the feasibility and application advantages of the double cooling source refrigeration unit.At the same time,energy analysis and exergy analysis are carried out when the unit is applied to the radiation induced terminal and different working conditions,which provides the basis for the application of the unit.Firstly,the theoretical model of the double cooling source refrigeration unit used in the radiation induced air conditioning system is built,and the determination of the main components and refrigerant quality of the unit is completed through theoretical analysis and“double evaporating temperature chiller”.Besides,the experimental platform is built.The results show:the operation mode of the evaporator series,parallel and independent refrigeration in the double cold source refrigeration unit can be effectively realized through the linkage control of the manual regulating valve and the electronic expansion valve in the refrigeration unit;zeotropic refrigerant R600a/R290 is used as the refrigerant of the unit because of its moderate saturated vapor pressure,liquid density and great environmentally friendly within the working temperature range and the thermal characteristics are qualitatively discussed based on the principle of the entranspy analysis.The measuring instrument and calculating models used in the construction of the experimental platform are used to estimate the error of the experiment.The error results are about 10%,so the experimental results own relatively high reliability.Secondly,the theoretical and experimental analysis is completed through the theoretical calculation and experimental platform of the refrigeration unit.The theoretical calculation and experimental analysis mainly focus on the evaporator series and parallel in the refrigeration unit.The results show:When the freezing water temperature is 7?(low temperature)/17?(high temperature)and the mass ratio of R290 is 0.6 under the evaporator series,experimental COP~b can reach 3.63;When the freezing water temperature is 7?(low temperature)/17?(high temperature)and the mass ratio of R290 is 0.7 under the evaporator parallel,experimental COP~d can reach 3.83;The discharge pressure and temperature are both moderate,and the experimental results are in agreement with the trend of theoretical analysis.Finally,the refrigeration unit is applied to the system of radiation induced air conditioning and energy analysis and exergy analysis are carried out for the unit modes'selecting for the system matching,and the typical summer working conditions of Nanjing is analyzed.The results show:The refrigerant mass ratio of the air handling unit is less than 0.85,the effect of the parallel evaporator operation is stronger than the series evaporator,and it is the opposite when the refrigerant mass ratio of the air handling unit is more than 0.85;the refrigerant mass ratio of the air handling unit of the typical summer working conditions of Nanjing is about 0.9,so the series evaporator is better.Exergy analysis provides optimized direction for various components under different operation modes,and the radiation induced terminal has the largest loss value in the two mode operation.Besides,when the evaporator is in series operation mode,the compressor has the maximum exergy loss in the refrigeration unit.While the evaporator is in parallel operation,evaporator has the maximum exergy loss.(when refrigerant mass ratio of the low temperature evaporator is less than 0.35,the high temperature evaporator has the maximum exergy loss,otherwise the low temperature evaporator has the maximum exergy loss)... |
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