Research progress on optimization of large temperature-lift vapor compression heat pump system
In the context of the"carbon peaking and carbon neutrality"strategy,large temperature-lift heat pump technology can not only save energy in low carbon,but also effectively utilize lower grade heat energy to develop into higher temperature field.In this paper,the research progress of performance optimization of large temperature-lift vapor compression heat pump system(large temperature-lift system)is summarized,and the feasible optimization means of large temperature-lift system are analyzed from refrigerant,component,cycle optimization and demonstration verification.Currently,the commonly used refrigerants in practical engineering of large temperature-lift systems are still mainly high GWP value refrigerants such as R134a and R245fa;in terms of screening refrigerants with high temperature-lift,carbon dioxide(R744)in natural pure refrigerants has a wide temperature range and excellent performance;water(R718)is one of the potential refrigerants for breaking through the ultra-high temperature(150℃)limit in large temperature-lift systems;organic pure refrigerants have developed rapidly,with R1234ze(Z)and R1336mzz(Z)having extremely low GWP values and excellent thermodynamic properties;the preparation of R32-based,HFOs-based,and CO2-based mixed refrigerants with low GWP values is currently a promising approach.In terms of component optimization,mature technologies such as compressor frequency conversion technology provide current solutions for optimizing components of large temperature-lift systems;the industrial products of magnetic bearing technology are becoming mature,which can effectively reduce the friction loss of large temperature-lift system;new component optimization ideas are provided by emerging technologies such as line structure heat exchanger technology for large temperature-lift system.In terms of cycle optimization,mature technologies such as vapour/liquid injection and multi-stage compression provide current schemes for loop optimization of large temperature lift system;the ejector technology and vortex tube technology have optimization effects on large temperature-lift systems,but are limited by the lack of engineering practical experience and unclear mechanism research.According to the demonstration and verification section,the technology of vapour injection is currently the most widely applicable and mature optimization technology for large temperature-lift systems in industrial application,and under certain conditions,it can increase the coefficient of performance value of large temperature lift systems by more than 20%;series multi-stage compression technology and cascade compression technology are powerful means to increase the temperature-lift range of the system and ensure low-temperature heating.
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