State functions/quantities in thermodynamics and heat transfer

In thermodynamics,it is essential to distinguish between state functions and process functions.The reason is that the simple compressible thermodynamic system is a bivariate-process system,and the change of internal energy,a state function,corresponds to two process functions,heat and work.Among the state functions in thermodynamics,entropy is a special one because it has to be defined through a process function,exchanged heatδQ,and a unique factor of integration,l/T.In heat transfer,it is shown that Fourier's law and the differential equation of heat conduction are both relations of state quantities alone,and process quantities appear when an integration with respect to time is applied.Moreover,an incompressible heat conduction medium element without conversion between heat and work is a univariate-process system governed by a single variable,temperature.In this case,the change of the thermal energy(“heat content”)stored in the system,a state quantity as a function of T alone,corresponds to only one process quantity,the transferred heat.Therefore,on the one hand,it is unnecessary to strictly distinguish between state quantities and process quantities in heat transfer,and on the other hand,there is no need to use a factor of integration to prove entransy a state quantity in heat transfer.Thermodynamics and heat transfer are two parallel sub-disciplines in thermal science.It is incorrect to deny entransy as a state quantity in heat transfer by the uniqueness of the factor of integration for entropy in thermodynamics,and entransy has significant physical meaning in the analysis and optimization of heat transfer processes.

An assessment method of annual climatic status in China using extreme climate indices:2021 as an example

A proper assessment of annual climatic status(ACS)is conducive to rationally formulating disaster prevention and mitigation measures.The former definition of ACS lacks either information on extreme climate or an intuitive grade feature service to the public.The ACS defined in the National Standard of the People's Republic of China(GBACS)only considers the accumulated climate effects of each weighted 10-d temperature/precipitation anomaly in a year.Under global warming,the losses caused by extreme climate events often have a significant impact on the grades of ACS,but this impact cannot be reasonably reflected by GBACS.This study proposed the assessment of ACS using extreme climate indices(extreme climate-based ACS(ECACS))and compared it with GBACS.The results indicated that GBACS and ECACS can be used to evaluate the ACS from different angles.The ECACS is an important supplement to the GBACS,especially considering the years with frequently occurring extreme climate events.The sum of GBACS and ECACS is a reasonable and comprehensive way to evaluate the ACS.The empirical orthogonal function(EOF)analysis indicated a uniform mode(EOF1)and a dipole mode(EOF2)in GBACS and ECACS in China.The interannual variation characteristics of ECACS in northern and southern China(EOF2 pattern)are consistent with real climate features,which is conducive to providing better and more detailed regional information in the ACS forecast service.The results have essential instructive and application value for ACS assessment and government decision making.