Research On Key Problems Of Cooling Capacity Tracbility Chain System For Air Conditioner

The cooling capacity traceability chain system for air conditioner guarantees the accuracy and the consisence of cooling capacity measurements.However,three key technical problems still exist in the current system: First,the lack of cooling capacity transfer apparatus;Second,the lack of field calibration method for room type calorimeter;Third,the further studies on the data analysis theory of inter-laboratory comparison and the uncertainty evaluation method of annual energy efficiency for variable frequency air conditioner.Therefore,these three key technical problems are studied in this paper with the purpose of improving the current cooling capacity traceability chain system.For the first problem,the water enthalpy method for the cooling capacity transfer is proposed,and based on which the cooling capacity transfer apparatus is designed and developed.Then,the transfer apparatus is experimental studied respectively in the national cooling capacity measurement standard apparatus(room type calorimeter)and the air enthalpy method apparatus.The experiment results and the analysis from the national measurement standard apparatus show that the absolute value of relative biases between the measurement results of standard apparatus and the output of transfer apparatus is less than 0.7% in the cooling capacity range of 1600 W ~ 5800 W,and the cooling capcity relative expanded uncertainties of the transfer apparatus are in the range of 0.8% ~ 1.6%(k=2),which verify the correctness of the water enthalpy method and the accuracy of the transfer apparatus.After the verification of accuracy,the transfer apparatus is measured in the air enthalpy apparatus,and the biases between these two apparatus are obtained.This process achieves the cooling capacity transfer from the measurement standard apparatus to the air enthalpy method apparatus.Furthermore,based on the latest international vocabulary of metrology,the statistical analysis method of resolution is proposed,and the cooling capacity resolutions of the room type calorimeter and the air enthalpy method apparatus are analyzed with the help of the transfer apparatus and the experiment results.For the second problem,the energy flows in the room type calorimeter under four measurement conditions are analyzed,and the influence factors of the indoor ambient cooling capacity measurement and outdoor ambient heating capacity measurement are are quantitatively studied by the uncertainty method.The analysis results show that the measurement of the cooling coiler,the electric power and the heat leakage of partition wall are three main uncertainty sources.In addition,the general metrology character requirements are proposed for room type calorimeter.Based on these requirements,the field calibration method is summarized,and two new system coefficients,which are background values of indoor ambient and outdoor ambient,are proposed.Then,based on the empty-load measurement condition of calorimeter,the measurement model and the measurement procedure of system coefficients are illustrated.Furthermore,in the period of one year,some window type room air conditioners are measured in the calorimeter,to which the calibration method and the new coefficients are applied.The measurement results show that the absolute value of heat balance ratio is lower than 2% in the cooling capacity range of 2000 W ~ 4500 W,and lower than 1% in the cooling capacity range of 4500 W ~ 7000 W,which improves the zero drift of heat balance.For the third problem,based on the common mean model and the random effects model for inter-laboratory comparison,the statistical principle and usage conditions for the uncertainty weighted mean are analyzed with various methods firstly.Then,under the usage conditions,a statistics which includes the linear estimator of reference value,of which weights are combined into a multi-dimension vector,is proposed.The Monte Carlo method is adopted to analyze the probability distribution of the statistics when the weights vector locates in different space: the statistics is(n-1)th-order chi-square distributed when the weights vector is located in a particular sub-space;the density curve of the statistics is nearly confined between the(n-1)th-order and the first-order chi-square when the weights vector is not located in the particular sub-space.Futher,the statistics which includes arithmetic mean is proposed.For the common mean model,this statistics can be applied to the hypothesis testing of comparison results;for the random effects model,the statistics can be applied to the variance estimation of random effects.Moreover,the geometric interpretation of the probability density functions multiplication is proposed with the expression of equations.Based on this interpretation,a generation method of random samples,which obey the multiplication of the probability density functions,is proposed.This generation method can be applied to the Bayesian analysis of inter-laboratory comparison.Finally,he uncertainty evaluation of annual energy efficiency is conducted with the Monte Carlo method,and the simulated procedures and results are given by examples.