Numerical And Experimental Research On The Influence Of The Perforated Baffle Structure On The Thermal Performance Of The Mixed Water Tank

Energy conservation has attracted the close attention of scientists.It has been known that global building energy consumption accounts for about 27% of the total energy consumption.Considered as one of the three important components of energy conservation(building,transportation and industry)at present,building energy efficiency is critical for controlling the temperature rise of the earth and reducing the uncertainty of carbon emissions.Since water-cooled chiller is an important cold and heat resource equipment of architectural environment,the accuracy of its energy efficiency rating and energy-saving in laboratory test of its performance are both of great significance.Water tank is the core component of performance test of water-cooled chiller and the water side working condition of the unit is mainly guaranteed by the water tank.Therefore,it is of great significance to improve the constant temperature performance of the water tank for the performance test accuracy of the water-cooled chiller,and to save building energy by optimizing the water-cooled chiller.The water temperature distribution of the water tank is greatly affected by the water flow inside the water tank.Therefore,setting baffles inside the tank,optimizing baffles’ arrangement and adjusting geometric configuration of baffles can promote the water temperature stability of the water intake.In this paper,the water tank for the performance test of water-cooled chiller is divided into three areas by baffles: A for heat transmission,B for heat balancing and C for thermostatic controlling.The method of computational fluid dynamics is used to optimize the geometric configuration of the water tank.First of all,the influence of the layout of transverse baffles and longitudinal baffles is studied.The proportion span is 0.382 m,0.500 m and 0.618 m,in other words,the combination of transverse baffle position(Y = 0.328 m,Y = 0.500 m,Y = 0.618m)and longitudinal baffles position(X = 0.328 m,X = 0.500 m,X = 0.618m)is 9 in total,and 8 combinations of 4transverse baffle and 2 longitudinal baffles geometries are further studied to obtain their influence on water temperature distribution.Thereafter,a better configutaiton is recommended.For the better model,the perforated baffles are used to replace the baffle openings,and the temperature distribution of the optimal model with perforated baffles under two extreme conditions(with minimum refrigerating capacity under nominal condition or with the maximum load under non-nominal condition)is simulated to verifythe adaptability of the model.Then,on the basis of numerical design,the water temperature distribution in five typical models slected according to the simulation result is measured and studied to verify the accuracy of the simulation results.further comparative analysis is made on the influence of four different perforation rate baffles(25%,50%,75%,100%)on the water temperature distribution of the water tank,and the best range of perforation rate is recommended.For the final water tank with the optimal configuration,the actual measurement is carried out under different working conditions(nominal lower limit,intermediate and upper limit cooling capacity conditions and non nominal maximum load conditions)to further verify the adaptability of the designed water tank.Finally,the evaluation index system is established to evaluate the water temperature distribution in the water tank,and the model with the optimal configuration is selected by comprehensive analysis and quantitative results accordingt to evaluation index data.The simulation results show that in the optimized water tank,the fluid gradually stabilizes in three areas,the fluid temperature gradually converges,and the intake water temperature is constant,which can ensure the inlet and outlet temperature conditions of the performance test for the water-cooled chiller.The experimental results are consistent with the simulation results.When the position of the baffle is X = 0.382 m,Y = 0.382 m,and there is no opening in the upper part of the baffle,the model has an ideal temperature distribution,and the actual operation effect is stable under different working conditions,with good applicability.Additonally,the recommended optimal perforation rate range is25% ～ 60%.The results of this study can provide some reference for the internal design of similar mixing water tanks with constant water temperature.