| Ethylene glycol coolant is used more and more in places now.Whether it is in the cold storage design,air conditioning room,ice storage or ground source heat pump or air source heat pump,will be involved in the choice of ethylene glycol pipeline.Ethylene glycol coolant numerical resistance along the different concentrations is very important.In this paper,the corresponding conclusions are obtained by solving the following problems: This study is based on experimental and simulation studies;firstly,the roughness of the pipeline was obtained by experiment and hydraulic characteristics of different concentrations of ethylene glycol at 20?.The relevant parameters are introduced into the simulation program to obtain the hydraulic characteristics of ethylene glycol at different temperatures.The test bench was built and debugged,Choose DN25 and DN40 two pipe diameter,DN25 pipe flow rate range is controlled at 1.1-2.0m/s,andDN40 flow rate is controlled at 0.7-2.0m/s,According to the test and simulation calculation,we can know the relative roughness of DN25 pipe diameter is 0.00563 and DN40 pipe diameter is 0.0359.The experiments were carried out with three kinds of concentration under the condition of the same roughness,so we know the variation of friction factors along with Reynolds number:When we chose the pipe diameter of DN25 and ethylene glycol solution is 20%,the trend of friction loss factors is around 0.0356 along Reynolds number arrange from 18000 to 33000;ethylene glycol solution is 25%,the trend of friction loss factors is around 0.0361 along Reynolds number arrange from 16000 to 33000,ethylene glycol solution is 30%,the trend of friction loss factors is around 0.0361 along Reynolds number arrange from 15000 to 27000.When we chose the pipe diameter of DN40 and ethylene glycol solution is 20%,the trend of friction loss factors is around 0.0643 along Reynolds number arrange from 18000 to 50000;ethylene glycol solution is 25%,the trend of friction loss factors is around 0.0661 along Reynolds number arrange from 16000 to 45000,ethylene glycol solution is 30%,the trend of friction loss factors is around 0.0671 along Reynolds number arrange from 15000 to 41000.The local resistance test of metal hose is carried out under DN25 and DN40 diameter;the results show that under the same roughness.The larger the diameter of the hose,the smaller the local resistance;the local resistance coefficient does not change with the change of concentration or only slight change when the fluid is same kind,he reason is that the change of dynamic viscosity has little effect on the energy dissipation of the metal hose in the range of the test concentration.By the test,when the fluid is water,we can choose the local resistance coefficient of DN25 is 2.89,the value of DN40 is 2.20;when the fluid is ethylene glycol solution,we can choose the local resistance coefficient of DN25 is 2.8,the value of DN40 is 1.8.In the process of design calculation,Whether it is water or glycol solution,we can choose local resistance coefficient of DN25 pipe is 3 and local resistance coefficient of DN25 pipe is 3.The experimental results and the simulation method are used to compare the resistance coefficient of water and glycol solution at 20?,the results is fitness.Using the same simulation method to simulate low temperature conditions.At-5 ? the working medium is a glycol solution of 23.6% mass concentration,The solution flow rate of 1.3 m/s-2.2 m/s was reduced from0.042 to 0.038 in the DN25 tube,In the DN40 tube,the solution flow rate is 1.1 m/s-2.2m/s and the drag coefficient is reduced from 0.066 to 0.065;At-10 ? the working medium is a glycol solution of 32.2% mass concentration,The solution flow rate of 1.3 m/s-2.2 m/s was reduced from0.044 to 0.041 in the DN25 tube,In the DN40 tube,the solution flow rate is 1.1 m/s-2.2m/s and the drag coefficient is reduced from 0.068 to 0.066;At-15 ? the working medium is a glycol solution of 40% mass concentration,The solution flow rate of 1.3 m/s-2.2 m/s was reduced from0.056 to 0.046 in the DN25 tube,In the DN40 tube,the solution flow rate is 1.1 m/s-2.2m/s and the drag coefficient is reduced from 0.0725 to 0.0695.It provides a reference for practical engineering calculation. |
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