The design example of this paper is a primary cooler for large reciprocating air compressor set for petrochemical refinery.
Design input and preliminary structure determination of 1.1 cooler
The original data for the normal flow rate: 3 /h 40 30300Nm, inlet temperature, gas composition, hydrogen, relative humidity 10; compressed gas from 110 to 40 for cooling, pressure drop is less than 0015 MPa; the temperature of the cooling water from 30 to 38, the maximum permissible pressure drop 005MPa; gas / water side fouling coefficient: 0.0002/0. 0008m 2.
1.2 calculation of the process check of the cooler (Rating) based on the known design parameters
In the process of input parameters, we should pay attention to the following points:
(1) the input of the material property parameters of the process medium is very important in the process parameters: for this example, a single medium can be selected from the software database. But for the cooler of air compressor, composed of many cases medium is a mixture from the database to select the appropriate material as the process medium, then the user can choose the custom component #, need to input the following key parameters for the process medium: the critical temperature, critical pressure, average latent heat, operating temperature of the gas. Liquid density, viscosity, specific heat, heat transfer coefficient. In addition to using APSEN program to select suitable state equation and simulate the physical parameters of the mixture, the most reliable method is to get it through document or patented process package file.
(2) in the input process parameters, the effects of saturated steam cooling and partial condensation should be taken into consideration in the first stages of the multistage compressor. This part is different from the conventional heat exchanger calculation, often often ignored, resulting in insufficient calculation of the cooling area.
(3) attention should be paid to the input of structural parameters: the national standard GB151 shell and tube heat exchanger has specified the size of the heat exchanger, but the general international commercial heat transfer software is designed according to TEM A and other foreign standards. There are some differences between them. Therefore, GB15 should be found on the heat exchanger of each structure size specified in the software program dialog box, enter these values according to the requirements of GB151, such as cloth tube, heat exchanger shell side wall impingement baffle spacing, the distance from the shell side inlet and side heat exchanger can be designed to meet the national standard.
1.3 adjustment parameters
After completing the parameter input, running the software, the program will give the calculation report. According to the report's prompt, we need to focus on the following control parameters and make corresponding adjustment, and modify the parameters to run again, so as to get the reasonable result.
(1) the heat transfer area, the design margin, the total heat transfer coefficient, the correction temperature difference and other parameters conform to the requirements.
(2) on the air side, the water side velocity and the Reynolds number are in a reasonable range.
(3) the pressure drop accords with the requirement of setting;
(4) in the flow path analysis, the proportion of effective flow is reasonable.
(5) no tube vibration, sound vibration; it will not cause fluid induced vibration due to the Carmen whirlpool, turbulence jitter, fluid elastic instability and so on.
Analysis of 1.4 calculation results
In the report information column, no abnormal information is given, and the cooler is stable and the control parameters are in good agreement. From the feedback from the use unit, it is also proved that the cooler meets the design requirements in the actual production process and runs well.
2 concluding remarks
The application of international business software to the process calculation of compressor coolers can be done:
(1) accurate calculation of the required heat exchange area and design margin;
(2) the physical change process of the process fluid in the heat exchanger tube is accurately analyzed.
(3) calculating the true circulation and gasification rate;
(4) accurately calculate the resistance loss of the tube and the shell medium.
(5) in the operation information column, various reports on cooler operation are provided, including vibration report, stable operation report, fluid velocity and flow pattern report, which is easy to realize the optimal design of cooler. Therefore, this method has very strong practicability and popularization value in the field of air compressor cooler process calculation.