A Drying Model Research And System Simulation For A Nylon Polymerization Heat Pump System

Heat pump is a kind of system which can upgrade low-grade energy to high-grade energy to achieve energy recycling. It's widely used in the chemical drying systems. Heat pump drying system can re-heating the exhaust gas which be discharged from the dryer. In this paper, the dryer tower's theoretical models have been established and computer simulation software of heat pump drying system has been developed, based on an actual nylon heat pump drying system. A set of real operation date for this system is also provided.Based on the physical model of the drying tower in the nylon heat pump drying system and the basic theory of heat and mass transfer, an algebraic model for the drying tower is been established which can describe the humidity and temperature of drying gas, as well as the moisture and temperature of material in the import and export of the drying tower. Newton descent method with a relaxation factor is been used to solve the algebraic model. From the solution, the heat and mass transfer coefficient model is obtained which can be used in the later model.In order to get more information in the drying tower, a differential model is derived. For the modeling and solving convenience, we introduce five basic assumptions, so the three-dimensional unsteady problem is simplified into one-dimensional stationary problem. The model contains four Ordinary differential equations which can be solved by classical fourth-order Runge-Kutta method. The results shows that the differential model that be derived can meet the basic physical facts. It is also show that the temperature distribution curve of the material along the tower is almost a Straight line, and also the drying gas. Thus, we attempted to use linear relations to improve the temperature distribution equations in the original model. Then, a improved model is received which is simpler than the original model. The error between the original model and the improved model is 9% or less. It's an acceptable error range in this kind of projects.The multi-stage centrifugal blowers used in the heat pump drying system are designed and developed by our fluid mechanical group. In this paper, the performance test of multi-stage centrifugal blower is carried out. By the test results, the design pressure ratio of five-stage centrifugal blower is 1.6. By using least-square method to fit the experimental points, multi-stage centrifugal blower performance curve and curve equation are got. The curve equations are the basis of the mathematical model of the fan modules for the subsequent simulation of heat pump drying system.In addition, a drying system simulation software named"heat pump drying system simulation software V1.0''is developed in this article, which is based on C + + and C # programming language. First, we write the dynamic link library files (dll files) for the device models in C++ language, and then, the man-machine interface is developed by C# language for system simulation visualization. The system can realize the simulation under different conditions of system operating parameters.