NUMERICAL SIMULATION OF SINGLE TUBE HEAT EXCHANGERS
Abstract
Whenever the fluid flowing inside a heat exchanger tube undergoes a change of phase, the fluid friction factor, heat transfer coefficient, thermodynamic and flow properties of the fluid vary significantly. Taking such variations into account, a mathematical model is developed to predict steady state performance of single tube externally finned heat exchangers. The heat exchanger model consists of a set of nonlinear coupled ordinary differential equations. A computational algorithm was developed to solve this set of equations. The programs to simulate steady state models for single tube condenser and evaporator were written in FORTRAN. Simulations for typical condenser and evaporator conditions were performed using the steady state models. The simulation results were found to be physically realistic. The computational algorithm for single tube condenser was used successfully as a building block to simulate multi-tube condenser. The computational algorithm developed in this investigation was validated against the experimental results published in the literature. The simulation results compared very well with the measured values. A series of numerical experiments was performed to study the effect of forcing function and method of integration on the response of the algorithm. From these numerical experiments, it was concluded that the algorithm was accurate and robust. The effect of axial conduction in the heat exchanger tube wall on the rate of heat transfer from the condensing and evaporating fluid flowing inside the heat exchanger tube was also studied under simulated conditions. Axial conduction in the tube wall was found to have a significant effect on the heat exchanger performance. However, the inclusion of axial conduction in the model increased the computation time significantly.
Degree
Ph.D.
Subject Area
Mechanical engineering
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