Condenser thermal performances, such as the back pressure and venting rate, are strongly affected by the tube arrangement. Condensers have three irreversible processes for the fluid flow, heat transfer and mass diffusion.The condenser venting rate is studied here based on an air mass entransy analysis. The air mass entransy increment rate for the steam and air mixture on the condenser shell side is expressed as a function of the distributed air mass fraction and the steam condensation rate to define the relationship between the condenser venting rate and the flow parameters. Condensers with three typical tube arrangements were analyzed numerically using the porous medium model. The results show that a bigger venting rate always corresponds to a smaller air mass entransy increment rate. The air mass entransy generally decreases in the air concentration region and increases in the air cooling region under the combined action of the air diffusion and steam condensation. The numerical results indicate that the air cooling region of a condenser should be carefully designed and the cooling tubes should be properly arranged to guide the steam flow so as to weaken air concentration,and consequently to decrease the venting rate.
The condenser performance is strongly affected by the tube arrangement.The steam pressure drop in the tube bundle influences the condenser back pressure,which is an important indicator of the condenser performance used to compare different condenser tube arrangements.The condenser shell side pressure drop is studied here using the mechanical energy loss of the steam flow in the condensers.The mechanical energy loss is due to the flow resistance of the tube bundle and the steam condensation.Three typical tube arrangements are analyzed numerically.The results show that a higher condenser shell side pressure drop for different tube arrangements always corresponds to a larger mechanical energy loss.The mechanical energy loss is mainly in the periphery of the tube bundle,indicating that the flow pattern and the mechanical energy losses are markedly determined by the tube bundle profile.The condenser shell side pressure drop can be reduced by reducing the total mechanical energy loss when the steam enters the tube bundle more uniformly.Thus,a well designed tube arrangement will reduce the mechanical energy loss,and also the shell side pressure drop.
