The Effect Of Process Layout On The Heat Transfer Performance Of Tube-and-fin Condensers

The performance improvement for heat exchanger is the key issue for energy saving.Its optimal design research has great importance both in theory and engineering value. The experiment and simulation method are applied to study the performance of condensers.This paper mainly studied the comprehensive performance influence of the layout for the condenser. The effect of refrigerant charge, air volume of evaporator side, refrigerant circuitry, layout of merging on the refrigerating system are investigated. The experimental results could be used to check the accuracy of the finned-tube condenser model. Different layout of condenser are simulated to find out the best district of merging. The exergy analysis method for the condenser is also discussed.The experiments for condenser are conducted in the enthalpy difference lab. According to the result of the experiments, under standard condition, the optimal refrigerant charge for this refrigerating system ranges in 1150~1200g. The optimal air volume rate of evaporator is about 1250 m3/h. Under variable working condition, the heat transfer performance and the COP of layout b is better than the other three layout. Accordingly, it was showed that merging in the second half of the finned-tube condenser can optimize the heat exchanger and the system. So that choosing a reasonable merging point in the second half of condenser tube is good for the condenser and the system. When the refrigerant charge is small, the influence of refrigerant circuitry on the heat transfer and pressure drop can be ignored. With the increase of refrigerant charge, the influence of refrigerant circuitry is important. Merging in the second half of the condenser can improve the uniformity of the heat transfer. In order to meet the balance of heat transfer and pressure drop, the best district of merging is at 0.1~0.4 of the dryness.Then, the simulation software is adopted to analyze different layout with the finned-tube condenser. Firstly, the soft should be checked by the experiment. According to the simulation results, the heat transfer and pressure drop are rising with the increase of the mass flow rate. But the general trend is different. The refrigerant mass flow rate has a great influence on condenser. The range of the optimal refrigerant mass flow rate for refrigerating system is 0.02~0.035kg/s. When the refrigerant mass flow rate is the same, the heat transfer increases firstly and then drops with the merging point moving up. But the pressure drop shows an accelerated increasing. The study found that when the best merge point is at therange of 0.1~0.4 of refrigerant dryness. It is good for optimizing the system. Merging early or not merging are not good for the condenser.Finally, the exergy analysis is adopted to analyze the comprehensive performance of the condenser. It indicated that the exergy destroyed is mainly caused by temperature difference. But, the exergy destroyed caused by pressure drop and the heat rejection cannot be ignored. For the low refrigerant mass flow, the effect of refrigerant circuitry on the exergy destroyed can be ignored. For the High refrigerant mass flow, the exergy destroyed is increasing with the moving up of merging points. The best merging point is at the range of48~50 of tube number.