دانلود رایگان مقاله انگلیسی تحلیل متغیر کنترل شده مبدل حرارتی جریان ضد بر اساس استخراج ترمودینامیکی - نشریه الزویر

Abstract

To optimize the controlled variable of counter flow heat exchanger, T-Q diagram inducing entropy angle and thermal capacity angle is used to analyze heat exchange process. The results show that selecting stream outlet temperature as controlled variable is incapable of perceiving overall variation of thermal capacity flow rates. The change of heat exchanger effectiveness isn’t completely consistent with heat transfer irreversibility, and cannot reflect the effect of remanent (flow-imbalance) irreversibility. The terminal temperature difference imposed by heat transfer irreversibility is the same at both ends. However, the remanent irreversibility makes the terminal temperature difference of one end deviate from the other. Based on maximizing the heat exchange amount and minimizing the irreversible loss, a new controlled variable named as heat exchanger comprehensive effectiveness is constructed, which is easy to be measured and calculated. It can reflect the effect of heat exchanger effectiveness, remanent irreversibility, and heat transfer irreversibility simultaneously.

4. Conclusions

Based on maximizing the heat exchange amount and minimizing the irreversible loss, a new controlled variable of counter flow heat exchanger, i.e. heat exchanger comprehensive effectiveness , is constructed by using T-Q diagram inducing entropy angle and thermal capacity angle. The T-Q diagram can more clearly reflect the relation between heat exchanger effectiveness , heat transfer irreversibility , and remanent irreversibility .

 Selecting the outlet temperature of one side stream as controlled variable has its limitations. It is incapable of perceiving all changes of thermal capacity flow rates.

 The heat exchanger effectiveness doesn’t show a completely consistent change trend with heat transfer irreversibility , and couldn’t reflect the influence of remanent irreversibility .

 The terminal temperature differences imposed by heat transfer irreversibility at both ends are the same. The remanent irreversibility results in that the terminal temperature difference of one end deviates from the other.

 The new controlled variable is easy to be measured and can reflect the effect of heat exchanger effectiveness, remanent irreversibility, and heat transfer irreversibility simultaneously.