Hello, I'm Jiyeon Choi studying in Korea.
I want to know how to calculate the effectiveness of heat transfer with two refrigerants phase-changing.
In other words, does anyone know how to calculate effectiveness when refrigerant 1 evaporates and refrigerant 2 condenses?
I don't know how to calculate NTU because both fluids have an infinite static pressure specific heat value...
Please help me.
I'm sorry for confusing you.
The effectiveness that I was curious about is the effectiveness that is said in the Ipsilon-NTU method.
You can calculate the efficiency considering either the phase change or the inlet and outlet temperature of both refrigerants.
In the phase change region of heat exchanger epsilo-NTU method wont work - because it is based on temperature change of single phase fluid streams (at least one of the streams has to be single phase). So basically you know the temperature difference in the part of heat exchanger where phase change occurs, in the part where at lest one of the fluids fully evaporates, or fully condeses - you can use epsilon-NTU in that part. So it is like dividing one heat exchanger into two smaller heat ex@changers.
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