Errors keep occurring when using Aspen EDR to perform a detailed design of the generator for lithium bromide absorption heat pumps
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The heat exchanger has been carefully designed: the steam driving force on the tube side is 550 kPa (saturation temperature of 155°C), with a temperature of 180°C. At the inlet on the shell side, there is a dilute lithium bromide solution with a temperature of 127°C, a pressure of 53.4 KPa, and a concentration of 59%; its saturation temperature is 134°C. The goal is to achieve an outlet temperature of 146°C for the dilute solution on the shell side. At this point, lithium bromide is in a two-phase equilibrium state, and errors keep occurring as shown in the diagram; I seek help from experts
Looking at the error message, it seems there’s still an issue with the material properties
Hello, since the working fluid I use is a lithium bromide aqueous solution, which is an electrolyte solution, there are no issues with simplified design; with a more detailed design, there are no problems with other heat exchangers either, except that the generator reports errors.
Is it because phase changes occurred in both the cold and hot fluids of the heat exchanger, resulting in calculation errors? ?
It doesn’t seem to be a phase transition issue; rather, the physical properties themselves are inappropriate – specific heat, enthalpy, etc. Were these physical properties generated automatically by Aspen? If it’s a manually entered suggestion, check its source
Hey, I used EDR to determine the specific structure of heat exchanger FS1, and its parameters roughly match those obtained during my preliminary design. However, when these parameters are imported into Aspen, the heat exchange requirements aren’t met. I wanted the exit temperature of the cold fluid from the heat exchanger to reach 146°C, with the pressure dropping from 53.48 Kpa to 51.468 Kpa; in reality, however, the temperature only reached 135°C and the pressure drop was higher, at 48.9 Kpa. Is it because the structure determined by EDR cannot be imported into Aspen?
To be honest, I’ve never done it in reverse; I always let Aspen do the calculations and then export the results. As for why you got this particular result, it’s impossible to determine just by looking at the graphs. One thing to keep in mind is that in Aspen you can get whatever result you want, regardless of the actual structural dimensions; so there’s no point in trying to verify something by working backwards.