Can the exergy loss of a device be negative?
Thread Content
When analyzing the exergy efficiency of the equipment, a situation occurred where the exergy efficiency was greater than 1; in other words, the exergy loss was negative. This is quite puzzling. I seek guidance. The thermodynamic data used in the calculations were obtained from HYSYS simulations
You only calculated the requirements for physics, but not those for chemistry, right?
Yes, only the physical exergy was taken into account; the devices with negative exergy losses were heat exchangers. Similar calculations in relevant literature do not consider chemical exergy. Negative exergy losses mean that the situation violates the second law of thermodynamics. Could it be that the operating conditions (pressure, temperature) I set are not realistic, making it impossible for such devices to function in actual production?
If it is just a heat exchanger, there is no need to consider chemical changes, as the components do not change. Check again how you set it up; the problem might lie there.
I changed the working fluid and adjusted the parameters; now the exergy loss calculated is positive. Also, when performing HYSYS simulations, are they based solely on heat balance? Are the results obtained sometimes unrealistic in practice?