In the chemical engineering case study session in 2017, for the question related to pump selection, there were two densities: one was 1081 and the other was 810
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There are two densities: one is 1081 when it’s cold, and the other is 820 after heating. The numbers are more or less like that; I can’t remember exactly. Which one should be used when calculating power? Using 1081 gives D as the answer; using 810 yields a value close to 15, so B is the choice. I’m not sure which density to use
I chose B; it should be selected based on normal production practices, as the question suggests considering energy savings
Using 810 for calculation saves energy, and there’s also a safety factor of 1.25； But 1080/850=1.27>1.25 ； I was very torn, but in the end I chose B
I calculated both as well, made a choice, and went with B
Hot operating conditions are more demanding on the equipment, so it is appropriate to use hot-state parameters for calculations.
I remember it like this: using a high starting density, the power calculated was 1.8+ KW (18?) I forgot), calculated based on actual operating density, it’s 1.5+ KW (15?) Anyway, more or less), the answers given are 1.5, 1.8, and 2.3. I chose 1.8. I think it’s possible to operate at a low load when starting up, but the load can’t be that low after all, as it needs to cover everything; that’s why I picked 1.8, though I’m still a bit unsure about it.
I think the same way as you; I chose 18 because I considered that since it’s necessary to ensure operation, and the goal is heating, then it’s best to opt for a density that allows for high heating temperatures while also helping to save energy. I’m not sure if my reasoning is correct.