Help: How to perform verification and optimization calculations for heat exchangers

Q = MI, where M is the mass flow rate and I is the enthalpy difference. In other words, it is the flow rate of the oil multiplied by the enthalpy value at the oil inlet minus the enthalpy value at the oil outlet; this is equal to the flow rate of water multiplied by the enthalpy value at the water outlet minus the enthalpy value at the water inlet. The enthalpy value of water can be found using enthalpy tables based on pressure and temperature, while the enthalpy value of oil requires knowledge of its specific heat capacity, data which can be obtained from tables or by asking the supplier

This post was last edited by wiseboy on 2018-8-15 08:27. “The actual oil temperature control is better than what was designed initially” – this indicates that your system was designed based on rough estimates, with a high degree of safety margin included. Many “designs” actually involve no calculations at all. This being better than what was designed requires sacrificing investment and operating costs, you fool.

I’ve come here to learn too*; I work in this industry as well

Having a margin in the design is something that should be taken into consideration from the start... If production increases and the workload grows, what will you do? Buy another piece of equipment as a replacement? Is there enough space and budget for that?? There’s no need to criticize whether the initial design was flawed; instead, it’s important to consider each company’s specific circumstances... ---------------------------------------------------------------------------------------------- For larger cooling systems: If the current cooling efficiency is lower than that of the original design and energy savings are desired, a comprehensive approach is necessary. Things like the water flow rate for heat exchangers or pumps should be recorded one by one, so as to determine the output of the existing water tower pumps compared to the actual demand. Then, the water flow rate for the heat exchangers can be adjusted. Ultimately, it’s also necessary to evaluate whether the water tower’s impellers need to be replaced. PS. An important point to note is that some equipment is quite tall, requiring a higher head pressure; therefore, careful evaluation is needed before replacing the impellers

The original poster also mentioned it’s a power plant, and power plants require relatively large design margins, because if there’s a problem with the equipment, it’s not possible to just stop the boilers and turbines so that repairs can be carried out. That guy upstairs who sells software always seems to say that the design is wrong.

This post was last edited by wiseboy on 2018-8-16 09:07. Since a large margin is required, the significance of performing calculations diminishes. That design includes a margin of safety, not just for power plants.

There should always be some design margin... Software only shows you the best-case scenario after calculations, including costs and operational aspects. But in reality, there are variations in the manufacturing process, and production/output levels can fluctuate. If we relied solely on the calculated figures, it would be impossible to manage things properly... ------------------------------------------------------------------------------------------------------------------------ There’s no need to be so strict when discussing things; it’s just a matter of discussion among everyone

This post was last edited by wiseboy on 2018-8-16 at 12:07. “If everything is determined by calculations, one would be ruined by that,” so are you saying that not using calculations means one can live well? Is rough guessing a good approach? ? What logic!

The so-called design margin – to give a simple example, imagine you want to buy children’s clothes. Most people would choose a size larger, so that the child can still wear it as they grow up. A margin works in a similar way. So how do you know what size to buy? You need to first determine what size is appropriate for the child, and then choose the corresponding size. The calculation for heat exchangers follows the same principle; the result obtained through manual calculation is what’s considered appropriate. Having an additional design margin simply means choosing a slightly larger size. --------------------------------------------------------------------------------------------------------- What I want to say finally is that the values estimated using programs are still based on manual calculations, with an extra factor added on. What’s the difference between this and the so-called design margin? If there had been no prior efforts by others, where would your software-based estimates come from? --------------------------------------------------------------------------------------------------------- I’m just discussing things objectively. It’s your choice if you want to promote your own products, but there’s no need for sarcastic comments. What people want is rational communication, not unreasonable insults. --------------------------------------------------------------------------------------------------------- If you try to insult me, I won’t engage in arguments with you. That’s all!!!

This post was last edited by wiseboy on 2018-8-16 at 19:55. Do you mean I should criticize you first? Are you the one who’s being jealous of others now? Really. And you said a lot; is the main idea that it’s better not to do any calculations and rely on intuition, because if you do calculate, you’ll get into trouble? Modern scientific design relies on calculations; if the calculations are not done correctly, then the results are wrong. It’s a principle that is clear and well-known, yet you still try to argue against it.