Component 33 vs. 46?

I Really Don't Like 33s

I see a lot of white diamonds (Comp 33s) in new users’ models. You’ll almost never see them in mine. I greatly prefer the Comp 46.

If you need to set some pipe properties, it IS easy to put a Comp 33 on a pipe and enter some numbers, as is done in the “700C-plant.ebs” model in the Examples folder:

P and T are given for one of them:

Lack of clarity

“Clarity is key”, I alway say. What are those white diamonds doing? You don’t know until you hover them, open them, or add some Value Fields:

Compare to the following version that is using Comp 46s. They automatically set to “Standard Ebsilon Colors” to show you what is setting pressure (red), temperature (green), or mass flow (white). Yes, this requires a Comp 46 for each property you want to set (you can only set one property), and you need tell it what property to set. It’s worth the effort… not just for clarity, but also for another even stronger reason I’ll talk about below.

But why are there still some Comp 33s?

Something they ARE good at — and essential for — is setting the fluid composition. Here, I’ve emptied the P-T-M specification cells, but left this setting on the Material Fractions tab:

Note that you can also use a Comp 1 to define fluid composition (at the beginning) of a pipe.

But what about the Controller’s Starting Value?

In all Controllers, the default setting for the Source of Start Value is “Externally”

meaning that something must put an initial value on the pipe. And yes, the Comp 33’s name is “General Input Value / Start Value”. That’s what is done in the sample model:

So what’s the flow in the pipe? Someone sees a white diamond setting T=20 and M=30, and might think the flow is 30 kg/s. But no. It’s 35.16 kg/s.

The 30 was just a starting guess. You don’t know that by just looking at it.

Again, the Comp 33 has caused confusion.

A Side Note Regarding Controllers

For controllers, I prefer to USE AN INTERNAL STARTING GUESS. Why use 2 components if you can do it with one? And I don’t need to hunt for where the thing is that’s setting the first guess.

Using an internal starting guess also reveals the very useful L2STARTOFF specification (the subject of a future post).

Off-Design Woes

This simple model has the condenser’s Design Pressure being set externally, using a Comp 33 on the steam pipe. The Design profile runs fine. Now, in off-design, it gives an Overdetermination in Pressure error because the condenser is calculating pressure, but the Comp 33 is also setting pressure.

To fix this, you would need to empty the Comp 33’s P specification in this and all off-design profiles.

Comp 46: great for Design / Off-Design

The Comp 46’s FFU specification has this super-useful setting:

So it turns itself off automatically in an Off-Design profile. There’s a nice visual cue also: the black flag disappears, so you know it’s off.

Pursue clarity, my friends.

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