RIMS tube diameter

[ba-brewer]

Is it best to have a tube just big enough to surround the element or is having some extra volume inside the tube around the element OK?

Seems like less volume would be better, but also not sure if you have a decent flow.

 

[BrunDog]

You are on the right track... as small as possible without overly restricting flow. You want turbulent flow around the element, but I think element watt density is the most important to reduce or eliminate local hot spots and caramelization.

 

[mabrungard]

The primary goal is to move the fluid through the chamber as quickly as possible so that hot spots are quickly bathed in new fluid and cooled. So have the chamber diameter at just above the element diameter is desirable. Having a larger diameter chamber will slow the overall fluid velocity in the chamber.

Don't forget that your tubing connecting all the pumps and chambers and vessels is probably in the half to three quarter inch diameter range, so a 1.5-inch diameter chamber is much larger and the fluid velocity will be lower.

 

[augiedoggy]

Is it best to have a tube just big enough to surround the element or is having some extra volume inside the tube around the element OK?

Seems like less volume would be better, but also not sure if you have a decent flow.

less is better for me... I use a 5/8 diameter cartridge heater in a 1" stainless rims tube.... the longer the element and rims the better due to longer contact time with heat and less watt density (my element is 36" long for this reason). I measure my flow with a flowmeter and its between 1.5 and 2.0gallons per minute... usually around 1.8... this is what I tuned my pid with.

 

[Throttle79]

I have been runin a 1.5" copper tube with 1/2" inlet and outlet for a couple of years now. My heating element is a 4500w standard watt density. I have had no issues with carmelizing or build up on the element. The key is keeping the liquid moving. The slower you flow the more time the liquid will have in the tube and the more heat transfer. I would recomend wiring an interlock safety into your controm to keep the heater from turning on untill the pump is turned on..... just my $.02mug:

 

[augiedoggy]

I would recommend wiring an interlock safety into your controm to keep the heater from turning on untill the pump is turned on..... just my $.02mug:

I did this myself and even though I got ridiculed here for it I highly recommend it. it has saved me more than once from dry firing.

 

[ba-brewer]

The primary goal is to move the fluid through the chamber as quickly as possible so that hot spots are quickly bathed in new fluid and cooled. So have the chamber diameter at just above the element diameter is desirable. Having a larger diameter chamber will slow the overall fluid velocity in the chamber.

Don't forget that your tubing connecting all the pumps and chambers and vessels is probably in the half to three quarter inch diameter range, so a 1.5-inch diameter chamber is much larger and the fluid velocity will be lower.

So if you have a higher velocity does that mean you can have a higher wattage density, or wattage density becomes less of an issue?

I found a formula that said velocity in pipes of different diameters is equal to velocity1*area1 = velocity2*area2, does this apply to a RIMS system?

I am wondering how much impact a 2" tube vs 1.5" tube would have. If that formula applies and I did my math right then it looks like velocity drops by 43%, that seem significant. Is it really significant and is it worth spending extra money to get a 1.5" RIMS tube vs a 2" tube?

 

[BrunDog]

Watt density becomes less of an issue at higher velocity. But you cannot always control your velocity... if you are getting a stuck mash at higher rates, you will need to turn the flow rate down.

 

[ba-brewer]

Seen this in the "RIMS for dummies" thread, does the statement about the rest of the system being more important then the tube itself hold true for most RIMS setups?

There are many factors more important than the tube size that affect RIMS efficiency. Mash tun size/shape, mash tun heat loss, batch size, OG, and flow rate will affect your success more than the tube size. Your tun design, specifically your false bottom can affect flow rate at OGs above 1.070 adversely. for example I know my flow rate is about right when the probe in the tube and the probe in the tun are only 2-3 degrees apart. my $0.02