Sorry this is such a long and rambling thread.
I'm brewing small test batches these days while I wait to get time to work on my new brewstand. The last 2 batches I did I used a microwave to heat the mash. I was less than enthused with the results, especially since I got low efficiency.
As some of you know, I am anxious to try mash heating with steam. Last night I did just that, brewing a cranberry ale using steam to heat the mash in a small cooler instead of using the microwave.
As some of you know I have a corny keg set up as a steam boiler. I did NOT test that this session. There isn't anything wrong with it, but it needs a minimum of 15L of water to submerse the element and it runs on 220VAC, so I used the pressure cooker to generate the steam for this session.
To test steam mash heating for small batches, I bought a 16 quart Coleman cooler and rigged it up with what I thought was a SS braid. It turned out to be a plastic braid. DOH ! More on that later.
The first thing I tested was using an old kettle to generate the steam.
This did NOT work well because the flapper on the kettle doesn't seal well enough, even if you push down on it and half the steam is lost. Not only that, but its a PITA to hold down the flapper.
Then I set up the pressure cooker. I removed the pressure relief valve and put a T beneath it. The pressure relief mechanism got re installed above the T. DO NOT REMOVE OR TAMPER WITH THE PRESSURE RELIEF MECHASISM ON A PRESSURE COOKER ! Luckily the pressure cooker had a 1/8" NPT port so all I had to do was thread fittings.
Although not shown on this picture, I installed a valve in the hose port of the T so that I could stop the steam flow while leaving the pressure in the cooker.
BTW: That hose is special high temperature hose from McMaster Carr. It works very well. I am impressed with it. I would use that hose over say a piece of copper pipe because the hose is very flexible and it insulates the steam from losing a lot of heat. I was worried the steam would condense in the hose and the heat would be lost, but that clearly doesn't happen with this hose.
The first thing I did was just submerse the steam hose in the water in the cooler. That did NOT work well at all. The pressure cooker will generate a large volume of steam and if you let it flow out the end of a hose, it makes big steam bubbles that float right to the surface and break above the water. What this means is that the steam energy isn't captured by the water. For the water (mash) to capture the steam energy (heat), the bubble has to collapse in the water. That doesn't happen if you just put a hose in the mash.
So then I rigged up a SS braided hose in the cooler. Here is a picture. Note: I later figured out the braid wasn't SS.
The braid seemed to disperse the steam, at least for the first 2 inches. The bubbles were much smaller and the majority of them broke before hitting the surface.
Using the braid, I could heat the mash very quickly, without even letting the pressure cooker build much pressure. I went from 48C to 78C or more in 5 minutes or so without turning the stove burner up or anything.
The steam makes a bubbling sound in the mash. It thoroughly mixes the mash where the steam bubbles are escaping.
But nothing is perfect. Problem #1 was that the braid wanted to float. It makes sense if you think about it. The steam doesn't turn into water until it is well into the mash, even if the bubbles are small. Steam is much, much lighter than water/mash, so the braid tends to float. This is a big problem. Even though my braid was plastic, I am sure that a SS braid would float as well. Think of sitting over a jacuzzi jet and your shorts filling with bubbles. That's what happens with the braid.
Problem #2 is that most of the steam escaped from the braid in the first 2 inches, resulting in very uneven heating. All the heat was released on one end of the cooler. This meant I had to stir the mash (!) to keep the temps even.
Other than that, steam heating worked excellent !
The temp was easily controlled by opening or closing the valve. There was no problem with temp overshoots. As soon as you turned off the valve, the temp stopped increasing. There was no scorching. The highest temp I measured in the mash with my digital temp sensor was 74C or 165F. The heating is very gentle. And yet the mash could be heated very quickly, especially if one let the pressure cooker build up some pressure before opening the valve.
So steam mash heating works well as far as I am concerned.
First, you don't need a big pressure cooker like I have. I used that one because we already owned it. One of the small 2 quart jobies would probably work fine. I only ran a few quarts of water in mine, just enough to cover the bottom of it. If you've read my steam posts, you know that pressure vessels can store superheated water and when you open the valve they will release tremendous amounts of stored energy. I wasn't doing that in this experiment because of the the small mash size. But it appears to me that even storing a few litres of super heated water works excellent.
I think a steam mash vessel needs a dedicated steam injection manifold because the steam needs to be distributed throughout the mash in a different manner than wort is typically collected. I think I am going to use a small copper pipe, say 1/4" diameter that runs right through the cooler. It will pierce both ends of the cooler. Said pipe will have 3 or 5 small holes in it to release the steam, spaced equally throughout the cooler. The holes will probably be pretty small, say 1/16". 15 PSI will really blow a lot of steam through a hole, so 3 holes like that should be good.
The steam line also needs a checkvalve on it because as soon as the valve on the pressure cooker was closed, the steam would condense in the hose and suck the mash out of the vessel. I had a hose clamping valve on the line, so I learned the close that first before closing the valve on the pressure cooker.
So, here is a picture of my first steam mashed beer in the fermentor. Its a cranberry ale.
The recipe is in this thread. http://www.homebrewtalk.com/showthread.php?t=22191
It was absolutely dead easy to brew with the steam masher. The only problem I had was a stuck sparge ! Details here. http://www.homebrewtalk.com/showthread.php?t=22529
I had to empty the cooler into a pail in pail sparge vessel to complete it. In spite of that fiasco, I still got a SG of 1.045 on 3.5 gallons of wort.
I'll try to add the steam injection tube to my cooler this week and brew another beer next weekend. I'm pretty busy these days, so it might not happen.