0:00
In this video I want to give you a tour of a flat plate heat exchanger
0:05
This is a pretty important part of a solar heating system. This one happens to be
0:09
made by a company called flat plate but it's also a generic term so it's these
0:15
kind of exchangers are made by a lot of other companies. This one is a 3 by 8
0:21
dash 14 so 3 inches wide from left to right 8 inches tall from top to bottom
0:28
and the 14 refers to the number of plates and if you were to count these
0:34
plates here you would find that there were 14 of them. Now one side of each of
0:40
these plates corresponds to a pair of outlets here on one side and the other
0:48
side of those plates corresponds to the opposite side. So for instance if some
0:56
cool water were to enter, sorry some hot water were to enter here from your solar
1:02
collector it would travel up and it would come out this side here. If some
1:09
cool water returning from your home after heating it were to enter here then
1:14
heated water would come out here. Now for purposes of flow rate and flow
1:22
path these two sides are separate they may never connect the liquid never
1:28
touches each other and if we had say the hot water from your collector coming in
1:35
here it would be coming in here and traveling up and then as it goes up it's
1:44
going to become progressively cooler as it transfers its heat to the other side
1:53
So here we have cooler water entering from your home after doing its job
1:59
heating your space so cooler is here and the flow is this way. It's very important
2:10
when you plumb these things that you have opposing flows. That's the only way
2:16
you're going to get maximum heat transfer from this exchanger and here's
2:22
why. Because as this hot as this water travels down here and it's getting
2:27
warmer it's getting progressively harder for it to pick up heat from the other
2:33
side of the exchanger. So the further this goes down the hotter the water we
2:39
want it to encounter on the other side of the exchanger. So that's why we have
2:44
opposing flows like this. We could plumb it so that both flows were
2:49
going in the same direction but we would have far less heat transfer than we do
2:55
with an opposing flow arrangement. So there's one other thing I want to
3:00
mention when it comes to plumbing a flat plate heat exchanger and has to do with
3:05
fittings like this valves like this you could just plumb this into your system
3:10
with connectors and pipes leading off but the problem is that these plates can
3:16
become coated inside with various sorts of things that inhibit heat transfer. This
3:24
is especially true if you're heating domestic hot water through one side as
3:29
I've shown in the plans because that's going to build up scale inside on those
3:35
plates and you need to be able to descale your exchanger. So that's where
3:40
valves like this come in. I'm not showing it hooked up here but this valve does
3:46
two different things. First of all it lets you shut off the flow to the
3:53
exchanger and that's going to happen on both sides and second of all it allows
3:58
you to gain access to the exchanger to connect a garden hose here well that'll
4:07
be connected to a pump pumping through vinegar or some other solvent that's
4:13
going to clean out the insides of the heat exchanger to clean off the surfaces
4:19
of the plates so that it works properly again. Now you definitely need to do that
4:24
when you have domestic water flowing through one side because it has minerals
4:28
in it and the minerals get deposited and after six months or a year your
4:32
exchanger is not going to be working very efficiently. My personal policy is
4:36
to, and this I've learned the hard way, is to include these kinds of fittings on
4:41
every part of every flat plate heat exchanger because you never know when
4:47
you're going to need to clean it out even if you're not expecting it
