"total system design" needs to be considered - not just one parameter.
IF, for example, a dual path heat exchanger is used, so the water flows at half speed, yet the same amount of water flows, you MIGHT get better efficiency AND more heat output.
You get more OF the heat into the house (higher efficiency), but less TOTAL heat into the house.
No I'm not. I'm just saying there are two things that could affect the total efficiency and heat output of the system, and they could be , to a point, at cross purposes.
No, they do a design analasys - and then they test it to prove it - and they DO instrument their design - at least in the primary stages.
After they have established what works and how - and what assumptions are valid - they go on experience. Often the documented experience of others.
At this point we do not have documented experience of anyone having done this - so doing a bit of experimenting is valid.
Scientific method - defined: a method of research in which a problem is identified, relevant data are gathered, a hypothesis is formulated from these data, and the hypothesis is empirically tested.
But we are not changing the surface area. The surface area is fixed for whatever heat exchanger he uses. We're just changing the volume of air passing through. Back to the original point that harry still disagrees with. And that was if you increase the airflow through a water to air heat exchanger, you get more heat out of it. The increase in heat that you get trails off exponentially until you finally have the air exiting and the water exiting at the same temperature. At that point you've extracted all the heat and the heat transfer has reached the maximum. Increasing it beyond that doesn't extract any more heat. I think we agree on that, don't we?
You agree that the same applies to a home radiator? The more air you put through it, the more heat you will transfer?
You agree the same applies to the auto radiator? The more air you put through it, the more heat you will transfer? (assuming of course the heat is there, ie the thermostat is wide open, car block is hot, etc)
You agree that is what the data sheet for the heat exchanger you provided shows?
No, that is not correct. You get the most heat transfer when the temperature delta is the greatest. If you send the water back to the solar array at say 110F instead of
90F, it will pick up less heat when it passes through the solar array. The amount of heat picked up is not fixed, it's directly affected by the temp of the incoming water. The cooler the water I put in, the more heat I can extract from the solar array.Yes, I acknowledged that in previous posts. I originally thought you were advocating putting them in the main airflow, which is why I said just put all the air through the heat exchanger. It's simple and you get the max heat extracted. You can see from the spec sheet on the heat exchanger the consequences of reducing the airflow. A typical furnace could move ballpark 1000CFM in heating mode. From the spec sheet, that gives 38K BTUs. If the airflow is cut to 500CFM, which is still 1/2 the available airflow, you get 28K BTUs out of the heat exchanger. i don't know what you think about giving up 1/3 of the available heat by restricting the airflow, but it doesnt' sound like a good idea to me.
I still have doubts about the viability of this thing based on how much heat you could get out of it. The OP never gave us data on the solar array. I'm betting that it's sized to a water heater and not capable of anywhere near the flow rate for the curve in the heat exchanger spec sheet. To get the 38K BTUs that heat exchanger has
6GPM of 140F water flowing. As I said before relative to a water heater, that's an entire tank of hot water in 8 minutes. Meaning I doubt the solar array has capacity anywhere near that. It's likely sized to a water heater application and could have 1/10th the heat output. In which case, the heat for the furnace likely isn't worth the trouble.
I don't need to do that to know that the more air that flows through a water to air heat exchanger, the more heat that is transferred. And that the cooler the water temp is that is entering a solar array, the more heat you get out. Both up to the total max heat tranfer that is possible of course, which would be when the water exiting is equal to the air or solar array temp.
But nobody is talking about using a dual path heat exchanger, nor is there any reason to use one in this application. And you can't find a water to air heat exchanger where you don't get more heat out of it the more air you put through it. The spec sheet you provided clearly shows that. Nor can you find a solar panel where you don't get more heat out of it the cooler the incoming water is. Those are the parameters that matter.
I can't get harry to agree that with a simple car radiator or home radiator, that the more air you move through it, the more heat you get out, until you hit the max. The max is where the outgoing water temp and air temp are equal. I thought you agreed on that point, no?
I'm not sure efficiency is the right term, but I agree that with the valve nearly closed, you extract all the available heat from a tiny bit of water and you get little heat into the house. And how do you get more of the heat from that water to air heat exchanger into the house? By increasing the airflow, per the datasheet. Agree?
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