Heating Help

Gravity fed radiant tempering

Dear,
I have a few questions about a gravity fed tempering system
“Tempering” is a system that emissions warmth to provide a basic warmth/heat in (old) buildings with solid masonry walls.
It was developed for old museums in Germany by Henning Grosseschmidt.
The tempering system guarantees a healthy, dry indoor climate in old buildings and this at the lowest heating cost. Moreover, the old walls in dry state shall also isolate significantly better. So this is a win-win situation.
 
You can go through the details in the following pdf:
http://www.temperierung.net/sites/default/files/Klima_in_Museen-The_Tempered_Building-Grosseschmidt.pdf
 
So the system works with the direct supply of warmth through (copper)pipes against/in thick  exterior walls.
I wanted to apply this system in my house by using steel-pipes and especially by using the system of (overhead) gravity heating.
That’s why I have the following questions:
In the subsequent scheme the riser(A) has a diameter of 1 ½ inches. 2  pieces of a 1 inch steel-pipe go from the top to the bottom of a 2000liter boiler.
Question 1: Will this system work on gravity only? Or do you think the horizontal pieces are too long?
Question 2: What should be the minimal descending slope/declivity of the horizontal pieces B, C and D?
Question 3: Can the lengths F, G and H be 100% horizontal or should they be given a declivity as well?  
 
Thank you in advance.
G
From cold and wet Belgium.

Uh, Dan?

I look forward to following this one!

Odd question ?

Do you find it a crazy idea ?

G

Odd question ?

Do you find it a crazy idea ?

G

Adaptation possibility

Eventually I will add one Cast Iron Radiator and one Finned Tube in the circuit.
Those two will be fitted in "parallel" to the basic-circuit. Just to put 'on' on really cold days or special occasions. But I would like if the Gravity Tempering worked also when those two are in 'off'.

 G

Interesting concept for sure...

I am still reading the information you provided, but from what I've read, you are basically idling the Mean Radiant Temperature of the spaces, and MRT drives the bus of human comfort. I am especially intrigued by the window tempering circuits. I am aware of at least one local engineer who has attempted to do the same thing here in Colorado. I have a radiant window product that completely eliminates the cold sucking effect of windows.

I think I want to finish reading the information you've provided before I render an opinion. Lots of information there.

ME

yes and no

Overhead gravity is the best. Perimeter radiant is often recommended. You have to consider vapor migration in masonry walls. In an old mansion with single pane windows, we tried radiant panels on inside wall hoping that heat beams would keep glass dry.

the proof of the pudding

Indead, the effectiveness of the tempering-system can be discussed.
The proof of the pudding is in the eating, for that part.

But is there nobody here who can tell me if the pipework in the first scheme (without radiators) will work without pumps ?

G

Difficult decision...

Somewhere, one of the dead men probably has a formula to show exactly how much flow you could expect, but it is all dictated by height, pipe size, connected loads and fluid viscosity (antifreeze).

Is there a reason you don't want to step into the current century and employ some of the most efficient pumps available? If you are designing it around "net zero" concepts, there are plenty of small efficient DC powered pumps. It would work MUCH better with a pump than with gravity.

As for pitch, I don't think that the measured fall is as critical as the continuous fall. It MUST fall gradually from the apex point back down to the heat source. The weight of the cold water falling is what will assist the less dense water rising.

How do you intend to control the flows through the system during non needed periods? Non electric TRV's work well, but I fear they would represent so much friction to flow that flow might cease.

ME

High mass application

Will your home in which you want to use this method be of high mass? Concrete construction.

This seems to be a prerequisite for this type of heating method.

As Mark mentioned efficient pumps of today's design would give you accurate flow rate calculations. More predictable out comes.

In the day of gravity flow designs there were no pumps to be used in the design fuel was cheap. So windows were opened to help control over heating issues. Times are different now. Lots of high tech hardware to implement is designs.

Gordy


Gordy

don't need slope

I can answer that horizontals don't need slope.
Why do you want to use steel pipes? Elbows reduce performance.
I recommend zero pressure for gravity systems. You suspend expansion tank at top of system and make sure it can withstand vacuum. Simplest way is to oversize horizontal pipe at top . Eccentic reducers If you fill from basement tap a drain at cold height that you can control from fill station. Note that you also need a top fitting to draw vacuum and break vacuum. The drain should be small because it will refill when water expands.
Control by temperature and keep in my mind the nonlinearity. Pressure relief is essential.
By the way it's the down pipe size that determines flow.

update

@Mark and Gordy:
The house was built in 1910 and has stone walls of 2 feet thick.  Enormously high mass.
The tempering will give approximately  100W per meter. So Just enough to keep the walls dry and to breake the cold. That’s already fine for  bedrooms and rooms in which  you do an activity. But it is no comfortable  temperature  for a livingroom. The extra degrees needed for that kind of comfort will, depending on the outside temperature, be provided by a (little) mass heater ([u][size=12][color=#0000ff]www.bergkachel.nl[/size][/color][/u]).
No worries concerning the opening of windows …
 
So, during the heating season the tempering-system will provide a basic warmth 24/24. Overheating is not  possible (more a sort of underheating).
24/24 circulation is the main reason for my gravity concept. The pump-energie becomes significant during these long periodes. Another reason is that gravity fed systems create a very slow and noiseless flow. The slow flow will also help to maintain the stratification in the boiler. This will help to provide for the hottest water  possible in the pipework during the entire  heating cycle (heating the 2000 liter every 12 or 24 hours).
A little loss of temperature between the beginning and the end  of the cycle is not a drama. The thick walls don’t react that fast on temperature changings and will average this effect by their mass.
No control of flow at all. Just the tempering ‘on’ when needed by heating up the 2000 liter gallon. And ‘off’ by not heating the gallon …
@Jumper,
 
I need a relatively large diameter for the gravity system, so copper will be too expensive.
I shall use the large type of 90° elbows.
Maybe a little slope will help the flow and  prevent blockage from airbubbels ? I thought it would be less aesthetical with a slope, but maybe I must leave the aestetics:  1 inch per 10 inches is safer ?
 
Can someone give the resistance of a horizontal(or horizontal + 10% slope)  1inche steelpipe ? (Is not in the old books of Dan’s library)

G

Pipe size is dictated by required flow...

type of pipe, roughness of pipe (don't forget what happens to steel over time). John Siegenthaler gives these formulae for calculating the pressure drop, but you are going to have to supply the required flow number, and quite honestly, I don't know what that would be in a gravity system.

A search of Engineeringtoolbox.com came up with the following attached formulas.

http://www.engineeringtoolbox.com/mannings-formula-gravity-flow-d_800.html

My scientific calculator left with my last child ;-)

Also, search Hazen-Williams and you will find the balance of the formula necessary to calculate pressure drop.

As for parasitic energy consumption, my Grundfos pump uses 30 watts/hour to move 3 GPM. THat calculates to 21.6 KWH per month. At $0.20 (high) per KWH, that would cost around less than $5.00 per month. Just saying for the sake of saying.

ME

rule of thumb

gravity flow is less than 10 fps. Usually a lot less. If the return ends with a terminal warming outside air, the circulation increases dramatically.