HEAT RECOVERY SYSTEMS
HEAT RECOVERY SYSTEMS
(OP)
Hi Fellows!
I have this real case:
Some years ago I draw and have supervised the refrigerating system installation in printing industry (serving as well as climatization system for the office-building) to serve a high rotating speed machine, which has an hot camera/room in its top to dry and fix the colours to the strip paper.
This hot space consumes a lot of energy. It burns natural-gas and combustion gas reaches temperatures nearly 350 ºC or 662 ºF.
That time, I strongly suggested to the client to consider (it should be a non-option condition since the start-up!) an obviously heat recovery system applied to the 26" diam. isolated steel chimney of that rotating machine to heat the industrial dome and/or a warehouse. Now he call on in hurry, Let´s do it, "for yesterday"!
I thinking to install a heat-exchanger, using thermal-fluid system with terminal ventilated thermal units and above all, having a very simple and reliable control solution.
Yours comments, ideas, tips, hints will be recognized and very appreciated.
Thank you.
Welch
So i have a few days to decide which is the best solution. applie thermal very beguinning s oblized sin-quoi- adviserecommeded
I have this real case:
Some years ago I draw and have supervised the refrigerating system installation in printing industry (serving as well as climatization system for the office-building) to serve a high rotating speed machine, which has an hot camera/room in its top to dry and fix the colours to the strip paper.
This hot space consumes a lot of energy. It burns natural-gas and combustion gas reaches temperatures nearly 350 ºC or 662 ºF.
That time, I strongly suggested to the client to consider (it should be a non-option condition since the start-up!) an obviously heat recovery system applied to the 26" diam. isolated steel chimney of that rotating machine to heat the industrial dome and/or a warehouse. Now he call on in hurry, Let´s do it, "for yesterday"!
I thinking to install a heat-exchanger, using thermal-fluid system with terminal ventilated thermal units and above all, having a very simple and reliable control solution.
Yours comments, ideas, tips, hints will be recognized and very appreciated.
Thank you.
Welch
So i have a few days to decide which is the best solution. applie thermal very beguinning s oblized sin-quoi- adviserecommeded





RE: HEAT RECOVERY SYSTEMS
How much heat is there?
How much of this heat can you use?
You haven't given much information.
RE: HEAT RECOVERY SYSTEMS
Y're right. Here is some data from that time, which now I'll confirm:
Flue-gases flow rate: 4950 Nm3/h or 173042 N(cfm) at 0ºC or 32 ºF;
Max. exhaust temp flue gases: 450 ºC or 842 ºF
Estimated mean flue gases specific heat: 1,080 kJ/kgºK
Suppose a recovery system introducing a deltaT in the flue gases side from 400 down to 180 ºC (or 698 to 356 ºF)with a transfer efficiency of 60 %, we can recover something like 250 kW or 335 Hp
Thanks again.
Welch
RE: HEAT RECOVERY SYSTEMS
There's something else I've forgotten: I can use all the recovered heat in the cold season, that's for sure!
Welch
RE: HEAT RECOVERY SYSTEMS
In one of the project we use the recovered heat from the flue gases to heat fresh air using heat pipe heat exchanger. This fresh air was use to preheat and dry the charge going to the main furnace and provided some fuel saving for the main furnace.
Lets say if you want to use this recovered heat for air/water heating purpose, heat pipe heat exchanger (HPHE) may be one of the alternative you can think about. HPHE is a bundle of copper tubes that are evacuated and sealed after charging partially with water. The latent heat of the water is used to transfer heat from one end of the pipe (evaporator or flue gas end) to another (condenser or recovery side).
RE: HEAT RECOVERY SYSTEMS
May I call your attention to the initial thread:
The application is to heat a warehouse where there are an hudge quantity of cylinders stip-paper, before going to production, that mean's quite a lot of thermal inertia and the requirement to have that material at least at 18 ºC or 64.4 ºF, before going into the machine. So I should use that heat to help to keep the ambiance temperature at 18 ºC, and only in 2nd step to call up an existing boiler.
I have done a more refined calculations and I got a recovery heat potential of 350 kW or 470 hp.
Thanks.
Welch
RE: HEAT RECOVERY SYSTEMS
A runaround coil is easier to control, but, given that one side of the circuit is in combustion exhaust gasses, the material of the recovery coil will be specialized to control corrosion from water and acids in the exhaust stream.
How do you heat the warehouse now? With air handlers? Unit heaters?
What is the climate where you want to recover heat?
RE: HEAT RECOVERY SYSTEMS
have a go through this link, it is not directly related to what you are doing but might give you some idea about drying techniques,
http://www.nrel.gov/docs/fy99osti/25885.pdf
willard3
you have a good point about the control of the heat pipe system. Most of the time, the isolation of the unit from the heat is not required as heat can be use for some secondary purpose or just exhaust to atmosphere as waste heat. About the second point, generally the heat pipes are coated with some material to minimise the corrosion effect e.g. copper heat pipe are coated with nickel layer to avoid the oxidation of the copper which add resistance to heat inflow process.
RE: HEAT RECOVERY SYSTEMS
RE: HEAT RECOVERY SYSTEMS
RE: HEAT RECOVERY SYSTEMS
Time for a silly question- are there levels of noxious/harmful compounds in the furnace stack gas that would prevent you from venting a portion of the gas directly to atmosphere?
snip
YES, there are noxious and harmful compounds in a furnace stack.
RE: HEAT RECOVERY SYSTEMS
RE: HEAT RECOVERY SYSTEMS
The process has reach some evolution and i have some data, which I want to share with the Forum, (comments are very welcome):
1. We have a natural gas combustion, so a lots of CO2, mainly;
2. Suppose at the beginning of the chimney, at that position the installation of a confined space with baffles elements, a kind of a chicana to force the combustion gases go along a labyrinthine path;
3.Suppose also a tranverse tubing surface normal placed to the combustion gases. Inside of those tubes we plane to induce circulating water which is heated then to a set-point temperature.
Thanks.
Welch
RE: HEAT RECOVERY SYSTEMS
You refer that you use the water heat during cold season? And during hot season, what will you do?
Did you considered an adsorption chiller?
RE: HEAT RECOVERY SYSTEMS
RE: HEAT RECOVERY SYSTEMS
CO increases
CO2 increases
Moisture increases
NOX increases
and etc.......
RE: HEAT RECOVERY SYSTEMS
RE: HEAT RECOVERY SYSTEMS
RE: HEAT RECOVERY SYSTEMS
To MedicineEng: The heat-exchanger is suppose to be combustion gases/water. So I don't have any harm people's respiratory problems possibility, at least from this source. This water will flow to serve terminal heating air-units in the factory area.
In summer, of course the heat-recover process is off.
Thanks for keeping alive this thread! By the way you just got a 2nd star, MedicineEng!
welch