Water circulation system with incorporated heat exchanger

[Komo421]

Hi all,

Im looking to design a circulation system. Water through the system must however remain at room temperature as close as possible. For this I want to incorporate a heat exchanger that interacts with a computer program so that the whole system runs autonomously; the heat exchanger pump and everything. I have an idea to use a computer interface usb board with thermocouples to measure the temperature at certain points. Im new at this so was wondering if anyone knows of a website, books, or other resources where I can find out more about similar circulation systems and how to design such a system.

Thanks in advance

 

[dbill74]

Hello Komo,
What you are asking for is definitely doable, however if you can provide some more information, it will help us better format our answers and advise.
To start with, what is the source of the water and temperature?
What is the heat exchanger for?
Is your water loop open or closed?

Although the water being at room temperature is unusual, the plumbing community does this all the time to provide hot water to showers, lavatories, washing machines, etc. A water heater heats incoming cold water (usually to 140 F) which is then run through a thermostatic mixing valve to temper the water to the desired temperature.

Locating the circulating pump (connected to an aquastat) on the return line near the water heater will ensure the water in the loop is at the desired temperature. Also helping to ensure the water in the loop is at the desired temperature is good insulation.

A.O. Smith and Lochinvar have good examples of how to pipe what you are looking for. Most modern water heaters have sufficient internal controls to give you a consistent outlet water temperature.
A.O. Smith's website is

http://www.hotwater.com

Lochinvar is

http://www.lochinvar.com

 

[Komo421]

Its common municipal water and the water is used for other equipment. The heat exchanger is used to cool or heat this water to room temp to be re-used again. I am not sure about the temperature of the water will have to find that out and it will probably be a open loop the water comes from an outside source but is collected in a sump from where the water is recirculated.

 

[EnergyProfessional]

what are you actually trying to accomplish? All I understand is you have a pipe running through a space and that water is supposed to stay at room temperature.
Are you trying to heat or cool anything? If you want to cool, the water needs to be colder, if heating it needs to be warmer than room temperature.

Typically an HVAC control system is used for such control, not a PC. A dedicated Building automation system by honeywell et all is very robust, reliable and made for such applications. a PC is not.

Are you doing some school homework and build your own controller, or an actual application you design to be installed? Sorry, I'm not really sure what your objective and if you give more detail we can help better.

 

[Noway2]

The heat exchanger is used to cool or heat this water to room temp to be re-used again. I am not sure about the temperature of the water

Here are a few other things to think about: The heat exchanger will have two isolated loop on it. It sounds like you want to control via the temperature of one of the loops, which you want to be room temperature. What is on the other side of the heat exchanger and will you be heating, cooling, or both on the (temperature controlled) process water and what determines this? The heat exchanger will also have an "approach" which is how close you can bring the the two temperatures but the actual resulting temperature will depend upon the relative temperatures and the relative loop flows. Will you be able to get enough flow on both loops to meet your flow and temperature needs?

 

[MintJulep]

the water is used for other equipment

Used for what purpose? To cool the other equipment down? To heat it up? To wash it? Something else?

The heat exchanger is used to cool or heat this water

Heat exchangers are no magic devices. They are, well heat exchangers. They allow heat to move from a hot fluid to a cold fluid without allowing the fluids to mix. If you need to heat your water then you will need a source of hotter fluid from somewhere. If you need to cool your water then you will need a source of colder fluid. If you need to both heat and cool your water at different times you will need sources of both hot and cold fluids, and a way to switch them.

remain at room temperature as close as possible

Room temperature is different for different rooms. Do you really mean that you need to keep the water temperature the same as the air temperature of some room, or do you need to keep the water temperature close to 20C? How close is "as close as possible"?