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29-10-2012, 06:07 AM #1
Desuperheater water flow control ideas
For a heatpump project, I need to control the flow rate of hot water through a tube in tube desuperheater. Depending on the operating conditions, I need to regulate the hot water flow from 0.16 GPM to 1.5 GPM to heat it to 120°F. What are good ways to do this?
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29-10-2012, 07:20 AM #2
Re: Desuperheater water flow control ideas
A temp driven regulator valve, can be a mechanical device or electro-mechanical device.
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29-10-2012, 07:50 AM #3
Re: Desuperheater water flow control ideas
Would temp lags not perhaps come into play, here - especially with low flows?
Engineering Specialist - Cuprobraze, Nocolok, CD Technology
Rarefied Technologies ( SE Asia )
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29-10-2012, 05:49 PM #4
Re: Desuperheater water flow control ideas
You might want to set up a face/bypass circuit where some of the water flows through a bypass, thus reducing the amount flowing through the heat exchanger.
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29-10-2012, 06:05 PM #5
Re: Desuperheater water flow control ideas
You might find here what you are looking for
http://www.watts.com/pages/learnAbou...s.asp?catId=64
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29-10-2012, 09:36 PM #6
Re: Desuperheater water flow control ideas
Thanks, chemi-cool. 131°F to eliminate Legionella Bacteria. There is not much penalty for this higher temperature because of the desuperheater counterflow design.
Could someone suggest a specific regulator valve, perhaps with a face/bypass circuit for my application?
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29-10-2012, 11:44 PM #7
Re: Desuperheater water flow control ideas
http://www.solarnetix.com/solar-heat...mo-zone-valves would be a start then you need a controller for it. It will need P I & possibly a little D control. A three way valve will divert some of the flow for by-pass of de-superheater.
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30-10-2012, 01:20 AM #8
Re: Desuperheater water flow control ideas
Hi Tesla,
It looks like the "3-Way Diverting Zone Valves from Belimo" is on/off only. How could I use it to regulate temperature with flow rate control?
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30-10-2012, 01:26 AM #9
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30-10-2012, 01:39 AM #10
Re: Desuperheater water flow control ideas
Nope, Belimo has modulation valves, look for 0-10vdc input. The valves and motor are separate. Danfoss also has a nice flow meter that can be inputted to a control to vary the valve based on flow and/or temp.
Also:
http://www.paw.eu/en/products/solar-...serstation.php
It isn't exactly what you want but the idea behind it is to vary the speed of a pump based on the tank temp on the other side of a HX. This gives you stead state DHW from a dead water tank, and the parts inside this thing, and the controller, can do what you want. It may take a bit of experimentation tho....
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30-10-2012, 04:56 AM #11
Re: Desuperheater water flow control ideas
Sorry I just said it would be a start and Belimo has the valves and actuators to do it (from a quick google) - as stated correctly above (thanks Mike) 0 - 10vdc is the best option. That's where the PID control would come in for modulation. I was also thinking more like 1/2" or smaller depending on the application.
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30-10-2012, 05:25 AM #12
Re: Desuperheater water flow control ideas
Maybe best to do a little sketch of what you intend for the application and what size is the refrig unit (heat pump)
The application may determine that energy recovery is better than straight out temp recovery.
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30-10-2012, 05:48 AM #13
Re: Desuperheater water flow control ideas
I'd love some design wisdom! Here's the condenser and desuperheater section of the PID showing operating conditions for November. Refrigerant lines are black. The inlet red desuperheater water line is piped from the cold water inlet of a hot water tank. The red desuperheater outlet returns to the outlet of the hot water tank.
Screen Shot 2012-10-29 at 10.44.02 PM.pngLast edited by microHydro; 30-10-2012 at 05:53 AM.
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30-10-2012, 06:34 AM #14
Re: Desuperheater water flow control ideas
If your draw, from the bottom and introduce back into the bottom via a sparge pipe and have a higher flow rate fixed, you will absorb more energy,
But if you have enough hot water without an element, then the one pass method is OK.
So what you could do on the cheap, is have a simple solenoid valve controlled by the outlet water temp, wait a bit more, there is a minimum flow device around solenoid valve that allows for the flow temp to be measured. I use 0.1L/M for this device (a long capillary tube works well)
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30-10-2012, 06:54 AM #15
Re: Desuperheater water flow control ideas
Thanks, Mad Fridgie
The idea is that I will draw unheated water from the bottom of the hot water tank with a pump, and return the optimally heated water to the top of the hot water tank. An electric element may or may not be active.
Please help me understand the operation of the solenoid valve topology. When the outlet temperature is low, the solenoid at the outlet closes. The capillary tube still flows hot water around the solenoid. When it is up to temperature, the solenoid opens. Have I got it?
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30-10-2012, 07:45 AM #16
Re: Desuperheater water flow control ideas
In reverse,
The sol valve control is correct (i have presumed that the water pump is off when the heat pump is off)
The term optimally heated, can either be greatest amount of energy or required temp.