View Full Version : Heat recovery from chiller?

02-18-2016, 01:54 PM
Has anyone used something like this: http://www.thermastor.com/heat-recovery-water-heaters/ ? Or the Mueller Fre-heater system http://uk.paulmueller.com/products/mueller-fre-heater ?

We were sold something similar years ago. It didn't produce significant warm water, and eventually failed (leaked between refrigerant circuit and water circuit), costing us a refrigeration compressor and $k to get the refrigeration oils out of our HL system. New boss wants to try again.

Admittedly, this system looks much better (on paper) than the POS we were sold--which turned out to just be a water-cooled condenser unit from a standard walk-in cooler, encased in an SS box.

02-18-2016, 02:18 PM
First, I should mention I have done work for Meuller in the past and I drink beer with a couple of guys at Therma-stor fairly often but I don't have any financial connection to either nor do I make any money off their products.

That said, I take it the POS that you had before wasn't from either of these companies? Therma-stor is pretty much the originator of the idea. I haven't heard any horror stories about their equipment for either the brewing industry, dairy industry or ice arena industries where I've seen that product used. With Meuller, I don't know that product specifically but I know they have a good reputation in the dairy and food processing industries.

If you are looking for a first person testimonial, Page at House of Brews (http://houseofbrewsmadison.com/) in Madison has/had the therma-stor unit installed. I'm not sure if he still has it but he's usually willing to share his opinion. I would be happy to get you contact information.

From personal experience, heat recovery from refrigeration systems doesn't work well if it is an ammonia system but can work for the halocarbon (e.g. R-404A, -507, -22) Refrigerants. The economics are usually towards a multi-year payback. It all depends on your refrigeration and hot water needs.

02-18-2016, 03:12 PM
Thanks, Dan--the direct reference was exactly what I was looking for.

Understandably, I'm leery--once bitten twice shy.

Oh, and no, the system we got bitten by was an apparently fly-by-night bunch--like I said, just a water-cooled condenser in a fancy SS box. It would heat a trickle of water a little bit.

02-19-2016, 03:00 AM
In the HVACR world these devices are called De-Superheaters.
A few things I have noted after laying hands on several different configurations are:
In typical residential or small tonnage HVAC they thermally saturate the water side due to inadequate water side usage, then the swing is the exact other direction once a hot water load is brought on the line. They do not really integrate well with off the shelf units and I seen many on ground source heat pumps [which are a total joke in the first place] that are quite ridiculuous.
You need to be able to capture the heat at the right rate and put into thermal storage to make it pay off.
The refrigeration machine has to be set up to deal with the extra condenser space. It is possible to have too much condensing surface with respect to operating conditions at the wrong times which will affect the media side performance in a negative way, so some implementations are a hack job that do not respect necessary High Side operating parameters.
In essence they need to be design retrofitted in a precise manner to work well in any way and the system may need modifications that are not run of the mill to optimize the device.
The conditions they are likely to work better in are in in areas where the cooling load is more substantial including the latent load and the condensing temperature is not way down low a large portion of the year. The more tons you have on line would be a consideration.
If I were doing it on a larger scale system I would have water flow regulator ported to the discharge line of the compressor as is done with straight water cooled systems to control head pressure, then loop the water out into a large thermal storage system with a pump system also having some type of thermal control and bypass on the main holding tank.

02-19-2016, 06:54 AM
Understandably, I'm leery--once bitten twice shy.

Completely understandable. I've seen lots of good equipment that got a bad rap either because it was misapplied by the installer or a competitor made a cheap knock off version.

As Starcat correctly points out, a lot of the problems encountered have nothing to do with the equipment but rather the application. If your hot water load and refrigeration don't line up...or you don't have enough storage tank for the hot water...its destined to fail. I do refrigeration design and my wife designs CIP systems. We are constantly approached with a request to use rejected heat to heat the cleaning water. On paper, its awesome. When the rubber hits the road, often the refrigeration can't make water that is hot enough, refrigeration load is lowest when you are cleaning and the size of the tank needed doubles the cost of the project.

As Starcat mentioned, another option is using a water-to-water heatpump...essentially a water cooled chiller. On one side you get cold water/glycol. Out the other side you get warm water. He's right that its often misapplied (like residential) but if you spec out the right chiller to begin with, it can be done successfully. Some form of thermal storage helps. An old boss of mine developed an ingenious version of this back in the 70's. It produced cold glycol and hot water for a high school. If hot water was needed but there was no refrigeration load, it was used to freeze water into ice (thermal storage). So in the cooling season, the ice was used to cool water that provided A/C to the school while hot water was used for the shower, cooking and the pool. In the winter, there was very little need for cold water, so he built a solar system that spent all day melting the ice so there was heat rejection capacity for the cooling load.

02-19-2016, 08:24 AM
Dan, Excellent and thanks.
Good to see a design person on the Forum with no doubt some angles I have never thought about.

All the best.
Please stay in contact.


02-20-2016, 01:59 PM
Sorry, Warren. Worse than design...academic, but I do get involved in a lot of design review, troubleshooting, system optimization, etc. for industrial (i.e. ammonia) systems. So basically if I've seen it in action, there's probably a problem with it.

02-20-2016, 02:00 PM
So, compared to recovering 140F cast-back cooling water, this is expensive and complex. We're not looking for 120F domestic water, probably can't use enough of the mildly heated water, it's expensive and complicated to do this right--and probably will reduce the efficiency of our chiller system.

It seems if we had a demand for lots of 120F water, and a separate system for it, this might make sense--but not as we are now.

02-21-2016, 10:46 AM
So, compared to recovering 140F cast-back cooling water, this is expensive and complex. We're not looking for 120F domestic water, probably can't use enough of the mildly heated water, it's expensive and complicated to do this right--and probably will reduce the efficiency of our chiller system.

It seems if we had a demand for lots of 120F water, and a separate system for it, this might make sense--but not as we are now.

There was a local guy a few years back who was doing several types of Solar installs and he was retiring and selling his company. Because I was interested in Solar and had never laid hands on Solar hot water, me and another guy took some of his used equipment to an Alternative Energy- Holistic Fair local one day. Essentially we had two old style Solar hot water panels 4x8 which I mounted on a trailer at an angle with a Small Solar Panel, 12V charge controller, battery, inverter and a recirculation pump ported to a 35 gallon barrel.
I set a digital Thermometer right in the well and we were running 130F on a fairly hot summer day. A number of the houses in town use Kent Alcorn's old setups and they love them. I am not fully up on the new Tech, but the evacuated tube collectors are supposed to the one of the best.
This would be the direction I would go if it becomes possible to do some preheat. There are several ways to go about it. The one I am familiar with is called drain back and its easy to conveive, set up and implement. You really need a mechanical room for your HX-well etc so it takes space to do it correctly. You don't need any fancy proprietary controller. The control scheme is not that complicated.

02-21-2016, 12:55 PM
Thanks, Warren.

We're looking to increase our brewery and pub efficiency--particularly as there are some pretty sweet incentives right now. Solar is definitely in our future, esp. for water heating/pre-heating.

We have lots of sunny days out here in eastern Oregon--not what most folks think of when (or if) they think of Oregon. There are several passive solar houses in our area that use very little if any supplementary heating, even in sub-zero weather (and I mean Fahrenheit!). One friend runs a few Copper Crickets--an older, passive solar heat collector--on his roof, which keep a 500 gal. reservoir at or above 160 F in the dead of winter. He uses this for domestic water heating and sub-floor radiant heating. Very cozy home. I helped install this system, which was a bit complicated as it uses a refrigerant and HX for heat collection. I've done some research on the newer systems, including evacuated tube, and I'm sold.

Now to find (make) room for more HL storage....