High Temp Heat Pumps

[US Iceman]

Hi Guys,

Have a question for you.

Do any of you have experience with high temperature heat pumps? Say about 80-82C condensing.

Are you using scrolls compressors with R-134a or something else? I'm looking for application information for different refrigerants or compressors at this operating temperature.

I would be interested to hear any and all productive comments and experiences you may have had in this area.

Thanks.

US Iceman

[bruceboldy]

Hey iceman

At Trane we have all kinds of heat pumps, but i do not know exactly what you are looking for. 82 is about 180 degrees

Does this mean 180 degree heating or working with 180 degree discharge.

let me know a bit more info I will give you a few good links for you to review.


bruce

[US Iceman]

Bruce,

I'm looking for 180F (82.2C) condensing temperatures. The actual discharge temperature will be slightly higher depending on the specific heat ratio of the refrigerant I end up using. Right now I'm looking at R-236fa.

Evaporating temp. is approximately 60F (15.5C).

I have an email request into Copeland for any information that might supply, but I'm open for other data and experiences.

Thanks.

[Josip]

Hi, US Iceman

I'm looking for 180F (82.2C) condensing temperatures. The actual discharge temperature will be slightly higher depending on the specific heat ratio of the refrigerant I end up using. Right now I'm looking at R-236fa.

Evaporating temp. is approximately 60F (15.5C).

Quite high condensing temp but still you need some centigrades to boil eggs

I would like to help but realy do not have experience

Best regards,

Josip

[US Iceman]

HI Josip,

I worked on one of these high temperature heat pumps a long time ago, but then you could use R-114. A really good refrigerant for high temperature work.

R-114 had an interesting characteristic. If you did not provide sufficient suction superheat, the gas could begin to condense in the discharge line as it cooled off.

R-236fa seems to have the same ability indicated in the PH diagram.

I think this project will be a lot of fun.

This heat pump is for generating hot water for CIP in a dairy farm.

[NoNickName]

Did you consider ZH/VI compressors from Copeland? They provide vapor injection to get high water temperature in the condenser.

[US Iceman]

Hi NoNickName,

Did you consider ZH/VI compressors from Copeland?

Not yet.

But, your advice is a good place to start. The client wants to use scrolls or Discus. If it was up to me, I would also be checking some of the open drive Bitzer compressors or something similar.

An open drive compressor would remove all of the motor cooling issues. But the hermetics are probably the best bet from a cost and replacement view.

Thanks for the input.

[Chris Burton]

I was thinking of making a test rig with 2 compounded recips with an open intercooler to achieve 80 c flow temps which would make it a direct replacement for gas fired boilers.

[US Iceman]

Hi Chris,

If you decide to pursue this, please share your experiences.

You are looking at the same market we were.

[TSK]

Whilst still "on the tools" I once worked in a plant room that had several Hitachi water chillers and a (Carrier Heat Machine) it actually bore that name, I did not get the chance to work on it but did give it a good coat of looking at. This unit had an 06D compressor working on R12 from memory and was belting away merrily providing 80C hot water from chilled water at 10c entering, later Hitachi brought out one of their own, a screw unit on R22, worked ok at first but the general high temps wore out the rotors too quick, needed more and more liquid injection to keep the discharge temp below 125C.
So check Carrier & Hitachi before doing your own R&D.

[US Iceman]

McQuay also has a line of chiller/heat pumps called the "heat amplifiers" I believe some time ago. So that might be an additional source to review.

[taz24]

Hi Guys,

Have a question for you.

Do any of you have experience with high temperature heat pumps? Say about 80-82C condensing.

Are you using scrolls compressors with R-134a or something else? I'm looking for application information for different refrigerants or compressors at this operating temperature.

I would be interested to hear any and all productive comments and experiences you may have had in this area.

Thanks.

US Iceman

I have a little experience with heat pumps.
What kw capacity are you looking at and is it only for hot water? 80c condensing so about 65 to 75c water temp? Why so hot. Is it to pre heat water for an industrial application or just for hot water?
Scrols are exelent and I agree with nonickname the ZH/VI compressors would work very well with this duty.
Cheers taz.

[US Iceman]

Why so hot?

Well, it's being driven by the process requirements. We are trying to see how what we can actually get out this. My goal is to shoot for 100C before we get this finished. I believe we can get this to the point of steam generation if all goes well.

The only reason we are looking at scrolls right now is due to the small capacity needed. I have some plans for much larger models, but we need to sell one first.

[taz24]

Well, it's being driven by the process requirements. We are trying to see how what we can actually get out this. My goal is to shoot for 100C before we get this finished. I believe we can get this to the point of steam generation if all goes well.

The only reason we are looking at scrolls right now is due to the small capacity needed. I have some plans for much larger models, but we need to sell one first.

I like the way you think.
Steam generation by heat pump technology is exelent. Its a bit out of my leauge.
Good luck Keep us informed on any progress.
Cheers taz.

[The MG Pony]

I just scored a nice R-22 rotery, goal isn't steam but hot water to heat the apartment. will R-22 work well for this or R-290? or perhaps even R-134a? it is a 17cc per rev.

[US Iceman]

will R-22 work well for this or R-290? or perhaps even R-134a?

You are on the right track. One of the first things to look at for a new application is first the operating conditions, and second, what impact the operating conditions will have on the selected refrigerant and ultimately, the components.

All components have some operating or application limits. i.e., maximum or minimum pressure, maximum or minimum differential pressures, etc. The same applies to temperatures.

The trick is to find a decent refrigerant that offers what you need for the application. Much the way R-502 was used almost universally for low temperature systems.

When you start to get into really bizarre stuff like I tend to find myself sometimes, you go back to the basics, and toss the assumptions out the window.

In a lot of cases, the common refrigerants are selected for the common applications simply because they work for most of the applications.

[US Iceman]

I like the way you think.

Thanks. I have a saying for the unknown...

I don't mind going out on a limb, as long as I know who holds the saw.

Which translates into; I retain some control over what happens, or I don't play.

[The MG Pony]

Thanks. I have a saying for the unknown...

I don't mind going out on a limb, as long as I know who holds the saw.

Which translates into; I retain some control over what happens, or I don't play.

hehe it would apear we think alike, I love R&D more then any thing. I said to one guy just toss me in the scrap heap and give me a month I'll build you some thing you didn't even know you needed!

[The MG Pony]

As for the project, thus far I have ordered and waiting arrival:

Coax-2150-S-08-108 Coaxial heat exchanger, 1.5Ton
V46AC-1C Head pressure modulated, flow control valve
17000BTU/pH @ 54F evap R-22 rotary (Have that now)
Temprite 340 series Oil sep (Have that now)

Evap I intend to use a 2 Ton evap as max expected lowest temp will be from -9 to -10C with occasional -20C periods with a 1Ton TXV (this should guarantee max heat scavenging from the air with out too many icing issues I think)

Compressor has built on accumulator. At the exit of the coaxial condenser I will have a sub cooler to ensure the refrigerant returning to the valve is cooled appropriately after I have taken off as much heat as I can. I will all so use a 2 to 3 pound receiver and utilize a pump down cycle to reduce slugging risk during the start cycle, the receiver will be placed out side near the TXV to add to sub cooling. Circulater pump will be placed on the hot side as to not heat the returning water that will be used for the condensing process, the final stage heat rejection will be don with a base board style radiator wrapped around the apartment.

Target air temp will be 21C to 25C, evap will be what ever ambient is due to it being greatly over sized
(Or so the plan is but never exceeding +10C this will be enforced with a PWM fan control that will cycle down the fan as that temp point is reached)

Condensing temp will probably be in the upper range, pending on room to radiator delta, and returning coolant delta

Hows all this sound so far?

[Chris Burton]

Carrier used to use R500 for heat reclaim machines on 30HR recip cillers but this was usaly fo 60 c leaving temp. Screw compressors are impratical for high temps due to their close tolerances.

[US Iceman]

Screw compressors are impratical for high temps due to their close tolerances.

Mycom used to build some screws for up to 100C I believe back in the 1980's or thereabouts using R-114. I don't know if these were standard production screws or if the tolerances were opened up a bit to allow for material expansion.

You raise a good point though. Every little detail either creates a successful project or one with many problems.

[The MG Pony]

Well after assessing my needs I have determined the min/max deltas for the water inside to achieve a 21 - 25C room temp, I figure a 30C delta should be enough. To achieve this with good convection air flow. My water has to be from 50 to 70C. After determining the needed condensing temps, I searched for refrigerants with favourable pressure ranges and this is the list I compiled so far What you guys think?

R134a NBP: -26.1C; Ct:101.1C; Cp:589psi; BTU/Lb:1,806
R152a NBP: -24.0C; Ct:113.3C; Cp:656psi; BTU/Lb:7,481
R401a NBT: -34.4C; Ct:105.3C; Cp:669psi; BTU/Lb:- ---
Least ideal far as Ct and Cp go
R022- NBP: -40.8C; Ct:096.2C; Cp:600psi; BTU/Lb:0,946
R290- NBP: -42.2c; Ct:096.7C; Cp:616psi; BTU/Lb:21,625

Ct = Critical Temperature
Cp = Critical Pressure
NBP = Normal Boiling Point

R-152a so far looks like it will have the lowest head pressures at a condencing temp rang from 50-70C being its Ct is 113.3C and it has good moving capacity per Lb.

Max evap temp will be closely tied to the ambient air temps, the absalute min here in BC will be -10 and rarely at that, average is -05C for midle of winter So again its evap pressur looks to be faverable for the average winter temps. Only concern is I only have access currently to R-12 and R-22 TXVs, I suspect they should work after the necicary super heat corrections are made to the TXV providing they are at all needed!

[The MG Pony]

Ok got a base line.

Air source evap/Condenser:
7.034Kw/H (2Ton)
Water source Evap/Condenser:
5.28Kw/H (1.5Ton)
Compressor:
4.98Kw/H (1.42Ton)

Target room temp: 25C (77F) max ,((Heating mode))
Target water temp for heating mode 50C (122F) - 60C (140F) realistic?

Temp range on the air source Cond/evap -10C (14F)max to a max of 40C (104F)
I think it best to use some thing to ensure sufficient super heat during heating mode for when the weather gets warmer, to ensure it stays within range for cooling the compressor, like using a PWM that slows the fan as super heat goes up.

Now how do I determin air speed needed for thees values? If you can help point me in the right direction to calculating it out. Thanks.

[NoNickName]

You need a differential regulator with two analogue inputs: one pressure transducer with saturation temperature scaled on the desired refrigerant, and one NTC or PTC for actual temperature reading.
The difference of the two readings will give you the SH. If the SH increases, reduce the fan speed; if the SH reduces, increase the SH.
Please note that this will be a two-degree of freedom system, as the TXV does exactly the same thing, and as a net result, hunting is expected.
In your case I would suggest to use a MOP TXV, which will ensure the SH will not exceed a determined threshold.

[The MG Pony]

So Ok select a TXV with an MOP. Now the water exchanger will be using a head pressur modulated flow control valve, I plan to set it to fix the head the best it can to a stable High side, with this wouldn't the TXV all ready be stable?

As for the fan I was going to use a thermaly controlled PWM unit scaled to the PT chart of the refrigerant I'm planning to use, would this not be good enough?

Part Numbers & Specs
- Coax-2150-S-08-108 Coaxial heat exchanger, 1.5Ton

- V46AC-1C Head pressure modulated, flow control valve (3/4 NPT)

- 2K17C3R126A 17000BTU/H @ 54F evap R-22 rotary

- Temprite 340 series Oil sep 1/4 ODS

Apartment chararistics:
Window surface area total: 285.75 M^2 (937.5 F^2)
Floor Surface area total--: 214.27M^2 (703 F^2)
Air Volume total----------: 1,714.195M^3 (5,624F^3)
Room Width: 5.79M (19')
Room Length: 11.28M (37')
Room Hieght: 2.44M (8')
Room wall thickness .127M (5") R-20

Windows are all single pain with wooden framing and no sealing, Walls have a Delta of 13.4C (56F) between inside & out side. Roof is R-50 about 2 feet thick.

So with that I estimate heat loss for the whole place + 25% to be 1.75Kw/pH (5,958.4 BTU/pH) Using the formula: U * A^2 * Dt(F) = BTU/pH

[Lowrider]

If I understand correctly you are going to use it to heat the building?

If so why go to all that trouble and simply use floor heating/ cooling which uses a max of 40deg C for heating and use a screw or scroll watercooled chiller on a well were you can "store" energy during summer for the winter?

Or perhaps I didn't read correct?

And even then, if you size the heaters correct you can even use 48deg C of water to heat the place!

I think your getting yourself into a lot of trouble if you don't think this trough! Although I do appreciate the challence you've provided!

[Lc_shi]

I know there's a high temp water source heat pump manufacturer in China, which shows the primary water temp is 40/47C and the hot water side is 78/85C. The refrigerant is patented mixture but I don't know what the exact component.It use semi-hermetic screw compressor.

regards
LC

[yaz]

Hi everyone,
I am new to subject but have done some researching and I would like to add something myself

To The MG Pony
You describe your apartment but you did not say why you wont to do this?!
I assume that you wont to lower CH costs and be more environment friendly so why don't you start with changing the windows for double sealed units?
A ventilation maybe a problem so you may think about forced one with recuperation, installing floor or wall heating will rise comfort and lower the temperature needed for CH. This way your HP can be Little bit smaller and the energy gain will be better.
I admire taking on challenge and would like to do the same for reasons stated above.
Thumbs UP!

[The MG Pony]

I rent so I can not replace windows unfortunatly, how ever I have put up 1" blue board foam on them. I been talking to more people and a real old boiler guy says for some thing this tiny I'd get away with even just 35C water.

Haven't found an A/C rated TXV so not much has been happening, I all so need an air coil.

[AYIBIBIO]

If I understand correctly you are going to use it to heat the building?

If so why go to all that trouble and simply use floor heating/ cooling which uses a max of 40deg C for heating and use a screw or scroll watercooled chiller on a well were you can "store" energy during summer for the winter?

Or perhaps I didn't read correct?

And even then, if you size the heaters correct you can even use 48deg C of water to heat the place!

I think your getting yourself into a lot of trouble if you don't think this trough! Although I do appreciate the challence you've provided!

HI,, I WILL LIKE TO HELLP A BIT. I THINK YOU CAN USE ANY GOOD R134a HEATPUMP TO HEAT THE WATER TO 40/C OR 50/C. I DON'T UNDERSTAND WHY YOU WANT TO HEAT WITH SUCH A HIGH TEMPERATURE. REMEMBER, YOU CAN'T GET NOTHING FOR NOTHING. INCREAS THE SIZE OF YOUR RADIATORS AND USE LOWER TEMPERATURES,, YOU WILL BE FINE.
DANNY,

[US Iceman]

Well, it seems someone has finally found this older thread.

Finding the desired heat pump supply temperatures is not altogether much different than refrigeration systems. If you want to maintain a 0°C (32°F) space temperature you certainly don't use a -40°C (-40°F) evaporator to do that.

Same with the heat pump. You should only be providing enough "lift" (thermal temperature rise) to meet the heating requirements of the heat exchangers and duty.

[nike123]

Hi AYIBIBO!
Why are you using capital letters all the time? That is called shouting in internet communication.

[AYIBIBIO]

Hi AYIBIBO!
Why are you using capital letters all the time? That is called shouting in internet communication.

HI MR. NIKE123. THANK YOU FOR YOUR REPLY. I THINK WE ARE NOT HERE TO TALK OR TAKE LESSONS ABOUT INTERNET. WE ARE HERE TO EXCHANGE INFORMATION ABOUT HVAC AND REF. THIS WILL BE THE LAST TIME I REPLY TO PEOPLE LIKE YOU WHO THINK THEY KNOW TOOMUCH. THANK YOU AND GOODLUCK WITH YOUR INTERNET EDUCATION.

DANNY.

[nike123]

HI MR. NIKE123. THANK YOU FOR YOUR REPLY. I THINK WE ARE NOT HERE TO TALK OR TAKE LESSONS ABOUT INTERNET. WE ARE HERE TO EXCHANGE INFORMATION ABOUT HVAC AND REF. THIS WILL BE THE LAST TIME I REPLY TO PEOPLE LIKE YOU WHO THINK THEY KNOW TOOMUCH. THANK YOU AND GOODLUCK WITH YOUR INTERNET EDUCATION.

DANNY.

I apologize, if I offended you with my comments. It was mentioned to be informative and not offensive.


P.S. One last advice: You always could add me on your ignore list!

[The MG Pony]

And Nike was quite correct it is offensive to scream in some ones face ie using all caps, it is the equivalent of one yelling in anothers face.

It is hard to share technical knowledge or ideas when the other is shouting all the time, Imagine if this where don by a coworker!

It is a good thing to practice as more people will wish to talk to one whom does not "yell" then one who does.

I mean no disrespect, I wish to help as did nike, alot of people who are not familiar with the net do not think much of it at first, but in the long run, by taking such a simple task to hand will greatly bring on more eas of use for you and you will find more willing to join in!

[Karl Hofmann]

Hi AYIBIBO!
Why are you using capital letters all the time? That is called shouting in internet communication.

He He He... Don't they all shout in Italy?... Well they did at me

Ice, 50-55c is just fine for heating, as has already been said... Perfect for underfloor and In the UK, wall hung radiators are now rated at 50c to take advantage of condensing boilers.. The holy grail is to be able to produce higher temperatures to supply domestic hot water at a reasonable temperature...65-70c.

[Gary]

I wonder how this project is progressing?

Something to keep in mind about rotary compressors: That accumulator is there for a reason. On a rotary the suction gas goes directly to the valves and the crankcase is on the high side. That's why the compressor body tends to run very hot.

Given the extreme compression ratio, I wonder if a two-stage compressor might be more appropriate... or perhaps a cascade system?

[AYIBIBIO]

And Nike was quite correct it is offensive to scream in some ones face ie using all caps, it is the equivalent of one yelling in anothers face.

It is hard to share technical knowledge or ideas when the other is shouting all the time, Imagine if this where don by a coworker!

It is a good thing to practice as more people will wish to talk to one whom does not "yell" then one who does.

I mean no disrespect, I wish to help as did nike, alot of people who are not familiar with the net do not think much of it at first, but in the long run, by taking such a simple task to hand will greatly bring on more eas of use for you and you will find more willing to join in!

NOW I WILL LIKE TO KNOW WHERE YOU GUYS GOT THIS INFORMATION,, YOU MAY BE RIGHT BUT I WILL LIKE TO KNOW THE SOURCE OF THIS (CAPS ON INTERNET MEANS YELLING) I,M NOT AN INTERNET OR COMPUTER EXPERCT BUT I,M SUSPECTING A WRONG INFORMATION HERE. TILL THEN TAKE CARE.

DANNY

[Josip]

Hi, AYIBIBIO

NOW I WILL LIKE TO KNOW WHERE YOU GUYS GOT THIS INFORMATION,, YOU MAY BE RIGHT BUT I WILL LIKE TO KNOW THE SOURCE OF THIS (CAPS ON INTERNET MEANS YELLING) I,M NOT AN INTERNET OR COMPUTER EXPERCT BUT I,M SUSPECTING A WRONG INFORMATION HERE. TILL THEN TAKE CARE.

DANNY

quote:

Sutton observes that netiquette, as its name suggests, is simply a reworking of the classic rules of common etiquette, as espoused by Emily Post or Miss Manners. She offers the following comparison between a 1922 etiquette rule by Post and a 1994 netiquette rule by Virginia Shea, observing that although the words may have changed, the intent of the advice ("Know something before you speak.") remains the same:[6][7]
Be courteous. Also, don’t use capital letters it’s known as SHOUTING OUT LOUD.

please, check those links...

http://en.wikipedia.org/wiki/Netiquette

http://www.google.com/url?sa=t&ct=re...WlJMC0g1EZvC8Q

....but, if you enjoy in capital letters....for some reason/s ...no problem

Best regards, Josip

[Electrocoolman]

Has anyone got experience with the new SANYO air to water heatpump? It uses CO2 as the refrigerant and will evidently heat to 70 deg C.

[Tesla]

Hi IcemanI done some homework for a shower heatpump system and of the common refrigerants R22 was best with a copeland scroll. If possible use some waste heat from the plant like grey water or superheat. My calcs showed I needed oil cooling and comp jacket cooler.

[US Iceman]

Hi Tesla,

My calcs showed I needed oil cooling and comp jacket cooler.

You touched on something that's important when dealing with these types of systems. These systems are not very common yet, so it is important to fully research any and all possible limitations that can affect the main components.

This becomes more critical as the temperatures increase because we are using "typical" refrigeration components often in uncharted territory.

[SteinarN]

Hotwater heat pump is an interesting subject. I considered to build such a heat pump some years ago. But in the end i chose an other solution. Se this post
http://www.refrigeration-engineer.co...8&postcount=14

The system i was considering was a system with R134A and Copeland Discus compressor. The Discus doesnt alow such CT as 80 degres C, but i planned to not care about it.

The compressor doesnt "see" the CT or ET, it only see the temperature and pressure. Max allowable CT is 55 degres C for R404A which coresponds to 25,7 bar abs or 24,7 bar rel. This pressure coresponds to roughly 81 degres C for R134A. Therefor the DP shouldnt disqualify 81 degres C in condensing.

15 degres evaporating is 4,9 bar abs or 3,9 bar rel. This coresponds to -6,5 degres C in evaporating for R404A. 15 C ET/81 C CT R134A returns the same pressures as -6,6 C ET/55 C CT R404A. This is inside the operating envelope for R404A for many Discus compressors. In other words, the electric motor and the physical strenght of the compressor(body) should be compatible with 15/81 R134A. The compression ratio is 25,7/4,9=5,24 which isnt that high.

The last matter to consider is the discharge temperature.

Discus compressors have the best isentropic efficiency of all compressor make and series i have examined. This also include most scroll compressors, especially when scrolls is operating outside their optimum isentropic operating range. The optimum isentropic operating range for scrolls can be in one corner, the other corner or the middle of the operating envelope. The isentropic effiency for Discus is in the range of 0,65 to 0,7 With an isentropic efficiency of 0,7 and 15 C ET, 20 C ST 81 C CT the DT will be roughly 100-105 degress C. This shuld be an accetable temperatur.

With zero subcooling that gives an heat COP of 2,8. However if it is possible to utilize an high degree of subcooling the COP will increase to 4,8 at 20 degress liquid temp (60 degres C subcooling).

With a properly calculated condenser it should be possible to acheive a water outlet at the same temperature as the coondensing temperature if my memory serves me right from 2 years ago.

[US Iceman]

HI SteinarN,

I have not rigorously studied your post but I agree with your comments. Most of these applications are outside of the "factory" envelope for standard applications. However, when you look at the basic parameters such as suction/discharge pressure and temperature for certain refrigerants the application envelope does meet the majority of reasonable application requirements.

I am supposed to be starting on a fairly large heat pump in the next few months so it should be interesting to develop a larger industrial heat pump.

[SteinarN]

Hi US Iceman.

I'm looking forward to be informed on the development of your heat-pump project. I will be pleased if i may be able to contribute something to your project.

[US Iceman]

I will be pleased if i may be able to contribute something to your project.

Thank you for your offer.

I have to wait to see what type of operating conditions are required and the final duty needed for heating. I am looking forward to this!!!!

[Cold Down Under]

I kinda stumbled onto this post by accident, funnily enough I have received a bizzarre enquiry today for a heat pump to condense at 119C (heat some chemical to 113C) and evaporate at 76C (cool and condense the same chemical after some other process). The enquiry is for 337 kW of heating with as much cooling (aiming for 314kW - unlikely) as possible. Am I talking with a crackpot and jsut tell him to go away and buy a boiler or is this even technically feasible?

[NoNickName]

Before anything else, you would need to choose the fluid.
As far as I know, no HC or HFC would work.

[US Iceman]

As nonickname states, for an application like this the selection and availability of the appropriate fluid (refrigerant) would be paramount before extending the conversation too far. Without doing any research my initial impression is that this falls into the category of a low vapor pressure hydrocarbon (possibly butane or something like this).

The second parameter that will get interesting is the application of the compressor to this temperature range. The condensing temperature is not much higher than what we might experience with discharge temperatures on an ammonia compressor. The evaporating temperature is a little on the high end, but might be workable.

With the low vapor pressure fluid the differential pressure across the machine should be low enough to be within operating envelope of the compressor design limits.

I don't think this is totally out of the question, but it will require some in-depth research and development to attempt. It's just another one of those weird and exotic applications that are so much fun!

[NoNickName]

Refrigerants which would thermodinamically work at those temperature are made up of heavy molecules. The two most promising, from a rapid research, are RC318 (AKA octafluorocyclobutane, C4F8) or R718 (AKA water).