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    Evap sizing tools



    Hi there,
    I am building a 2 stage ASHP to run with solar for floor heating and DHW and must be good down to -20C. In Canada 99% of all the ASHPs are designed to do air heating and to me that sucks. I am a wet head and hate ductwork. Also, we cannot get inverter/variable speed compressors here for some reason Danfoss and others don't sell them (unless my research is shyte)

    I am looking for a good sizing tool for the outdoor coil so I can design a few different models. Does anyone know of a generic sizing tool that would work here.

    Mike



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    Re: Evap sizing tools

    http://www.coolit.co.za/

    Some very useful software on this site.
    Engineering Specialist - Cuprobraze, Nocolok, CD Technology
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    Re: Evap sizing tools

    Thanks for your info on the site. I'm not sure it has the tools I need such as fin spacing and tube diameter and spacing etc. but maybe I need to look deeper.

    BTW advice on making heat pumps that will have a COP of at least 2.5 at -20C would be appreciated. The system will always be air to water and for heating and DHW only. My customers are seldom interested in cooling.

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    Re: Evap sizing tools

    It has ALL the tools you need to design a decent evaporator, or condenser.
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    Re: Evap sizing tools

    Quote Originally Posted by MikeHolm View Post
    Thanks for your info on the site. I'm not sure it has the tools I need such as fin spacing and tube diameter and spacing etc. but maybe I need to look deeper.

    BTW advice on making heat pumps that will have a COP of at least 2.5 at -20C would be appreciated. The system will always be air to water and for heating and DHW only. My customers are seldom interested in cooling.
    What water temp are you after?
    You will need to be a real smart cookie to sort this one, not the sort of thing you will find in a text book

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    Re: Evap sizing tools

    There is a real push for low heat loss custom houses and retrofits where i live. The houses are often too close together to make GSHPs financially viable (must do expensive vertical drilling) and we rely on nucs and hydraulic for most of our electricity so from a CO2 point of view, getting off gas is good, even though we have lots of it.
    Matching floor heating (30-40C) temps with two stage ASHPs seems a good way to go. The only problem is we have occasional -20C winters and 35C summers with high RH so sizing is a challenge and I am wanting to the most out of this at -20 as i can. As yet, no larger (Daikin, Mits etc) manufacturer makes an air to water HP for sale in North america although that is going to change.
    So, I am combining it with some active solar heat, a solar wall as an input to preheat the evap coil but designing the right coil size is very important.
    On the condenser side, I am looking at the temps above for most use + 50C for DHW and I will be using BPHEs with long thermal length to transfer to a water tank. Bit of a task.....and I do need some help.

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    Re: Evap sizing tools

    There are many commercial heat-pumps available. Doesn't make too much sense to re-invent these, unless it is for a hobby. It will take quite some effort to generate the kind of experience required, if you want to become a heat-pump designer.
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    Re: Evap sizing tools

    You should really bite the bullet and install a ground loop system. Canada is far too cold for Air source units to be efficient.

    You'll get two benefits from a ground loop. You should get COP's of 4.5 and up and you could also install an intermediary heat exchanger and passive cooling in the summer.

    In a climate like yours this makes the most sense.

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    Re: Evap sizing tools

    There have been a number of studies completed here that show that GSHPs sold in north america do not have the COPs that are claimed. That said, unless you are in a climate with 60 days of -20C, an ASHP will outperform a GS on an annual basis especially if it is a system such as the Mits.
    We used to have some rebates from the Federal government but they have removed them all and most people cannot afford the $30k+ to put the ground loops and HP in to meet the demand. We do have a lot of stupidly large houses over here so the average size of system is 5 ton and sometimes multiples of them. That's a lot of trenching or drilling.

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    Re: Evap sizing tools

    Quote Originally Posted by MikeHolm View Post
    There have been a number of studies completed here that show that GSHPs sold in north america do not have the COPs that are claimed. That said, unless you are in a climate with 60 days of -20C, an ASHP will outperform a GS on an annual basis especially if it is a system such as the Mits.
    We used to have some rebates from the Federal government but they have removed them all and most people cannot afford the $30k+ to put the ground loops and HP in to meet the demand. We do have a lot of stupidly large houses over here so the average size of system is 5 ton and sometimes multiples of them. That's a lot of trenching or drilling.
    I would completely disagree with you on the above. An ASHP will never outperform a ground loop system once it is installed properly. You cannot take the heatpump in isolation either. You must design the UFh to the lowest temp possible. We design to 30C.

    We have Groundsource heatpumps running COP's of 7.6 and SPF's of 6.2 (recorded on a high performance monitoring system). You won't touch that with a ASHP, especially a Mits or Daikin who are not, in all practical terms, heatpumps which are suited to UFH systems.

    You

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    Re: Evap sizing tools

    All this is fine with the equipment you have in Europe but in many ways you are way ahead of North Americans. For one thing, you may be able to build your own HP and get it passed by the local authority but here, we have no such thing as a CE designation so with few exceptions almost all installations need to have CSA or UL approvals which cost many $1000 and cannot be changed easily. The option, of course, is to install without permits. This is a much longer discussion anyway and not for this post.

    I design heating systems for houses that can run with output temps of no more than 35C, DHW excepted, and the houses are typically 100-200m2 but look at the average system here where the heat loss is much higher (some provincial governments in Canada have actually reduced insulation requirements within the past 20 years due to builder pressure) and most houses in Canada are low mass houses (stick frame and insulation) so they are harder to retrofit for low temp systems.

    Other than the houses with lots of land area which are in the country, most of my work is in the city where we would have to drill down at a cost of $50/m and the average size of system (monster homes excluded) would require 4-5 80m bore holes. Most people cannot afford this and there is little in subsidy and in the city there is no room anyway.

    COPs here of 6-7 for GSHPs are unheard of. We don't have access to the equipment you have. Inverter compressors are not available (Danfoss and others won't sell theme for some reason).

    More to come but I've got to walk the dogs.

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    Re: Evap sizing tools

    Quote Originally Posted by MikeHolm View Post
    All this is fine with the equipment you have in Europe but in many ways you are way ahead of North Americans. For one thing, you may be able to build your own HP and get it passed by the local authority but here, we have no such thing as a CE designation so with few exceptions almost all installations need to have CSA or UL approvals which cost many $1000 and cannot be changed easily. The option, of course, is to install without permits. This is a much longer discussion anyway and not for this post.

    I design heating systems for houses that can run with output temps of no more than 35C, DHW excepted, and the houses are typically 100-200m2 but look at the average system here where the heat loss is much higher (some provincial governments in Canada have actually reduced insulation requirements within the past 20 years due to builder pressure) and most houses in Canada are low mass houses (stick frame and insulation) so they are harder to retrofit for low temp systems.

    Other than the houses with lots of land area which are in the country, most of my work is in the city where we would have to drill down at a cost of $50/m and the average size of system (monster homes excluded) would require 4-5 80m bore holes. Most people cannot afford this and there is little in subsidy and in the city there is no room anyway.

    COPs here of 6-7 for GSHPs are unheard of. We don't have access to the equipment you have. Inverter compressors are not available (Danfoss and others won't sell theme for some reason).

    More to come but I've got to walk the dogs.
    If you need 400m of bore that means the heatpump would be in the region of 23kw. Thats a crazy figure. You need to seriously look at your insulation levels if thats the heatloss on a 200sqm build. In Austria, where they have a similar climate to yours. A house of that size would normally be heated by a 8kw HP.
    The unit I referred to was not an invertor unit. It was single phase capacitor start. Just a very well designed HP with a very well designed UFH and DHW system

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    Re: Evap sizing tools

    It has always bugged me that we have such big houses here and the average construction for a house built in the 70s will have a heat load of 120w/m2. The houses I work on now are far better than that but the housing stock built since the 60s has a life expectancy of less than 80 years and much of it will be less than 50 years. Most people here have no idea what well built house looks like.

    None the less we typically size the GSHP systems at 4kw/hole as I said above and 16kw+ would be appropriate for a lot of stick frame homes (no one likes much electric back up but it is going to happen anyway). My house is a 1918 clay brick with no insulation in the walls (160m2) and I heat for a lesser cost (using the same heating system) than a 1990 200 m2 stick frame home (150mm of fibreglas bat insulation, vapour barrier and an air barrier on the outside and then a brick veneer or siding.

    I use my house as a test bed for all my solar systems as well as boiler work etc. Now I want to reclaim the waste heat going down drain, store it, and use it as a supplementary evaporator on cold days but I don't know how to size coils in tanks. Anyone want to chime in on this one? The goal is to keep a minimum 5-10c water in a 500l tank and either use it to 1] help defrost the outside coil or 2] add some extra heat coming back to the system on really cold days (-15 or colder). I will use a R410 and a Copeland scroll. I like brain teasers.

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    Re: Evap sizing tools

    Quote Originally Posted by Bigfreeze View Post
    I would completely disagree with you on the above. An ASHP will never outperform a ground loop system once it is installed properly. You cannot take the heatpump in isolation either. You must design the UFh to the lowest temp possible. We design to 30C.

    We have Groundsource heatpumps running COP's of 7.6 and SPF's of 6.2 (recorded on a high performance monitoring system). You won't touch that with a ASHP, especially a Mits or Daikin who are not, in all practical terms, heatpumps which are suited to UFH systems.

    You
    COP 7.6 for an installed system, this has to be the exception to the rule.
    Is this DX system or with a secondary loop?
    What temp is the ground.
    You say you design 30C, supply or return?
    Please indicate SST and SCT of these systems, when they have been running for an hour or two.

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    Re: Evap sizing tools

    Quote Originally Posted by MikeHolm View Post
    There is a real push for low heat loss custom houses and retrofits where i live. The houses are often too close together to make GSHPs financially viable (must do expensive vertical drilling) and we rely on nucs and hydraulic for most of our electricity so from a CO2 point of view, getting off gas is good, even though we have lots of it.
    Matching floor heating (30-40C) temps with two stage ASHPs seems a good way to go. The only problem is we have occasional -20C winters and 35C summers with high RH so sizing is a challenge and I am wanting to the most out of this at -20 as i can. As yet, no larger (Daikin, Mits etc) manufacturer makes an air to water HP for sale in North america although that is going to change.
    So, I am combining it with some active solar heat, a solar wall as an input to preheat the evap coil but designing the right coil size is very important.
    On the condenser side, I am looking at the temps above for most use + 50C for DHW and I will be using BPHEs with long thermal length to transfer to a water tank. Bit of a task.....and I do need some help.
    You do need help?
    -20C ambient, 120W/M2, 200M2 house 24hours a day
    576Kwhr/day, solar again in your neck of the woods is around 2Kwhrs/day/M2 (in winter) lets say 25% by solar, you would need 72M2 of solar surface area, this does exclude any losses that may occur.
    So what is wrong here, is it -20C all day long? If not then you would not need 120w/M2. You will always have losses 24/day, but does the heating run 24Hrs/day. More than likely not, so your actual watt/M2 includes recoving heat when the heating is Off, and is oversized to allow for a reasonable reaction time, which also requires hotter water to enable quick response of heat transfer through the floor.
    You need to do a load profile, of losses (ambient related), work out your averages for performance. Rate your heat pump around these averages.
    Also Have alook at vapour injection on R404a, very big working enverlope

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    Re: Evap sizing tools

    Hi Fridgie,
    the 120w is a design load, not an average. I come from the boiler world and we have a lot easier time designing the system. Typically, find the worst load, add a bit for pick up, know your supply temp and pop in the boiler. At least for me it is that easy.

    HPs are different in many parts of Canada. From a greenhouse gas point of view (BTW, the current Canadian govt does not believe in global warming...I'm not kidding ) , it is better for me to use electricity which is currently made up of 25-30% hydraulic, 40% nuc (and that won't change) and most of the balance is NG. Coal is being phased out and we have the best FITs for solar PV at $.80/kwh. I want to get off gas.

    Anyway. Electrical prices in Ontario are about $.09 for peak hours and $.05 for off peak 9pm to 7am. Gas right now is the equiv of about $.03/kwh

    From a pricing point of view, the HP makes sense. I already build basements with 200mm of mass in the floor and store heat during the night for radiation during the day but I don't always have that opportunity.

    Anyway, for my house, the peak at -20 is probably about 60w/m2 at this point. The average in January here would be a -15 night temp and a -7 or so daytime temp. The last time i recall -20, 24 hrs a day was in 1994 when we had it for 30 days straight. We were out fixing a lot of heating systems that year.

    I care less about the cooling needs than the heating needs. The average subdivision owner(ie: crap house) wants to keep the t-stat at 20 in the summer and 23 in the winter so it is no wonder we are the worst per capita user of energy in the world.
    The large temp swing is important but my market is more focused on the heating so I think I should concentrate on that.

    Given the above, should i still look at R404? I haven't done so yet.

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    Re: Evap sizing tools

    Quote Originally Posted by mad fridgie View Post
    COP 7.6 for an installed system, this has to be the exception to the rule.
    Is this DX system or with a secondary loop?
    What temp is the ground.
    You say you design 30C, supply or return?
    Please indicate SST and SCT of these systems, when they have been running for an hour or two.
    No, we have quite a few units running an SPF of 6+, while the majority of the rest would be 5.5+.
    They are mostly DX systems.
    The design of 30C refers to the flow temp into the ufh. The ground temp would average between 6 and 8 degrees at 1m deep.

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    Re: Evap sizing tools

    Coolpack predictions for R-134a.



    Ideal case. Zero approaches for both evaporator & condenser. COP,hp = 8.510.



    Perhaps a little more realistic. With approaches of 5K & 3K for evap & condenser respectively. COP,hp = 6.215.
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    Re: Evap sizing tools

    Quote Originally Posted by Bigfreeze View Post
    No, we have quite a few units running an SPF of 6+, while the majority of the rest would be 5.5+.
    They are mostly DX systems.
    The design of 30C refers to the flow temp into the ufh. The ground temp would average between 6 and 8 degrees at 1m deep.
    Forgive my ignorance what is SPF?

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    Re: Evap sizing tools

    Quote Originally Posted by MikeHolm View Post
    Hi Fridgie,
    the 120w is a design load, not an average. I come from the boiler world and we have a lot easier time designing the system. Typically, find the worst load, add a bit for pick up, know your supply temp and pop in the boiler. At least for me it is that easy.

    HPs are different in many parts of Canada. From a greenhouse gas point of view (BTW, the current Canadian govt does not believe in global warming...I'm not kidding ) , it is better for me to use electricity which is currently made up of 25-30% hydraulic, 40% nuc (and that won't change) and most of the balance is NG. Coal is being phased out and we have the best FITs for solar PV at $.80/kwh. I want to get off gas.

    Anyway. Electrical prices in Ontario are about $.09 for peak hours and $.05 for off peak 9pm to 7am. Gas right now is the equiv of about $.03/kwh

    From a pricing point of view, the HP makes sense. I already build basements with 200mm of mass in the floor and store heat during the night for radiation during the day but I don't always have that opportunity.

    Anyway, for my house, the peak at -20 is probably about 60w/m2 at this point. The average in January here would be a -15 night temp and a -7 or so daytime temp. The last time i recall -20, 24 hrs a day was in 1994 when we had it for 30 days straight. We were out fixing a lot of heating systems that year.

    I care less about the cooling needs than the heating needs. The average subdivision owner(ie: crap house) wants to keep the t-stat at 20 in the summer and 23 in the winter so it is no wonder we are the worst per capita user of energy in the world.
    The large temp swing is important but my market is more focused on the heating so I think I should concentrate on that.

    Given the above, should i still look at R404? I haven't done so yet.
    Yes i would still consider R404a for your application, somes comps are rated to a SST -40C.

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    Re: Evap sizing tools

    Quote Originally Posted by mad fridgie View Post
    Forgive my ignorance what is SPF?
    Seasonal performance factor. Average COP over 1 yr or 1 heating season.
    Our figures would include production of hot water as your COP will drop during DHW production.

    Just regarding what refrigerant to use. We run ASHP's that run down to -30. They use R410a with copeland scrolls. Evap size and fin spacings should be one of your primary concerns.

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    Re: Evap sizing tools

    Quote Originally Posted by Bigfreeze View Post
    Seasonal performance factor. Average COP over 1 yr or 1 heating season.
    Our figures would include production of hot water as your COP will drop during DHW production.

    Just regarding what refrigerant to use. We run ASHP's that run down to -30. They use R410a with copeland scrolls. Evap size and fin spacings should be one of your primary concerns.
    Thanks about SPF,
    (Unless my Copeland program is out of date), If you are running at -30C ambient, then you are running the compressor well outside the working enverlope.
    I agree that how you configure the coil is VERY important.
    To achive your quoted SPF, your evap has to be in a flowing water table. Are you using the french based system (begins with an "A" I think)

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    Re: Evap sizing tools

    Hi Bigfreeze and Fridgie,
    There is one big difference between the situation here and in Ireland and that is ground temp. We can count on 6-8C up until about mid December, give or take a week, but after that we get to 0c pretty quickly. Our footings must me a minimum of 1.2m down to stay below freezing and that time I mentioned above in 1994 it went down to 2m. If you google a Manitoba Hydro heat pump study, you should get an indication of this problem.

    If I can keep the evap coil around 0c for much of the time by adding some waste heat from different areas of the house I should be able to boost the COP during those times. I did see an article from the US that showed a 8-10 percent increase in COP using vapour Injection and r410 and using an internal HX and separating the gases after the evap.

    Christmas dinner is on the table so I must go. Hope you are having a good holiday.

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    Re: Evap sizing tools

    And there lies the rub, as they say. Evap coil design. I will go through everything Fridgie has mentioned for the standard type aluminum and copper coils but the design of a loop in a wast heat tank is another issue. The vapour injection should, I assume, help in keeping liquid from the compressor but where should I add the waste heat, assuming both senarios, vapor injection or a straight 410a scroll? Gotta watch the head pressures.

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    Re: Evap sizing tools



    Refrigerant R134a. Source (ground/air/other) at 0'C. Approaches of 5K & 3K on evap & cond respectively. COP,hp = 4.862.



    Refrigerant R410A. Source (ground/air/other) at 0'C. Approaches of 5K & 3K on evap & cond respectively. COP,hp = 4.691.



    Are you really sure that you want to use R410A in this application?
    Last edited by desA; 26-12-2010 at 07:14 AM. Reason: Source (ground/air/other)
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    Re: Evap sizing tools

    Air source Des, not ground source, for Mike.

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    Re: Evap sizing tools

    Quote Originally Posted by mad fridgie View Post
    Air source Des, not ground source, for Mike.
    Therefore, I'd think it should get worse...

    Corrections made to above post.
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    Re: Evap sizing tools

    Thanks guys,
    There seem to be good and bad for 410a over 134 (with 134 slightly winning) but this is at 0c. What will happen at -5, -10, etc. Yes I am going to try to save up some waste heat from elsewhere but I will have to figure out when to start using it and how. Is the the dip on the chart after the evap just before compression due to sub cooling? It appears that the assumption is that enough supplemental heat will be inputted to keep suction at 6 bar. How much room is ther to play with?

    Mike

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    Re: Evap sizing tools



    The state information for R134a, for the case at 0'C. Compare these operating pressures to those for R410A.

    Don't these R410A pressures concern you?
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    Re: Evap sizing tools

    The range is less but is 2000+kpa an issue for 410? Enthalpy is is lower with 134 but COP is higher. Is there enough range for a lower temperature operation? I assume that at some point low pressure will fails a lockout.

    So much to learn and understand. I appreciate the comments.

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    Re: Evap sizing tools

    Quote Originally Posted by MikeHolm View Post
    The range is less but is 2000+kpa an issue for 410?
    You will need to think a bit more about the condenser you'd like to use for the ufh. What happens if the refrigerant side lets go at 20+ bar?
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    Re: Evap sizing tools

    Quote Originally Posted by desA View Post
    You will need to think a bit more about the condenser you'd like to use for the ufh. What happens if the refrigerant side lets go at 20+ bar?
    Its quite normal for 410 heatpumps to be running head pressures of between 20 and 30 bar for hot water production. You'll be running 20 bar for heating alone.

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    Re: Evap sizing tools

    What kind of condensers are they using?
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    Re: Evap sizing tools

    Quote Originally Posted by desA View Post
    What kind of condensers are they using?
    Plate heat exchangers

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    Re: Evap sizing tools

    Quote Originally Posted by Bigfreeze View Post
    Plate heat exchangers
    Standard compact brazed heat-exchangers?
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    Re: Evap sizing tools

    Quote Originally Posted by desA View Post
    Standard compact brazed heat-exchangers?
    BPHE but specially designed for heat pump applications

    Check out the swep website or other major manufacturers, you'll find them there

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    Re: Evap sizing tools

    SWEP's NHP high pressure HX's are rated up to 45bar

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    Re: Evap sizing tools

    Quote Originally Posted by Bigfreeze View Post
    SWEP's NHP high pressure HX's are rated up to 45bar
    All well & good, so far. I ask again - what happens when the refrigerant side lets go with R410A at 20+ bar?

    Plate HE's have a reputation for developing fatigue cracks.
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    Re: Evap sizing tools

    Yes, swep or alfa laval etc. But for the dhw I would like to find a way to go directly to an internal coil in a tank but for this particular design I will go with a BPHE. The more I can eliminate pumps the better the system COP.

    I will be going to a minimum 300l buffer tank so I can have a close deltaT on the refrig side and a 10C deltaT on the UfH.

    When I get home I will get the specs for the BPHE and let you know. I'm working off the iPad and have no access to my info. What I remember is that the system is about 14kw and the HE is 26 plate, 10cm by 40cm(approx) by memory so I could be off a bit.

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    Re: Evap sizing tools

    Quote Originally Posted by desA View Post
    All well & good, so far. I ask again - what happens when the refrigerant side lets go with R410A at 20+ bar?

    Plate HE's have a reputation for developing fatigue cracks.
    Like anything, if it goes it goes. It inside the casing of the machine so presents no danger to anyone. Most likely it will go at a plate between the water and the refrigerent in which case it will vent to the water system, your safety valve will pop and the water will shoot down the drain. Worst case scenario is you lose your refrigerant circuit.
    If 410a freaks you out, stay away from CO2

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    Re: Evap sizing tools

    A standard brazed compact HE - SWEP, Alfa Laval et al, are NOT safe in applications where excessive, sudden venting can occur. Be warned well in advance.

    Besides filling the water system with oil, a very nasty explosion can occur. This is irrespective of the refrigerant type involved. Pressure relief valves are generally designed to cope with gradual pressure rise - not a sudden pressure release. Sudden pressure releases generally require a few more safety aspects to be engineered into the system.
    Last edited by desA; 26-12-2010 at 06:08 PM.
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    Re: Evap sizing tools

    The particular HEs have braze joints for the refrigerant and threaded ones for the secondary loops.

    None the less, I agree that max pressure limits should be observed but what are they really?

    All the NIBE, Danfoss etc. hPs use plates so what are they doing right?

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    Re: Evap sizing tools

    Quote Originally Posted by desA View Post
    A standard brazed compact HE - SWEP, Alfa Laval et al, are NOT safe in applications where excessive, sudden venting can occur. Be warned well in advance.

    Besides filling the water system with oil, a very nasty explosion can occur. This is irrespective of the refrigerant type involved. Pressure relief valves are generally designed to cope with gradual pressure rise - not a sudden pressure release. Sudden pressure releases generally require a few more safety aspects to be engineered into the system.
    People far more qualified than myself have decided they are fine for their applications. I just purchase their products, as do hundreds of other installers across europe.
    Besides the condenser sides of these systems are not subject to temperature shock. The temperature invariably gradually increases as the system comes up slowly in temp.
    The evap side is far more likely to fatigue due to temp shock than the condenser side is.

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    Re: Evap sizing tools

    Also, I believe the HEs are pure nickel brazed so the pressure ratings are higher.

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    Re: Evap sizing tools

    The big question remains, what is the proper way to inject the waste heat near the suction side of the compressor? A long HE will induce a pressure drop but How will the added heat affect it and what temp water should the water side of the injector HE be set to? The goal bing to fool the compressor to think it is -5c not -15c outside.

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    Re: Evap sizing tools

    Quote Originally Posted by Bigfreeze View Post
    People far more qualified than myself have decided they are fine for their applications. I just purchase their products, as do hundreds of other installers across europe.
    Besides the condenser sides of these systems are not subject to temperature shock. The temperature invariably gradually increases as the system comes up slowly in temp.
    The evap side is far more likely to fatigue due to temp shock than the condenser side is.
    You may want to research into vented condensers. You may get away with standard condensers most of the time, but there will be the time when they will fail you. Yes, I am fully aware of the types of systems supplied into Europe.
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    Re: Evap sizing tools

    Quote Originally Posted by MikeHolm View Post
    The particular HEs have braze joints for the refrigerant and threaded ones for the secondary loops.

    None the less, I agree that max pressure limits should be observed but what are they really?

    All the NIBE, Danfoss etc. hPs use plates so what are they doing right?
    It has little to do with the maximum operating pressure rating, but more to do with the severity of a potential failure. This must be thought through.

    If your application ufh can withstand a sudden release of high pressure into it - then all well & good. I wonder how many ufc applications are designed to cope with this...
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    Re: Evap sizing tools

    Quote Originally Posted by MikeHolm View Post
    The big question remains, what is the proper way to inject the waste heat near the suction side of the compressor? A long HE will induce a pressure drop but How will the added heat affect it and what temp water should the water side of the injector HE be set to? The goal bing to fool the compressor to think it is -5c not -15c outside.
    I suspect that you may well need to talk to MadFridgie in regards to his new 'Wonder Widget'...
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    Re: Evap sizing tools

    Quote Originally Posted by desA View Post
    It has little to do with the maximum operating pressure rating, but more to do with the severity of a potential failure. This must be thought through.

    If your application ufh can withstand a sudden release of high pressure into it - then all well & good. I wonder how many ufc applications are designed to cope with this...
    Pretty much all. I've seen ufh pipe tested to 35bar before it burst. The most you'd ever get if a system failed is about 10 bar

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    Re: Evap sizing tools

    Quote Originally Posted by Bigfreeze View Post
    Pretty much all. I've seen ufh pipe tested to 35bar before it burst. The most you'd ever get if a system failed is about 10 bar
    A sudden 20+ bar failure would surely result in a sudden 20+ bar system exposure. Sudden pressure ruptures have a significantly worse effect than a sustained, or gradual pressure release. Component design pressures are based on a sustained operating pressure, not sudden (shock) loads.

    But, I'm sure you already knew all of this.
    Last edited by desA; 27-12-2010 at 04:31 AM.
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