12-03-12, 02:51 PM | #1361 |
Helper EcoRenovator
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I found a masters thesis on Coaxial Borehole Heat Exchanger which comes up with interesting conclusions about earth coupled heat exchangers comparing the two pipe system we use. It is very detailed with lots of testing. It can be found at
http://www.kth.se/polopoly_fs/1.2039...0Guillaume.pdf Analysis of a Novel Pipe in Pipe Coaxial Borehole Heat Exchanger Hope this helps . Charlesfl |
12-04-12, 01:46 PM | #1362 | ||
Supreme EcoRenovator
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Quote:
I think that this paper will get more attention when conclusion number six is stated: Quote:
Previous suggestions regarding coaxial boreholes have been largely dismissed because the cost of coaxial borehole pipe was high relative to the 'U' shaped pipe, and by putting in more of the cheaper pipe, the same heat could be extracted for cheaper. However, a 40% improvement is not to be ignored. On first analysis, a 40% improvement seems very attractive. But this does not mean that 40% more heat can be harvested from a given piece of ground over the long term. Thermal depletion would surely result, unless the boreholes were spaced farther apart. What it does suggest however, is that 40% fewer boreholes might be need to be deployed. Since the earthwork is the biggest expense of a GSHP system, this is significant. * * * Taking this all back to a DIY perspective, the additional difficulty of home-fabricating insulated, coaxial borehole pipe might be a deterrent to potential DIY readers. They should know that the 'U' shaped borehole pipe has been widely used successfully, in many parts of the world, and there is plenty of engineering data available to correctly size a U-pipe loop field for specific locations and soil types. Best, -AC
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12-05-12, 12:30 PM | #1363 |
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Have not spotted this posted before and stumbled across it today. Some really good stuff here from basic leak detection through to HC refrigerants.
Reports, Guidelines, and Tools | GreenChill | US EPA |
12-07-12, 07:31 AM | #1364 | |
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Quote:
rgd. r290- stuff and design parameters of the equipment at small size. Not easy to dig up but pls. google first: ISRN KTH/REFR/07/58-SE and then you get this kind of view: [PDF] Experimental Investigation of Refrigerant Charge ... - DiVAkth.diva-portal.org/smash/get/diva2.../FULLTEXT0... - Käännä tämä sivu Annoit tälle +1. Peruuta Tiedostomuoto: PDF/Adobe Acrobat - Pikakatselu kirjoittanut W Fernando - 2007 - Viittausten määrä 2 - Aiheeseen liittyviä artikkeleita SE-100 44 Stockholm, Sweden. Stockholm, February 2007. Trita REFR Report No. 07/58. ISSN 1102-0245. ISRN KTH/REFR/07/58-SE. ISBN 978-91-7178-569- ... .... and click again ... and allow the file get loaded! |
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12-07-12, 10:43 AM | #1365 | |
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Quote:
Thank you dc€x for finding & sharing this valuable document. I have added it to my personal collection of most relevant information. Below, is the 'Conclusion' section of the report and I encourage fellow hackers to become familiar with the information contained in the report. Code:
Conclusions The heating energy demand of a new single-family European house is generally in the range of 100 - 150 kWh/(m2yr). However, it could be lower or higher than the given range depending on the conditions of the house. A heat pump with the heating capacity of 5 kW could be able to provide full or part of the heating need of a single-family house. Heat pumps of this size generally give average COP1 higher than 3 and this value could be further increased by proper selection of components, use of high temperature level heat sources and low temperature level heating systems, etc. The ground as heat source and floor heating systems are encouraged to obtain higher COPs and stable operations of the heat pump during a heating period. The refrigerant is one of the most important elements of any heat pump and refrigeration system, since it greatly affects the efficiency of the system and compatibility with the environment. The ozone depletion potential (ODP) and global warming potential (GWP) of commonly used refrigerants are considered as major environmental problems. Safety is the other major concern for refrigerants. Many synthetic refrigerants are considered as excellent candidates if their high ODP and GWP are neglected. Particularly, environmental effects of synthetic substances are still a concern due to the many possible unknown effects and, therefore, research interest has been more focused on applications of well characterized natural refrigerants. Although environmental concerns and safety issues are forcing major shifts from traditional choices of refrigerants, other aspects are also being considered in selecting a suitable refrigerant for a particular refrigeration application. Propane is a natural refrigerant that does not have any ozone depletion potential and has a very low global warming effect compared to most commercially available refrigerants. It is non toxic, chemically stable while inside the refrigeration system, compatible with most materials used in HFC equipment and miscible with commonly used compressor lubricants. Propane has very good thermodynamic and transport properties that closely resemble those of HFC refrigerants, making it possible to use with well known technologies. However, the main concern with propane is its high flammability. To decrease risk, refrigeration and air conditioning systems using propane should be designed to operate with small refrigerant charges and zero refrigerant leaks. This project has shown that, it is possible to design a heat pump for the typical requirements of a single-family house giving high COP and operating with low refrigerant charge. The project has focused on the design of heat exchangers with small internal volume. The reported results show that the mini-channel heat exchangers have better heat transfer performances compared to plate heat exchangers or heat exchangers with large diameter channels. This allows designing more compact and safer refrigeration equipment with high performances. The high solubility of propane in most compressor lubrication oils should be considered when selecting lubrication oil for propane refrigeration compressors. Generally, it is recommended to use lubrication oil with higher viscosity grades for propane than with R22 for proper lubrication. Several oils were proposed for use with propane by some lubricant manufactures. Select Lubricants has recommended SL18-Series (Synthetic hydrocarbon base) and SL34-Series (Polyoxyalkylene Glycol) compressor lubrication oils for use with natural gas and propane. CPI Engineering Services has recommended CPI-1518-Series (polyglycols based) for propane compressors. Tests showed that propane is much less soluble in PAG oil than in POE. The reported heat pump can be operated with about 200 - 230 g of refrigerant propane, giving over 5 kW heating capacity at typical Scandinavian heat source/sink temperature levels. Further reduction in the charge is possible by use of less soluble oil, by using compressors with lower oil charge and/or smaller internal volume and by redesigning the end caps of the aluminium tube heat exchangers. Since propane is highly soluble in compressor lubrication oil, the amount of refrigerant that could rapidly escape in case of an accident or leakage would be less than 150 g. The experimentally tested scroll compressor, which was originally recommended for refrigerant R407C worked well with refrigerant propane. * * * As an aside, the report states that a 5KW heat pump should be sufficient for all or most of the heating needs of a typical modern European house. 5KW is the same as 1.4 Tons, which should serve as a wakeup call to those of us in the US & Canada, that our EcoRenovating work is far from done... Best, -AC_Hacker
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12-08-12, 08:08 PM | #1366 |
Less usage=Cheaper bills
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That would cover me to about 10f/5c but only with a 1.4 output at that temperature, which isn't the case. We usually get to -20f/-30c on a yearly basis overnight and usually a weeks worth of nights at -10f/-25c temperatures. That would be tons of resistive or other backup heat here. How cold does it get in Europe?
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12-08-12, 09:34 PM | #1367 | |
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Quote:
Add up the hours of -20C temps and see if it makes sense to have another heat source, like propane, just for the odd occasion. Sweden has the highest building code standards in Europe for insulation so we do have a way to go. |
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12-13-12, 09:40 PM | #1368 | |
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Quote:
I'm not exactly sure what the typical temperatures are in the part of Canada where Randen lives, But he has gone GSHP (with some solar assist) for his home and his shop. That's the way to do it. Best, -AC
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12-14-12, 05:34 AM | #1369 |
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We used to get -30C regularly. I remember one winter in 93 or 94 where it was -25C steady for almost 6 weeks. Every heating guy and plumber was working flat out fixing frozen and broken water lines and heating pipes.
Those days are gone. The last few years we have seldom had temps much below -15C with some -20C at night, but not many. New technology is allowing ASHP to get lower and lower in ambient temp and having a gas or electric back up can still make financial sense. It might be the choice between $40k for vertical wells and $20k for an ASHP with some solar (for example) and if the annual heating cost is less than $1000with GSHP and $1200 with ASHP, is it worth it to go GS? |
12-14-12, 12:23 PM | #1370 |
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Understanding Superheat and Subcooling for correct charge
In preparing to hack my air source heat pump, I am trying to understand the tools used for getting the correct charge. I have a Fieldpiece SMAN3 unit that hooks up to the lines and can help determine the Superheat and Subcooling. I hooked it up the other day and below is what it read. The dry bulb was 59 degrees in the heated building.
I have R290a installed in the unit already. It has been working for almost a year on this charge. It was filled to be about equal to the charge of the R22 that was in there. The plan is to install a switching valve to go between ground source and air source. But I would like charge the unit to an optimum charge with the propane refrigerant before adding the ground source part of it. This unit was manufactured for R22. What could I do to make it more efficient with the R290a? |
Tags |
air conditioner, diy, gshp, heat pump, homemade |
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