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  • buenijo's Avatar
    Yesterday, 07:44 PM
    I will fire the furnace this weekend if all goes to plan, and share the results - good or bad. I made the previous post primarily for education purposes. It is interesting. However, I decided years ago that desiccant evaporative cooling is not the ideal air conditioning configuration for my system. The best approach is a lithium bromide chiller. I did some very limited testing about 7 or 8 years back after acquiring a few pounds of lithium bromide from EBay. I tested the substance based on density and boiling point just to verify it was the stuff I bought, and it passed with flying colors. All I did with respect to testing was learn how to evacuate practically all air from a system by using a combination of cheap refrigerant vacuum pump and steam displacement. Take suction at a low point and start with warm water in the system. As the pressure in the system falls, the warm water boils. Water vapor is less dense than air, and so it rises to the top in the system to displace the air to the suction hose at the bottom. I verified the near complete absence of air by observing the lithium bromide chill the small mass of water down to 32F (after the system was isolated, the lithium bromide solution absorbed the water vapor in the system taking the pressure so low that the small mass of water continued to boil and cool to 32F). The other useful facts I determined is low cost DC mag drive pumps work perfectly under a high vacuum, and 6" schedule 40 PVC pipe holds a high vacuum well. My design is unique for chilling a mass of water DIRECTLY, then circulating the chilled water to a fan coil unit under vacuum. Why not? I mean, the pumps don't care. So, this eliminates a heat exchanger and lowers the chiller water temp - all else equal. The steam engine exhaust condenser would heat the lithium bromide solution that is under vacuum to boil off the water previously absorbed. This very low pressure steam is condensed by the lowest temperature ambient source available meaning air, but a body of water would be ideal. The liquid water from this condenser returns to the chilled water mass in the evaporator. The main challenge is achieving a high rate of absorption and evaporation with a low cost and compact design. I have a design worked out, but it's not something I will pursue until after the test engine is completed. The performance of this kind of system shows a cooling rate 70-80% of the rate heat is released at the condenser - which represents roughly the latent heat capacity in the steam engine exhaust of 20,000 - 25,000 BTU/hour for my 1 KWe engine design (assuming it all gets condensed to heat the solution)... So, about 1.2- 1.7 ton cooling (14,000 to 20,000 BTU/hour). Commercial units show about 10 watts electricity per ton of cooling rate. However, this figure considers only the thermodynamic cycle which includes only the pumps. It does not consider the additional energy for air moving equipment and chilled water circulation to fan coil units. Most small commercial evaporator fans show 50 watts per ton. I estimate a chilled water circulation pump would require 20-30 watts for my system. If water cooling were not available, the a condenser fan would consume more power than the evaporator fan. About 200 watts DC per ton is a reasonable estimate - roughly 4-5 times less than vapor compression.
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  • buenijo's Avatar
    07-03-2020, 09:34 AM
    Just sharing some interesting videos. In previous posts somewhere in another thread I discussed desiccant evaporative cooling as a promising means to provide space cooling using heat from a small steam engine system. An engineer on YouTube made a very good video describing his test unit. A follow-up video: DISCUSSION: The testing was not under controlled conditions, so I do not consider the results meaningful. There is a lot of room for improvement. A fully optimized desiccant evaporative cooling system could be very impressive. In particular, the approach would be most effective in regions that are both hot and humid as desiccants can take humidy to much lower levels as compared to vapor compression systems. What I like most about this kind of system is the low tech (low voltage DC power can be used, no refrigerants, no special tools for repair). It can be simple and last indefinitely with infrequent low cost maintenance. However, to be practical, it must be effective while significantly reducing electricity consumption relative to vapor compression units.
    15 replies | 1578 view(s)
  • buenijo's Avatar
    06-27-2020, 05:47 PM
    A gasification furnace is the most efficient way to burn wood. That noted, a properly designed and operated rocket stove is effectively functioning as a gasification furnace. The benefit of a gasification furnace design is superior control over the production of the fuel gas and supply of secondary air. This control makes it possible to show high efficiency over a wider power range and with a wider range of biomass fuel sources. First test furnace at full power: First test furnace at roughly 1/4 full power:
    15 replies | 1578 view(s)
  • buenijo's Avatar
    06-27-2020, 01:54 PM
    Just sharing a pic of the new combustion chamber: I can fire the unit now. However, I would like to first make a furnace hopper extension. The fuel capacity is rather low without a hopper. I will share results when available. It will be a few weeks. ADDENDUM: Just a comment to illustrate one aspect of my design philosophy. You can see the combustion chamber is simple. Indeed, "simple" was precisely my goal! A goal for any engineering project should be to avoid unnecessary complexities. Unfortunately, my shoestring budget makes this a time consuming process. Often an ideal component is simply too expensive. However, there is a fringe benefit. Namely, if the furnace works well, then I can replicate it both cheaply and quickly. For example, I am confident I could assemble a second unit (complete furnace and combustion chamber) from start to finish in a single 8 hour period.
    15 replies | 1578 view(s)
  • buenijo's Avatar
    06-21-2020, 01:09 PM
    I mounted some heavy duty casters on the base and drilled the air supply holes to the fire tube. The only thing that remains before firing the furnace is to install insulation in the combustion chamber. This is relatively easy. Some good news is I've been offered a practically unlimited supply of small wood splits including a lot of eucalyptus. For those who don't know, this wood is extremely energy dense at well over 30 million BTU per cord (nearly twice as dense as untreated pine lumber) - and burns really hot! Some advise against burning it in traditional fireplaces due to the high oil content, but it's ideal for a gasification furnace. I will try to describe the basic design. Consider the basic Top Lit Up Draft wood gasifier (called a TLUD):
    15 replies | 1578 view(s)
  • buenijo's Avatar
    06-15-2020, 01:27 PM
    The new furnace and combustion chamber are mounted on one end of a 2' x 3' heavy steel shelf with the 24vdc blower fan mounted underneath. This shelf will eventually accommodate the rest of the system. Right now the shelf is on leveling mounts, but I will eventually switch to casters before it gets too heavy. I went through a few minor iterations before arriving at the current design that proved surprisingly easy to fabricate and assemble. I could build a second unit quickly - so hopefully it tests well. Incidentally, ease of fabrication and assembly is a major part of my basic design that seeks to minimize costs. NOTE: With a sufficiently powerful blower fan, the dimensions of my furnace and combustion chamber can support a furnace output much higher than required for my 1 KWe steam engine design. Personally, I consider anything over 1 KWe as overkill for most applications I have considered for my system. However, if the base system proves to work well, then it can be scaled up easily.
    15 replies | 1578 view(s)
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About buenijo

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About buenijo
Navy veteran. Degrees in math and physics.
Alternative energy. Economics. Political philosophy. Exotic reptiles.
Whatever pays the bills.
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Computer and Technical:
Scientists and Engineer


“The beginning of wisdom is to call things by their proper name.” - Confucius.
"When plunder becomes a way of life for a group of men living together in society, they create for themselves in the course of time a legal system that authorizes it and a moral code that glorifies it." - Frederic Bastiat
"Being well adjusted to a sick society is not a measure of health." - Jiddu Krishnamurti


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