Lots of Theory, Little Experience

marx290 · 03-12-13, 03:55 PM

I guess I can share some links now. I've been keeping a refrigeration blog for about two months now. Nothing special, mostly ideas and little actual trials.

musings on entropy

No groundbreaking technologies there, but I've got some projects I plan on building in the near future!

Here's some pics from a dehumidifier I salvaged to run on propane and one I fashioned to heat a cooler full of water with a copper condenser.

jeff5may · 03-20-13, 07:41 PM

Welcome to the forums! Sorry I missed this post, been busy in other threads.
I have 2 of these type of units, given to me for various reasons. The smaller, a 4kbtu, has been designated as an organ donor. The compressor is my vacuum pump and pulls down to around 300 microns or so. The condenser is my reclaimer coil, which connects at its discharge end to a T with a schrader on top and a valve very similar to what you are using on the bottom. It does a great job, and hasn't failed me yet.
The larger, a 6kbtu, has yet to find a new purpose. It awaits spring to be transformed into a water heater like the A7. HV23T built one of these in no time flat, and it worked so well he installed it immediately.

This stuff is fun and addictive if you're the tinkering type. Just remember that you're working with explosive fuel gas and don't blow anything up. Respect the propane, it really can kill you.

What I suggest is that you invent a water heating refrigerator. It could be plumbed straight to the kitchen sink to provide on-demand, essentially free hot water as a by-product of normal operation. Heck, you could even put a hot water tap in the front door next to the ice dispenser. Now that would be cool...

marx290 · 03-20-13, 09:36 PM

That dehumidifier pictured there served me well, but I think the compressor is going to get pulled for a crude recovery machine to recycle (maybe reuse) refrigerant from donors.

That valve pictured was given to me by a friend and it worked great. For my next project though, I think I'm going to use a needle valve with flare connections. I've found NPT fittings notorious for leaking.

In regards to propane, I try to use common sense and respect, but sometimes when we're experimenting, stuff happens. AC_Hacker warned me about the dangers of propane as well. When I lived in Pennsylvania I had a detached garage where I worked on this stuff, but now I share a roof with other tenants. I had reservations before about continuing with propane and after AC_Hacker's warning and suggestion to use R-134a, I think I'll make the switch. I never wanted to use a proprietary toxic refrigerant, mostly on principle, but for safety's sake I think I will. Besides, the thermal properties of R-134a and others are well known which makes analysis easier.

I agree, this stuff is a lot of fun. I don't have a great deal of experience, but I have a lot of ideas. I read a lot of technical literature. I've been collecting antique refrigeration books and I'm interested in reviving some really good ideas. I worked with those machines pictured above, but other than that, all I have is theory. I feel like I gained the confidence to keep going and bring some of my ideas to life. Once I find a job, I'm going to buy a new brazing torch (I sold my oxy/acetylene set before we moved) and get back into it.

I'm a fan of any technology that serves more than one purpose. Using the waste heat of refrigerator to heat domestic water is a good idea. Although I've yet to attempt it, and I certainly don't like to waste heat in one part of the home while generating it in another in a water heater; from what I can tell, the condenser temperatures required to heat water to 50C would be much higher than with an air cooled condenser. Obviously a heat pump water heater does it, but the that heat is usually sourced from ambient temperatures not the freezer evaporator temperature of a refrigerator. I just wonder how that big of a temperature spread and compression ratio would affect the COP of a refrigerator. I've read estimates of a COP of 2.0 and even 3.0 in domestic refrigerators, but I'm guessing that's during pulldown or when it's really loaded up. I bet they are closer to 1.0 once they are down to temperature. But, that doesn't mean we should waste the heat.

I would think that condenser heat would serve to make an excellent preheater for a domestic hot water supply. I think the condenser pressure could be lower, generating a higher COP for the refrigerator. I have been thinking that last few days about a greywater sourced heat pump water heater and a good test of the idea might be a 110VAC setup under the kitchen sink. My wife cooks a lot, so I clean up a lot of dishes (by hand), and I use a lot of hot water in the process. Knowing all that high quality energy is going down the drain drives me nuts, so I might just do something about it!

A refrigerator condenser sourced preheater would make a lot of sense in the fully integrated home.

BTW, I was just reading a post of yours earlier today on pipe insulation. Thanks for the info!

jeff5may · 03-21-13, 04:29 PM

I wasn't trying to run you away from using propane, just giving you a heads up. Pretty much all of the organic refrigerants carry their own set of baggage and dangers. With the FC gases, they are all like nerve gas, and most of them are also flammable. Not to mention their impact on the atmosphere.

As for me, I would rather have a leak using natural refrigerant doing experiments. I start up a fan before tinkering and have the unit ready to remove power immediately if the need arises. I reclaim and recycle all the gas I can whether it is flammable or not. Other than that, general shop safety takes care of the rest. A little forethought keeps you from getting caught with your pants down, so to speak.

If you are considering using R134a as a working fluid, butane(r600)/propane(r290) "Care 30" blend is the HC gas that works with those types of systems. I believe it is about half and half of each gas. It performs more like R12 than R134a does. In fact, the "super frosty" automotive cans have some butane and/or propane in them to make it work better than straight R134a. But you cannot just drop in R134a into a system that was designed for R22 without suffering a drastic performance loss.

If this sounds confusing, it is. Besides the learning curve associated with the cycle, there are also different gases to consider. The manufacturers are scrambling to try to find viable replacements for gases people in the industry have been comfortable with for a long, long time. The truth is that none of them really know what the industry will settle on next, so they just promote them all.

GAS2010.com is a good place to look to compare different gases. Their site has a common-sense breakdown for non-engineer people. It's a good place to start to understand the situation the HVAC/R industry is facing. I especially like the "Future Refrigerants" section, as well as the "Natural Refrigerants section. They really put things in the proper perspective, unlike most other websites. Happy reading!

03-12-13, 03:55 PM	#1
marx290 Vapor Compression Goon Join Date: Mar 2013 Location: Portland, OR Posts: 63 Thanks: 11 Thanked 22 Times in 11 Posts	Lots of Theory, Little Experience I guess I can share some links now. I've been keeping a refrigeration blog for about two months now. Nothing special, mostly ideas and little actual trials. musings on entropy No groundbreaking technologies there, but I've got some projects I plan on building in the near future! Here's some pics from a dehumidifier I salvaged to run on propane and one I fashioned to heat a cooler full of water with a copper condenser.

03-20-13, 07:41 PM	#2
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	Welcome to the forums! Sorry I missed this post, been busy in other threads. I have 2 of these type of units, given to me for various reasons. The smaller, a 4kbtu, has been designated as an organ donor. The compressor is my vacuum pump and pulls down to around 300 microns or so. The condenser is my reclaimer coil, which connects at its discharge end to a T with a schrader on top and a valve very similar to what you are using on the bottom. It does a great job, and hasn't failed me yet. The larger, a 6kbtu, has yet to find a new purpose. It awaits spring to be transformed into a water heater like the A7. HV23T built one of these in no time flat, and it worked so well he installed it immediately. This stuff is fun and addictive if you're the tinkering type. Just remember that you're working with explosive fuel gas and don't blow anything up. Respect the propane, it really can kill you. What I suggest is that you invent a water heating refrigerator. It could be plumbed straight to the kitchen sink to provide on-demand, essentially free hot water as a by-product of normal operation. Heck, you could even put a hot water tap in the front door next to the ice dispenser. Now that would be cool... Last edited by jeff5may; 03-20-13 at 07:44 PM.. Reason: Idea

03-20-13, 09:36 PM	#3
marx290 Vapor Compression Goon Join Date: Mar 2013 Location: Portland, OR Posts: 63 Thanks: 11 Thanked 22 Times in 11 Posts	Indeed, that would be cool... That dehumidifier pictured there served me well, but I think the compressor is going to get pulled for a crude recovery machine to recycle (maybe reuse) refrigerant from donors. That valve pictured was given to me by a friend and it worked great. For my next project though, I think I'm going to use a needle valve with flare connections. I've found NPT fittings notorious for leaking. In regards to propane, I try to use common sense and respect, but sometimes when we're experimenting, stuff happens. AC_Hacker warned me about the dangers of propane as well. When I lived in Pennsylvania I had a detached garage where I worked on this stuff, but now I share a roof with other tenants. I had reservations before about continuing with propane and after AC_Hacker's warning and suggestion to use R-134a, I think I'll make the switch. I never wanted to use a proprietary toxic refrigerant, mostly on principle, but for safety's sake I think I will. Besides, the thermal properties of R-134a and others are well known which makes analysis easier. I agree, this stuff is a lot of fun. I don't have a great deal of experience, but I have a lot of ideas. I read a lot of technical literature. I've been collecting antique refrigeration books and I'm interested in reviving some really good ideas. I worked with those machines pictured above, but other than that, all I have is theory. I feel like I gained the confidence to keep going and bring some of my ideas to life. Once I find a job, I'm going to buy a new brazing torch (I sold my oxy/acetylene set before we moved) and get back into it. I'm a fan of any technology that serves more than one purpose. Using the waste heat of refrigerator to heat domestic water is a good idea. Although I've yet to attempt it, and I certainly don't like to waste heat in one part of the home while generating it in another in a water heater; from what I can tell, the condenser temperatures required to heat water to 50C would be much higher than with an air cooled condenser. Obviously a heat pump water heater does it, but the that heat is usually sourced from ambient temperatures not the freezer evaporator temperature of a refrigerator. I just wonder how that big of a temperature spread and compression ratio would affect the COP of a refrigerator. I've read estimates of a COP of 2.0 and even 3.0 in domestic refrigerators, but I'm guessing that's during pulldown or when it's really loaded up. I bet they are closer to 1.0 once they are down to temperature. But, that doesn't mean we should waste the heat. I would think that condenser heat would serve to make an excellent preheater for a domestic hot water supply. I think the condenser pressure could be lower, generating a higher COP for the refrigerator. I have been thinking that last few days about a greywater sourced heat pump water heater and a good test of the idea might be a 110VAC setup under the kitchen sink. My wife cooks a lot, so I clean up a lot of dishes (by hand), and I use a lot of hot water in the process. Knowing all that high quality energy is going down the drain drives me nuts, so I might just do something about it! A refrigerator condenser sourced preheater would make a lot of sense in the fully integrated home. BTW, I was just reading a post of yours earlier today on pipe insulation. Thanks for the info! Last edited by marx290; 03-20-13 at 09:38 PM.. Reason: typo

03-21-13, 04:29 PM	#4
jeff5may Supreme EcoRenovator Join Date: Jan 2010 Location: elizabethtown, ky, USA Posts: 2,428 Thanks: 431 Thanked 619 Times in 517 Posts	I wasn't trying to run you away from using propane, just giving you a heads up. Pretty much all of the organic refrigerants carry their own set of baggage and dangers. With the FC gases, they are all like nerve gas, and most of them are also flammable. Not to mention their impact on the atmosphere. As for me, I would rather have a leak using natural refrigerant doing experiments. I start up a fan before tinkering and have the unit ready to remove power immediately if the need arises. I reclaim and recycle all the gas I can whether it is flammable or not. Other than that, general shop safety takes care of the rest. A little forethought keeps you from getting caught with your pants down, so to speak. If you are considering using R134a as a working fluid, butane(r600)/propane(r290) "Care 30" blend is the HC gas that works with those types of systems. I believe it is about half and half of each gas. It performs more like R12 than R134a does. In fact, the "super frosty" automotive cans have some butane and/or propane in them to make it work better than straight R134a. But you cannot just drop in R134a into a system that was designed for R22 without suffering a drastic performance loss. If this sounds confusing, it is. Besides the learning curve associated with the cycle, there are also different gases to consider. The manufacturers are scrambling to try to find viable replacements for gases people in the industry have been comfortable with for a long, long time. The truth is that none of them really know what the industry will settle on next, so they just promote them all. GAS2010.com is a good place to look to compare different gases. Their site has a common-sense breakdown for non-engineer people. It's a good place to start to understand the situation the HVAC/R industry is facing. I especially like the "Future Refrigerants" section, as well as the "Natural Refrigerants section. They really put things in the proper perspective, unlike most other websites. Happy reading!