Absorption Process for Refrigeration

1. Yes.
2. Ammonium hydroxide can be used.

what????? please be specific of what is really in mind, WHAT IS DARK SIDE OF THE FORCE

The Force is an energy field generated by all living things. It flows through us and binds the Universe together. The Dark Side is the powerful side driven by one's darker emotions such as anger and fear.

How about the Dork side of the Farce? Maybe I should append it as my byline!

For some time there have been large-size absorption chillers for air conditioning, using water as the refrigerant and lithium bromide as the absorbent. Typically they are powered by combustion or waste heat. I'm not sure of the temperature required, but as I recall passive solar heat is only borderline warm, hence not very efficient. However, a company called Rotartica now makes a domestic-sized solar-powered water/lithium bromide chiller. Check out their site.

In addition, a solar concentrator type of collector would produce higher temperatures and greater efficiencies. Such an approach seems promising, but I don't yet know of any manufacturers.

Your question is a good one, and interesting. I would think there might be some profitable R&D that could be done.

I have published few papers on this issue.One of the papers is a fasibsilty study to use soalr energy to aircondition a hospital in Oman.In this paper, feasibility study to operate one of the interior hospitals in Oman using green energy as a main source of energy is discussed. Two options of using green energy are presented. Since it is a hospital, to begin with, it is proposed to check the feasibility of using green energy as a hybrid system i.e. in normal conditions 60% of the hospital power is taken from the green energy and in case if any problems happen to the green energy source the hospital will switch over to the conventional source of energy. The study comprises of techno – commercial aspects of implementing the green energy in a hospital. Methodology to implement the proposal, subject to the availability of fund, is summarized. Conclusions based on the study are listed in this paper. I have prposed Li-BR water absorption system.

Oman would seem an optimum location for this concept. Unfortunately, you gave no titles or means of access to the papers you have published. Are any available on the Web, for instance? Even better, are there any reports of actual installations and how successful they are?

It was only a feasibility study. We are interested to implement the study. Following with the concerned officials. This paper was presented lat year in an international conference organized by the Caledonian college of Engineering Muscat. I will post the web site and other details soon.

ive been in the GCC for almost 5 years, and if this concept will success in the future its very effective to minimize the use of cfc and mostly the burning of fossil fuels particularly.

Good idea - go googling http://en.wikipedia.org/wiki/Absorption_refrigerator and loads more

I've run 2 absorption air conditioners. They were both water chillers and the "A" coil in my furnace was designed for water. They both used ammonia - water systems and natural gas to heat. My first was a Bryant and the second one was a Whirlpool. They both had high side temperatures of about 400 degrees F and pressures in excess of 250 pounds if I remember correctly. Chillers have been used a lot in large steam driven systems both in industry and commercial office buildings.

I considered making one for solar for a while. Some problems are the high temperatures require focused collectors and all the associated problems such as special materials ( like steel lines).

The only other refrigerant I've heard of being used is water - lithium bromide. I know that was used in nuclear subs for air conditioning.

I recommend you use the heat to offset heating needs and get a high efficiency air conditioner. You'll at least be able to find someone that can work on those .

R-245fa is a low-temperature refrigerant used in lo-temp geothermal power generation. Use solar energy to evaporate (boil) the refrigerant. The only power input needed would be a pump to maintain low pressure in the condenser and return the condensate to the solar panels. Since a lot of building A/C load is solar gain, this would be perfect to suppliment a conventional A/C system, perhaps by pre-cooling the air. The system could also be set up to add solar heat on sunny but cold days.

Commercial units of absorption are available in the market. When waste heat is available at a relatively cheaper price absorption units are recommended. Most of commercial units are with Lithium Bromide -Water combination. Ammonia- Water combination is used for industrial and process applications. Solar energy can be used to generate steam using suitable solar collectors. Steam can be used either for air conditioning purpose or to generate power by using stem turbines. Solar energy is the energy of Future . We , Engineers, have to put our best efforts to use solar energy wherever possible to save planet earth for future generation.

I was once told that the ammonium based systems were considered dangerous due to potential leaks from corrosion. How does the Lithium -brominde compare? Can an existing ammonia based system be switched to use Lithium bromide?

It is interesting to crunch the numbers on an NH3/water absorption unit.

The critical temp of NH3 is, from memory around 120C and the critical pressure around 125psi. (I'm going on memory here because I'm too lazy to look it up - it's buried among a heap of other stuff.)

It is feasible to run the separation of the NH3 and H2O at around 90C, possibly lower.

Even flat plate collectors can reach that if the flow is small in relation to the collector area.

The advantage of NH3 is that the system runs above atmospheric pressure so inleakage of air is no problem. In addition, the smell of NH3 rapidly alerts everyone to leaks, and leaks are easy to find with soapy water.

LiBr systems use water as refrigerant at pressures well below atmospheric.

Because of the very low density of water vapor at, say 10C, the size of piping and size (& hence cost) of the system tends to go up.

The main advantages over NH3 are:

1. Fractional distillation isn't needed to separate the solution from the water vapor.

2. LiBr is not very corrosive.

Disadvantage is that the entire cycle must be carried out below atmospheric pressure when solar (flat plate) temperatures are used.

The advantages of NH3 are:

1. Cheap.

2. Not corrosive to steel (although drastic with Cu). Al also seems OK (I've had mixed results when checking this one).

3. Working pressure above atmospheric at all times.

4. Capable of reaching temps down to -33C (LiBr can't get below 0C, and struggles to reach that)

5. Volumes of circulating refrigerant/absorbent are small for a good output.

I based things on flat plate collectors as concentrating collectors don't work in overcast conditions, as the diffuse light makes it impossible to focus. Flat plate collectors still work being affected only by the reduced insolation.