Saturday, February 2, 2013

Ammonia/Water - Absorption Refrigeration System



Process Description


Some liquids like water have a great tendency for absorbing large amount of certain vapors (NH3) and reduce the total volume quite. The absorption chiller refrigeration system differs basically from vapor compression system only in the method of compressing the refrigerant.

In the absorption refrigerating system, the compressor is replaced with an absorber, generator and pump. Figure 6.7 shows the schematic diagram of a vapor absorption refrigeration system.

Ammonia vapor is extracted from the  NH3 strong solution at high pressure in the generator by an external heating source. In the rectifier, the water vapor which carried with ammonia is removed and only the dried ammonia gas enters into the condenser, where it’s condensed.

The pressure and temperature of cooled NH3 solution is then reduced by a throttle valve below the temperature of the evaporator. The NH3 refrigerant at low temperature enters the evaporator and absorbs the required heat from it, then leaves it as saturated vapor.

The low pressure NH3 vapor is then passed to the absorber, where it’s absorbed by the NH3 weak solution which is sprayed also in the absorber as shown in Fig.6.7. After absorbing NH3 vapor by the weak NH3 solution (aqua–ammonia), the weak NH3 solution becomes strong solution and then it is pumped to the generator passing through the heat exchanger.

In the pump, the pressure of the strong solution increases to generator pressure. In the heat exchanger, heat form the high temperature weak NH3 solution is absorbed by the strong NH3 solution coming from the absorber.

As NH3 vapor comes out of the generator, the solution in it becomes weak. The weak high temperature NH3 solution from the generator is then passed through the throttle valve to the heat exchanger. The pressure of the liquid is reduced by the throttle valve to the absorber pressure.


vapor absorption refrigeration system ammonia water


Why Do We Use Ammonia/Water ?


Because most commercial and industrial refrigeration applications occur at temperatures below 32 F and many are 0 F. As a result, a fluid which is not subject to freezing at these temperatures is required. So the lithium bromide/water cycle is no longer able to achieve this conditions, because water is used for the refrigerant.

Also the required heat input temperatures must be at least 230oF. It should also be remembered that the required evaporation temperature is 10 to 15oF below the process temperature.


Use of ammonia/water equipment in conjunction with geothermal resources for commercial refrigeration applications is influenced by some of the same considerations as space cooling applications. Figure 13.5 illustrates the most important of these. As refrigeration temperature is reduced, the required hot water input temperature is increased.


What About COP ?


Figure 13.6 suggests a minimum hot water temperature of 275oF would be required. For example, for a +20oF cold storage application, a 5oF evaporation temperature would be required.

For geothermal resources that produce temperatures in this range, it is likely that small scale power generation would be competing consideration unless cascaded uses are employed. Figure 13.7 indicates another consideration for refrigeration applications. The COP for most applications is likely to be less than 0.55.

As a result, hot water flow requirements are substantial. In addition, the cooling tower requirements, as illustrated above, are much larger than for equivalently sized vapor compression equipment.



temperature for ammonia water


cop for ammonia water absorption refrigeration system



Figure 13.8, shows these two cycles is substantially higher COP, over a much broader range of generator input temperatures than the conventional lithium/bromide cycles. The superior performance is achieved by operating the chiller input stage at constant temperature, rather than constant pressure as in conventional systems. This has the effect of reducing the thermodynamic irreversibilities in the absorption cycle (Wahlig, 1984).


cop for single effect ammonia water absorption refrigeration system




Related Articles:






8 comments:

khalid abdullah said...
This comment has been removed by the author.
khalid abdullah said...

Chill Zone has been supplying, installing, and servicing refrigeration and air conditioning equipment for 6 years. We take great pride in offering a personal service to meet and support the needs of all our customers at affordable prices. We can source refrigeration ni
equipment for all commercial businesses from local shops to large enterprise organisation. We provide a range of equipment from leading manufactures covering budget range to high quality.

edsmith945 said...

Thank you for sharing information about ammonia removal. Municipal wastewater treatment poses two key challenges: nitrogen pollution and waste sludge disposal.

Lodie Venter said...

Hi we are ammonia refrigeration contracters based in cape town South Africa, we want to desighn an absorption plant but need some help with the desighn of the vessels and condensers and pipe sizing.
Can someone help me please?ontact me at lodie@a-r-e.co.za

hotinthekitchen said...

I'm so glad that I don't have to worry about pollutants or my food getting contaminated. I got great commercial refrigeration equipment from Roger & Sons and I never have to worry! 1 less worry in life can make a world of difference.

Ener Save said...

http://enersavebiz.blogspot.com/2013/07/hydrocarbon-as-green-gas-for-air.html -hello, we need some help here. your opinions is highly appreciated

adson stone said...

When looking for a used commercial refrigerator, it is best to physically inspect the unit yourself, so buying online isn’t the best option. You’ll want to check everything inside and out for excessive wear and tear. Pay special attention to the door gasket and evaporator fins. A cracked or dried out gasket will need to be replaced. If the evaporator fins are bent, the machine will suffer decreased performance. Look for signs of mold or corrosion. Check the frame and doors or anything else that is metal for signs of corrosion that indicates poor maintenance. If you are physically inspecting the unit, smell the inside. If it smells musty or moldy, do not buy, because that musty smell can affect the flavor of your food. Call the manufacturer with any questions. If you have any questions about the performance of the unit, it is best to call the manufacturer because they can give you an idea of what might be going wrong and how much repairs can potentially cost.
commercial kitchen equipment Melbourne

Mineral Water Dealers in Gurgaon said...

we are the 20 Liter Mineral Water Bottles, Mineral Water Manufacturers in Gurgaon we provide the best Mineral Water which also provide 20 Liter Mineral Water Supplier,Bisleri Water Suppliers in Gurgaon from the Mineral Water Bottling Plant so that we are the Mineral Water Companies in India,Mineral Water,20 Liter Water Bottle Manufacturers,20 Liter Water Bottle Dealers,20 Liter Mineral Water Bottles,Bisleri Water Suppliers in Gurgaon,Mineral Water Plants in Gurgaon,Mineral Water Companies,Mineral Water Supplier in Gurgaon,Mineral Water Companies in India,Mineral Water Dealers in Gurgaon,Mineral Water Supplier,Mineral Water Dealers

Post a Comment

Twitter Delicious Facebook Digg Stumbleupon Favorites More

 
Design by Free WordPress Themes | Bloggerized by Lasantha - Premium Blogger Themes | 100 Web Hosting