Permitted (O) – Carbon steel – Stainless steel – Aluminum – Other nonmetallic materials such as PTFE are permitted (if they will not break down) Source: http://www.ashrae4greenville.com/resources/Newsletter/2014/Intro-to-Ammoni-Refrigeration.pdf Not permitted (X)
– Copper and copper alloys such as brass are prohibited (but allowed for bearing materials) – Zinc (in continuous contact with ammonia) – Non-metallic materials that degrade upon exposure
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A simple and easy understanding on the ammonia refrigeration cycle to create chilled water.
Extracted from http://www.aboutammoniarefrigeration.com/
How common is ammonia refrigeration? Many years ago, the food and beverage industry embraced ammonia refrigeration. The economic advantages alone made it the refrigerant of choice for cold storage facilities and food processing facilities as well as the dairy and meatpacking industries. Almost all of the food on the family breakfast, lunch and dinner table passes through an ammonia refrigeration facility before reaching your grocery store including fresh fruits and vegetables, meat, poultry and fish, frozen convenience foods, milk, cheese and ice cream, and beverages such as soft drinks, beer and wine. How long has ammonia been used as a refrigerant?Ammonia was among the early refrigerants used in mechanical systems, and it's the only one of the early refrigerants to secure a lasting role as a refrigerant. Mechanical refrigeration was developed in the 1800s based on the principle of vapor compression. The first practical refrigerating machine using vapor compression was developed in 1834 and by the late 1800s refrigeration systems were being used in breweries and cold storage warehouses. The basic design of the vapor compressor refrigeration system, using ammonia as a refrigerant in a closed cycle of evaporation, compression, condensation, and expansion, has changed very little since the early 1900s. When was ammonia first synthesized?Ammonia was first synthesized in 1823 by reacting air and hydrogen. The first commercial production of synthetic ammonia began in 1913. Presently, there are an estimated two billion metric tons of ammonia present in the world. Of this amount, approximately five percent is man-made. Approximately 18 million metric tons of ammonia are produced annually in North America alone, and of this amount, less than two percent is used for refrigeration. Why is ammonia referred to as a natural refrigerant?Ammonia is a common, naturally occurring compound in the environment that breaks down naturally into hydrogen and nitrogen molecules (the atmosphere consists of nearly 80% nitrogen and hydrogen). Ammonia is made up of one atom of nitrogen and three atoms of hydrogen, with the chemical symbol NH3. Ammonia is a key element in the nitrogen cycle, and under normal conditions, is essential for many biological processes. Ammonia can be found in water, soil, and air, and is a source of much needed nitrogen for plants and animals. In fact, ammonia is among the most abundant gasses in the environment. When was the first commercial use of ammonia refrigeration?Ammonia was first used as a refrigerant in the 1850s in France and was applied in the United States in the 1860s for artificial ice production. The first patents for ammonia refrigeration machines were filed in the 1870s. By the 1900s, ammonia refrigeration machines were being commercially installed in block ice, food processing, and chemical production facilities. By the 1920s, ammonia refrigeration was being applied to ice rinks. During the 1930s, air conditioning markets began to develop, first for industrial applications and then for human comfort. The use of smaller units for domestic refrigerators increased substantially between 1920 and 1930. How is ammonia refrigeration used today?Ammonia refrigeration has been the backbone of the cold storage and food processing industries since the early 1900s. Ammonia refrigeration is the most cost effective and energy efficient method of processing and storing frozen and unfrozen foods. It is the workhorse for the post-harvest cooling of fruits and vegetables, the cooling of meat, poultry, and fish, refrigeration in the beverage industry, particularly for beer and wine, refrigeration of milk and cheese, and the freezing of ice cream. Practically all fruits, vegetables, produce and meats, as well as many beverages and juices, pass through at least one facility that uses an ammonia refrigeration system before reaching our homes. Ammonia refrigeration is also used in the chemical industry. Does ammonia refrigeration have other modern day uses?Recently, air conditioning provided by ammonia refrigeration systems has found applications on college campuses and office parks, small scale buildings such as convenience stores, and larger office buildings. These applications have been achieved by using water chillers, ice thermal storage units, and district cooling systems. In Europe, where regulatory regimes have encouraged new applications, ammonia refrigeration systems are used safely for air conditioning in hospitals, public buildings, airports, and hotels. Ammonia refrigeration provides air conditioning for the International Space Station and Biosphere II. Installation at power generation facilities represents an emerging application of ammonia refrigeration. As per cited from Danfoss website, CVQ is an electronically operated constant-pressure pilot valve that functions together with
the EKC 361 electronic system or an EKC 366 controller. CVQ enables the electronic (and thus the remote) control of a ICS or PM main valve. The CVQ valve is used to maintain a constant pressure at the ICS or PM main valve inlet side and can, via suction pressure regulation, very accurately control the temperature of a medium from an air or liquid cooler, etc. Today, CVQ valve is widely used in Cold Room, Palm Oil Industry (shortening or margarine plant) due to it's fast response toward changes of suction pressure. Typical installation of CVQ valve Image Credit: MYCOM
Reciprocating Compressor (Open Type) is the most common and mature compressor found in the market. Some of the popular brand in the market are MYCOM, Grasso, Vilter and Sabroe. The open type reciprocating compressor is driven by an external motor via direct drive or belt drive. The crankshaft is then move the piston up and down to generate the suction force for the refrigerant. The refrigerant vapor is then sucked into the compressor. After compressing the refrigerant to high pressure, the refrigerant (high pressure high temperature) is discharged to condenser. ADVANTAGE: 1. High Coefficient Of Performance, especially during partial load 2. Mature Technology 3. Parts and technician are easily available 4. Lower Initial Cost DISADVANTAGE: 1. More moving parts means higher chances of breakdown - Overhauling is recommended after 1 year of service 2. More vulnerable to liquid flood back 3. Relatively smaller capacity compared to Screw Compressor 1. Lower Costs Ammonia is the cheapest refrigerant. The price per kg for R22 is about 2.5 times and R134a is about 7.0 times the price of ammonia. For a large cold storage, the operation costs are 20-30% lower with ammonia than R22. Besides that, only half as much material needs to be purchased to charge a system because the density of ammonia is half of halocarbons. Refrigerant Cost
** Density of at 1.013bar at boiling point: 682kg/m3 (ammonia liquid), 1413kg/m3 (liquid R22) and 1376kg/ m3(liquid R134a) 2. Better Coefficient of Performance (COP) Ammonia is up to 10% more efficient than other refrigerants. As a result ammonia systems use less electricity than other system.
3. Higher Heat Transfer Coefficients Based on the heat transfer correlations provided by ASHRAE Handbook of Fundamentals, the ratio of heat transfer coefficients for ammonia relative to R22 are:
4. Better Efficiency Due to its highly favorable thermodynamic properties (high latent heat of vaporization), ammonia requires less primary energy to produce a certain refrigeration effect compared to other commonly used refrigerants. Evaporating one pound of liquid ammonia absorbs about 161 Watts compared to 12 to 25 Watts for Freons.
**Latent heat of vaporization (kJ/kg) is the heat absorbed when a substance changes phase from liquid to gas. 5. Smaller pipe dimensions required for the same refrigerant capacity Ammonia requires smaller pipe sizes for a large system spread over a large area due to less drop in saturation temperature compared to Freon. In suction lines at the same drop in saturation temperature, a given pipe will provide 2 to 3 times more refrigerating capacity with ammonia than R22. 6. Immediate detectability of leaks Ammonia has pungent odour and even small leaks are immediately detected. Many people refer to ammonia as "self-alarming"--you don't need a leak detector to determine that there is ammonia present. This is an important advantage over freon where large quantities could escape without detection. Ammonia leaks are found quickly and repaired. 7. Great tolerance to water contamination Modest contamination with water does not usually interfere ammonia system operation. With ammonia, water stays in solution and does not freeze out and block orifices. 8. Environment friendly Ammonia is an environmental friendly as it has zero Ozone Depletion Potential (ODP) and zero Global Warming Potential (GWP). It has no effect on ozone layer and no direct part on global warming.
9. Ammonia is not miscible with Paraffinic and Naphthenic Lubricants This characteristic of non-miscibility makes lubricant management in ammonia systems quite simple. The very small amount of lubricant that escapes the lubricant separator will be released by the ammonia in the evaporator and it can be removed (drained) easily. This characteristic is ideal for industrial systems. PRINCIPLES OF EVAPORATIVE CONDENSERS
The vapor to be condensed is circulated through a condensing coil, which is continually wetted on the outside by a recirculating water system. Air is pulled over the coil, causing a small portion of the recirculating water to evaporate. The evaporation removes heat from the vapor in the coil, causing it to condense. KEY BENEFITS OF EVAPORATIVE CONDENSERS
Referring to http://baltimoreaircoil.com.au/products/evaporative-condensers Image Credit: BAC, EVAPCO |
AuthorProject Engineer with 10 years experience in ammonia refrigeration system Archives
November 2016
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