Colmac Coil has developed and patented a new low temperature DX Ammonia system, which makes it possible to apply DX Ammonia at suction temperatures down to -45.5°C (-50°F).The Ammonia Piping Handbook serves as a guide for the design and implementation of DX Ammonia from +10°Cto -45.5°C(+50°F to-50°F). Addressing the problems of low temperature NH3 systems DX ammonia has been applied with some success inmedium and high temperature systems with suction temperatures about -6.6°C (+20°F); however, to date, it has not been used successfully at freezer temperatures. When the suction temperature is below approx. -6.6°C (+20°F), certain characteristics of ammonia result in the very poor performance of evaporators. In the newly published DX Ammonia Piping Handbook, Colmac Coil outlines how its new technology hasad dressed and mitigated these following issues:
1. Separation of liquid and vapor phases
When temperatures are below -6.6°C (+20°F), direct expansion with ammonia results in stratified/wavy two-phase flow patterns. Colmac Coil has developed a new technique which, when applied to the inside of evaporator tubes, causes the liquid NH3 to coat the entire inside surface of the tubes by capillary action. This enhanced tube technology allows for low temperature DX ammonia to perform as good or better than bottom feed pumped ammonia circuiting.
2. Refrigerant distributor technology
Colmac Coil has also developed (patent pending) a new refrigerant distributor technology, the Colmac Tank Distributor, which has the following characteristics:
2.1.Refrigerant pressure drop across the tank distributor during operation is very low, only 2-4 psi.
2.2Any oil or debris entering the tank distributor is captured in a drop leg (which is an integral part to the design) before it can enter the coil and foul tube surfaces. 2.3.Performance of the tank distributor is completely insensitive to liquid temperature (subcooling) 2.4.Graduated orifices in each distributor tube allow for equal distribution of refrigerant to all circuits over an extremely wide operating range of 0% to 700% of ratedcapacity. 2.5.Graduated orifices and large diameter distributor tubes allow full flow (minimal restriction) of hot gas during hot gas defrost. 2.6.The number of parallel evaporator circuits possible in a single tank distribut or can be as high as 48.
3. Removal of water from ammonia
DX ammonia evaporator performance can be significantly reduced by even a small amount of water (1-3%) in the system. Especially in freezing systems, which operate at suction pressures below one atmosphere (in a vacuum), water must be effectively removed during operation. Colmac Coil has developed an effective ammonia distillation vessel design and installation strategy, both of which are described in the DX Ammonia Piping Handbook.
Key Benefits of DX Ammonia
Reduced ammonia charge Simplified controls Energy efficient dry suction line Reduced line sizes Fast, energy efficient defrost Elimination of ammonia re-circulator pumps DX AMMONIA PIPING HANDBOOK [ΠΗΓΗ:http://www.ammonia21.com/] |