About the authorAmmonia Refrigeration Installations
Ammonia refrigeration systems are complex by their very nature. A system can be comprised of a mixture of various manufacturers equipment such as evaporators, compressors, control valves, condensers, and vessels. Secondly, you can have various forms of each of these components. Screws or reciprocating compressors. Evaporative or shell & tube condensers. Flooded, direct expansion, or liquid overfeed coil circuiting.
Compounding this is the application of those components to different requirements for cooling or freezing. In addition to the above, the system designer has to make the entire system work through varying weather conditions while continuing to operate efficiently through a range of loads (full load to part load).
In some instances you might see recommendations where flooded evaporators are used without regard to operating charge because that’s the way it is done. In others you might see very large high-pressure receivers for a once in a lifetime pump down. You may see head pressure controls provided to ensure high-pressure for hot gas defrost systems or liquid transportation.
Secondly, the application of these components to a specific refrigeration duty may stipulate the need for larger refrigerant charges or certain ancillary devices, such as surge drums, pressure regulators, etc.
Up to this point, the system is still on paper. You still need to get it installed properly. Then, there are control systems that will need to be installed. Therefore as you can see there are a lot of opportunities where things can go wrong.
How could this process be improved?
Training is an opportunity to describe the basic operational requirements of each component, its operating limits, and how that operation/performance can be impacted by the interaction with other components. Another aspect is; has the system designer accounted for all operating conditions or only full load conditions in the summer?
Coordination is another issue. Will the controls company have the same viewpoint for controlling the system as the system designer envisioned? Will all required information be passed along to the parties that come after the system is designed on paper?
Installation begins after the job foreman is tasked with making all of this work. Then at start-up let’s ask another question. Who does the commissioning of the system to ensure the rated performance capabilities are achieved?
Each of these topics are an opportunity for training to be passed along from one area to another in hopefully a coordinated fashion. The overall impact of the decisions made in the above areas also has a bearing on the success of energy conservation aspects of the refrigeration system operation.
Tags: energy conservation, part-load efficiency, System design
