About the authorMike Fisher has over 35 years of experience with refrigeration systems. This background includes; service, installation, equipment manufacturing, research and development, project management, consulting engineering, system design and packaged systems.
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Energy conservation is a very interesting field. With the advances of technology we have items like solar panels for energy generation or water heating, battery technology for energy storage and new forms of lighting like LED lamps. A recent article on LED lamps caught my attention recently and I thought it would be a good example for comparison to ammonia refrigeration systems.
When you try to evaluate the cost of operation what do you look for? The total of the monthly utility bill, the cost of energy, or something else? Utility charges are based on rate tariffs. These are the prescribed methods for billing users for the electricity and natural gas they consume.
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By now many of the States in the upper midwest have experienced very cold weather. As some have found, winter time presents some occasional challenges for starting or operating an ammonia refrigeration system.
Since the advent of the mandated Process Safety Management program (PSM) the industrial refrigeration sector has been faced with attempts to maintain lower refrigerant charges (re: inventories of refrigerant used in the system). To date, most of the efforts expended focus on keeping the ammonia refrigerant charge under 10,000 pounds. To a degree, this has largely centered around minimizing the quantity or use of gravity-flooded air-cooling evaporators or flooded shell and tube heat chillers. While these methods will drastically reduce the total refrigerant charge, other methods can be applicable. These typically involve re-thinking the basic premise for the use of a refrigerant and the application of specific sub-systems that are used in ammonia refrigeration systems.
I often see people interested in heat recovery asking questions about desuperheating. This mode of heat recovery is based on circulating a fluid such as water through a heat exchanger to aid in transferring heat from one location to another. One of the major issues with utilizing the superheat of the discharge gas from a refrigeration systems is; there is not a lot of available heat! The available superheat in the discharge gas from a compressor is only a small percentage of the the total available heat energy.
I usually observe the surroundings and watch for the color change of the trees during this time of the year. As I was driving back from a project this last week I happened to notice something I thought was slightly ironic. At one bend in the highway there were patches of steam over the horizon. These are certainly more visible during this time of year with cooler ambient weather conditions. As I drove closer to the facility the source of the steam became apparent.
For those who own and operate large ammonia refrigeration systems the consequences of this legislation may be far reaching.
Disregarding any political or environmental viewpoints on this subject one issue that should be interesting to discover is the impact of this legislation on associated energy costs, if the bill passes.
Owners and managers of cold storage warehouses are often faced with minimizing their operating costs. The energy used by the refrigeration system is often a major contibutor to this cost of operation. In the attempt to limit the energy used and its subsequent cost various methods can be utilized.
What impact does location have on your energy use? Obviously, if you are located in the South or Western part of the US your ambient temperatures (wet bulb or dry bulb, depending on condenser type) will be higher year round. This can limit your efforts to lower the discharge pressure.
If you are like a lot of other ammonia refrigeration system end-users you are trying to reduce your costs associated with energy usage. You may be exposed to a constant barrage of ideas or methods of what to do. One of the more popular concepts is: decrease the discharge pressure.
OK, now what? Someone said I need to do this and everyone talks about it, but what should I do?
