Produce Processing recently published the following article here.
Comments by Bruce I. Nelson, President, Colmac Coil Manufacturing
With regard to energy saving/efficiency for industrial food refrigeration systems and operation, what are the most common (or biggest) areas of inefficiency you tend to come across?
There are many opportunities to save energy and increase operating efficiency with industrial food refrigeration systems. Some opportunities are related to the components themselves, the compressors, condensers, refrigerant feed system and pipework, and evaporators found in the system.
- Were the components selected with energy efficiency in mind when the plant was built?
- Have the components been properly maintained over the life of the plant?
- Was the control system properly designed and is it being operated optimally at full and part load?
Other building design and operational issues will also affect the power consumption of the refrigeration system such as, doorway design, activity, and maintenance, lighting systems, underfloor heating, and thermal envelope and vapor barrier integrity. This is a big topic and too much to tackle in a single article!
What are your recommendations on ways to improve it, whether it be through new equipment or technology or employee training or whatever?
As a manufacturer of air cooling evaporators having had the chance to observe many operating refrigeration systems over the years, we see the design and operation of defrost systems as a significant opportunity to save significant amounts of money with a relatively small investment. It has been shown (see: Optimizing Hot Gas Defrost) that as much as 60% of the heat that is expended during a defrost cycle is lost to the refrigerated space due to convection of heated air and evaporated moisture. This wasted heat can very effectively be captured at the air cooler by installing return air defrost hoods and discharge air socks (see: Energy Efficient Defrost).
Other benefits having to do with reduced amounts of frost and ice accumulating on ceilings walls are also realized when installing these accessories. The low cost and high efficiency of the hoods and discharge socks typically result in a simple payback of 1 year or less. With these devices installed defrost time can be reduced, in many cases by as much as 50%, and we find that other problems are solved such as ice accumulation in drainpans.
Proper hot gas defrost piping both internal and external to the evaporator is also critically important to the energy efficiency of the defrost cycle. In a word, the fewer and shorter the defrost cycle for a given evaporator the better. The author has seen evaporators defrosting for as much as 60 minutes when with proper piping of the pan loop, coil, and control valves the defrost should last no more than 10 minutes. i.e. Six times more heat is going into the room during the 60 minute defrost than is necessary!
- Return air hoods and discharge socks
- Proper piping and reduced defrost times