Most shoppers take for granted the freshness and wide selection. Contractors whose main concern is the mechanical refrigeration that helps extend the shelf life of the products also may not give much of a thought as to how the food items got to the refrigerated units they service.
Rapid refrigerated transport ends up being an important part of the food delivery equation.
Once fresh food products leave the farm or the processing plant, proper temperature control is essential. Products in trailers and containers must be kept within a narrow temperature range to prevent spoilage and maximize product life. For frozen products, maintaining low temperatures ensures food quality. Allowing the temperature to drift outside the optimum range can shorten the shelf life of foods.
TRANSPORTATION APPLICATIONSSpecialized refrigeration equipment is needed for transportation applications. The loads that need cooling are often large, yet the refrigeration systems must be extremely compact. A single refrigeration unit must be capable of providing cooling for any product, from ripening bananas to frozen meat to ice cream, with up to three different temperature ranges, and sometimes all three in one load. Government regulations are becoming stricter and proof of continuous proper storage temperatures is becoming a requirement.
Resistance to vibration and corrosion are critical parameters in the selection of components, too, because the systems operate in a harsh environment. At sea there is salt spray, and significant changes in temperatures from morning to night. Traveling by rail or truck, containers and trailers are subject to physical shocks, vibrations, and changes in the heat load.
Manufacturers have had to develop refrigeration components to deal with such situations. For example, TU expansion valves from Danfoss are said by the company to be compact, strong, and lighter than comparable traditional brass-bodied valves. Their stainless steel construction is designed to make them resistant to corrosion over a wide range of temperatures.
The TU valve is deep drawn from a sheet of stainless steel. Developers of the technology said it is less subject to inertial shock than a heavier brass valve. It is less affected by vibration, and improves the overall resistance to the system to vibration, the company states.
Another component in the transportation equation is filter-driers. The Eliminator® brand is an example of a component that is coated to resist both salt spray and swings in temperature.
For more information, contact Danfoss Air-Conditioning & Refrigeration at 410-931-8250.
Publication date: 11/04/2002