Parallel-compressor systems for refrigeration made their debut in the grocery store industry in the late 1980s, providing an alternative to the traditional split systems, or individual condensing units, used throughout commercial and industrial applications. Today about 90 percent of food stores use them in new construction and as replacement systems in existing stores. There has not, however, been similar adoption in industrial refrigeration.
Despite their advantages, parallel-compressor systems are not as widely used for applications in the food processing and manufacturing industry as they could be. With a switch from individual condensing units to parallel-compressor systems, operators can realize lower installation costs, reduced energy consumption and improved preservation of food products, among other benefits.
Solving Multiple Problems for MDS Foods
MDS Foods Inc., headquartered in Massillon, Ohio, began operating its first cheese-processing facility in 2008. Typical of food-processing plants, the refrigeration system consisted of individual condensing units and traditional evaporator design.
When it came time to build a second cheese-processing facility, MDS wanted to incorporate certain improvements in the refrigeration system. Chief among them were cost effectiveness, efficiency and a better processing-room environment.
The 40,000-ft2 facility includes a 16,000-ft2 area that requires medium-temperature refrigeration. The refrigerated space comprises a packing room, processing room, strip-and-clean room, and a shipping-and-receiving area.
MDS worked with Hillphoenix and commercial-refrigeration contractor Mathis Refrigeration, Murfreesboro, Tenn. After a review of the options, the team decided that a parallel-rack option was the best solution, according to Chris Vaught, vice president of technical services for MDS.
Parallel-rack systems were recommended by Donny Mathis of Mathis Refrigeration. Compared with individual condensing units, they are more energy efficient, cheaper to install and cost less to maintain, he says. For this reason, more light industrial facilities are looking to use parallel racks.
Installing Parallel-Rack Refrigeration Equipment
Mathis Refrigeration installed two parallel-rack systems side by side behind the building. Had MDS chosen to use a traditional split system, installation would have required supplying electrical power to each of six individual condensing units. Similarly, refrigerant piping would have needed to be run from each condensing unit to its respective evaporator. Instead, each of the two parallel-compressor systems required:
- A single-point electrical power connection.
- A single liquid line.
- A single suction line.
This approach simplified installation and lowered costs.
Efficiency. The focus on energy efficiency has intensified over recent years. Refrigeration systems present one of the most significant opportunities for reducing energy consumption in industrial and commercial applications. Parallel racks lend themselves to increased efficiency by being more responsive to refrigeration load. Where traditional split systems are designed to meet maximal load conditions and are either “on” or “off,” parallel-rack systems can match full load all the way down to approximately 10 percent of design load.
Changes Made in the Cheese-Processing Room Refrigeration System
The anti-caking agent used in processing shredded cheeses presented a different challenge. In MDS’s older facility, airborne dust from the agent settles in evaporator coils, blocking airflow and reducing refrigeration to the room. MDS combats this problem with air filters and intensive maintenance to keep evaporator coils and the processing room clean.
For the new facility, their goal was to prevent or minimize the problem. For that, Hillphoenix brought Colmac Coil, Colville, Wash., into the project. Part of the solution came from special design of the evaporator coils and fins: Low velocity coils were designed to reduce air circulation of dust from the anti-caking agent, and fin spacing was increased to reduce dust accumulation. The other part came from designing the evaporators for use with a wash-down system that automatically rinses the coils with water each day. To withstand daily rinsing, the evaporators are equipped with a wash-down duty motor and constructed of stainless steel tubes and aluminum fins.
Vaught notes that lots of efficiency was lost due to coil clogging in the older facility, which also increased maintenance costs and decreased equipment life expectancy. In the new facility, the integrated cleaning has enabled MDS to go from monthly to quarterly deep manual wash-downs of the coils. The design also allows for much easier access, enabling them to clean the entire coil surface.
“We’re able to meet our quality and sanitation standards while saving time and money,” Vaught said.
Comfort of employees working in the processing room also improved. According to Vaught, the design of the coils also makes the room feel 5 to 7°F (2.7 to 3.9°C) warmer than traditional evaporator coils when the air is blowing directly onto employees.
In large part, the success of the refrigeration project depended upon the expertise brought in from the industrial and commercial worlds. MDS needed a solution to the evaporator problem caused by the anti-caking agent — a problem not common in commercial refrigeration — and the solution came from experience in industrial refrigeration.
Achieving cost-effective installation and energy-efficient refrigeration is relevant to industrial and commercial facilities. For that, MDS relied on a contractor experienced in food retail refrigeration, where parallel-compressor systems were developed and honed to provide efficiency for commercial refrigeration and a viable alternative for light industrial refrigeration. PC
Editor's Note: This article was published with the headline, "Breaking with Tradition to Build a Better Cheese-Processing Facility," in the January/February 2017 issue of Process Cooling.