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Understanding Industrial Refrigeration: A Q&A with Chuck Taylor, PE
In 2018, Smithfield Foods celebrated the grand opening of a new cold storage distribution center that would serve the northeastern United States. Having the right partners was critical to the success of this complex and innovative project. Chuck Taylor, PE, is one of those partners. Chuck is now the Senior Vice President of Engineering for Republic Refrigeration and has been working in industrial refrigeration for 30+ years. We talked with him about what made the Smithfield Foods project so unique and how industrial refrigeration is changing.
Read our case study about Smithfield Foods’ distribution center.
Q: Tell us a little about your background. How did you get into industrial refrigeration systems and what do you like about your work?
When I graduated in 1984, I went to work for Patterson Enterprises. I didn’t know what refrigeration was, let alone industrial refrigeration, but they were one of the largest contractors at the time. I had stumbled into industrial refrigeration by accident and have loved it ever since. Two years later I joined The Stellar Group. I held just about every position available from refrigeration engineer to the senior vice president where I was responsible for all industrial refrigeration activities.
Q: We recently partnered with you on a cold storage distribution center for Smithfield Foods. What makes that refrigeration system unique?
Smithfield wanted a facility that utilized the latest refrigeration technology, was energy efficient, and minimized the risk of large charge ammonia systems. They were dedicated to leading the industry in both sustainability and responsibility. The facility ended up achieving LEED Silver certification.
We used anhydrous ammonia for our refrigerant (0 GWP, 0 ODP) and configured the system architecture around electronic direct expansion technology. This technology enabled us to refrigerate the entire 400,000-square-foot distribution facility with less than 9,000 pounds of anhydrous ammonia. A typical distribution facility using the industry-standard ammonia liquid overfeed architecture would have required approximately 60,000 pounds of ammonia. This new technology represented an 85% reduction in anhydrous ammonia.
This remarkable reduction was achieved using direct expansion of liquid feed. Direct expansion liquid feed has been around since the beginning of refrigeration and is the primary delivery system for synthetic refrigerants. Because ammonia has so much thermal capacity per pound, conventional direct expansion valves have never worked well for ammonia refrigeration, especially in low-temperature applications. The development of electronic direct expansion valves has revolutionized industrial refrigeration and this project is a perfect example of its potential to provide reliable and efficient refrigeration at a significantly reduced refrigerant charge.
Every component of the system was evaluated to minimize refrigerant charges and improve the overall reliability of the system. The system had two suction levels, a +18 °F and a -20 °F. Both accumulators were designed to operate dry, but the potential for some liquid carryover had to be considered. Because the head of the vessel could hold a very large volume of liquid before being managed, a drop leg was added to each vessel to accumulate liquid in small quantities and be measured and managed. We used a separate glycol loop for oil cooling to minimize charge and passed it through an evaporative condenser to reject heat of compression to the atmosphere. The more constant the liquid temperature and pressure are that feed the direct expansion valve, the more accurate it will control. Thus, we designed the system so that no matter what the condensing head pressure was, the liquid feed temperature and pressure were maintained at a constant level. Finally, we installed an anhydrator on the low-temperature vessel and configured it such that any liquid that did come back to the suction accumulators ended up in the anhydrator and was boiled off to remove any water that might intrude in the system.
Q: How is the refrigeration system at Smithfield Foods helping them improve their operations?
Because the refrigerant charge was less than 10,000 lbs of ammonia, Smithfield was not required by OSHA to implement a Process Safety Management (PSM) program. However, because Smithfield is dedicated to the safety of its employees and the community at large, they developed a full PSM program anyway. Because of the technology used, the system was significantly simpler than a conventional recirculated system, so it is easier to operate and maintain. In addition, the system was specifically laid out to facilitate continued service and operations. A few of the items added to facilitate maintenance include:
- Overhead rail system for removing compressors and motors.
- All valves were located within 7’-6” of either floor or roof for easy maintenance including vessel and condenser valves.
- All evaporators were located on the roof so every component of the refrigeration system could be accessed and maintained without having to go into the plant.
- Because maintenance for the refrigeration system was moved to the roof, the roof was designed with re-enforced access paths to each piece of equipment. This means no ladders are needed.
- A high-pressure pump was added as a backup to the lowest pressure vessel in order to pump any liquid in the low-pressure vessel back to the storage receiver.
Q: The system was designed with energy performance in mind. A few of the items included to maximize efficiency include:
- Floating suction pressure
- Floating condenser pressure
- Condensing pressure controlled to maintain the lowest possible condensing with respect to the ambient wet bulb.
- Maximum condenser pressure limited to 12 °F above ambient wet build.
- System designed to be able to operate down to 65 °F SDT.
- VFD for all condenser fans.
- VFD for all room evaporators and controlled from remote temperature sensors.
Q: How have industrial refrigeration systems changed over the years? Where are they headed?
There has been more innovation and change in the industrial refrigeration industry in the last 5-7 years than the previous 30 years combined. Historically, innovation was not looked upon favorably, and “that’s the way we always design it” was the norm. Then, government regulations started driving change. First, the EPA successfully banned ozone-depleting HCFC refrigerants (R-22) and started looking at banning high global warming HCF refrigerants. The potential to ban workhorse refrigerants like R507 and R404A sent the commercial refrigeration market into a tailspin and started the commercial market looking at the potential use of natural refrigerants.
At the same time, a fertilizer plant in Texas exploded, basically leveling an entire town. This energized the government to significantly increase regulations on the use of very hazardous materials, in which anhydrous ammonia is considered. Significant pressure was imposed to reduce refrigerant chargers and the industrial market began to look at ideas and concepts develop in the commercial market to package and reduce refrigerant charges.
Consequently, the merging of industrial and commercial refrigeration began, each borrowing ideas from the other. What has come out of it is successful technological breakthroughs like Low charge DX ammonia systems, distributed refrigeration systems like the Evapcold product line, low charge ammonia chillers and CO2 / NH3 Cascade systems. All of these and many more are now standard system configurations offering the advantages of natural refrigerants while minimizing the risk of large charge ammonia systems. At the same time, Transcritical CO2 has made huge strides in the industrial and commercial market providing a natural refrigerant alternative to synthetic refrigerants. We are even seeing standard offerings with hydrocarbons for commercial applications. For the first time, viable alternatives to high global warming refrigerants are being developed that can compete on a first cost and energy bases with synthetics in the commercial market.
Read more about Smithfield Foods’ Distribution Center.