Secondary and Indirect

For its advocacy of its Cool-Fit™ piping system, GF Piping Systems discussed secondary and indirect refrigeration systems in a product brochure.

“The design of refrigeration systems in supermarkets is going through a state of flux probably never seen since the conception of man-made refrigeration some 130 years ago. The main drivers are concerns regarding the environment and compliance to regulations being enforced locally and globally to reduce refrigerant charges,” stated the literature.

Everyone is working toward the same fundamental goal: being environmentally friendly at no extra investment cost. To achieve these goals, the brochure stated it would appear certain that secondary piping will be playing a major role in the design of the future.

“Whether in CO₂ cascade systems with medium-temperature indirect glycol refrigeration or complete indirect systems with salt solutions for both low- and medium-temperature operations, secondary systems will play an important part in the future, efficient, maintenance-free running of the complete refrigeration plant. … When correctly designed, using dedicated components, secondary systems can provide lower running costs, increase quality of food (weight loss reduced), and improve reliability by reducing maintenance.”

The company noted that the only open question would appear to be investment costs.

“Here, the cost of the components can increase investment costs. The primary reason for this is the present relatively low demand for secondary components. As demand from end users increases, the investment costs will rapidly decrease, and experience in areas of the world where secondary systems are commonly used has shown that investment can be reduced to present levels compared to traditional direct-hydrochlorofluorocarbon (HCFC) systems.

Transcritical CO₂

In discussing Micro Thermo Technologies’ products for transcritical CO₂ (TC CO₂) systems, Parker Hannifin Corp. prepared a report on the advantages and benefits of TC CO₂.

“Transcritical CO₂ systems are desirable because they use no hydrofluorocarbon (HFC) refrigerants,” stated the document. “Transcritical CO₂ systems, in particular, have very good heat rejection — which is captured and re-used for space and water heating — and overall lower cost of ownership due to lower energy and refrigerant costs.

“Once the decision was made to move forward with a pilot store utilizing transcritical CO₂ as a refrigerant, a number of challenges had to be overcome. Among those challenges were the need for specialized compressors and a way to control them and the very high pressures that are utilized in transcritical CO₂ systems. Since both of these subsystems were new and relatively unfamiliar to this food retailer, the support needed to specify, install, commission, and support these systems was critical.

“Micro Thermo Technologies provided rack controls, case controllers, condenser controls, temperature and pressure monitoring, and the Alliance software management suite that ties all the subsystems together and monitors and collects data from the entire system.”

Getting A Boost

Hillphoenix’s Advansor system factors in as a TC CO₂ booster system. That booster approach was used in a Pick ‘n Save supermarket in Menomonee, Wisconsin.

“The Advansor Transcritical booster system entirely eliminates the use of HFCs,” stated a case study examining the application. “Increasingly, food retailers are moving toward more sustainable natural refrigerants, including CO₂, glycol, and ammonia. In addition to the green appeal of CO₂, it’s a much less-expensive alternative to HFC refrigerants at around $1 per pound.

“So, why haven’t more retailers made the switch? CO₂ systems are still relatively new to supermarket applications, and some question the higher capital cost involved with CO₂ systems.

“The technology does cost more money, but the installation cost is lower than similar systems we’re using elsewhere. Also, CO₂ is cheaper on the operation side compared to glycol and other refrigerants.

“The Advansor Transcritical CO₂ booster system utilizes CO₂ as the only refrigerant covering both medium- and low-temperature loads.

“CO₂ has a high-temperature heat of rejection, making it ideal for heat reclamation applications and efficient hot gas defrosting,” stated the company.

“CO₂ systems operate under much higher pressures than conventional HFC-based systems. Many CO₂ systems require steel piping throughout and carry a higher risk of pressure-related system breakdowns. The Advansor system eliminates those concerns by perfecting the use of pressure-reducing valves so that everything inside of the store operates under lower pressures, as it would with an HFC-based system,” stated the study. “Contractors can use copper piping, and retailers can rest easy knowing their Advansor systems maintain pressures within a range normally found in traditional DX [direct expansion] systems.”

TXVs

Thermostatic expansion valves (TXVs) are also coming in for change, as noted by Danfoss with its TU TXV with f-charge. “There is a highly engineered bulb charge and superheat setting designed for low, stable superheat across low- and medium-temperature refrigeration ranges. By minimizing superheat, systems run more efficiently, saving energy,” stated a Danfoss product brochure.

“By maintaining a consistent temperature, product shrinkage is reduced. The new bulb charge and superheat setting require no or little field adjustment, and the bimetal connections require no wet wrap while brazing, so installation and setting time is dramatically reduced. The valve features an exchangeable orifice design, which means that, with one valve and five orifices, you can replace any of 10 valves, thus reducing truck stock. The valve’s laser-welded element ensures diaphragm integrity, extending life compared to plasma-welded valves, and the stainless steel capillary tube ensures a trustworthy installation by protecting the most common breakage point of TXVs.”

Publication date: 9/8/2014

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