Condensers. motor watts may also be realized.

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2 Condensers The air cooled condenser is one of the 4 basic components of a the refrigeration cycle, yet over time its full potential and features have been stripped down to the basic function of rejecting heat in order to reduce first cost. Condensers are designed to perform the single function of condensing refrigerant, but are not designed to allow for degraded performance when dirt accumulation and corrosion have set in after a short period of operation. Fowling of the secondary, or finned surfaces of a condenser will degrade system performance by elevating system s head pressure causing the compressor to expend more energy for the same net refrigerating effect, and at the same time reducing its expected life. In addition, condensers used in off-the-shelf condensing units are designed to cover a wide operating range (suction temperature and ambient) and are not built to meet the specific applications. These issues are compounded where there are multiple condensing units operating various refrigerated fixtures and applications. A typical YUM KA60 fastfood outlet will have up to two condensing units for the walk-in cooler, and one condensing unit for the walk-in freezer. Although the KA60 layout does not use remote air cooled, the rack concept can be expand to include condensers for the ice machines, and drink machines. While the cooler and freezer units arrive factory installed on the outdoor walk-ins, in many cases these units are spread over the roof with multiple roof penetrations for piping and electrical services, and each with there own fractional horsepower fan motors draining energy and maintenance costs from the operation. A solution to such a problem is to consolidate all of the larger condensing units into one rooftop unit with a single multi-circuited condenser coil (see Fig. 1.) There are a number of advantages to a multi-compressor rack system that need to be explored, and one of the primary features is that only one condenser coil is required with 2 fan motors to handle the heat rejection requirements of the entire store. The result is that many individual condenser fan motors can be reduced from 6 to 2, and depending on the quantity and power draw of the motors, a reduction in fan Figure 1 (Typical multi-compressor rack layout) motor watts may also be realized. The selection and sizing of the condenser can be engineered to include features and benefits not realized in an off-the-shelf design. Allowing for a larger condenser can afford the

3 following benefits and features; subcooling, reduced refrigerant charge, and redundant capacity for high ambient conditions and/or condenser fowling. A properly sized condenser with subcooling circuits will allow the systems to take full advantage of floating the head pressure when outdoor ambient temperatures drop. A rule of thumb is that for every 1º drop in ambient, ½% in energy reduction can be realized. Floating the head pressure is not a new concept, but has traditionally been used in larger horsepower systems, and not in smaller systems. Hence, the reason for off-the-shelf condensing units having no subcooling circuit. The subcooling circuit ensures that the liquid refrigerant entering the expansion valve is free of any flash gas, which is even more prevalent when head pressures are low due to low ambient temperatures. Flash gas will cause erratic performance by the expansion valve, and in turn will reduce the evaporator s performance. In addition subcooling takes advantage of the free cooling effect when ambient temperatures are lower, and will increase capacity by ½% for every 1º of subcooling. XDX The XDX Xstream device coupled with the XDX Adjustable Refrigerant Metering Evaporator Device (A.R.M.E.D.) are a multi-functional add on feature to a refrigeration system evaporator that changes the characteristics of the refrigerant flow pattern through the evaporator. This change converts a typical Stratified Wavy flow pattern in the evaporator tube to a more heat transfer efficient annular flow pattern (see Fig 2.) There are two primary advantages of annular Gas Liquid Refrigerant Oil Gas Liquid Refrigerant & Oil Mixture Stratified Wavy Flow Annular Flow Figure 2 flow 1) even primary heat transfer surface (i.e.: evaporator tube wall) temperature from inlet to exit of the evaporator, and homogeneous mixing of liquid refrigerant and oil. This minor change in refrigerant flow has shown to have major refrigeration advantages as witnessed in field test at an operational fastfood outlet in California to be discussed shortly. In addition, Carrier (ICS) is currently field testing XDX components at operating YUM restaurants in the state of Florida. In addition, to the improved heat transfer performance and energy savings created by the Xstream device, there are a number of ancillary benefits that can enhance the compressor s

4 expected life and can reduce a store s maintenance costs. Many have to do with lubrication issues, which according to Copeland Corporation is a primary cause of compressor failure. The annular flow created by the Xstream device substantially improves oil return back to the compressor, as well as lowering the compressor discharge temperature which often exceed the critical point for oil breakdown. The improvement in evaporator performance, which creates a smaller TD, and slightly higher suction pressure, also causes a reduction in head pressure as shown in the Pressure- Enthalpy (P-H) graph in figure 2a. These changes in the systems operating pressures in effect are reducing the compression ratio, which reduces energy consumption, but also lowers the operating stresses on the compressor, and enhances the compressor s operating life by reducing wear-and-tear. Figure 2a (P-H chart) Refrigeration cycle with XDX Refrigeration cycle without XDX Guardian Electronic Controls Electronic controls are becoming more accepted in refrigeration than ever before. There has been a reluctance to use electronics because of issues with replacement part availability, operating environments and the industry knowledge. But as time has gone on, electronics are becoming more sophisticated and user friendly. A newly developed electronic controller for individual refrigeration systems, has been field tested and is ready for market release (see Fig. 3) The controller uses the latest EPROM microchip technology, and Figure 3 (Guardian Controller) past industry stumbling blocks to create a control system that has features and advantages that are unsurpassed in its price range. The control has a number of basic algorithms to allow it to control box temperature, defrost, superheat, alarms conditions, as well as advanced routines that allow the user to adjust the electronic/electric expansion valve response by adjusting the PID variables, remote access through a Windows based program, master slave configuration, and a compressor protection feature, to mention a few. The system allows for application any of the electric or electronic

5 valves available on the market today, these include the Sporlan SIE bi-polar stepper valve, Parker 625 electric valve, Alco ESVB Bi-polar stepper valve, Parker HP/HF Pulse Width valve. The board has a 3 character alphanumeric display that can be remotely positioned from the unit, as well as a detachable relay section for easy field service. The circuitry has been fully filtered to protect it from RF interference that can be created by gas spark ignition systems typically found in fryers and grills. Alarm conditions and states can be set, and algorithms have been built-in for contingency situations such as a failed sensor. In addition the board has an automatic reset that will restart the board should there be an unusual event that would shut the board down such as a low voltage condition. Such contingencies, and features are unparalled in a board of this size. Performance and Field Test Results A field test was coordinated with a fastfood chain outlet located in Southern California. The store has one walk-in cooler and one walk-in freezer with a refrigerated drink machine connected to the Coldzone multi-compressor condensing unit. The Coldzone system has the following features: low and medium temperature R404A system, subcooling circuits, XDX Xstream devices with ARMED adjustable orifice, Sporlan SEI electronic expansion valves, Parker ERC electronic controller, 12,000 BTU Coldzone electric defrost freezer coil, 13,000 BTU Coldzone air defrost cooler coil, and 2 ice/drink machine condenser circuits. At the franchisee s discretion, the Hoshizaki ice machine was connected to a separate Hoshizaki condenser. The store has been in operation since November 2002 and, the system was fully instrumented for data acquisition. Data was collect by a hyper logger as well as with the Parker ERC controller via phone lines and by the Internet. A sampling of the data was evaluated for a two week period in January 2003 period, and was matched to historical data from identically sized store located in Illinois with the same outdoor temperature profile. The results of the test and additional observations are as follow. The evaporators had seen a marked increase in performance, more specifically almost a doubling of the evaporator s output measured as a the Temperature Difference (TD) between the liquid refrigerant and the room air temperatures. The evaporators were selected for a 10º TD, (25ºF suction, 35ºF room for the cooler, and 20ºF suction, -10ºF room for the freezer.) The reality observed is that both evaporators are operating as if they were selected for 5º TD operation. This change in performance reduced pulldown times, reduced defrost periods, reduced number of defrosts per day, reduced frost accumulation in the room and on the fins, and reduced energy consumption. The freezer pulled down 30% faster than the baseline store. This is significant because no refrigeration system is ever in a steady state condition for any extended length of time. A

6 freezer and cooler are as dynamic as the activity in the store, from defrost cycles, to product being loaded into the boxes, to product being removed on a repetitive basis, to checking inventory, the doors are opened and closed for varying periods of time, allowing warm humid air to infiltrate into the refrigerated space. Faster pulldown time allows the box to attain the required storage temperature quicker, and resulting in less thermal shock to the product. The number of defrost period on the freezer were initially reduced to one per day, and then reduced further to one every 3 days. One of the inherent characteristics of the Xstream device is the creation of an even frosting pattern across the entire finned area of the evaporator. Contrary to current evaporators where frost builds unevenly and typically at the inlet air side of the finned surface, with the Xstream device the frost builds evenly on the entire fin from top to bottom, air inlet side to the air outlet side. This effect is caused by the annular flow inside the evaporator tube by the liquid refrigerant, which maintains the tube wall at a consistent temperature from inlet to outlet. With an even frost build-up on the coil the amount of moisture that would adhere to the coil is spread across the entire finned surface, and does not throttle the air gap between the fins and thus starving the evaporator of air. Defrost periods were also quicker because of the thinner and evenly distributed frost pattern across the fins. Defrost times for the freezer averaged 19 minutes on the freezer as shown in figure 4, versus 30 minutes for other evaporators. Because of the tighter TD in room created by the Xstream device, the amount of moisture in the air is maintained much closer to its dew point. Even though air retains less moisture at Figure 4 (Freezer data) lower air temperatures, maintaining a tighter TD (5º versus 10º) results in less refrigeration needed to meet the room temperature requirements. The typical 10ºTD defrost-refrigeration cycle takes the following path. When the system goes into defrost, the frost on the coil melts and a percentage of moisture is reintroduced back into the room by steaming, and a percentage is expelled from the room down the drain. As the system goes back into refrigeration and the room temperature drops, the steam created during defrost has brought the moisture level in the room back up to 100%, and freezes back onto the fins of the evaporator as well as on the walls, ceiling, and evaporator outlet. The system reaches the room set point temperature during pulldown, and has also brought the room s moisture level down to an equilibrium point below the dew point as well. When the door is opened to the room after the pulldown cycle, warm moist air infiltrates the room increasing the room moisture level back up to saturation. The next time the system start up to satisfy temperature, it will also need to remove

7 the added moisture from the room in order to satisfy the room temperature. This is a vicious cycle, and the main reason for having to have frequent defrost cycles over a 24 hour period. The Xstream device limits this cycle by allowing the refrigeration system to operate closer to the rooms dew point, and thus eliminating frequent defrosts, and in turn reducing energy consumption. Energy consumption was reduced in relation to the baseline store, and was annualized to a savings of $ This calculation is based on the following parameters: KWh Savings per Year 2,190 $.12KWh $ Peak Demand Reductions in KW $ Savings by converting evaporator fan motor from Shaded Pole to PSC $ Estimated Total Annual Saving $ The store franchisee will realize a Return On Investment in 9.0 months. It is worthwhile to note that the baseline store has electronic controls and floating head pressure control. When extending the energy calculation to systems using mechanical expansion valves, and flooded head pressure controls, the savings calculate to be $ In addition to energy savings, the advanced refrigeration rack can provide improved product shelf life, and additional food safety in the cooler and freezer. This is especially true in the cooler where refrigerated products are at a greater risk of perishing. Figure 5 shows sample data from a 2 week operating period where the cooler temperatures were maintained at an average temperature of 33ºF. This keep product stored at a temperature well below the 41ºF threshold Figure 5 (Cooler data) for food safety, and provided a buffer for any temperature spikes that could occur during loading or unloading of the cooler. In addition, the lower storage temperature can enhance shelf life by reducing bacteria growth. A study performed by Silliker Laboratories concluded that product with a traditional shelf-life of 3.3 days would have a 5 day shelf-life when temperature is held constant. The data from this study supports the claim that the XDX refrigeration concept can produce a significant increase in product shelf-life. Improved shelf life will result in less waste, and reduction in risk of spoiled product, resulting in the store s financial performance. Quantifying such savings depends on the store s operating procedures, traffic, etc, but numbers have been estimated in the range of $25 to $100 per week, or $1,300 to $5,200 annually.

8 After evaluation of the initial performance data, further changes were made to the test store s compressors. Data reveled that the two compressors were operating well below their expected operating times because of improved system performance created by the Guardian controller and the Xstream device. The freezer compressor was operating 73% of the time, and the cooler was operating 20% of the time. This is meant that the equipment was performing better than expected and that the compressors could be reduced in size by approximately 20 percent in order to take advantage of a lower power draw. A program has been set in place to reduce the compressor sizes by at least 20% at the test site, and then chart performance. Results are still pending but are expected to yield additional energy savings, as well as reduce the initial refrigeration equipment cost. Summary Taking a fresh approach to enhancing the traditional vapor-compression refrigeration cycle by incorporating a series of performance enhancing devices and minor design changes has shown to return a number of long-term benefits as well as a return on the investment (9 to 24 months on average depending on feature set, application, energy costs, and climate conditions). In addition, the benefits gained from the enhancements such as subcooling, floating head pressure, Guardian, XDX, condenser circuits, etc., as well as using a multi-compressor rack, can reverse the accepted foodservice paradigms of higher operating costs and operational disruptions. Defrost problems, ice and frost build-up in the freezer box and on stored product, high maintenance costs, down time due to maintenance, etc, are real issues that can be eliminated or reduced, thus in effect increasing the return-on-investment over the life of the equipment. The refrigeration systems are a definite necessity to any foodservice installation as food products need to be, 1) readily available, 2) kept safe, and 3) kept fresh. The current refrigeration systems perform these basic necessities, but in most instances, do not do it efficiently, effectively, or with any redundancy for temperature spike, or reduction in performance due to aging and fowling of the equipment. Serious consideration needs to be given to the overall operation costs of the traditional refrigeration system in comparison to an enhanced system. Figure 6 depicts annual and cumulative savings using a YUM Brands KY-60 store configuration with two 1.5 HP coolers, and one 3 HP freezer. Savings are calculated for estimated energy reduction and product shrink. Product shrink was assumed to be $25 per week for due to expired shelf life and/or spoilage. Energy savings are based on $0.12 per KW-h, and a reduction in demand charges of $15 to $32 ($50) (9 months at lower rate /3 months at higher rate) in California. Estimated preliminary equipment price difference for a rack system incorporating Guardian, XDX,

9 etc., will be approximately $3,500. Although maintenance costs will be a factor in calculating savings costs, it is has been taken out of the equation for simplification. Based on past experience, it can be assumed that there is a strong probability that at least one of the 3 compressors will fail during a 10-year period. A single compressor failure can run between $1000 and $1,500 to repair, plus any lose stored product due to a rise in temperature. Such failures can Figure 6 - Cumulative Savings Using Enhanced Rack System on KY-60 store Estimated Annual Savings and Cummulative Totals ($) $25,000 $20,000 $15,000 $10,000 $5,000 $0 -$5,000 ($1,370) "19 month ROI for upgraded system" $930 $3,230 Energy Savings Reduction in Product Loss Cumulative Savings $5,530 $7,830 $10,13 0 $12,430 $14,730 $17, Year(s) in Service $19,330 be reduced, through the enhanced features of the rack system. Excluding the additional financial advantages from the savings shown in figure 6, i.e.: working capital improvement, interest, etc., the advantages of an enhanced rack system can far out weight the upfront feature of a lower first cost basic refrigeration system.