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1982 IIAR Technical Papers
New Orleans, LA
4th Annual Meeting
A New Concept for Freezing Cartoned Products
Author: G.C. Briley
The "VRT" (Variable Retention Time) Freezer for cartoned or packaged products is a major advance in Long Retention Freezer Design. It combines the advantages of counter flow heat exchange with Programmable Logic Control (PLC) and a simple mechanical system to provide an economical, automated approach to long retention freezing.
Purging and Purgers for Ammonia Refrigeration Systems
Author: Charles C. Hansen III
Most ammonia refrigeration systems have within them, for various lengthy periods of time, non-condensibles which are causing extra power consumption. This is because the majority of plants are not purging adequately or at all due to lack of understanding of the theory and benefits or even actual fear and distrust of the automatic or manual purger. Much of the effective purging which is done happens primarily in hot weather when there is a serious condensing pressure problem and a serviceman/troubleshooter is called from the corporate staff or from an independent service organization. Few plants are routinely purging systematically. Many plant operators only think of purging when condensing pressures are very obviously high, say 20 to 40 psi, above normal. There is a need for better understanding of how to detect air in systems and these techniques should be used routinely. In general, put purgers into every new system, add purgers as plant capacity increases, and replace or repair purgers which are not functioning.
Frozen Foods Warehouse Air Unit Defrosting with Inverted Bucket Traps
Author: L. L. Loyko
In order to conserve energy and to avoid suction pressure jumps during defrosting, Safeway Stores, Incorporated has been including inverted bucket traps into its design for hot gas defrost valve assemblies. These valve assemblies were, in each case, installed in recirculated ammonia systems. Safeway has had good success in all of its +35 F. Warehouses with these valve assemblies; however, in the -10 F Frozen Food Warehouses and -20° F Storage Rooms for the Ice Cream Plants there was, on the first installations, a problem of leaving ice on the bottom tubes of the coils, with the heaviest ice build up being on the air entering side. the problem was defined as a failure to drain condensed liquid In the course of analyzing these installations, ammonia from the bottom of the mils, and the solution arrived at was to pass a small amount of gas around the bucket traps through an orifice or a hand expansion valve. The amount of gas passed into the downstream suction lines was calculated to be equal to less than 1% of the full load gas generated by the coils at the design temperature difference of 12 F. This amount of gas was small compared to the gas passed into the suction line by bypass pressure regulators in older Safeway systems and, thus, represented an increase in energy savings and other advantages of bucket trap defrosting over those older systems. Gas bypass orifices and hand expansion valves have now been installed in six locations in the U.S. and Canada and the air units are defrosting completely. This paper presents Safeway's observations and analyses of the systems as well as a design criterion for the system including the calculations for sizing the components. The calculations are all based on passing an amount of either liquid or gas that will give an average coil outlet velocity of 10 FPM per circuit being defrosted. The 10 FPM velocity figure is based on on-site observations of several installations incorporating different coil manufacturers and different circuit arrangements.
Heat Recovery and Heat Pump Applications in Ammonia
Author: Vagn Villadsen & Flemming V. Boldvig/Sabroe
Heat Recovery and Heat Pump Applications in Ammonia Plants (1982)-The paper mentions a few examples of heat recovery and heat pumps utilizing the heat of condensation in ammonia refrigeration plants. Sooner or later all possibilities for recovering of waste heat will become viable. While it is not always simple to design such systems, nor easy to persuade the investor, it is nevertheless suggested that refrigeration engineers should meet the challenge, which is hidden in the saying, that our biggest source of energy in the foreseeable future is that which is wasted at present.
100 Years of Ammonia Refrigeration
Author: M.W. Garland
The information presented herein is from publications written prior to 1920, conversations with consultants, engineers and operators with experience dating back to 1890, and my own observations from 1920 to the present time including patent studies and publication information.
Fields of Application for Ammonia Compressors
Author: J.A. Noyes
The refrigeration compressor, be it of the reciprocating (piston) type or the screw type is the heart of the system and its health is dependent upon the correct selection and application of other components on the system. A full understanding of the capabilities of the compressor itself are vital, so that it can be selected and operated at all times within its field of application and by doing so can be assured of a long, trouble free and efficient life.
Data Acquisition and Control of Screw Compressors Using Telecommunications and Other Communication Links
Author: S. E. Klinger, F. M. Laucks and A. J. Marshall
In October, 1980, a new technology in screw compressor control was announced to the refrigeration industry -- solid state microprocessor control. This system has eliminated the need for gauges, thermometers, relays timers, pressure and temperature switches and indicators. The microprocessor scans various pressure and temperature transducers, as well as input/output modules and makes decisions on this information to control the compressor. The information from the transducers is displayed on an alpha-numeric display for operator readout. The microprocessor can be operator programmed for various modes of control and safety failure although the safety limits are predetermined and cannot be programmed beyond these limits. Multiple first out safety annunciation points are also programmed. The microprocessor control panel has RS-232-C communications capability which is an industry standard interface to video terminals, printers and computers. This year this capability has been extended and now opens new doors to refrigeration plant monitoring and control. By having an intelligent controller on the screw compressor package, it can now be interfaced to higher level systems which have capabilities and flexibility far beyond the programmable controller.
The Development of the Hallscrew Compressor for Ammonia Refrigeration
Author: G. W. Ashmole
It is apparent that the single screw compressor has interesting geometric features which enable it to combine the advantages of a positive displacement machine with many of the advantages of a balanced rotary machine with respect to low bearing loads. An evaluation of the single screw compressor is not complete without looking at the possibilities for development beyond the immediate horizons. Other geometries are available within the single screw concept which potentially allow small sizes of compressor and high pressure ratios to be achieved with improved performance. These geometries involve the use of conical main rotors and cylindrical gate rotors and have already been produced in the air compressor field. The possibilities for the reduction of oil with the consequent elimination of much of the ancillary equipment currently required by screw compressors is a major aspect of ongoing single screw development. The fundamental geometry and the materials of construction of the Hallscrew are both conducive to the achievement of these goals in the near future. This would then permit the screw compressor to be applied throughout the refrigeration industry with no more complication than that traditionally expected with reciprocating machines.
Piping is Piping…Or Is It?
Author: William V. Richards
With the present popularity of flooded and liquid over-feed systems in freezing plants, there exists many potential operating cost penalties due to pressure drop in overfeed risers. A new method for sizing over-feed risers to minimize pressure loss is described in this paper. Some calculated losses are shown for several different riser designs. Also two alternative methods for eliminating riser losses are reported along with field results using liquid return systems and primary coolant systems.
Life-Cycle Cost of a Cold Storage Door Repair or Replace
Author: George C. Balbach and Thomas D. Pease
The cold storage door is a unique piece of equipment. It is an integral part of any facility, and the only moving part of the structure. The door is essential to the material handling system and plays a major role in determining productivity, the prevention of energy loss and profitability. Not surprisingly, the door requires a lot of attention. It must be maintained, repaired and kept clean. This is why we will repeatedly stress great care in door selection to assure minimum maintenance and maximum reliability. Every product, however, has an Economic Life, defined as that period of time after which it should be discarded or replaced because of reduced profitability. This paper will examine a door which may be near the end of its Economic Life and suggest a process for determining available alternatives and making an effective decision.