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1989 IIAR Technical Papers
11th Annual Meeting
The CFC Issue --- What and So What! An Update!
Author: Sydney M. Miner, P.E.
The list of industry or government organizations involved in the CFC issue is too lengthy to comprehend. Almost all are involved in activities relating to research, regulation, standards development, training, political activism, etc. At the outset, I will relate this subject to the overall subject of research. The search for alternate refrigerants to replace the targeted CFCs is being carried on aggressively around the world. What has IIAR been doing and what should we be doing? As industry leaders in industrial refrigeration we should be interested in and following all of the developments regarding the CFC issue. In particular, this should involve training and proper procedures for conversation (emissions control), leak prevention, reclaim AND switching to alternate refrigerants.
Growing Opportunities for Ammonia Users
Author: W.F. Stoecker
The intensive search for suitable replacements for the banned CFCs is focusing on nonfully halogenated CFCs, mixtures of two or more refrigerants, and also on some traditional refrigerants, such as air, water, hydrocarbons, and ammonia. Ammonia is a well-entrenched refrigerant in industrial service and has numerous advantages, such as low cost, as well as favorable physical, thermodynamic, and transport properties. Also, because of its odor, ammonia is self-alarming in the event of a leak. Along with its many advantages, ammonia has one major drawback-the low concentrations in air that constitute toxic levels. Ammonia cannot seriously be proposed as a replacement for the banned CFCs in all situations, but those applications should be identified where the advantages of ammonia can be exploited and its risks can be circumvented. This paper proposes that in addition to the expanded use of ammonia in industrial applications, certain water and antifreeze liquid chilling applications should be advanced.
A History of Thermosyphon Oil Cooling
Author: Henry B. Bonar II
Thermosyphon cooling offers a viable alternative for effectively cooling oil, through the use of the gravity/hydraulic effect of two-phase refrigerant flow through an oil heat exchanger. This would eliminate the need for secondary fluid circulating pumps, maintaining and cleaning of heat exchangers, and would preclude mixing liquid refrigerant (in injection sytems) with lubricating oils during the compression process. This should provide a mechanically simpler and more efficient total work process. Although applicable to all forms of refrigerant compression, it is of particular significance to screw compressors which require large quantities of oil to both lubricate and seal clearances of rotating lobes during compression.
Wet Air Cooling
Author: Steven M. Benz
The practice of cooling and storing fruits, vegetables and flowers in a high humidity atmosphere has been practiced for many years in the U.S. using technology which has advanced little since its introduction. Recently, this practice has gained wide attention in Europe as growers and distributors react to several market forces demanding improved control over food quality. This new interest has stimulated the development of more efficient Wet Air Coolers and the mating of Wet Air Cooling with improved thermal storage systems. The purpose of this paper is to give examples of the current practice in Europe for cooling and storage of fruits, vegetables and flowers.
Removing the Mystery from Computerized Refrigeration Control Systems
Author: David A. Murphy and Arthur J. Marshall
The intent of this discussion is to explain the basic elements, functions, and techniques required to apply a digital control system to an industrial environment. This discussion will explain how to monitor parameters in the industrial environment and convert these parameters such as temperature and pressure to binary numbers so that the diqital control system can be programmed to react to these parameters. The scope of this discussion will not include programming techniques, but will include digital I/O, sensoring, A/D conversion, and D/A conversion.
Designing the 1988 Olympic Bob-Sleigh and Luge Facility
Author: Robert T. Crawford
The unique features built into the refrigeration system of this facility are: (a) The size of the plant at 4410kW (1255 T) is the largest in the world, because of the unpredictable weather conditions and the long season that it is intended to operate. (GI Precautions taken for the safety of the public are numerous. The use of seal cap valves, all welded construction, elaborate expansion piping to each evaporator, heavy piping insulation that tends to camouflage the piping and the design to avoid public contact with any refrigeration devices except where absolutely necessary. (b) There are over l00km (62 miles) of small bore piping to make up the evaporators including about 90km (56 m.) of 33.4mm (1") pipe, 1000 refrigerant valves from l0mm (1/4") to 350mm (14") nominal with over 600 on the track alone and 175m3 (95T) of liquid refrigeration grade ammonia. (c) The use of direct refrigerant in the evaporators keeps costs down. It is estimated that if an indirect refrigeration system using brine had been used then the plant capacity would had to have been increased by at least 30% and operating power would have increased at least 60%. This would have resulted in an increase in overall track costs. (d) Mixture of reciprocating and screw compressors was used for optimum operating cost and maximum flexibility. (e) Thermosyphon cooling was used for oil cooling of the screw compressors for simplicity and operating cost saving.
Removal of Ammonia Vapors After a Spill
Author: John N. Mittendorf
Is Positive Pressure Ventilation a new and more cost effective approach to effectively remove ammonia vapors within a structure? This concept is currently being used and promoted by numerous fire departments around the country as a fast and effective means of clearing a structure of heat, smoke, toxic gases, and in some cases, directing fire away from firefighters during fire suppression and overhaul operations. To understand Positive Pressure Ventilation, lets take a look at the term "Ventilation" and how it can be applied to removing ammonia vapors from a structure.
Liquid Refrigerant Level Control - An Update
Author: John Yencho
The monitoring and control of liquid level in refrigeration systems is a very important key to proper operation of the systems. Because the normal refrigeration vapor cycle is a two phase system, liquid and gas exist together in various vessels within the piping circuit and must be controlled to an extent determined by the complexity and size of the refrigerant charge. Liquid level controls for refrigeration are primarily used in the industrial and large commercial systems. Therefore, this discussion will talk about the use of mechanical, electro-mechanical and electronic level controls with regard to ammonia and large fluorocarbon systems. It will not touch on the liquid level control of oil as in the crankcase of reciprocating compressors or in oil separators nor on other associated system liquids such as chilled water, condenser water, or various brines.
Proper Selection and Application of Motor Starters on Screw Compressors
Author: David E. Walton
The expensive down time and costly rewiring described in our case histories can be avoided by paying attention to the selection and application of the motor starter prior to the installation of your screw compressor. The recommended steps are: (1) Select the proper type of starter. (2) Coordinate the selection of the starter with the compressor manufacturer's equipment. (3) Make sure the starter has proper motor protection.
Static Ice Systems
Author: Thomas H. Pakradooni
The use of air agitation keeps the tank at a uniform temperature which ensures building of ice from the top to the bottom to be consistent. The air agitational so eliminates any possibility of water channelling through warm sectors of the tank. This would, in turn, melt ice off at greater rates at different points of the tank. In addition to air agitation and pipe spacing, water circuits are utilized to improve even ice melting. Wherever batch loads occur, static Ice Builders have a home. They provide a sure means of ensuring chill water regardless of fluctuations in demand. The Ice Builder, for many years, has been referred to as a flywheel implying that it will keep providing the chilled water even though its subjected to sudden load shocks.
Dynamic Thermal Energy Storage Systems
Author: Gary S. Chafee
The recent emphasis on Thermal Storage equipment is occurring for two reasons: A. Electrical rates structured specifically to encourage thermal storage to more effectively utilize existing generating capacity. B. The innovation of harvesting thermal storage equipment. Since many of you are aware of the incentives being offered by utility companies, this paper will focus on dynamic, ice harvesting thermal storage equipment.
Economic Evaluation of Static vs. Dynamic Ice Storage Systems
Author: Steve Horton
A static ice storage system is one in which the ice remains on the evaporator surface. A dynamic ice storage system harvests, or "shucks" ice, into a storage bin. An economic evaluation means different things to different organizations. The economic guidelines used here to evaluate the two types of ice storage technology are first cost and operating cost. A more complete analysis might include economic indicators such as simple payback, rate of return, and net present value.
Hydraulic Shock in Ammonia Systems
Author: L. Lane Loyko
Since my first hydraulic shock failure case, I have worked on several others. Failure sizes have varied from 1 1/4" to 24" in circumference. All have started in welds. All have been associated with low temperature systems with refrigerant temperatures below -20°F. All have been associated with hot gas defrost. Where analytical calculations have been done, estimated surges have been at pressures above relief valve settings but there has never been evidence of the relief valves lifting. Failures have always been associated with excess liquid in the failed component and there was always the possibility that the component was completely full of liquid.
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