CONSTRUCTIVE FEATURES OF TRANSCRITICAL BOOSTERREFRIGERATION SYSTEMS
Journal Title: Прогресивні техніка та технології харчових виробництв ресторанного господарства і торгівлі - Year 2017, Vol 2, Issue
Abstract
Natural refrigerants are becoming increasingly important (air, water,hydrocarbons, carbon dioxide and ammonia) in connection with the measures whichare taken by the international community for reducing of production andconsumption of ozone destruction substances and greenhouse gases. Dioxide of carbon (carbon dioxide, СО2, R744) is one of the most promisingnatural refrigerants, which can be used as working substance in variousrefrigeration systems. Distinctive feature of refrigeration systems which operate on the base oftranscritical cycle with use of CO2 is the state of overcritical fluid in whichrefrigerant is on the high pressure side, it causes high values of the heat transfercoefficient and low values of viscosity. Transcritical refrigeration systems with useof CO2 became widespread in refrigeration systems of retails. Compared withtraditional plants with use of chlorofluorocarbons (CFC) refrigerants, the use of thetranscriptial system under moderate climate allows reducing annual energyconsumption by 15–20%. To date, transcritical booster refrigeration systemsbecome the most widespread. The booster system is a system where two stages ofcompression of one refrigerant exist. The computational pressure in the highpressure section, as a rule, is from 90 to 120 bars, working pressure is from 45 to100 bars. The main difference of the transcritical booster refrigeration system is theheat exchanger; it is gas cooler which is intended for cooling of the compressed tohigh pressure refrigerant. The construction of the gas cooler compared to the existing traditionalcondensers is much more complex, including increased working pressure (up to 150bars), which is almost in 4 times higher, and in 2 times higher temperature(+150°C) and it has a number of features. One more significant constructive difference is the necessity to maintainintermediate pressure in the receiver of the transcritical refrigeration system in caseof idle time. Increasing of the maximum working value of pressure for system’scomponents should be taken into account. For the system with use of CO2, thepressure under idle time can reach values of 65–80 bars (which corresponds to thetemperature of 25–30°C). It exceeds the maximum working pressure of most components of the system and requires additional measures for pressure reducingand maintaining. The auxiliary cooling system of the receiver and partial release of CO2 intothe atmosphere are the most commonly used measures for pressure maintainingunder the transcritical refrigeration plant stoppage. The vaporizers of transcritical refrigeration plants are not exposed toparticularly high pressures. Usually the maximum working pressure is within 45–60bars. Such pressure does not require special construction of evaporator, but onlysome adjustments to the thickness and diameter of the pipes. The sizes of the158pipelines of plants can be significantly reduced due to the efficiency of CO2. Usuallythe diameter is from 3/8 "to 5/8", and it is possible to use evaporators of smallersizes for necessary productivity providing.It is necessary to note one more important constructive feature it is thepossibility of efficiently use of recuperation for receiving hot water for technologicalneeds and heat-transfer agent heating in transcritical systems with use of CO2. Allheat is highly potent, that is why actually all overheating can be used by shutdownof gas cooler if it is necessary.
Authors and Affiliations
Володимир Потапов, Олена Петренко, Дмитро Семенюк
Keywords
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- EP ID EP248178
- DOI 10.5281/zenodo.1108567
- Views 69
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