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Mathematical description on the operation of mining electric air refrigerator |
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Mathematical description on the operation of mining electric air refrigerator Authors: K. Filek, B. Nowak, J. Roszkowski
This article attempts to describe mathematically the operation of a rnining rcfrigerating system of air cooling, which consists of an evaporator functioning as a proper air cooler, a compressor of cooling factor, a condenser and an expansion valve regulator. Surface heat exchangers (an evaporator, a condenser) were considered as units with variable parameters of media along their axis; heat exchange (air, freon, water) takes place berwecn these media. Descriptions of the operation of a counter-current evaporator and also of a co- and counter-current condenser were presented by means of sets of ordinary differential e±uations, algebraic e±uations and boundary conditions for differential e±uations. How a compressor affects parameters of a cooling factor was described by means of an equation of isentrope (isentropic compression of freon) and the influence of an expansion valve regulator by means of an equation of isenthalpe (isenthalpic expansion of freon). While describing an evaporator the possibility of water outdropping from air during the cooling process and also the existence of a zone in an evaporator, where freon is present in an overheated state, were taken into consideration. For this reason an evaporator was divided into two zones from the side of air and two zones from the side of freon, obtaining in a general case three zones different from each other because of e±uations describing them. Similarly, when describing a condenser the existence of three zones was taken into consideration: cooling of gaseous freon, freon condensation and cooling of liquid freon. Theoretical considerations were illustrated by a calculation example, whose results were presented in the form ofgraphs.
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2011