engleski

A Simple Model of a Thermostatic Expansion Valve Suitable for Control Purposes

The thermostatic expansion valve model, suitable for control purposes is developed as a part of a dynamic model of a refrigeration machine. A set of experimentally acquired values is used to determine coefficients of polynomials describing valve needle displacement and the refrigerant flow area for any combination of evaporator leaving refrigerant pressure, bulb temperature and position of a static superheat adjustment screw. Refrigerant mass flow is evaluated with known flow area and pressure difference between condenser and the evaporator of a refrigeration machine. Bulb dynamics is taken into account through the exponential function, using the bulb time constant, which was determined experimentally. It has been shown that simulation results correspond well with data achieved by measurement on a real refrigeration system.

modeling; refrigeration system; thermostatic expansion valve; transients

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