Simulação de um refrigerador em ciclo de adsorção movido a gás natural por circuito de termossifão

Abstract

This work presents a procedure to calculate the mass flow rate in a closed thermal siphon circuit. It also presents the coefficient of performance of a sorption refrigerator with indirect heating. The basic systems components are a heating unit (a linear burner, an adsorber (filled with porous material - zeolith 13X), two heat exchangers and a gas feeding tank) and a cooling unit (an adsorber, a condenser and an evaporator inside the cool chamber). The refrigerator operates in an intermittent cycle, with a heating phase: the burner heats the thermal oil directly, it carries heat to the adsorber by natural draining. In the adsorber, the desorption occurs, and the water is released from the adsorber as vapor, then, it is condensed in a heat exchanger by a water counterflow, then liquid water flows by gravity to the evaporator; and a cooling phase: the burner is set off, the oil is cooled in an exchanger, by another water counterflow and returns for the adsorber. In the cooling circuit the pressure drops down, when reaches water saturation pressure, part of the water in the evaporator evaporates and the other is cooled, making frozen water or ice depending on the application. The procedure uses the physical parameters of the thermal siphon circuit and the thermal properties of the working fluid (thermal oil) to numerically estimate the mass flow rate through these new components, which were designed for this application. Other system parameters, such as performance coefficient, were also calculated. The numerical procedure was developed in FORTRAN and allows the use of various parameters in the calculation. The results show that for this new designed refrigerator, the mass flow hate of oil was of 6,12x10-3kg/s, the performance was 0,22 and a natural gas consumption of 0,222 kg for a 5,0 kg of ice production.