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In this paper, a dimensionless dynamic mathematical model is proposed, in order to analyze the response of single stage absorption refrigeration systems according to operating and geometric parameters. Suitable control volumes are defined in order to obtain the system dynamic response. Mass accumulation in the components is neglected, and the system is divided in two regions: i) the absorbent/refrigerant solution in the thermal compressor, and ii) pure refrigerant in the condenser, expansion valve and evaporator. The temperatures at each control volume are calculated in time with a system of ordinary differential equations (ODEs) for the refrigerant side, and with a system of non-linear algebraic equations for the absorbent/refrigerant solution side of the refrigerator. The model equations are based on conservation of mass and energy principles, and simple functions to evaluate the thermodynamic properties of the ammonia–water system. Two sets of experimental data from an absorption refrigeration prototype were used to carry out model adjustment (set 1), followed by experimental validation (set 2), which showed good qualitative and quantitative agreement, within the experimental uncertainties. Dynamic simulations were conducted to assess the adequacy of model assumptions. Since accuracy and low computational time were obtained, it is reasonable to expect that the mathematical model could be used as a reliable design, control and optimization tool for absorption refrigeration systems. [ABSTRACT FROM AUTHOR]

Abstract: The behavior of active magnetic regenerators (AMR) can be described by means of a one-dimensional set of equations. A lot of geometrical, thermo-physical and magnetic parameters influence the behavior and performance of an AMR, together with external controls and operating parameters. Literature data on AMR performances, both experimental and numerical, are given in different conditions and configurations, so that a consistent comparison among different results is not straightforward, and sometimes even not possible. In this paper the most relevant parameters are outlined, by means of a derivation of the dimensionless 1-D AMR equations. The resulting reduced number of key parameters simplifies the performance optimization procedure. Moreover, if the proposed dimensionless set of parameters is reported each time in corresponding scientific work, a comparison of experimental or/and numerical results would become much more feasible and easy to be performed. [Copyright &y& Elsevier]

Abstract: In order to obtain a better reliability, consistency and accuracy of results obtained with a numerical simulation of an AMRR (active magnetic regenerator refrigerator), a dimensionless numerical model was developed, which can equally be used for determination of regenerator’s heat transfer coefficient and simulation of passive heat regenerators or AMRR operation. Regenerator’s heat transfer coefficient α f, is a crucial input parameter in the simulation of AMRR operation and has a primal effect on the outcome of a solution. This paper deals with a derived dimensionless model and discusses errors involved when using different models for heat transfer coefficient and AMRR operation simulation. [Copyright &y& Elsevier]