Modelling of a medical refrigerator: Comparison between experimental and numerical results

Abstract

In the present work, a charge-sensitive numerical model under \textit{Matlab} environment is developed to simulate the blood bank refrigerators line of \textit{B Medical Systems}, a Luxembourg-based pioneer in the medical equipment industry, specialising in research, development and the manufacturing of professional refrigerators, freezers and solutions for safe transport and management of blood and vaccines.\\

A particular focus is given on the capillary tube modelling. In the case of small-scale units, the refrigerant flow inside the capillary tube is choked, which results in the settlement of a maximum mass flow rate in the system along with a critical pressure level. The detection and computation of these critical conditions are of utmost importance for the cooling system performance simulation. A dichotomy-like algorithm is self-implemented for the capillary tube.

The numerical simulation of cool-down and stable running conditions tests is carried out. The different modelling assumptions led to convergence issues for the cooling system model, mostly due to an improper refrigerant charge prediction in the heat exchangers. This model being highly implicit, large tolerances on the residuals had to be implemented to achieve convergence. It results that the proper simulation of the heat exchangers is of utmost importance for a charge-sensitive model.\\

An experimental simulation of a specific refrigerator is also carried out. The experimental and numerical results comparison put into light the difficulty to accurately model the temperature spatial distribution inside the cabinet and their evolution through time.