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42 Graţiela Maria Ţârlea et al. Conform celor arătate în Fig. 2 consumul electric al sistemului frigorific funcţionând cu agentul frigorific R717 este cu 15% mai mic decât în cazul utilizării agentului frigorific R404A si R507A. Aceasta reducere aduce un câştig semnificativ din punct de vedere al costurilor precum şi al impactului ecologic asupra mediului înconjurător. Conform celor prezentate în Fig. 3 se poate observa un coeficient de performanţă mai mare în cazul agentului frigorific R717: cu 6% faţă de R404A şi cu 7% faţă de R507A. În concluzie se poate afirma că optimizarea sistemului frigorific cu vapori într-o treaptă de comprimare prin înlocuirea agentului frigorific R404A cu agentul frigorific R717 aduce un câştig din punct de vedere al eficienţei energetice, costurilor şi un avantaj din punct de vedere al mediului înconjurător prin reducerea gradului de poluare.
BULETINUL INSTITUTULUI POLITEHNIC DIN IAŞI Publicat de Universitatea Tehnică „Gheorghe Asachi“ din Iaşi, Tomul LVIII (LXII), Fasc. 4, 2012 Secţia CONSTRUCŢII DE MAŞINI INFLUENCE OF ENVIRONMENTAL AND CONSTRUCTIVE FACTORS ON THE VAPORIZERS PERFORMANCE Received: November 3, 2012 Accepted for publication: November 30, 2012 BY NICOLAE BARA 1 and MARIN BICA ∗2 1 Frigotehnica SA Bucharest 2 University of Craiova Abstract. Correct design and choice of vaporizers are very important for refrigeration systems proper operation and for their efficiency. A wrong sized vaporizer may produce an excessive decrease of the vaporization temperature, and reducing it with every degree corresponds to a reduction in cooling power with approx. 3…4%. This is why the vaporizer can not be dissociated from its liquid supply system. In practice, often a proper rebound refrigerant corresponds to each type of vaporizer. The measurements for vaporizers with the rib step between 2 mm and 3.5 mm were performed on the Thermotechnics Laboratory stand from the Faculty of Mechanics of Craiova. The most pronounced air cooling occurs for the rib step value equal to 2 mm. So, it is confirmed the statement that the rib step has to be chosen for each type of heat exchanger, after carefully testing on laboratory stands. Key words: vaporizer, refrigeration system, rib step. 1. Introduction Vaporization is the thermodynamic process through which the refrigerant changes its state of aggregation from liquid to vapors, absorbing heat from the cold source represented by the cooled environment. In any refrigeration machine the vaporizer is the unit absorbing heat, achieving the machine useful effect. ∗ Corresponding author: e-mail: marinbica52@gmail.com
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