Mathematical modeling and energy consumption evaluation of R-600a refrigeration systems for vending machines using efficient heat exchangers

This study presents the SVIEE-R vending machine as a sustainable solution for reducing CO₂ emissions in the retail sale of cold packaged products, maintained at refrigeration temperatures between 5°C and 8°C. The system operates on a 12V DC cooling unit, utilizing R-600a refrigerant, which has a low Global Warming Potential (GWP = 3) and zero Ozone Depletion Potential (ODP). Unlike conventional vending machines, the SVIEE-R is specifically designed for off-grid applications, integrating a flexible, dynamic, data-driven analytical tool for performance evaluation, prediction, and optimization. The novelty of this work lies in the combination of a natural refrigerant and an energy-efficient design tailored for autonomous operation in remote locations. To enhance energy efficiency, an adaptive mathematical model is developed for the vapor compression refrigeration system of the vending machine. This model integrates thermodynamic principles, geometric parameters, and operational conditions to optimize performance. The key performance metrics, validated through experimental data with deviations below 10%, confirm the model's accuracy. The Coefficient of Performance (COP), determined using the Nusselt-Jürges correlation, ranged between 1.321 and 1.476, emphasizing the critical role of evaporator geometry and condensation temperature in system efficiency. This study provides a framework for adapting energy-efficient refrigeration technologies to diverse operational environments, thereby advancing the implementation of sustainable refrigerants in small-scale cooling applications.