To improve the efficiency of a diesel internal combustion engine (ICE), the waste heat carried out by the combustion gases can be recovered with an organic Rankine cycle (ORC) that further drives a vapor compression refrigeration cycle (VCRC). This work offers an exergoeconomic optimization methodology of the VCRC-ORC group. The exergetic analysis highlights the changes that can be made to the system structure to reduce the exergy destruction associated with internal irreversibilities. Thus, the preheating of the ORC fluid with the help of an internal heat exchanger leads to a decrease in the share of exergy destruction in the ORC boiler by 4.19% and, finally, to an increase in the global exergetic yield by 2.03% and, implicitly, in the COP of the ORC-VCRC installation. Exergoeconomic correlations are built for each individual piece of equipment. The mathematical model for calculating the monetary costs for each flow of substance and energy in the system is presented. Following the evolution of the exergoeconomic performance parameters, the optimization strategy is developed to reduce the exergy consumption in the system by choosing larger or higher-performance equipment. When reducing the temperature differences in the system heat exchangers (ORC boiler, condenser, and VCRC evaporator), the unitary cost of the refrigeration drops by 44%. The increase in the isentropic efficiency of the ORC expander and VCRC compressor further reduces the unitary cost of refrigeration by another 15%. Following the optimization procedure, the cost of the cooling unit drops by half. The cost of diesel fuel has a major influence on the unit cost of cooling. A doubling of the cost of diesel fuel leads to an 80% increase in the cost of the cold unit. The original merit of the work is to present a detailed and comprehensive model of optimization based on exergoeconomic principles that can serve as an example for any thermal system optimization.

Cyclone separators are widely used for gas–solid separation due to their robustness and low operating cost. This study focuses on the experimental validation of a single cyclone configuration and the development of a MATLAB-based numerical framework. The model employs a Euler–Lagrange approach to capture centrifugal, drag, and gravitational forces acting on spherical polyethylene particles (D = 5 mm). Laboratory-scale measurements of airflow, pressure drop, and separation efficiency showed strong agreement with the numerical model (deviation < 6%), confirming its reliability for the single cyclone case. Beyond this validated framework, exploratory simulations were carried out for series and parallel cyclone configurations to provide predictive insights into possible design trade-offs. Unlike high-fidelity CFD–DEM models, which are computationally intensive and allow detailed turbulence and particle–particle interactions, the present MATLAB model is simplified but transparent and fast to implement. Its originality lies in demonstrating a low-cost, experimentally calibrated tool that can support preliminary design decisions. The multi-cyclone results should be interpreted as predictive trends, as no direct experimental validation was possible within the present setup. These findings offer preliminary guidance for balancing efficiency, energy demand, and throughput in applied mechanics of multiphase flow systems.

This study investigates steady-state conductive heat transfer and water-vapor diffusion through the external wall of a refrigerated warehouse with a specified load-bearing wall assembly. The formal analogy between heat conduction and mass diffusion is stated and used to establish a practical calculation framework for estimating heat and moisture ingress through multilayer cold-store walls. Calculation routines are presented to determine the temperature field and the corresponding water-vapor saturation and partial-pressure distributions across (and within) the insulation layer, enabling the identification of regions prone to interstitial condensation. The analysis highlights the roles of (i) the vapor diffusion resistance of the vapor barrier layer, (ii) the thermal resistance of the insulation, and (iii) key outdoor boundary conditions in governing condensation risk. Increasing insulation thermal resistance reduces external heat gains; however, it may also increase the likelihood of condensation in layers close to the cold side by lowering local temperatures and saturation pressures. Among external parameters, outdoor relative humidity exerts the strongest influence on interstitial condensation risk. For the investigated wall assembly, increasing outdoor relative humidity by 50% shifts the condensation onset location within the insulation toward mid-thickness. The effects of vapor barrier diffusion resistance, insulation thermal resistance, and changes in outdoor conditions (relative humidity, temperature, and wind speed) are reported in tabulated form and illustrated through pressure–position and temperature–position profiles.

The present work proposes a phase change material-based defrosting system (PCM-DS) for vapor compression refrigeration systems (VCRSs). The primary objective is to determine the optimal PCM mass and refrigerant mass flow rate required to melt 1 kg of accumulated evaporator ice. A steady-state macroscopic thermodynamic model, governed by global energy balances and driven by experimental boundary conditions, evaluates the VCRS in both cooling and defrosting operating modes. The PCM-DS is not installed on the experimental setup. The latter is used to obtain experimental data to be used as inputs in the steady-state model. Among the three candidates investigated (OM42, OM46, OM48), OM42 was selected for minimizing system mass and volume constraints. Results demonstrate that integrating the PCM-DS induces only a 3% reduction in the theoretical coefficient of performance (COP) compared with a 5.6% reduction in the case of using the electric heater defrosting (EHD). The core innovation of this work involves proposing and evaluating three distinct energy storage management strategies: unique superheating, unique bypass, and intermittent bypass. The results show that the highest COP is obtained for unique superheating (2.93), followed by unique bypass (2.82) and intermittent bypass (2.81). The work conducted proves the theoretical feasibility of such PCM-DS.