This investigation aims to compare the experimental and theoretical ammonia boiling heat transfer coefficient in a plate heat exchanger (PHE). Measured data were gathered during functioning of a single stage vapor mechanical compression refrigeration system placed in the Thermal Systems Research Center of the Technical University of Civil Buildings Bucharest (TUCEB). Experimental values fall within the range of 1377–3050 W/m²K. Theoretical values were obtained from 12 correlations confirmed by the literature to date, developed for similar working conditions. The experimental values are close to the theoretical ones for Shah and Jokar correlations applied for a vapor quality of 0.5. The theoretical values are in the range of 1440–2076 W/m²K and 1558–2318 W/m²K, respectively. Shah correlation predicted 82.35% of all data within the ±30% error band at an MAE value of 14.23%, and Jokar et al. predicted 76.47% of all data within the ±30% error band with an MAE value of 17.7%.

This study evaluates the performance of a flat-plate solar collector thermal system located in Bucharest, Romania, by combining experimental measurements (December 2024–April 2025) with numerical modeling. The system, coupled to a 4000 L tank and using a 30% glycol–water mixture, was monitored for irradiance, wind speed, temperature, flow rate, and humidity. Monthly irradiance averaged 448–584 W/m², and wind speed 2.3–4.3 m/s. Instantaneous efficiency ranged from 25.09% to 73.25% (mean 52.96%), with CUF (capacity utilization factor) ranging between 6.55% and 9.38%. Total heat losses were 4.80–7.79 kW and dominated by top losses (3.60–5.59 kW). The model reproduced the manufacturer’s efficiency curve within 5% for data obtained in the spring, with winter deviations of up to 37% due to weather variability and aged insulation. The results provide reference values for the CUF and loss coefficients of flat-plate collectors in temperate continental climates and can support retrofit and sizing decisions.

The paper presents a technical and economic analysis regarding the sandwich panels with polyurethane insulation layer (PUR) used in cold stores’ construction. The authors determine the optimal thickness of the insulating layer (OIT) corresponding to the 5 climatic zones in Romania. The operating and investment costs for cold and frozen storage in these 5 climatic zones have been assessed. The results obtained from the analysis show that regardless of the climatic zone, the OIT for cold storage is 150 mm and for frozen storage is 180 mm. The investment cost increases by 41% and the expenditure on operating energy decreases by 8.3% for 180 mm for cold storage in comparison to OIT. Moreover, this tendency is maintained as well in the other case of frozen storage, where, by increasing the thickness above OIT at 200 mm the investment cost is increased by 20% and the expenditure in operating energy is decreased by 6.7%. The SEC has an average value of 54.83 kWh·m³/yr for cold storage and 74.55 kWh·m³/yr for frozen storage respectively. The average values obtained in the paper were compared with those presented in the literature and resulted in deviations of about 1.58% for refrigeration, and hence 4.1% for freezing.

This paper presents a banana ripening chamber system for Romania. The system comprises two main parts: the refrigerating unit, with a cooling capacity of 47.5 kW, and a fresh air supply system for ethylene exhaust during the ripening process (1000 m³/h). The proposed solution replaces the classical one-stage vapor compression with R134a. The new solution presented in this study has a proven fruit ripening solution that includes the 3Es; it is eco-friendly (low GWP refrigerant R1234ze(E)), economical, and energy efficient (AHU with heat recovery). The advantage of the new system results from an increasing coefficient of performance, with 7.34% owing to decreasing the power consumption of the compressors. Regarding heat recovery, the annual energy consumption for ventilation is lower, using (annual average) 41% less energy than without heat recovery.

Food-industry refrigeration must simultaneously reduce electricity use, replace high-global-warming-potential refrigerants, and make better use of rejected heat. This systematic review synthesises 101 peer-reviewed publications from 2015 to April 2026. Searches in Web of Science Core Collection, ScienceDirect, Scopus and IEEE Xplore identified 435 records; after deduplication, retrieval and full-text eligibility assessment, 101 publications were included and coded across four overlapping directions: heat recovery and useful heat valorisation (D1), energy efficiency and low global warming potential (GWP) refrigerants (D2), renewable energy sources (D3), and modelling, validation and control (D4). A structured descriptive appraisal considered study design, validation, uncertainty reporting, operating relevance and economic or environmental boundaries. The central research gap is the absence of integrated, experimentally validated studies, as these directions are still pursued largely in isolation rather than combined on a single installation. The urgent priority is therefore a comprehensive demonstration that unites refrigerant substitution, staged heat recovery, renewable-energy and storage integration, and dynamic monitoring and control on an operating food-industry installation, evaluated against a measured baseline across representative periods in each season using technical, energy, economic, environmental and operational indicators that capture the overall efficiency gain of the installation.