The need to decrease the sizes and masses of heat exchangers while preserving their performance has stipulated the development of compact heat exchangers with mini and micro channels (MCHE). It is supported by the need for increased recuperation of heat energy, facilitating better energy efficiency with strict limitations for space, material and cost. The adequate substitution of conventional heat exchangers with MCHE requires maintaining the same heat load, not exceeding the allowable pressure losses. The different ways to increase the compactness are analysed, including the change of hydraulic diameter, and the use of various methods of heat transfer intensification by changing the channel geometry and flow structure. The Nusselt numbers and friction factors correlations for plane tubes and criss-cross flow channels of plate heat exchangers are compared. A newer form of the core velocity equation has been developed, which allows comparison of the performance of MCHE heating surfaces with different enhancement techniques in specific process conditions. The results of the calculations illustrate the influence of the channel's hydraulic diameter and length on the MCHE performance for channels with the considered methods of heat transfer intensification. The ways to decrease channel size to mini and micro scales are determined. The recommendations on choosing the best channel geometry and size, depending on specified process conditions and stream nature, are formulated.

The efficient use of energy is a prerequisite for the sustainable development of modern society. It requires increasing heat recuperation in various energy-reliant systems, which is possible with heat transfer devices of intensive action, operating in conditions of limited space for installation and material availability for their production. This is achieved by heat exchangers with mini- and micro-channels, regarded as the next generation of heat transfer equipment. A survey of publications on heat transfer and pressure losses in mini- and microchannels is presented, with focus on their thermal-hydraulic performance. It includes straight channels of various cross-sectional forms, channels with enhanced heat transfer for electronic cooling, additively manufactured microchannels, crisscross flow channels of microturbine recuperators, and plate heat exchangers. A novel Micro Heat Factor for the comparison of mini- and microchannels thermal-hydraulic performance is derived. For the detailed estimation of channel performance in specified process conditions, accounting for the differences in hydraulic diameters, the equation for optimal fluid velocity is proposed. The comparison of thermal-hydraulic performance for different types of mini- and micro channels is performed, and the possibilities of their use in heat exchangers at specific applications are discussed, followed by directions of future studies.

Social impacts in packaging supply chains remain underexplored compared to environmental and economic aspects, despite their growing relevance in sustainability decision-making. This study applies Social Life Cycle Assessment (S-LCA) to evaluate the social sustainability of three carrier bag types: low-density polyethylene (LDPE) plastic, polylactic acid (PLA) bioplastic and kraft paper. The assessment is conducted using OpenLCA by integrating primary data with the SOCA V2 database, and focuses on four stakeholder groups, including Local Communities, Society, Value Chain Actors, and Workers. Social impacts are quantified across life cycle stages and stakeholder categories. Results are expressed as “medium risk hours,” a relative indicator used for comparative hotspot identification. The results indicate that Society and Value Chain Actors face high to very high risks (>40%) across all materials, highlighting potential areas for improvements. The PLA bioplastic bag exhibits the highest social impacts during raw material production, while the kraft paper bag performs worst in manufacturing and end-of life treatment. Overall social impacts rank PLA bioplastic highest (95.79 medium risk hours), followed by kraft paper (54.45), and LDPE plastic (35.15), a ranking that challenges common assumptions about the sustainability of bioplastics and paper alternatives. This quantitative social impact analysis provides clear, data-driven insights into social risk hotspots and improvement opportunities.