Wu Chen

To address the heat dissipation challenge of Light-emitting diode (LED) lamps in plant factories, this study proposed a novel phase-change heat-storage cooling device designed for LED lamps which worked as artificial light source required for plant growth. Using single-layer cultivation racks and a container plant factory as research objects, computational fluid dynamics (CFD) models were established with COMSOL Multiphysics software to simulate the temperature field distribution of the LED lamps, cultivation layers, and the overall plant factory. A comparative assessment was conducted on the operational performance and annual energy consumption (EC) between a container plant factory with conventional natural cooling for LED lamps and one equipped with the proposed heat-storage cooling device, under typical temperature conditions. The results demonstrated that, compared with conventional natural air cooling, the new heat-storage cooling device, operating at an ambient temperature of 26 °C can lower the LED lamp wall temperature by 10 °C, the LED bead temperature by 9 °C, and the internal cultivation rack temperature by 1.5-4 °C. Moreover, across ambient temperatures ranging from −10°C to 40°C, the temperature fluctuation of the plant canopy could remain within 3 °C. Energy-consumption analysis of a 20-foot container plant factory under the meteorological conditions of Shanghai city indicated that the heat-storage cooling design could achieve energy savings of 13.1%. These findings highlight the distinct advantages of the proposed phase-change heat-storage cooling device for temperature control during the illumination period in plant factories.

Antibubble is a unique fluid system characterized by a thin air film encapsulating a liquid core, a structure that endows them with excellent resistance to external contamination. The protective air film effectively isolates the internal liquid, demonstrating significant potential in applications such as encapsulation, controlled release, and targeted delivery in fields including medicine and materials science. However, the practical application of antibubbles has been constrained by the lack of high-throughput preparation methods. This paper presents an efficient high-throughput method for antibubble generation and systematically investigates its formation dynamics using high-speed imaging technology. Experimental results show that under vertical vibration, periodic pressure changes induce the formation of a penetrating jet within the confined bubble. The jet undergoes a pinching neck process, forming a primary droplet that subsequently experiences a collision with the bottom surface of the bubble, leading to the generation of an antibubble. Based on experimental results, this study constructs a regime map of antibubble generation behavior under different vibration frequencies, acceleration conditions, and confinement conditions. Theoretical analysis indicates that the antibubble generation frequency can reach fi = 1/2T under ideal conditions, while the maximum generation frequency measured in experiments is 12 per second, showing good agreement with theoretical predictions. This method provides a reliable framework for the large-scale production of antibubbles and lays an important foundation for further research into their properties and cross-disciplinary applications.

Proton exchange membrane fuel cells (PEMFCs) offer a promising zero-emission power solution for maritime transportation, yet thermal management remains challenging due to localized overheating and non-uniform temperature distribution. To address the trade-off between pressure drop and thermal performance in marine PEMFC cooling plates, this study developed and systematically evaluated six flow channel configurations through CFD simulations. Parametric analysis coupled with orthogonal experimental design was employed to explore the effects of secondary flow channel number (N), angle (α), width (d), and spacing (L). The results demonstrated that Type B (parallel flow with secondary channels) reduced the pressure drop by 28.2% while achieving the highest cooling efficiency coefficient (2.66 × 10⁴) compared to conventional configuration. Range analysis further ranked parameter sensitivity and identified optimal parameter combinations for distinct optimization objectives: thermal performance (N = 7, α = 30°, d = 0.5 mm, and L = 2.5 mm), pressure drop (N = 8, α = 75°, d = 1.5 mm, and L = 2.5 mm), and cooling efficiency (N = 8, α = 90°, d = 1.5 mm, and L = 2.5 mm). These findings provide practical guidelines for designing cooling plates that address thermal-hydraulic requirements in marine PEMFC systems, advancing their viability for maritime propulsion applications.

Marine air-conditioning systems face high energy consumption, particularly in humid marine environments. This study is an experimental investigation of the effects of rotating wheel speed and regeneration temperature on the performance of the system, which is a dual-stage desiccant dehumidification fresh-air pre-treatment system using ship waste heat as the regeneration heat source and seawater-assisted cooling to improve the efficiency of energy use. The results showed that the dehumidification capacity and efficiency of the system improved with an increase in the rotating wheel speed from 6 to 10 r/h and in the regeneration temperature from 80 °C to 110 °C. Optimal performance was achieved with a rotating wheel speed of 10 r/h and a regeneration temperature of 110 °C, balancing the maximum dehumidification capacity, energy efficiency, and waste heat utilization.

Antibubbles are a special spherical structure generated in liquids surrounded by a thin air film. The collapse of antibubbles has been regarded as a feasible method for generating microbubbles. This paper demonstrates an experimental study on the antibubble collapse focusing on the effect of rupture time and location. With the help of a high-speed camera, the detailed collapse dynamics for different rupture times and locations was presented. The collapse velocity was found to vary significantly with the rupture time and location. An upgraded theoretical model was proposed to elucidate the effect of the air film thickness distribution due to drainage on the collapse velocity. This study should stimulate further investigation on the antibubble collapse, especially the size distribution of the generated microbubbles.

Recovering the waste heat of a marine main engine (M/E) to generate electricity was an environmental way to minimize the carbon dioxide emissions for ships, especially with organic Rankine cycle (ORC) technology. The M/E had variable loads and operating times during voyage cycle, which directly affected the ORC thermodynamic potential. In this paper, a voyage cycle-based waste heat utilization from the M/E was introduced to provide reliable evaluation for proposing and designing ORC. The effect of various M/E loads and operating times on ORC performance among three dry-type substances was analyzed. The environmental impact was presented based on the data from one voyage cycle navigation of objective container ship. The results showed that Cyclohexane was capable of net power while Benzene was more suitable for thermal efficiency. The evaporator and condenser were the main irreversible components of the ORC system and required further optimization. Taking the operational profile into consideration, the evaporation pressures were 922–1248 kPa (Cyclohexane), 932–1235 kPa (Benzene) and 592–769 kPa (Toluene), respectively. During the voyage cycle, the carbon dioxide emissions were 99.68 tons (Cyclohexane), 96.32 tons (Benzene) and 60.99 tons (Toluene), respectively. This study provided certain reference for the design and investigation of ORC application to further improve the energy efficiency for container ship.

Based on the analysis of the waste heat distribution characteristics of a typical ship two-stroke low-speed main engine (model: MAN 8S65ME-C8.6HL, the specified maximum continuous rating SMCR: 21,840 kW) under different loads, two different types of organic Rankine cycle (ORC) systems, namely the basic system (BORC) and the preheated system(PORC), were constructed to recover the ship main engine’s exhaust gas waste heat and jacket cooling water waste heat. Using the thermodynamic simulation model of the system, the main performance indexes, including net output power of the two ORC systems were studied with the variation of seawater temperature and main engine load, and the annual ship fuel saving and annual carbon emission reduction generated by the two systems were compared and analyzed. It was found that the maximum net output power of the BORC system and PORC system were 445.3 kW and 491.3 kW, respectively, when the ship’s main engine load was 100%, and the outboard seawater temperature was 20 °C; the maximum thermal efficiency was 12.84% and 12.71%, respectively; under the annual operation, the fuel saving of BORC system and PORC system can be 456 tons and 510 tons, respectively, and the carbon emission reduction was 1416 tons and 1581 tons, respectively. The analysis found that the net output power of the PORC system is always greater than that of the BORC system. When the outboard seawater is lower, and the main engine load is more than 80%, the net output power difference between the PORC system and BORC system gradually expands, and the improvement of ORC system performance is more evident by adding a preheater. It can be concluded that when the ship was mainly operated in the sea area with low seawater temperature and the main engine was running under high load most of the time, selecting the PORC system to recover the waste heat of the main engine was more advantageous.