Why increasing water flow rate can increase the absorption efficiency in gas absorption column ?4 answersIncreasing water flow rate can enhance absorption efficiency in a gas absorption column due to the improved dynamics and hydrodynamics within the system. As water flow rate increases, the range of possible air flow rates decreases until flooding onset, indicating a more controlled absorption process. Additionally, higher liquid flow rates have been shown to increase CO2 removal efficiency in various absorption studies, such as with non-precipitating potassium carbonate promoted with glycine and monoethanolamine (MEA) solutions. The absorption efficiency benefits from the increased liquid flow rate by facilitating better contact between the gas and liquid phases, leading to more effective absorption of the target gas components like CO2, ultimately improving the overall performance of the absorption column.
How does the flow rate affect the heat transfer coefficient in a falling film evaporator?5 answersThe flow rate significantly influences the heat transfer coefficient in a falling film evaporator. Studies have shown that under the same channel width, the initial heat flux of subcooled boiling increases with an increase in flow rate, following a linear trend. Additionally, an increase in bubble generation frequency leads to a rise in the wall heat transfer coefficient. Experimental results indicate that the total heat transfer coefficient increases notably with a decrease in channel size at high flow rates. Furthermore, in the case of using enhanced tubes in the evaporator, the average heat transfer rate is higher compared to plain tubes, with differences in Nusselt numbers among different tube designs. These findings collectively highlight the intricate relationship between flow rate and heat transfer efficiency in falling film evaporators.
Why the hot water flow rate increase, the efficiency decrease in a heat exchanger using plate heat exchanger?4 answersWhen the hot water flow rate increases in a plate heat exchanger, the efficiency of the heat exchanger decreases. This is because the increased flow rate leads to a decrease in the residence time of the hot water in the heat exchanger, reducing the amount of time available for heat transfer to occur. As a result, the heat transfer rate and effectiveness of the heat exchanger decrease, leading to a decrease in efficiency. Additionally, the increased flow rate can cause deformation of the plates in the heat exchanger, affecting heat transfer and pressure drop characteristics. Therefore, it is important to carefully consider the flow rate in order to optimize the efficiency of a plate heat exchanger.
Why increasing the mass flow rate would decrease the cycle efficiency ORC?5 answersIncreasing the mass flow rate in an Organic Rankine Cycle (ORC) can decrease the cycle efficiency. This is due to several factors. First, at higher mass flow rates, there may be increased pressure drop and frictional losses in the system, leading to a decrease in efficiency ^[Pang et al.]. Additionally, increasing the mass flow rate can result in a decrease in the temperature difference between the heat source and the working fluid, reducing the thermal efficiency of the cycle ^[Pili et al.]. Furthermore, higher mass flow rates can lead to increased losses in the expander, such as leakage and internal flow losses, which can further decrease the overall efficiency of the ORC ^[Pang et al.]. Therefore, while increasing the mass flow rate may be beneficial in terms of increasing power output, it can have a negative impact on the cycle efficiency of an ORC system.
What are compactness area-to-volume ratio in shell and tube heat exchanger?5 answersThe compactness area-to-volume ratio in shell and tube heat exchangers is an important factor for improving performance and reducing equipment volume. Several papers discuss the impact of different design parameters on compactness. Xu et al. propose a shell-tube heat exchanger with vortex generators to improve flow uniformity and decrease the size of the evaporator. Fu and Zhang present a shell-and-tube multimedium heat exchanger with a compact structure that increases the heat transfer area of the tubes and reduces the equipment volume. Yamashita et al. investigate the effects of tube diameter and heat exchanging length on the heat transfer characteristics, showing that thinner tubes contribute to higher performance and compactness. Sasaya et al. describe a shell-and-tube heat exchanger with a refrigerant inlet header and a distribution plate to enhance heat exchange efficiency. Wang and Bao propose a shell and tube heat exchanger with a liquid separator assembly to improve the distribution of refrigerant and enhance overall efficiency.
What effect of tube from in rectangular heat exchanger in thermal energy storage ?5 answersThe effect of tube shape in a rectangular heat exchanger on thermal energy storage is investigated in several papers. Ghalambaz et al. found that changing the location of heat exchanger tubes can significantly affect the melting rate, with tubes placed too closely together overheating each other and reducing overall heat transfer. Faghri discusses a modified tube and shell heat exchanger with micro heat pipes that enable rapid and efficient transfer and storage of thermal energy. Kuźma proposes a heat exchanger tube with a coaxially positioned inner element, such as a resilient insert with fins, to increase heat exchange surface area and agitate the flowing agent. Anggara et al. investigate the effect of heat transfer fluid (HTF) temperature on PCM melting time in a shell-tube geometry experiment, finding that higher HTF temperature leads to decreased melting time. Muto and Matsuo discuss a heat exchanger tube with improved endurance to chipping, achieved by changing tube specifications, such as the dimensions of fluid circulating holes.