Volume 43, Issue 3

An overall synthesis of biology and non-equilibrium thermodynamics remains a challenge at the interface between the physical and life sciences. Herein, theorems from finite-time and control thermodynamics are applied to biological processes to indicate which biological strategies will succeed over different time scales. In general, living systems maximize power at the expense of efficiency during the early stages of their development while proceeding at slower rates to maximize efficiency over longer time scales. The exact combination of yield and power depends upon the constraints on the system, the degrees of freedom in question, and the time scales of the processes. It is emphasized that biological processes are not driven by entropy production but, rather, by informed exergy flow . The entropy production is the generalized friction that is minimized insofar as the constraints allow. Theorems concerning thermodynamic path length and entropy production show that there is a direct tradeoff between the efficiency of a process and the process rate. To quantify this tradeoff, the concepts of compensated heat and waste heat are introduced. Compensated heat is the exergy dissipated, which is necessary for a process to satisfy constraints. Conversely, waste heat is exergy that is dissipated as heat, but does not provide a compensatory increase in rate or other improvement. We hypothesize that it is waste heat that is minimized through natural selection. This can be seen in the strategies employed at several temporal and spatial scales, including organismal development, ecological succession, and long-term evolution. Better understanding the roles of compensated heat and waste heat in biological processes will provide novel insight into the underlying thermodynamic mechanisms involved in metabolism, ecology, and evolution.

This study represents the exergy analysis of the evacuated tube parabolic trough collector and the cascaded latent heat storage system using multi-temperature phase change material (PCMs) during the charging process. The objective of the work is to control the losses and increase the efficiency of the system. The exergy analysis has been conducted on the basis of the first and second laws of thermodynamics in a parabolic trough collector with various mass flow rates of the heat transfer fluid (HTF). The overall variation of exergy efficiency of the collector with varying mass flow rate of the HTF is 5.9 %. The thermodynamic analysis of the cascaded latent heat storage system has been done during the charging process in which the PCM absorbs energy from the HTF and undergoes a phase transformation from the solid to the liquid state. The exergy analysis is conducted by varying the mass flow rate of the HTF in the storage system for both insulated and non-insulated systems. It is noticed that the variation of exergy stored for 5 and 10 liters per minute is 24.609 kW and 40.48 kW, respectively. It is concluded that the high range of energy and exergy stored in the system is achieved by the high flow rate of the HTF.

This work presents the results of the mathematical modeling of the fast traveling wave propagation phenomenon in the fixed-bed catalytic reactors according to a simple (basic) mathematical model with a reversible reaction. Qualitative and quantitative research is used to study the behavior of separatrices’ trajectories of the system’s non-linear ordinary differential equations. Special attention has been paid to the non-equilibrium thermodynamic methods. The entropy balance equation is constructed and analyzed under the assumption of the simple mathematical model of physical and chemical processes. The influence of key physical and chemical parameters on the fast traveling wave properties is studied. The phenomenon of fast traveling wave propagation in the fixed-bed catalytic reactors provides a vivid example of a spatiotemporal dissipative structure in active heterogeneous medium. These dissipative structures are shown to exist near the thermodynamic equilibrium.

A series of polyvinyl alcohol (PVA)/Fe 3 O 4 -coated cellulose acetate mixed matrix membranes were analyzed for Cd and Ni removal, both experimentally and theoretically. The effect of the coating layer on the metal ion rejection performance was investigated using molecular modeling approaches. Lower energy requirements for the detachment of ions from the coating layer were calculated. Our results imply that the coating layer interacts with metal ions to a much lower extent than the substrate layer does. Smaller mean square displacement data were calculated in the coating layer than in the substrate layer, which indicates a lower diffusivity of ions in the coating layer. This in turn shows the coating layer efficiently prevents ion transfer and provides higher retention/rejection. We conclude that applying a coating layer with lower Fe 3 O 4 content would enhance the ion rejection performance of cellulose acetate mixed matrix membranes. The addition of Fe 3 O 4 particles increases the number of active sites and the surface area, while a high content of these particles must be avoided as they may surround functional groups of polymer chains and also increase the porosity, which decreases the rejection performance of membranes.

Nanostructured ceramic membranes have shown considerable separation performance. In this work, an analytical model is developed to evaluate the separation performance of porous ceramic membranes in gas separation applications. The model takes into account three layers, i. e., (1) active layer, (2) interlayer, and (3) support layer. For estimation of sorption at the interface of feed stream and membrane, the partition coefficient model was used and the unsteady-state conservation of mass equation coupled to molecular models of the diffusivity coefficient was used to predict the permeation of penetrant hydrogen gas through a ceramic membrane. It was observed that the model can be readily applied to other systems of interest as a predictive tool.

While in the classic Curzon–Ahlborn and Novikov engines the temperatures of the heat baths are kept fixed or follow a deterministic time function, it is the aim of this work to study the impact of fluctuating heat bath temperatures. As an example serves a solar power plant, where the stochastically varying cloud cover leads to fluctuations in the temperature of the hot heat bath. This solar thermal power plant is modeled as a stochastic endoreversible system. On the basis of this model the maximum expected work output of the power plant and the corresponding optimal control policy is derived. For the considered system it is found that the maximum expected work output changes with the reversion speed of the hot temperature depending on the relation of the starting hot temperature and the temperature of the power plant’s receiver. Additionally, it is found that the maximum expected work output increases with the hot temperature’s fluctuation strength.