Cool Thermal Energy Storage: Water and Ice to Alternative Phase Change Materials

Cool thermal energy storage has a long history dating back to ancient times with modern developments beginning in the mid-nineteenth century where blocks of ice were cut from frozen lakes for cooling applications. Today, the prevalent mode of thermal energy storage is the utilization of ice tanks in commercial buildings for peak shaving and load shifting. In this chapter, a summary of different types of water/ice thermal energy storage systems is provided; an overview of alternative phase change materials for use in cool thermal energy storage is given; and alternative phase change material thermal energy systems, their implementation, challenges, and outlook are also discussed

Assessment of Conventional and Air-Jet Wheel Deflectors for Drag Reduction of The DrivAer Model

Aerodynamic drag is a large resistance force to vehicle motion, particularly at highway speeds. Conventional wheel deflectors were designed to reduce the wheel drag and, consequently, the overall vehicle drag; however, they may actually be detrimental to vehicle aerodynamics in modern designs. In the present study, computational fluid dynamics simulations were conducted on the notchback DrivAer model—a simplified, yet realistic, open-source vehicle model that incorporates features of a modern passenger vehicle. Conventional and air-jet wheel deflectors upstream of the front wheels were introduced to assess the effect of underbody-flow deflection on the vehicle drag. Conventional wheel-deflector designs with varying heights were observed and compared to 45◦ and 90◦ air-jet wheel deflectors. The conventional wheel deflectors reduced wheel drag but resulted in an overall drag increase of up to 10%. For the cases studied, the 90◦ air jet did not reduce the overall drag compared to the baseline case; the 45◦ air jet presented drag benefits of up to 1.5% at 35 m/s and above. Compared to conventional wheel deflectors, air-jet wheel deflectors have the potential to reduce vehicle drag to a greater extent and present the benefit of being turned off at lower speeds when flow deflection is undesirable, thus improving efficiency and reducing emissions

Advances in Spacecraft Thermal Control

Spacecraft thermal management is critical for ensuring mission success, as it affects the performance and longevity of onboard systems. A comprehensive overview of the state of the art in spacecraft thermal control solutions, as well as a design methodology framework for efficient and effective thermal management, is provided. Various thermal control solutions, including coatings, insulation, heat pipes, phase-change materials, conductive materials, thermal devices, actively pumped fluid loops, and radiators, are discussed along with the primary sources of heat loading in space. The need for accurate modeling and analysis of the thermal environment to identify appropriate thermal control solutions and design pathways is highlighted. Future innovations in thermal management, such as new materials and technologies that have the potential to further improve the efficiency and effectiveness of thermal control solutions for spacecraft, are explored

Thermodynamic Model of CO2 Deposition in Cold Climates

A thermodynamic model, borrowing ideas from psychrometric principles, of a cryogenic direct-air CO2-capture system utilizing a precooler is used to estimate the optimal CO2 removal fraction to minimize energy input per tonne of CO2. Energy costs to operate the system scale almost linearly with the temperature drop between the ingested air and the cryogenic desublimation temperature of CO2, driving siting to the coldest accessible locations. System performance in three Arctic/Antarctic regions where the proposed system can potentially be located is analyzed. Colder ambient temperatures provide colder system input air temperature yielding lower CO2 removal energy requirements. A case is also presented using direct-sky radiative cooling to feed colder-than-ambient air into the system. Removing greater fractions of the ingested CO2 lowers the CO2 desublimation temperature, thereby demanding greater energy input for air cooling. It therefore is disadvantageous to remove all CO2 from the processed air, and the optimal mass fraction of CO2 desublimated under this scheme is found to be ~0.8-0.9. In addition, a variety of precooler effectiveness (ε ) values are evaluated. Increasing effectiveness reduces the required system power input. However, beyond ε = 0.7, at certain higher values of desublimated CO2 mass fraction, the CO2 begins to solidify inside the precooler before reaching the cryocooler. This phenomenon fouls the precooler, negating its effectiveness. Further system efficiencies can be realized via a precooler designed to capture solidified CO2 and eliminate fouling

Natural Convection from Circular Cylinders

This book presents a concise, yet thorough, reference for all heat transfer coefficient correlations and data for all types of cylinders: vertical, horizontal, and inclined. This book covers all natural convection heat transfer laws for vertical and inclined cylinders and is an excellent resource for engineers working in the area of heat transfer engineering

Thermodynamic Model of CO2 Deposition in Cold Climates

A thermodynamic model, borrowing ideas from psychrometric principles, of a cryogenic direct-air CO2-capture system utilizing a precooler is used to estimate the optimal CO2 removal fraction to minimize energy input per tonne of CO2. Energy costs to operate the system scale almost linearly with the temperature drop between the ingested air and the cryogenic desublimation temperature of CO2, driving siting to the coldest accessible locations. System performance in three Arctic/Antarctic regions where the proposed system can potentially be located is analyzed. Colder ambient temperatures provide colder system input air temperature yielding lower CO2 removal energy requirements. A case is also presented using direct-sky radiative cooling to feed colder-than-ambient air into the system. Removing greater fractions of the ingested CO2 lowers the CO2 desublimation temperature, thereby demanding greater energy input for air cooling. It therefore is disadvantageous to remove all CO2 from the processed air, and the optimal mass fraction of CO2 desublimated under this scheme is found to be ~0.8-0.9. In addition, a variety of precooler effectiveness (ε ) values are evaluated. Increasing effectiveness reduces the required system power input. However, beyond ε = 0.7, at certain higher values of desublimated CO2 mass fraction, the CO2 begins to solidify inside the precooler before reaching the cryocooler. This phenomenon fouls the precooler, negating its effectiveness. Further system efficiencies can be realized via a precooler designed to capture solidified CO2 and eliminate fouling