Cold Storage and Release Characteristics of a Thermal Battery Unit Using Solid Nitrogen and Solid Nitrogen Impregnated in Metal Foam
Large cold storage capacity is very important to maintain the stable working condition of a superconducting magnet. Solid nitrogen is frequently used for cold storage at cryogenic temperatures. In this paper, we report the experimental investigation of the cold storage and cold release characteristics of a thermal battery unit using solid nitrogen, as well as the combination of solid nitrogen and copper foam under different conditions. In order to enhance the heat transfer without significantly compromising the cold storage capacity, the copper foam is adopted to enhance the effective thermal conductivity of solid nitrogen. It is found that the copper foam can effectively enhance the cold release process, making the cold energy stored effectively utilized.
Concept of Cold Energy Storage for Superconducting Flywheel Energy Storage System
A superconducting flywheel energy storage (SFES) system is an energy storage device with unprecedented small kinetic energy loss by utilizing diamagnetic levitation property of superconductor. The system, therefore, is expected to be one of the most promising candidates in the application of renewable energy field such as PV (photovoltaic) or wind energy development where the power generation is intermittent. An innovative concept to store cold thermal energy as well as kinetic energy in the SFES system is proposed in this paper to decrease required cooling energy during the energy storage period. We have found that the cooling energy can be considerably decreased by the suggested cooling concept. The methodology of cold thermal energy storage is introduced, and the experimental validation is carried out. A specially designed thermosiphon is adopted as a thermal bridge between the high temperature superconductor (HTS) bulks and the cold head of cryocooler, and the working fluid of the thermosiphon is utilized as the thermal energy storage material. Solid nitrogen is generated in the thermosiphon by surplus electricity, and then the mock up HTS bulks are successfully cooled around 64 K by the existence of solid nitrogen even though the implemented cryocooler is turned off.
Laminar heat or mass transfer in rectangular channels and in cylindrical tubes for fully developed flow: comparison of solutions obtained for various boundary conditions
Abstract A comparison is made of results obtained with various boundary conditions at the wall of the channels. By comparing blood Sherwood numbers for finite wall resistance with those for constant concentration boundary condition only a small variation is found for various points along the blood channel.