Energy management and recovery

Energy management is treated by first exploring the energy requirements for a cryogenic tunnel. The requirement is defined as a function of Mach number, Reynolds number, temperature, and tunnel size. A simple program and correlation is described which allow calculation of the energy required. Usage of energy is also addressed in terms of tunnel control and research operation. The potential of a new wet expander is outlined in terms of cost saved by reliquefying a portion of the exhaust. The expander is described as a potentially more efficient way of recovering a fraction of the cold nitrogen gas normally exhausted to the atmosphere from a cryogenic tunnel. The role of tunnel insulation systems is explored in terms of requirements, safety, cost, maintenance, and efficiency. A detailed description of two external insulation systems is given. One is a rigid foam with a fiber glass and epoxy shell. The other is composed of glass fiber mats with a flexible outer vapor barrier; this system is nitrogen purged. The two systems are compared with the purged system being judged superior.