Consideration of sub-cooled LN2 circulation system for HTS power machines

Abstract

Articles you may be interested inSub-cooled liquid nitrogen cryogenic system with neon turbo-refrigerator for HTS power equipment AIP Conf. ABSTRACTWe consider a sub-cooled liquid nitrogen (LN) circulation system for HTS power equipment. The planned circulation system consists of a sub-cool heat exchanger (subcooler) and a circulation pump. The sub-cooler will be connected to a neon turbo-Brayton cycle refrigerator with a cooling power of 2 kW at 65 K. Sub-cooled LN will be delivered into the sub-cooler by the pump and cooled within it. Sub-cooled LN is adequate fluid for cooling HTS power equipment, because its dielectric strength is high and it supports a large critical current. However, a possibility of LN solidification in the sub-cooler is a considerable issue. The refrigerator will produce cold neon gas of about 60 K, which is lower than the nitrogen freezing temperature of 63 K. Therefore, we designed two-stage heat exchangers which are based on a plate-fin type and a tube-intube type. Process simulations of those heat exchangers indicate that sub-cooled LN is not frozen in either sub-cooler. The plate-fin type sub-cooler is consequently adopted for its reliability and compactness. Furthermore, we found that a cooling system with a Brayton refrigerator has the same total cooling efficiency as a cooling system with a Stirling refrigerator.

Dynamic simulation of 10 kW Brayton cryocooler for HTS cable

“…5 and 6), and the possibility of freeze-out of LN emerges as a crucial design issue [10,11]. Yoshida et al presented two design ideas to avoid the freeze-out of LN flow, including a tube-in-bath type HX and a two-stage type of plate-fin HX [10].…”

“…5 and 6), and the possibility of freeze-out of LN emerges as a crucial design issue [10,11]. Yoshida et al presented two design ideas to avoid the freeze-out of LN flow, including a tube-in-bath type HX and a two-stage type of plate-fin HX [10]. Chang et al experimentally demonstrated that cross-flow heat exchangers are effective in avoiding the complete clog-up of all passages, mainly because the temperature distribution is two-dimensional [11].…”

Neon turbo-Brayton cycle refrigerator for HTS power machines

“…The design of the sub-cooled LN heat exchanger is also ongoing [8]. In 2012, it will be demonstrated that the cooling system can cool the practical HTS transformer.…”

Sub-cooled liquid nitrogen cryogenic system with neon turbo-refrigerator for HTS power equipment

“…Figure 1 shows a conceptual flow diagram of our cooling system, and a photograph of the refrigerator is shown in Figure 2. The refrigerator consists of a turbo-expander, a two-stage turbo-compressor, a main heat exchanger and a sub-cooler [10]. Specifications of the turbo-expander and the turbo-compressor are shown in Table 1.…”

“…In order to prevent LN from freezing, a newly designed sub-cooler based on a plate-fin type was made [10]. The refrigerator performance was first checked, and LN circulation system performance was also checked.…”