Forced Circulation of Nitrogen Gas for Accelerated and Eco-Friendly Cooling of Metallic Parts

Abstract

As nitrogen is nonreactive and non-flammable, it can provide a quick and simple medium of cooling and environment protection. One disadvantage of nitrogen cooling is its lower heat transfer coefficient than water. Despite its lower cooling capacity, nitrogen cooling can produce cleaner products, thereby eliminating the need to wash the parts and dispose of the contaminated water. In this study, an innovative nitrogen cooling system was developed for an accelerated and eco-friendly cooling of metallic parts. The dry nitrogen gas, transported via the nozzle of a cryogenic liquid nitrogen tank, is passed into the cooling chamber and exchanges heat with the workpiece. The heated nitrogen gas is forcibly transported to the chiller, where the heat is reduced, and the cooled gas is circulated again. The performance of this nitrogen cooling system has been evaluated with cooling experiments of sintered tungsten heavy alloys. The nitrogen-cooled product shows a clean surface with improved mechanical properties. Furthermore, nitrogen induces less distortion compared to water cooling, thus reducing the post-machining costs.

Nitrate Water Contamination from Industrial Activities and Complete Denitrification as a Remediation Option

“…Conversion of this gas to liquid nitrogen has been carried out globally in industries and is used for cooling metallic industrial equipment used under high pressure and heat. The same cooling characteristics of nitrogen lead to the commercialization of its liquid form, where it is even transported in cryogenic liquid tankers due to increasing global demand [32]. Nitrogen is an essential element for all life forms, as it is an integral part of amino acids and proteins in all life forms, and part of the purines and pyrimidines that make up the DNA and RNA molecules in all biological entities.…”

System Development for Diffusion Bonding of Multiple Unit Tubes to Produce Long Tubular Tungsten Heavy Alloys

“…(a) (b) In the stabilization of the material properties of the diffusion bonded tube, a post heat treatment was performed at 1150 °C for 8 h [34,35]. The bonding quality of diffusion bonded products was estimated in terms of mechanical properties such as the hardness, tensile strength, and elongation.…”

Effects of Laser Beam Parameters on Bendability and Microstructure of Stainless Steel in Three-Dimensional Laser Forming

“…When the beam diameter was in the range of 0.25-1.0 mm, the cooling rate was in the range of approximately 6,660 up to the maximum of 7,147 for the sample with a hatch spacing of 1.0 mm. The equiaxed dendrites of the austenite around the center of the track could be formed upon rapid cooling at the heated surface (nucleation of small grains in Figure 8b,c), which led to a slightly higher microhardness (Figure 11) [30,31]. The larger hardnesses of the samples obtained at D b = 0.7, 1.0, and 1.3 mm (h s = 0.5 mm) (approximately 209, 218, and 215 HV, respectively) could be attributed to the larger strain hardening induced by the bending strain (Figure 6b).…”