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.
Highlights
An innovative nitrogen cooling system has been developed for accelerated and eco-friendly cooling of metallic part
An innovative nitrogen cooling furnace system was developed in this study for achieving a high-quality cooling process
The implementation tests using tubular tungsten heavy alloy (THA) confirmed that nitrogen gas cooling is an eco-friendly cooling medium, which can produce cleaner products
Summary
An innovative nitrogen cooling system has been developed for accelerated and eco-friendly cooling of metallic part. In this cooling process, the dry gaseous nitrogen is rapidly circulated and exchanges heat with the workpiece that it contacts, resulting in an accelerated cool-down. Selection of a cooling medium is mainly based on chemical composition, dimension, and desired surface quality of the parts [1,2,3]. The function of the cooling medium is to control the rate of heat transfer from the surface of the quenched parts, and the most commonly used cooling media is water. The surface oxidation, environmental contamination, and thermal distortion during water cooling have been problematic in industrial applications [1,2]
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