New methods of testing heat leak in cryogenic vessels

Abstract

The heat leak in a cryogenic vessel is currently analyzed using a standard test based on measuring loss product. The test requires 72 h to complete; in addition, it requires that gas is discharged from the vessel to equalize the vessel pressure with the atmospheric pressure before the test can be performed. Therefore, the test is ineffective and wastes gas. In this study, new methods using constant pressure, constant flow rate, and self-pressurization are proposed to resolve the limitations posed by the standard test. Based on the heat leak transfer process and energy equations for cryogenic vessels, all factors, including temperature, pressure, latent heat, that influence the heat leak in cryogenic vessels are determined and analyzed. For a given cryogenic vessel, according to the equation between heat leak, temperature, and pressure, new test methods are proposed. Tests were conducted applying the new methods. The test results of each method showed that the heat leak in the cryogenic vessel was calculated accurately. We concluded that the new methods are effective and save significant amount of gas compared with the standard method.

Keywords

• Cryogenic vessels
• Heat leak
• Self-pressurization
• Flow rate