GB/T 18443.5-2010Testing method of performance for vacuum insulation cryogenic equipment - Part 5: Static evaporation rate measurement (English PDF)

4.2 Test method

4.2.1 Use the wet gas flowmeter to measure the gas flow passing through the flowmeter after the liquid in the measured piece evaporates within a unit of time, and calculate the Percentage Loss of Product per Day and the static evaporation rate with the measured gas flow. The schematic diagram of the test device is shown in Figure 1.

4.2.2 Use the gas mass flowmeter to measure the gas mass flow passing through the mass flowmeter after the liquid in the measured piece evaporates within a unit of time, and calculate the Percentage Loss of Product per Day and static evaporation rate with the measured gas mass flow. The schematic diagram of the test device is shown in Figure 2.

4.2.3 When the effective volume of the measured piece is not more than 5 m3, it is allowed to use the weighing method to measure. When the weighing method is used for measurement, after the measured piece is charged to the rated filling quantity, place the measured piece on the weighing instrument, and measure the mass of the cryogenic liquid evaporated in the vacuum insulated cryogenic equipment with the weighing instrument. Use the evaporation measured with the weighing method to calculate the Percentage Loss of Product per Day and static evaporation rate.

a) When the range of the flowmeter is less than or equal to 5L/min, the accuracy needs to reach 0.5%; when the range is greater than 5 L/min, the accuracy needs to reach 1.0%;

b) The rated flow of the flowmeter shall be compatible with the gas flow evaporated by the measured piece;

c) There shall be ambient temperature, ambient pressure, and flowmeter inlet temperature and pressure measurement devices;

d) The maximum weighing of the weighing instrument used in the weighing method shall be 1.2~

2.0 times the full load mass of the measured piece, and its accuracy shall meet the following requirements.

--- When the maximum weighing of the weighing instrument is 5T<=t< 10T, its allowable deviation shall not exceed 1 kg;

--- When the maximum weighing of the weighing instrument is 3T<=t< 5T, its allowable deviation shall not exceed

0.5 kg;

--- When the maximum weighing of the weighing instrument is 1T<=t< 3T, the allowable deviation shall not exceed

0.2 kg;

--- When the maximum weighing of the weighing instrument is t< 1T, its allowable deviation shall not exceed

7.1 Flowmeter method

7.1.1 Liquid nitrogen is generally used as the test medium.

7.1.2 During measurement, the fullness rate of cryogenic liquid shall be the rated fullness rate.

7.1.3 After the liquid filling is completed, it shall be standing for at least 48h. During the standing period, the venting valve of the vacuum insulated cryogenic equipment shall be opened.

7.1.4 When the gauge pressure of the inner liner is close to zero, connect the flowmeter to the venting pipeline. After the flowmeter is connected, except the venting valve is opened, the other valves of the measured piece shall be all closed.

7.1.5 After the flow of evaporated gas is stabilized, collect and record the indicated value of the flowmeter, ambient temperature, atmospheric pressure, flowmeter inlet temperature and pressure with a time interval that shall not be more than 1 h; the data recording time shall be 24 h.

7.1.6 Calculate the static evaporation rate of the measured piece and compare it with the static evaporation rate of the previous 24 h. When the variation range of the static evaporation rate is less than 5%, the recorded data is valid; when the variation range of the static evaporation rate is greater than 5%, it is allowed to record the data once again; the recording time shall not be less than 24 h, and the data are final record data.

7.2 Weighing method

7.2.1 Except for special requirements, the test medium shall be liquid nitrogen.

7.2.2 During measurement, the cryogenic liquid fullness rate shall be rated fullness rate.

7.2.3 After the liquid filling is completed, it shall be standing for 48 h before the start of recording data. During the standing period, the venting valve of the vacuum insulated cryogenic equipment shall be opened.

7.2.4 When the gauge pressure of the inner liner is close to zero, except the venting valve is opened, the other valves of the measured piece shall be all closed; record the initial data of the weighing instrument at the same time.

7.2.5 Record the data of the weighing instrument when the time interval is 24 h and 48 h.

8.1 Percentage loss of product per day alpha0

8.1.1 When the wet gas flowmeter is used for measurement, the percentage loss of product per day alpha0 is calculated according to formula (1). Where. alpha0

--- The percentage loss of product per day, and the unit is percentage per day (%/d); qv

--- The daily average value of volume flow of evaporated gas, in cubic meters per Where. alpha0

--- The percentage loss of product per day, and the unit is percentage per day (%/d); qg

--- The mass of gas evaporated within 24 hours, in kilograms per day (kg/d); rho1

--- The density of the saturated liquid at standard atmospheric pressure (101.325 kPa), in kilograms per cubic meter (kg/m3); V

--- The effective volume of the measured piece, in cubic meters (m3).

8.2 Calculation of static evaporation rate

8.2.1 The static evaporation rate of high vacuum multilayer insulation alpha20 is calculated according to formula (4). Where. alpha20

--- The static evaporation rate, and the unit is percentage per day (%/d); alpha0

--- The percentage loss of product per day, and the unit is percentage per day (%/d); h

--- The latent heat of vaporization of the saturated liquid at test ambient pressure, in kilojoules per kilogram (kJ/kg); hfg

--- The latent heat of vaporization of the saturated liquid at standard atmospheric pressure (101.325 kPa), in kilojoules per kilogram (kJ/kg); Ts

--- The temperature of the saturated liquid at standard atmospheric pressure (101.325 kPa), and the unit is Kelvin (K); T1

--- The daily average ambient temperature during the test, and the unit is Kelvin (K); T2

--- The saturation temperature of the cryogenic liquid that is corresponding to the daily average pressure in the measured piece during the test, and the unit is Kelvin (K).

8.2.2 The static evaporation rate alpha20 of the vacuum insulation of the powder or fiber is calculated according to formula (5). Where. alpha20

--- The static evaporation rate, and the unit is percentage per day (%/d); alpha0

--- The percentage loss of product per day, and the unit is percentage per day (%/d); h

--- The latent heat of vaporization of the saturated liquid at test ambient pressure, in kilojoules per kilogram (kJ/kg); hfg

--- The latent heat of vaporization of the saturated liquid at standard atmospheric pressure (101.325 kPa), in kilojoules per kilogram (kJ/kg); Ts

--- The temperature of the saturated liquid at standard atmospheric pressure (101.325 kPa), and the unit is Kelvin (K); T1