GB/T 6999-2010Relative humidity tables for environmental test (English PDF)

2.1

Tables 2 to 5 were using spherical or cylindrical mercury thermometer measuring wet and dry bulb temperature in lookup table with relative humidity. The formula as follows.

U = eew ×

100% = etw-AP (T-tw) ew ×

100%

Where.

U --- relative humidity;

e --- the actual vapor pressure, kPa;

ew --- dry bulb temperature t corresponding to the plane of pure water saturation vapor pressure, kPa;

etw --- wet-bulb temperature tw corresponding to the plane of pure water saturation vapor pressure, kPa;

A --- psychrometer coefficient, °C -1; its value due to the type of wet and dry bulb thermometer wet and dry bulb thermometer bulb and wind speed at the decision, as shown in Table 1;

P --- Pressure, kPa; respectively 110kPa, 100kPa, 90kPa, 80kPa four grades;

(T-tw) --- the difference between wet and dry bulb temperature, °C; taking the difference is 0 °C ~ 16.0 °C; wherein the interval 0 °C ~ 5.0 °C 0.1 °C; 5.0 °C ~

Table 1 psychrometer coefficient A value table

Wet and dry bulb thermometer type

Wind velocity

0.4m/s 0.8m/s 2.5m/s

Spherical 0.857 × 10-3 0.7947 × 10-3

Columnar 0.815 × 10-3 -

0.8662 × 10-3 2.2 Table 6 for the flat water saturation vapor pressure ew (etw), kPa; calculated as follows.

lgew = 10.79574 (1-T1/T) -5.028lg (T/T 1) 1.50475 × 10-4 1-10-8.2969 (T/T 1-1 [])

0.42873 × 10-3 104.76955 (1-T1/T) - [] 1 -0.21386

Where. T1 = 273.16K (triple point of water temperature; K, absolute temperature)

T = 273.15 t

3.1 look-up table method

3.1.1

pressure measurement P, single-digit rounding.

3.1.2

measurement of wet and dry bulb thermometer bulb at a wind speed V, based on wind speed V and the type of wet and dry bulb thermometer isolated corresponding wet in Table 1

Coefficient table A.

Note. Measured wind speed and wind speed in Table 1 below is not the same, you can choose a small difference with the measured wind speed of a wind speed.

3.1.3

readout mercury wet and dry bulb thermometer dry bulb temperature and wet-bulb temperature t tw, and find the wet and dry bulb temperature difference (t-tw).

3.1.4

isolated portion corresponding in Tables 2 to 5, according to P, A, and wet and dry bulb thermometer mercury type.