I Downloaded from https://www.everyspec.com MIL-STD-810-D 19 July 1983 METHOD 505.2 SOLAR RADIATION (SUNSHINE) ., SECTION II 11-1 AUAUTUS ,, ... . !. II-1.1 Yest ‘fac~ ., . .. ,. .. -.,._ ,- a. The required facility consists of a chamber or cabinet, auxiliary instrumentation, and a solar lamp bank. Thie apparatus must be capable of maintaining and monitoring the required conditions of temperature, airflow, and irradiation. ,..> b. For prooedure 1, the possible cooling effects of airflow over the test specimene must be considered. An airflow of as little ae 1 m/s can cause a reduction in temperature rise of over 20 percent.
It is essential, therefore, to control and measure the rate of airflow, which should be as low as possible consistent with achieving satisfactory control of temperature. Adjustments of the temperature within the enclosure and control of chamber gradients by suitable heating and cooling of the walls of the enclosure eliminate the need for high air velocities. The air velocity shall be maintained between 0.25 and 1.5 m/s (50 to 300 ft/min). c. The volume of the test chamber shall be a minimum of 10 times that of o the envelope volume of the test item. d.
The solar radiation source area shall be such that the length and width of the test item shall be no more than one-half the same dimensions of the lamp bank and may be composed of either radiant heat-producing lamps (for procedure I) or lamps that simulate the solar spectrum (for procedure II or both I and II). e. The Irradiance shall have a maximum intensity of 1-120W/m2 (*1O%),and the radiation falling on the test item shall be uniform to within ~10% of the desired value, with the spectral distribution given in table 505.2-II.
Where thermal effects only are to be assessed, deviation from this spectral distri- bution is permitted, but the irradiance must be adjusted to give an equivalent heating effect. In order know: to calculate this adjustment, it is neceseary to , .’.. (1) The spectral surfaces, and reflectance or transmittance of the irradiated (2) The spectral used (and also the effect energy distribution of the particular lamps being z of any associated reflectors or glasses). The radiation shall be directed onto the test item and shall irradiate the entire surface of the test item facing the solar radiation source. The value of 1120 MST’HOD505.2 ig JUIY 1983 505.2-10