An adiabatic saturation psychrometer

Abstract

An adia ba tic satu ratio n psychromet e r for measuring the hum idity of gases, as well as the va por conte nt of va po r-gas mlXtures, IS descrIb ed: The. In strum ent be ha ves in accord a nce with pred ictions d e du ~ed solely fro m thermodyna mIc consIde ra tIO ns. With wa ter-air, water-hyd roge n, carbon te trac hlo~ld e-h y d roge n , carbon te trac hlond e-oxyge n a nd tolu e ne-air sys te ms, a t roo m te mperature, atm osphe rI c pressure , a nd ~a s flow ra tes ? f 1.3 to 5.2 liters pe r minute, measured we t-bulb te mpe ratures agree WIth calc ul ated the rm od yna mIc ~e t-bul b te mpe ra tures" to within the acc uracy of th e measureme nts a nd the uncertamtl es I~ the publIshed the rm od yna mic da ta used in th e co mputa tions. For the wa te r-aIr syste m, the syste ma tIc a nd ra ndom errors du e to these sources a re es tim a ted a t 0 027 deg C and 0.01 9 deg C re~p ective ly. The agree me nt be tween the cal c ul a ted and measured we t-bulb te mper ature. IS 0.029 deg C , whle h a t a dry-bulb te mp erature of 25 C and a n a mbie nt pressure of 1 ba r is e qUlv ~l e nt to a n unce rtalllty In rela tive humidity whic h va ries fro m 1/8 to 1/4 perc ent. The tim e con-~tant IS a fun ctIOn of the gas flo w rate; at fl ow rates of 3_ 75 to 5_2 lite rs per minute, the tim e co nstant IS of the ord er of 3/4 mmute.