In the early years of the twentieth century, the vapor absorption cycle using water-ammonia systems was popular and widely used but, after the development of the vapor compression cycle, it lost much of its importance because of its low coefficient of performance (about one fifth of that of the vapor compression cycle).
In the early years of the twentieth century, the vapor absorption cycle using water-ammonia systems was widely adopted but eventually fell out of favor after the development of the vapor compression cycle due to its relatively low efficiency compared to the latter.