一八八一年七月的一天,美国总统加菲尔德遇刺受伤。时值暑天,医院里闷热难耐,美国政府请工程技术人员谢多设法降低病房的温度。谢多早年在矿山工作过,熟知矿井坑道输送空气的技术,他想,空气经过压缩后温度会升高而向周围环境放出热量,如果再将空气恢复原来的常压状态,应该会吸收热量。他反复进行试验后,就在加菲尔德总统的病房旁边装了一台空气压缩机,把压缩后的空气经过 On a day in July 1881, U.S. President Garfield was assassinated. At the time of hot summer days, the hospital was sweltering. The US government asked Xie, an engineering technician, to try to lower the temperature of the ward. Xie Duo worked in the mine in the early years. Knowing well the technology of conveying air in mine tunnels, he thought that after the air is compressed, the temperature will increase and heat will be released to the surrounding environment. If the air is restored to the normal pressure, it should absorb heat. After repeated tests, he installed an air compressor next to President Garfield’s ward and passed compressed air through it.