Hot end loss at pulse tube refrigerators

Most pulse tube refrigerators need an additional heat exchanger at the hot end of the working space in contrast to other refrigerators with regenerators. There is a periodic, alternate gas flow which passes through this hot heat exchanger. Due to this fact the hot heat exchanger has to be considered not only with a desired recuperative effect but also with a regenerative effect. This regenerative effect of the hot end heat exchanger acts as a loss. In this contribution the so-called hot end loss is described by means of an orifice pulse tube refrigerator and is compared with that of a four valve pulse tube refrigerator. Experimental investigations on a four valve pulse tube refrigerator verify this loss. An orifice pulse tube refrigerator without hot end loss is presented.